Tailwind Build

6th November 2011 - Carburettor heat control

2011-11-06T16:17:00.002Z

One more little job completed today. A semi-circular shaped hole was cut out in the top of the airbox and one half of a piece of hinge match drilled to its straight forward edge. Then an aluminium flap was created to completely fill the normal entrance to the airbox when at right angles to the airbox top. This took lots of iterations of filing and testing to exactly fit the shape of the fibre-glass bottom of the airbox. Once this was a good fit it was match drilled to the other side of the hinge. The holes were then deburred and dimpled to take countersunk rivets. These were set so that the flush surface is inside the airbox to provide minimal disturbance to the airflow when in the normal open position. Then an actuator arm was rivetted to the top of the flap and drilled for a cable connection. The top of the airbox was then bolted to the carburettor and the actuator cable measured and cut. The system is designed so that the cable pull holds the flap open against the airflow when carb heat is required. In the normal closed position the control is fully forward and the cable is assisted by the airflow to keep the flap tight to the top of the airbox and allow the cold air into the carburettor. The hot air intake is mounted over the semi-circular cut out and is spaced off it to allow the heated air to spill into the cowl when carb heat is not required. When heat is required the suction of the carburettor will ensure hot air enter the airbox. The six tabs on the underside of the airbox top-plate hold the K&N filter in position.

4th November 2011 - Lower cowl nearly complete

2011-11-04T17:18:00.001Z

It has been slow progress over the last few days. The weather has been poor so I haven't been able to get the fuselage outside and I'm spending time waiting for resin to cure. Finally though the airscoop is fully bonded to the cowl and the air intake created and lined up with the airbox. The process for creating the air intake is to cut the hole in the airscoop to match the intake to the airbox then shape and insert a foam plug that projects into the airscoop. Glass cloth is then laid up around this plug to create a tube on the inside of the airscoop that matches the airbox. The airbox will then have a rubber seal riveted around the intake that fits over the tube in the airscoop that has been fabricated. This ensures that outside air is rammed into the airbox by the propeller and speed of the aircraft increasing the effective air pressure at the carburettor and therefore the engine power. I just need to wrap one final layer of glass round the lips of the air intake to protect them and final fill and sand then the lower cowl will be finally ready for priming.

1st November 2011 - Brakes and cowl

2011-11-01T19:01:00.001Z

The first job today was to complete the installation of the brakes. The top end of the master cylinder pistons were connected to the brake bars on the rudder pedals. Then the fluid intakes were connected to the "T" junction on the fluid reservoir. Finally, the fluid outlets were connected to the AN fittings screwed through the floor. These will then connect to the brake lines running down inside the leg fairings. Next the front cheek panels were covered on the inside with the same self-adhesive felt fabric as the baggage compartment walls. These were then clecoed into place ready for riveting to the firewall.
The posting on the 26th October shows how I had had to cut the airscoop in half horizontally in order to increase its depth. Yesterday, I had put a first layer of glass on the inside of the gap to join the two halves and put a slurry of resin and microballoons on the outside to level up the surface. I had also put a first layer of glass over the joint between the top section of the airscoop and the cowl proper. Today, the joints were sanded to create a key and two extra layers of glass were glued into place over both the joints. The three layers should be enough for a final result but I'll check it tomorrow to see if I think it needs one extra layer. Then the cowl was inverted and a slurry of resin and microballoons used to filet the intersection between the airbox and cowl. This can be easily sanded once set to get a clean smooth joint. Any resin left over from each layup is mixed with some white pigment and painted onto the inside of the cowl. Once completed properly this will seal the inside of the cowl and allow any drips from the engine to be easily seen. Finally three layers of glass were applied to the joint in the airbox. Once this is set I will filet the inside of the joint to make sure that the air can flow smoothly into the filter.

31st October 2011 - Spraying the underside

2011-11-01T18:00:00.002Z

It was good weather today so the aircraft was tipped on its nose once more to spray the underside with the white EkoPoly topcoat. The paint has gone on pretty well with no runs or other serious blemishes. However the edges of the finishing tapes are very obvious. Before I do any more painting I'm going to have to make sure these are really stuck down and lie as flat as possible. However, this sort of learning experience is one of the advantages of doing the bottom first. This is not a view that is going to be routinely seen!

While the paint was drying I made a start fibre-glassing the cowl and airbox with the vinyl-ester resin that arrived this morning. Pictures of this tomorrow. Once the paint was properly dry the brake master cylinders were installed on their pivot and the front lower skin was positioned and clecoed and screwed into place. The fitting to the rear left of the skin is the fuel tank breather inlet and there is a hole to the rear right which will take the transponder antenna. I'm not fitting this yet as they are very vunerable and there is a high likelyhood I would break it off before ever flying. In order to fit this later I've drilled a 1" access hole in the inner front floor which will be filled with a rubber bung but will allow the transponder antenna to be installed and also, if required, serviced or replaced once the aircraft is in service.

30th October 2011 - Dzus fasteners

2011-10-31T17:12:00.001Z

I decided to use Dzus fastners to fasten the cowl to the mount strips. These are not the completely flush types (which are silly money!) but appear as a flat screw head on the outside. They take a quarter turn with a screwdriver to fasten and unfasten. The cowl mounting strips were removed and the cowl mounting pilot holes drilled out to 7/16" to take the raised surround of the Dzus "nut". Then 1/8" holes were drilled for the mounting rivets. The mounting strips and the fasteners were dimpled to accept countersunk rivets. AN426AD4-4 rivets were inserted and set using the pneumatic squeezer. Then the holes in the cowl were drilled out to take the Dzus "screws". The mounting strips were then clecoed back into place and the cowl replaced and checked for fit. Then the front inner floor was also installed and screwed into place and the rudder system installed.

28th October 2011 - Starting painting

2011-10-28T18:18:00.001+01:00

I want to rivet the forward fuselage cheeks and forward outer floor to the firewall but...
I can't do that until I install the rudder pedals and brakes but...
I can't do that until I install the forward inside floor but...
I can't do that until I install the forward outer floor but...
I can't do that until I have painted the underside of the fuselage so...
Today I set to to do that. I brief trial proved that painting the underside with the EkoFill primer/UV blocker was not going to be possible lying on the floor. However, without the tail feathers the airframe is currently pretty much neutrally balanced when in flying attitude and the centre of balance moves forward as the tail lifts. So the wheels were chocked and a cable attached to the horizontal stabiliser carry through and very carefully the aircraft was allowed to tip forward until the engine rested on some foam padding. This allowed enough access to the underside to work and get access with the spray gun.
The process is first to clean the fabric with some special cleaner that Stewart supply and then to wash off the detergent leaving the fabric damp. Then the first coat of EkoFill is brushed on with a foam brush. Once this is dry a second coat was brushed on using the brush at right angles to the first coat. Painting the tail while standing on a step ladder was slightly bizarre and the passing local traffic seemed distracted! While this coat was drying I decided to make a first attempt at using the Stewart EkoPoly top coat. I had previously prepared the spinner so this was an ideal test subject. The paint was mixed with the catalyst and then thinned with distilled water and then 4 coats were sprayed on alternating in direction about 10 minutes apart. The first coat came out as tiny globules of paint rather than a mist. This was diagnosed as having too little gas pressure so once this was corrected the painting was much more even. There is a little bit of an orange peel effect but this should polish out and was probably caused by the first coat. After 3 hours the fuselage seemed dry and some 320 grade open coat sandpaper was used dry to remove any blemishes. Then the paint gun was prepared for 4 coats of the primer (2 coats in each direction). These were applied as per instructions about 10 minutes apart and resulted in an even light-proof covering of the fabric. This is critical as the fabric is degraded by ultra-violet light and left outside unprotected will loose 85% of its strength in a year. The fuselage was then gently returned to a more normal attitude and returned to the workshop where the paint can harden overnight.

27th October 2011 - Main gear leg fairings

2011-10-27T16:04:00.001+01:00

It is an unpleasant day, rainy and cold, so I needed a task that could be accomplished inside with the aircraft in the workshop. I had acquired the blanks for a pair of the old style aluminium Vans gear leg fairings so fitting these seemed like and ideal job. First the fairing were cut to size to fit between the fuselage and the wheel. The fairings are joined at the back by inserting the pin in a length of aluminium hinge. The key to a neat job is to have the hinge positioned so that when the fairing is flexed around the gear leg it pulls the trailing edge of the fairing together precisely. Pieces of scrap steel tube were used to simulate the ends of the gear legs and with the rear edge of the fairings taped together the correct position of the sides of the hinges marked. The hinge pin was then removed. The ends of the hinge were match drilled to the fairing and then a rivet fan spacing tool was used to get an even line of rivets. In theory you are not supposed to drill through the fan to avoid opening up the holes, just use them to mark, but I'm sure I'm not alone in ignoring this advice. Once all the holes were drilled they were dimpled to accept countersunk rivets. With the thin aluminium and the thin hinges this could be done through the two together which ensures a very good fit. Then the rivets were set using the pneumatic squeezer - it is great to have these tools left over from the RV build. The result is a exactly spaced set of perfect rivets - this is one of the most satisfying jobs when it comes out well. The fairings were then wrapped round the gear leg and the natural position of the top of the legs in the fairing established. This was marked and then slots cut in the top of the fairings stop drilled at their bottom ends. Stainless steel jubilee clips were then used through the slots to fasten the fairings to the leg. Before flight they need very accurately aligning fore and aft with weight off the wheels as if misaligned they act as mini rudders and can put the aircraft out of balance.

26th October 2011 - Cowl, Airscoop, and Airbox

2011-10-26T18:53:00.001+01:00

The first job today was to roughly cut out the lower cowl for the airscoop. The lower cowl was then match drilled to the cowl support strips in the same way as the upper cowl. This immediately revealed a problem. The airbox stuck out way below the cowl at the front and was also about an inch further below the cowl at the back than the depth of the airscoop. I assume the RV9 has a greater vertical cross section than the Tailwind hence the difference. Whilst I was pondering what to do about this I removed the cowl to finalise the fit between the upper and lower cowls.

It was clear that the only solution was some fairly major fibreglass surgery. The first job was to get the top of the air intake on the airbox to align just below the bottom of the lower cowl. Notches were cut in the flange of the top plate of the airbox just in front of the filter and the plate bent up about 15 degrees. Reinforcing angles were cut out and clecoed on the inside of the flanges to hold the angle. Then the fibreglass box was cut in half and the front section angled to match the bend. Slots were cut in the front edge of the rear section and heat used to bend the tabs in to butt join accurately with the front section.

Next the airscoop was cut in half horizontally. The lower cowl was cut out to match the top section of the airscoop which was then taped in place. The cowl was then refitted to the aircraft. This allowed the bottom section of the airscoop to be positioned which showed that it needed to be about 1/2" lower at the front and 1" at the back. The sides of the bottom section were notched to allow the front to curve up slightly. Some scrap aluminium was clecoed to the top section of the airscoop and the bottom section positioned to allow a small amount of clearance from the airbox. This was then drilled and clecoed to the aluminium.

I've ordered some vinylester resin which is what was used to construct the cowl so once this arrives I can glass over the various joints, spaces and notches. The resin can also be mixed with microballoons to make a lightweight filler to smooth over the various joints. The final job will be to make the flexible joint between the front of the airbox and the airscoop. This was pretty tricky on the RV but at least I've done it once before.

25trh October 2011 - Cowl and air filter

2011-10-25T19:47:00.000+01:00

I received a delivery from Vans today with some of the bits I need to make progress firewall forward but first job today was to carefully cut out the fabric round the hinges in the elevators, flaps, and ailerons with a soldering iron to free the hinges. Once this was done, strips of 0.040" aluminium were cut and match drilled to the firewall to provide the mounting for the cowl. Spacers were also cut and match drilled to fit between the cowl mounting strips and the inside lip of the firewall. The idea is that the thickness of the aluminium skin plus the spacer plus the firewall should be equal to the thickness of the cowl so that when it is fastened to the mounting strip it lies flush with the fuselage side. Then the upper cowl was positioned and match drilled to the mounting strip at 4" spacing. This will be fastened in place using Dzus fasteners to make it easy to remove.
The lower cowl has to be cut out for the airscoop that feeds air into the filtered airbox so the basic construction of the airbox was started to allow the requisite measurements to be established. I need to construct the carburettor heat control and then I can rivet it together. The airbox kit is from Vans and is identical to the one I'm using on the RV9A.

24th October 2011 - Pitot mount and engine controls

2011-10-25T10:07:00.000+01:00

I fancied a change of task today so decided to fabricate a mount for the pitot tube. I had a pitot left over from a Cessna I had owned that the CAA decided was not the correct part number for that plane so had to be replaced. The standard Wittman pitot is a tube through the leading edge and whilst this is light and simple it has a couple of drawbacks. At high angles of attack it is reported to significantly under read and it is vunerable sticking out from the front of the wing (and also possibly dangerous to eyes whilst the aircraft is on the ground). The conventional pitot should be more accurate as the underside of the wing will channel air past it even at high angles of attack and is certainly less vunerable. The starting point for the mount was purchasing a length of streamlined steel tubing 2.023" x 0.857" x 0.049" which is a standardly available size and fits perfectly around the stem of the pitot - I presume this is deliberate. Then a plate of 0.063" steel sheet was cut to fit round the streamline tubing and a second plate drilled to attach to the rear of the wing main spar. These were then jigged against the spar using some scrap timber and the joint tack welded to get exactly the correct angle (don't try this if you are gas welding!). Then the plates were removed from the wing and the streamline tube welded into position and the joint between the plates final welded. The pitot then screws into the bottom of the streamline tubing.
The cable safes have arrived from ACS so I also mounted the cable support bracket between the sump and the carburettor and clamped the cable outers into place. The controls cables were cut to length and the controls adjusted so that full throttle and full-rich mixture both were achieved with the controls almost, but not quite, fully forward.

23rd October 2011 - Covering completed

2011-10-23T15:53:00.000+01:00

The last six finishing tapes were applied to the flaps and right aileron this morning so all the covering is now complete other than a clean-up and cutting out round the hinges. Whilst doing the covering of the smaller components I've been leaving the fuselage out on the drive so, as winter approaches, I've bought a large tarpaulin that can cover it completely to protect it against the elements and keep the fabric protected from UV before it is painted. Wrapped like this, it should also be safe to leave it out overnight which will mean I can do the skinning of the wings in the workshop without moving the fuselage to the airport.

22nd October 2011 - Six more finishing tapes to go

2011-10-22T19:32:00.000+01:00

Today I made progress on the right aileron and the two flaps. There are now only six more finishing tapes to go - the leading edges of the three components and three tapes round the counterbalance on the aileron. Various bits from Vans including an air filter kit should arrive on Tuesday so if I get the covering finished by then I can get back to working on the firewall forward.

21st October 2011 - Still covering

2011-10-21T19:20:00.000+01:00

I had assumed that the fuselage would be the most difficult and time consuming covering job but the empennage and wing components together seem to be taking much more time and effort. Today (started at 09:30, finished at 19:00 with an hour for lunch and other jobs) I applied the remaining finishing tapes to the elevators and left aileron and did the basic wrap of the fabric round the two flaps. So the end of the covering is in sight but still at least a couple of full days work needed to finish up the basic covering of the flaps and the right aileron and then tidy all the hinge cutouts and remove any surplus glue from all the bits of the airframe.

20th October 2011 - The last rib stitch

2011-10-20T18:55:00.000+01:00

Yesterday I rib stitched the elevators and then applied the finishing tapes over the stitches. That completes the stitching for the aircraft. Stitching seems to be one of the tasks that builders dislike but on the Tailwind there is relatively little to do as the wings are sheeted so there was just enough to do to be interesting without becoming a major chore.
Today I started covering the left aileron. This uses a complete wrap of cloth from the leading edge around the trailing edge and back to the leading edge. The ends are folded over to complete the covering and then a separate piece of cloth was used to cover the counterbalance horn. Next job is the remaining finishing tapes for the elevators, the tapes for the aileron and then on to the other aileron and flaps.

11th October 2011 - Back to covering, elevators and HS

2011-10-11T19:24:00.000+01:00

I'm waiting on various deliveries before I can continue with the firewall forward so today was a good opportunity to get on with some covering. The finishing tapes were applied to the horizontal stabilisers and the elevators were covered to the point of rib stitching. One sentence to describe, one day to do! I won't be able to get any work done for the next few days but later next week should see progress being made again.

10th October 2011 - Fitting the cowl: part 1

2011-10-10T19:49:00.003+01:00

I'd bought a cowl from Brian Alley back in September 2009 (The cowl arrives) and it has been stored in its shipping crate since then. Today I decided to make a start cutting it to fit. The first job was to get the join at the front to fit and cut out for the prop extension. Lots of sanding and use of a rotary burr on the inside angles got this to a good fit. The inside of the air intakes and the front of the sides were then match drilled together to fix the position of the joint between the cowl halves. Then the spinner backplate was installed on the prop drive extension to set the length for the cowl and first the lower cowl and then the upper cowl cut roughly to length. Temporary aluminium strips were clecoed to the firewall top, sides and bottom. Then the lower cowl was positioned and drilled and clecoed to the side and bottom aluminium strips. The upper cowl was then positioned and the correct overlap between the back of the upper and lower cowl established and the two halves match drilled and clecoed together. Then it was a case of marking minor changes to the rear of the two halves to centre vertically and horizontally the spinner backplate in the cowl opening and to ensure that there was an even gap of about 3/16" between the front of the cowl and the rear of the backplate, removing the cowl, making the adjustment, rechecking and repeating and repeating and repeating.....
Eventually a good fit had been established and it was time to take some pictures despite dusk falling. The next jobs are to properly cut and make the side joins, to fit the airscoop which will feed air to the carburettor, and to match drill and rivet permanent mounting strips to the firewall which will carry the cowl mountings.
I hope the pictures show what a super product Brian has produced. His cowl carries the lines of the fuselage perfectly and then blends them into the spinner surround. It also fits perfectly width-wise at both the top and bottom. Of course the overlap of the sides can be adjusted to make them fit perfectly as well. Using my O-235-C2C engine and a 4" propellor extension I had to cut off about 1-1/2" from the back of the cowl.

7th October 2011 - Carburettor control mount

2011-10-08T12:32:00.004+01:00

The outer shields of the throttle and mixture controls need terminating on the engine close to the carburettor leaving the inner core to operate the carb levers. This needs some sort of bracket fabricating which was the task for today. One standard way of doing this is to bolt the bracket between the carburettor and the sump which is the approach I have adopted. First holes for the air intake and the attach bolts and a relief hole for the throttle arm to match the depression in the sump were cut out of a flat sheet of 0.071" 4130 steel using the CNC router (top of the picture). Then the routes of the cables were marked onto the sheet and the positions of the cable outer support tabs established. The tab for the mixture cable is at the very bottom of the picture and the tab for the throttle above and to the left. An angle grinder was then used to cut along the sides of the tabs and they were bent up into position. The throttle cable operates at right angles to the bracket base but the mixture control is at an acute angle of about 75 degrees. Next two pieces of steel were welded between the tabs and to the base to support them. Then the carb was positioned on the bracket and the vertical position of the cable runs marked to give a straight run and two pilot holes were drilled in the tabs. I've ordered a pair of "cable safes" from ACS which will clamp the outer cable through the holes in the tabs. The pilot holes will be enlarged to fit these when they arrive. I'm using bare end control cables as these can be cut to exact length. Finally some lightening holes were cut out to save a bit of weight.

The view of the bracket is from the bottom of the engine with the front at the top and the cables coming in from the bottom.

6th October 2011 - Aligning the alternator

2011-10-06T19:34:00.001+01:00

It is incredible how much time seemingly simple jobs can take. The bracket on the engine I bought was originally intended for a generator and it was not possible to get the pulley of the alternator aligned with the flywheel with it as supplied. In order to rectify this it was necessary to cut off both mounting tabs and re-weld them further back and wiith a slightly different spacing. After repeated tack welds and test fits a perfect alignment was achieved and the welds completed. The bracket bolts to three of the crankcase joining bolts at the front of the engine and the original design has a tie bar from the front generator mounting bolt to the starter motor, presumably to stop the generator applying a twisting force to the case bolts and risking damaging the engine case. This bracket was not supplied with the engine so this was fabricated from some 0.090" 4130 steel sheet. Then an old over-long alternator belt was cut and used to measure the belt length required to get the alternator adjustment somewhere in the middle. This was then joined with tape and taken to the local car part shop where a 914mm belt matched the test length. Back home this was fitted in place and was exactly the right length. So a full day's work and one very small step forward!

5th October 2011 - Installing the engine

2011-10-05T19:54:00.002+01:00

As a change from covering I decided to install the engine. This needs to be in place to fit the cowl and build the baffles which control the cooling airflow around the engine. Both of these are likely to be biggish jobs. The engine had been returned from the shock load inspection without cylinders which were not part of the inspection and were stored separately. In this state it was easy to manually lift the engine up onto a bench and then the aircraft could be positioned to align the mounting bolts. Once these were in place the cylinders were installed together with the fuel pump, the vacuum pump, the magnetos, the starter, the priming lines, the tacho drive, and the cylinder head temperature sender. I still need to make a bracket to support the throttle cable and mixture cable before I can mount the carburettor. Also, the alternator I'm going to be using doesn't align with the flywheel pully using the standard Lycoming mount so this will need to be modified. The engine is unpainted at the moment. Once everything is set up and the cowl and baffles are complete I will remove the engine as a complete unit and paint it before final assembly of the aircraft.

3rd October 2011 - The last priming?

2011-10-03T19:21:00.001+01:00

The weather was good today so I got the last bits and pieces primed with the epoxy primer. This included the ailerons , flaps, rudder connection tabs, and spinner.
The spinner is a spun aluminium construction so has numerous rings of concentric surface texture. Once the basic primer coat was dry I applied numerous coats of a high build primer, sanding between each coat, to slowly bring the surface up to a smooth level. Tomorrow the paint from Stewart should arrive so I will have a first go at painting the spinner to a final colour.

2nd October 2011 - Fuselage covering complete

2011-10-02T17:38:00.000+01:00

Over the last few days I've been adding the finishing tapes to the fuselage. The rivets for the top surface arrived in the post yesterday so they were inserted and the finishing tapes stuck in place over them. Then the finishing tapes along the join between the fuselage sides and bottom were applied. This was fairly messy laying on the ground and gluing over my head - the glue doesn't wash out of your hair but you can pick it off bit by bit. Finally the tape over the rudder post was applied.
The other little job completed was the bit of rework on the counterbalance on the left aileron. This was slightly out of alignment with the aileron and would have stood proud above the wing surface with the aileron in neutral position. So this was cut off the aileron spar and re-welded in the correct position.
Next job is to prime the aileron and flaps ready for covering them. The weather in the UK should be good for another couple of days so hopefully I will be able to get this done soon.

29th September 2011 - Rivet holes and more tapes

2011-09-29T18:52:00.001+01:00

The stringers along the top of the fuselage need drilling for the pop rivets which will keep the fabric attached. I'm using 48" lines of rivets at 2" spacing on the outer stringers and 54" of rivets at 2" spacing along the centre stringer as per advice from Jim Clement. So the challenge was to drill 70+ holes in the centre of the circular stringers accurately spaced out without the drill bit wandering off centre and wrecking the fabric! After a bit of thought I decided to make a jig which would align the drill along the centre of the stringer and provide the spacing. I used a semi-circular router bit in the CNC router to machine a shallow channel in a bit of scrap aluminium. Then the router bit was exchanged for a 1/8" drill bit and the router programmed to drill two holes exactly 2" apart in the centre of the channel. The channel accurately located the jig over the stringers. Once the first hole was drilled in a stringer a spare drill bit was inserted through the jig into the ready drilled hole and then the second hole drilled through the other hole in the jig. Then it was just a case of moving the jig one space, with the spare drill bit popped into each new hole in turn and drilling through the other hole. It took about 30 minutes to make the jig and less than 10 to then drill the holes. I also then applied the finishing tapes over the bottom stringers and those on the left side of the aircraft. I now need to wait for the rivets to arrive from ACS before I can finish up the top of the fuselage and also still need to do the finishing tapes along the bottom longerons. I've also run out of 2" finishing tape which I need to complete the horizontal stabilisers and will also need for the elevators, flaps and ailerons so an order went in for another 50yds of that as well.

27th September 2011 - Tapes

2011-09-29T18:32:00.002+01:00

The next few days are going to be spent applying finishing tapes to the fuselage and vertical and horizontal stabilisers. I'm following to Stewart manual and videos precisely. Rib tapes are stuck at one end and the glue allowed to dry to a reasonably strong bond. Then the glue is applied along the rib until just before the other end. All excess glue is wiped off with a paper towel. The tape is pulled tight to cause it to conform to the shape of the covering and the glue again allowed to dry. Finally, the tapes are cut to length and the end glued. The joints between the fuselage sides and top and bottom will be reinforced with 3" finishing tape. In this case the tape is folded in half to get a centre line. The centre of the longeron is painted with a glue line which is allowed to get tacky. Then the tape can be positioned accurately over the longeron centre. The glueline is ironed to thermal soften the glue and bond the centre of the tape in place. Next the tape ironed flat against the top and side. Finally the edges of the tape are lifted and glue appled about a foot at a time with the excess wiped off. So far I've got the tapes completed for the vertical stabiliser, the top fuselage side joints, the right fuselage side stringers, and the horizontal stabiliser ribs. I've also applied the reinforcing tapes along the top stringers ready for the fabric attach rivets.

26th September 2011 - Rib Stitching

2011-09-26T20:15:00.002+01:00

I needed to rib stitch the vertical stabiliser before I could apply the finishing tapes to it and the rest of the fuselage and I had also only got the covering of the horizontal stabilisers to the point of being stitched so that was the task for today. One of the tedious but exacting jobs in rib stitching is marking out and making the holes for the stitches. In order to speed this up I spent some time making a jig. I used the CNC router to create a pattern of holes spaced 1-1/2" apart lengthwise and 1/2" apart side to side in a piece of aluminium strip. Some additional holes were also drilled in the middle of the strip. The centre point of a rib was then marked on the stabiliser in a couple of places and these were lined up in the middle holes in the jig. Then I used a fine taper bit on the soldering iron to make holes for the stitches through the parallel rows of jig holes. The net result was a perfectly straight line of evenly spaced holes along the rib. Then it was a case of putting the stitches in. Luckily I had videoed the demo done in the fabric covering course I'd done so after a quick refresher I completed the stitching of the two horizontal stabilisers and the vertical stabiliser. Rotating the horizontal stabilisers on the spar carry through made it easy to work on them. This leaves just the elevators to be stitched but I need to do the basic covering of these first.

24th September 2011 - Right fuselage side covered

2011-09-24T19:17:00.001+01:00

I attached the fabric on the right side of the fuselage today so the basic box is now covered. The fabric over the windows on both sides was cut out using a soldering iron which seals the edge of the fabric and cuts accurately along the line of the window opening. In addition it was used to pierce all the holes for the screws to attach the window to the frame. You can also see round the inside of the left window frame the black self adhesive neoprene strip which will create a watertight seal with the glazing. It is a bit scary having a hot soldering iron near the pristine fabric - one slip....
However, all went well so next job on the covering is to apply all the tapes to cover the seams and protect the fabric where it lies on the stringers.
The rear shot show the upright vertical stabiliser as viewed from the rear; contrast yesterday's photo.

23rd September 2011 - Top and left side covered

2011-09-24T09:38:00.005+01:00

I've put in two very full days of work on the covering and have made good progress . First the inspection rings were glued into the Vertical stabiliser (VS) and floor. These are first attached to the inside of the fabric and then a patch 1" greater in radius in glued over the top, also on the inside. Finally the centre section will be cut out and the removable panel installed.
Next the right side of the VS was covered and the reinforcement tapes glued along the ribs ready for the rib stitching. The top of the fuselage was then covered. The tricky bit is getting the junction between the VS and the top skin. The top fabric was wrapped round the bottom tubes of the VS and into the VS itself. Then a finishing tape was applied to the outside to reinforce the joint.
Finally the left side was stuck in place. This has a cut out for the horizontal stabiliser spar carry through and for the rudder cable. Also it was glued to the plate for the static port. The picture of the right side of the fuselage shows the interior open for the last time until the right side skin is applied.

All of the fabric is shrunk with a domestic iron that has been calibrated at 250, 300, and 350F. The fabric is ironed twice or more at each temperature to slowly tighten it and remove any creases. The result is a smooth and taut surface ready for sealing and painting. The final picture shows the rather strange way in which rudder offset is created in the Wittman design to offset engine torque - this hadn't been obvious until the fabric was on. The VS main spar is perfectly upright and the top of the rudder is aligned exactly fore and aft, but the front spar is offset to the left at the bottom - you can see how it is out of line with the stringer which is centred. This creates the illusion that the whole VS is canted over which isn't the case.

Next job is obviously to close the right side and then it is on to finishing tapes over the seams and over the stringers. The fuselage itself in the design is a lifting body so the top surface will be under negative pressure in flight. To stop the top fabric ballooning off the frame it will be pop-riveted to the stringers.

21st September 2011 - Covering underway

2011-09-21T19:41:00.000+01:00

Yesterday and today I've started covering the fuselage. First the bottom cover was glued to the outline of the floor. This goes all the way from the rear of the aircraft to the rear of the front bay so it is the longest piece of material needed. In order to make best use of the fabric I wrapped the front section round the sides and used it to cover the panel underneath the doors. In this way the side pieces will only need to go to the rear of the dor opening. I'm using the Stewart Systems covering which uses a water based glue that seems to be latex based and is a fetching shade of blue.
Then the left side of the vertical stabiliser (VS) was covered. This meets the top decking at a right angle. Many aircraft blend the top deck covering into the vertical stabiliser but the construction of the Tailwind has tubing specifically set to create a right angle joint. Next job is to glue access panels into the VS and the floor to allow the horizontal stabiliser bolts to be installed and to allow the elevator pushrod connection to be made to the elevator horns. Then the right side of the rudder can be completed.

19th September 2011 - Putting it all together

2011-09-20T09:57:00.003+01:00

I've finished painting everything apart from the flaps and ailerons so it was time to put everything together and check all the controls work properly before starting the covering. First the strut brackets were final bolted onto the wing spars. In line with requirements from the LAA, the holes for the attach bolts had been bushed and the 1/16" ply reinforcement replaced with 1/4" 12 ply. This provides a very strong mount for the attach brackets and it was possible to torque the bolts to full tightness without any risk of crushing the mount. The wings were then bolted into position and the flaps and ailerons installed. Packing pieces were inserted between the flap and aileron hinges and the wings to simulate the thickness of the wing skins and ensure the mounts were in the correct place.

The interior photo shows how the flap and aileron pushrods pass through the windowsills in the baggage compartment. The edges of the holes are lined with Rayrim edging. This is ready glued and is installed with a heatgun neatly protecting the edges.

The biggest issue has been with rigging the ailerons. The seat back support fabricated as shown in the plans (the end is just showing at the bottom left of the interior picture) fouled the aileron pushrods when I did the first test fit some weeks ago. To solve this it was necessary to remove and re-weld this to the interior of the door upright rather than to the rear and to replace the diagonal section with a two part welding that moved the tubing forward and in away from the pushrod. This solved the issue and the aileron linkages now operated very freely and without touching any of the aircraft structure.

The test fit revealed two bits of rework. First the right flap was too close to the fuselage side when the thickness of the flap and fuselage covering was considered so the inner rib was cut off, the tubing smoothed where the original weld had been and the rib re-welded 1/4" further out. Also I've positioned the counterweight on the left aileron about 5 degrees above where it needs to be to fit neatly into the slot in the wing in the neutral aileron position. This will need to be reworked but that's a job for another day. The bottom picture shows the rear seat belt attach, the elevator pushrod passing through the centre support and the static pressure ports and piping.
Last job for the day was to set up a 8x4 workbench in the garage, remove the wheels, and carry the fuselage into the garage and put it on the bench ready for starting covering. I haven't weighed the fuselage in its current state but carrying it was just possible with two people and I can just about rotate it on the bench by myself.

15th September 2011 - Back from sand blasting

2011-09-16T18:17:00.002+01:00

I collected the various bits of metalwork from the sandblasting today so next job is priming and painting. You can see from the photo the perfectly clean surface of the metal after cleaning. Compare this with the pictures of the flap and aileron a few days ago. Actually the cleaning is not done with sand or aluminium oxide which are both too fierce for the thin material used in building an aircraft. Instead, a fine glass bead is used which does the job without any damage. The only problem is that the metal now corrodes instantly if there is any moisture around. Just picking up a piece with bare hands will result in brown finger prints appearing within minutes. So the job over the next few days is to prime all the pieces and topcoat where necessary. The complete list to do includes both flaps and ailerons, both lift struts, the aileron pushrods, the flap and aileron horns, the strut attach brackets and the two parts of the elevator pushrod linkage. This will take me until mid next week weather permitting and then the final internal components can be installed in the fuselage (elevator and aileron pushrods) and the fuselage is ready to start covering. I've ordered and received the covering material which is Diatex 1500 - a direct replacement for Ceconite 102 but with a rather finer weave which is easier to fill with paint and can give a better finish. Also ordered from the US is the paint for the Stewart system that I will be using.

5th September 2011 - Baggage Compartment

2011-09-05T18:36:00.000+01:00

I'm using lightweight plastic sign board for the walls of the baggage compartment. To trim this I've found some self adhesive felt fabric. So this was stuck in place and the baggage compartment walls screwed into place. The seat belts have also been installed as the bolts securing the centre cable and outer lap belt halves will be difficult to get at once the fuselage is covered. Finally the rear window frames were installed as the fabric covering will go over these. I'm waiting for the last components (struts, flaps, ailerons) to be returned from sandblasting then I will do one last trial fit of the wings and all control serfaces and if all is well the covering of the fuselage can then start. In the mean time I need to order the covering fabric so it will probably a week or so before I can get going.

2nd September 2011 - Plumbing the vacuum system and installing the coaming

2011-09-02T19:41:00.002+01:00

The last system to be installed on the panel was the vacuum system for the Attitude indicator (AI) and direction indicator (DI). The system is completely conventional. The vacuum pump on the engine pulls air through the regulator mounted on the firewall which maintains a 5PSI pressure differential. The regulator has two inlets, one is connected to the VAC terminal on the AI and one to the VAC terminal on the DI (blue pipes). The AIR terminal on the DI is then connected directly to one of the outlets on the air filter. The other outlet on the air filter is connected both to the AIR terminal on the AI and also via a "T" connector to the AIR terminal on the vacuum gauge. The VAC terminal on the gauge is connected to the GAUGE terminal on the AI. The GAUGE terminal on the DI is blocked off. In this way the gauge measures precisely the pressure drop across the AI. So in summary the vacuum pump sucks air from the air filter via the AI and DI.

Up until today I've had a catch 22 which needed solving. The tank had to be installed before the coaming in order to complete the routing of all the cables, pipes, and tubes from the panel. However, the coaming had to be installed before the tank in order to get the tank neck through the hole in the coaming. The solution was to cut out a small section of the coaming around the fuel tank. The sides of this piece were then riveted to three strips of aluminium to act as support for the rest of the coaming. These were match drilled to the coaming and nutplates installed on the underside. This small section could then be screwed into position on the firewall together with the formed piece of aluminium which closes the gap to the lower edge of the windscreen. The remainder of the coaming was then slotted into position. The two formed strips which support the side windows were then inserted and the coaming screwed into place. Next all the screws that connect the panel to the combing and fuselage cross member were installed. Finally, a piece of glue lined edging strip was heatshrunk into place round the lip of the coaming to protect the edge and/or the pilot! So that is the panel absolutely complete and installed. Hopefully it won't need to come out again. The coaming is removable in case of future problems but in service this will also require removal of the windscreen - not difficult but a bit tedious. I'm very pleased with the way this has turned out. I wanted something in keeping with the type of aircraft but fully functional and ergonomically laid out - I think I have achieved this.

1st September 2011 - Terminating the rudder cables

2011-09-02T18:54:00.001+01:00

The rudder cables had been terminated at the front when the basic cable routing had been laid out. Now that the floor panel which they pass through was in place it was possible to terminate the rear of the cable. First the rudder was installed, centred and and clamped into position. Then the rudder pedals were clamped together in a neutral position with the rudder horns precisely vertical. The rudder cables were then terminated using nicopress fittings around AN100 thimbles and AN111 rollers. Glue lined heatshrink tubing was applied over the nicopress fitting to exclude any moisture and protect against the sharp cable ends. The cables were cut so that the holes in the rollers were 4cm from the holes in the rudder horns. Two pairs of coupling plates were then fabricated from strips of 1/2" x 0.063" 4130 steel plate to join the cable ends to the rudder horns. These just need priming and painting and then the rudder system is ready for when the aircraft is assembled ready for flight.

31st August 2011 - Fuel tank installation

2011-08-31T19:20:00.002+01:00

The fuel tank is now permanently installed in the aircraft. First job was to locate and attach neoprene rubber protection strips everywhere on the fuel tank where it could conceivably touch the fuselage structure as the aircraft vibrates in operation and also where the cables run between it and the firewall. Then the fuel tank was slotted into position and the support straps positioned and bolted to the tabs on the cross member at the top rear of the tank bay. The controls were inserted through the tunnels in the tank and through the firewall and the nuts which secure them to the panel tightened. The 1/8" tubing for the primer were also passed through the firewall. The inlet to the primer pump was terminated and attached. The outlet will wait until the engine is attached as the far end has a brazed on nipple which must be screwed into the primer lines to get the length correct. A length of 1/4" aluminium tube was connected to the tank breather inlet in the filler neck and routed behind the firewall to the breather inlet under the floor on the right hand side of the front bay. Next the fuel system was connected using 3/8" aluminium tubing from the tank to the electric boost pump and then on to the gascolator. I think all the preparation work on the aircraft wiring and plumbing has worked well - the installation looks neat and tidy - not normally my strong point! Next job is to plumb up the vacuum instruments and I think I'll also insert some plastic tubing round the control cables through the fuel tank to avoid any risk of chaffing.

30th August 2011 - Painting some of the interior

2011-08-30T19:12:00.002+01:00

I want to final install the fuel tank and run the rudder cables before covering the fuselage so I needed to get the tank painted together with one section of the floor which the rudder cables run through. Today was dull but dry so it was an opportunity to get these done together with some other bits and pieces. The paint is a catalysed polyurethane which dries to a hard finish. As usual painting outside a selection of the local flies decided to embed themselves in the wet paint but hopefully these will polish out once the paint is fully dry.

29th August 2011 - Left flap and aileron - all welding complete!

2011-08-29T14:46:00.002+01:00

I think I have just completed the last welded joint on the airframe. This was the attachment of the small plate round the aileron hinge top surface to provide a flat surface to attach the fabric. This completed the left aileron and flap assembly which was constructed in a similar fashion to the right flap and aileron. This is another of those jobs that I have been putting off. The construction is not particularly difficult but does require a lot of cutting, fitting, melting and pouring lead, brazing and welding. The trailing edge which is folded stainless steel is brazed on and brazing always needs significant clean-up to remove any residual flux - another job I dislike. Now that the metalwork is complete I can take the last few pieces to be sandblasted ready for priming.

7th June 2011 - Autopilot servo and aileron stops

2011-08-29T10:53:00.002+01:00

The Trio autopilot servo was final installed with the linkage to the control column. This will provide wing levelling, course setting and GPS following. It is critical for servos that the linkage cannot go "over-centre" and get jammed so the wings were temporarily rigged to set the aileron travel and stops set up using Delrin rod mounted on 3/8" tubing stubs and secured using cotter pins and washers. With the correct aileron travel set the servo arm moves through an angle of about 45 degrees either side of the middle which should be adequate travel to provide plenty of control whilst being absolutely within safe limits. The top picture provides a good view of the way the cable routing works and keeps the cables out of the way of the controls. The bottom picture shows the Delrin bush within which the flap torque tube rotates.

31st May 2011 - Finishing the lift struts

2011-08-29T10:41:00.003+01:00

The lift struts had been cut to length and the top tack welded when the wings were first fitted to the aircraft Fitting the lift struts
However, the top end needed to be final welded and a supporting rap of 0.071" steel sheet cut and bent to fit to provide additional strength. This was a fairly long and tricky bit of work that I had been putting off for some time. However, a satisfactory result was achieved and the struts were test fit to the wings to ensure that the shoulders of the struts fitted properly into the brackets bolted to the wingspar.
Then the hinges for the left aileron and flap were cut and welded. As with the right wing a fillet of braze metal was run into the acute angle of the hinge to ensure that the joint was robust. You can see in the hinges holes drilled in what will be the top of the hinge - these will be used for lubricating the hinge.

12th March 2011 - Installing the stringers

2011-08-29T10:29:00.001+01:00

The stringers provide support for the fabric covering of the fuselage and help create a curved shape. They are made from 1/2" aluminium tubing and are pop rivetted to the semicircular support tabs welded to the frame. This means that the outside of the tube that will support the fabric is completely smooth. There are three stringers along the top of the fuselage and two on the sides and bottom

28th August 2011 - English Summer

2011-08-29T10:03:00.007+01:00

I've had little chance to work on the Tailwind recently but hopefully will now be able to get going again. I have managed to get a bit done over the last few months so will post a few updates to catch up on progress. The weather forecast for today said sunny periods in the morning with light drizzle from 16:00 onwards. This was the scene at 11:00 in the morning! I had installed the left wing to start rigging the flap and aileron when the "light drizzle" started. With the help of my wife and next door neighbour we got the aircraft covered and 20 minutes later the rain had stopped so no damage done but having to work outside is a bit limiting

4th March 2011 - Fitting the spinner

2011-03-04T17:54:00.002Z

I'm waiting for some decent weather to do some painting so I took the opportunity to fit the spinner to the prop and prop extension. I had purchased a spun aluminium spinner "new old stock" intended for a Piper Cherokee 180. These are very expensive but I got this one at a good price. The problem was that the backplate and frontplate were cut out for a SAE #2 prop fitting and my engine is a SAE #1. I started by drilling a new set of SAE #1 spaced holes in the two plates using the CNC router. These were set 30 degrees out from the originals. Then the rivets holding the fillets underneath the propellor were drilled out and the fillets also moved 30 degrees, re-riveted and re-shaped to fit my propellor. The cut-outs in the spinner were also then shaped to fit and the spinner match drilled through the existing holes to the backplate. An additional 4 nutplates were riveted to the backplate and the spinner screwed to it. The existing holes were then used to match drill new holes in the spinner. This means there are now 8 screws holding the spinner to the backplate rather than the original four - should be stronger. Next the front plate was screwed in place in the spinner and the gap between the prop and the front plate measured. This was 8mm so a piece of 8mm aluminium plate was procured and a crush plate cut out on the router. A 1/8" aluminium spacer, the front plate, the crush plate the propellor and the backplate were then bolted to the prop extension and the spinner screwed into place. New holes were then drilled in the edge of the front plate through the existing holes in the spinner - again 30 degrees round from the originals. The original nutplates in the frontplate were then removed and re-riveted into their new positions. Finally the length of bolts needed to attach the propellor to the extension was accurately measured and AN bolts with drilled heads procured. These need to be exactly the correct length to ensure that the threads don't bottom but do show through the propellor lugs in the extension. The final job looks pretty good - a spun aluminium spinner for less than half the cost of the cheapest fibre-glass alternative. The only slight compromise is that the original cut-outs in the spinner were for the metal prop on the Cherokee and are about 1/4" too high leaving a slight gap above the front of the propellor. The sides and bottom are a perfect fit. I'll have a think about whether and how I could close these gaps for cosmetic purposes but they won't effect the performance in the air

20th February 2011 - Wiring Complete

2011-02-20T17:37:00.000Z

All the wires are in and everything is tied up, tested and working. The panel was deliberately designed to be sympathetic to the generation of the Tailwind but provide good useful information to the pilot. The full specification is from top to bottom and left to right:
Starter engaged warning light
magneto switches
master switch
starter push button
digital compass
vacuum gauge
mode S transponder
tachometer
pilot headset
Airspeed indicator
Trio Easypilot autopilot head (away for service)
Location for Attitude indicator (vacuum plumbing still to be done)
Location for Directional Indicator
Primer
Altimeter
Vertical Speed indicator
Carb Heat control
Carb Temp, Oil Pressure, Voltage and Autopilot engaged warning lights
Multi-function display as described previously
Garmin SL30 Nav/Comm
King KMD150 GPS
Throttle and Mixture controls
Intercom
Oil Pressure and Temperature
Switched breakers for Nav lights, strobes, Fuel Pump and Autopilot
Cabin Heat control
Fuel Gauge
EGT and CHT gauge
Breakers for the Alternator field and Starter solenoid
Loudspeaker switch
Emergency power switch
2 spare 2-1/4" instrument cut-outs
Power outlet
passenger headsets
As can be seen in the pictures, the throttle, mixture and carb heat controls pass directly from the panel through the firewall. They will be final installed through the tubes installed in the fuel tank. In addition the primer lines will also go through the fuel tank. All cables pass over the fuel tank and then route under the floor to the rear of the aircraft or through the firewall as applicable. The routes through the firewall are protected with large grommets which themselves will eventually be protected with stainless steel shields and high temperature sealant in the engine bay.
looking at the firewall from inside the cabin, the main cable bundles are from left to right.
Magneto cables (kept clear of everything else to reduce possible interference), Comm and transponder antenna, instrumentation cables, GPS and Nav antenna cables, Main power lines, switched power lines (e.g. lights, strobes etc.)

14th February 2011 - One more wire and the panel is complete

2011-02-14T18:28:00.001Z

The panel wiring is now complete with the exception of the wire for the "push-to-talk" for the radio where I'm waiting on more wire to arrive from Steinair. At the bottom left of the panel is the display for the remote digital compass. The aircraft wiring is complete except for cables for the right nav light, the strobe power, the push-to-talk and the remote compass sender.

13th February 2011 - Wiring

2011-02-12T18:32:00.001Z

Work is progressing on wiring the aircraft. Most of the major cabling is now in and all of the cables through the firewall are in place and the engine and gear mount final installed - no pictures until I've cable-tied it all in!

One bit that is fully cabled in is the information panel I have built for the aircraft. This shows from top left to bottom right:
Switchable time of day or flight elapsed time derived from the GPS
Outside air temperature
System Voltage
Track over ground in degrees true (compare the magnetic track in the GPS display
Ground speed in knots
Carburettor temperature
Alternator charge current

In addition the unit flashes the voltage annunciator slowly for one minute and then illuminates it permanently if the system voltage drops below 12V. If the voltage rises above 15V the annunciator flashes fast warning that the voltage regulation may have failed and the alternator should be turned off.

The unit also controls the carb temperature annunciator which illuminates to show a warning between -5 degree C and +10 degrees when there is possible carb icing conditions. The other annunciators which are not controlled by the system monitor show low oil pressure and when the autopilot is engaged.

8th January 2011 - Firewall and wiring

2011-01-08T17:48:00.002Z

Having spent ages working out the order to install things in the fuselage I've made a start. I have decided to cover the fuselage on its wheels which means I can do most of the interior fit out and wiring before covering. The biggest puzzle has been the order in which to install the panel, fuel tank and combing in order to make both the install and future maintenance easy and minimise the amount of repeatedly installing and de-installing things during the build. So I'm now committed. The first job was to cover the interior of the firewall with some self adhesive felt material I found. This makes a nice finish and should damp vibration a bit. I tested the material for the impact of both heat and flame and it passed with flying colours - refusing to burn at all and just shrivelling a bit when a 400 degree C heat gun was played on it. The firewall was first screwed to the tabs on the frame and then the major firewall mounted components added. Then the panel with the power distribution unit was temporarily installed. The major power cables were then cut to length and terminated: switched power, unswitched power, earth, starter energise, main contractor energise, alternator field, starter warning, ammeter sense. The last picture shows the power distribution unit. This implements the Z11 schema for a generic light aircraft electrical system as documented in the Aeroelectric connection manual by Bob Nuckolls. The small fuseblock provides unswitched power for the power socket, clock and via a switch emergency power for the endurance bus. The large fuse block is the endurance bus and is powered either by the starter contactor via a diode or the emergency power switch. All essential services will be wired to this (radio, transponder, intercom, etc.) The bus bar connecting the fuses and switches is the main power bus. The two pullable fuses on this are for the alternator field and starter. The four switches are for the fuel pump, the nav lights, the strobes, and the autopilot (a separate switch for this is a mandatory requirement in the UK). The terminal strip along the bottom provides a ready supply of earth connections.

2nd January 2011 - High/Low Voltage warning system

2011-01-02T18:47:00.021Z

A voltage low warning light is mandatory for all aircraft in the UK. Commercial versions are available but quite expensive so I constructed one. This flashes a warning light slowly when the system voltage drops below 12V and then after a period leaves the light on to avoid being too much of a distraction. It also flashes the light fast if the voltage rises above 15V. In addition the unit outputs the voltage on a opto isolated serial output so it can be read into the system monitor I've also built. The circuit and program is very simple and uses a Picaxe 08M microprocessor to do all the hard work. If you want to copy it and don't need the serial output just omit the optocoupler.

2nd January 2011 - Preparing the fuselage for covering

2011-01-02T17:03:00.011Z

New years resolutions -
1: Keep the blog up-to-date
2: Do more on the build this year than last.

I haven't done much over the last few months but there is a little to report. I'm getting the fuselage ready for covering which means I want to make sure any internal structures that are going to be difficult to install post-covering are in place (e.g. the static system shown in the first picture) . I also want to avoid a mistake I made on my RV9A build when I painted the interior late in the build which made it tricky to get a reasonable result.

So I have final painted (in white polyurethane ) all tubing which will be exposed in the finished aircraft - door frames, front spar carry through, etc. I've also painted many of the aluminium pieces that will be installed. I'm now waiting on some decent weather to finish spray the fuel tank and to prime the control push rods. These all need installing before covering the fuselage.

I've also trial fit the panel and this has resulted in some mods. First, although I had put the radio at the top of the stack to clear the top of the tank I hadn't left enough clearance for the cross member that runs above the tank. Solving this meant moving the radio and GPS up 1/2" and fabricating a filler panel at the bottom of the stack.

I also realised that the way I had built the power distribution on a tray but with the switches and fuses screwed through the panel would make it very difficult to wire and maintain. So I cut out the panel round the holes for the switches with the router and made a front panel for the power distribution tray with holes cut in this for the fuses and switches. To keep it neat I then also cut out an insert for the hole in the panel so that everything is flush. I programmed the router to cut the insert with a clearance of 0.1mm all round to allow for painting (still to be done). As always I'm amazed at how accurate a MDF homebuilt system can work. The result of this work is that it will now be possible to remove five screws on the front of the panel and then drop the power distribution tray down to replace fuses and make any changes to the wiring.

Third, I had installed a 3-digit seven segment display at the bottom right of the panel. This will be connected to the digital compass I have built for the aircraft. The hole was cut on the CNC router and a red lens cut out to fit inside it. This looks very neat and tidy but unfortunately I had located it 3/16" too low and the display was fouling on the panel support cross member. I solved this by slicing the cross member in half horizontally where the display fits, removing about 2" of the top above the slice and then welding a flat plate cap over the missing section. Once filed and painted this looks fine but it all takes time. The other thing I've been building over the last months is various electronic bits and pieces for the aircraft - more of these in later blogs.

19th September 2010 - Wing Struts

2010-09-19T20:02:00.002+01:00

As per advice a small amount of dihedral (0.2 degrees) was introduced to both wings. This is to allow some shrinkage in the struts when the top is welded. Then the wing struts were attached to the fuselage and marked to length with the top level with the centres of the bolt holes in the strut attach brackets. The wing struts were then cut to length and the front and rear edges notched to fit between the brackets. Next sections of douglas fir were cut and planed to fit into the struts. These protect against any possibility of compression failure under negative G loads. Two sections of 1/2" x 0.065" tubing were cut to length the fit between the strut attach brackets and reamed out to take a 3/8" bolt to act as bushings at the top of the strut and then bolted into place. The end of the strut was then flattened to fit neatly against the tubing and the dihedral rechecked. With everything set up as required the struts were then tack welded to the bushing. The temporary wing supports were removed leaving the wings mounted via the three bolts which will hold them in flight. Finally it was all dismantled again. Next job is to final weld the top of the struts.

19th September 2010 - Setting the wing incidence

2010-09-19T19:06:00.004+01:00

First today, the fuselage was levelled fore and aft and left to right and chocked in position. Then the wings were bolted into place and the dihedral set to zero as per the plans. All the measuring I'd done http://tailwindbuild.blogspot.com/2009/09/15th-september-2009-rib-rework.html paid off as the front and rear spar spacings exactly matched the fuselage brackets on both sides and the spar attach bolts slid comfortably into place in both the wings. A block was cut to create an exact level between the front and rear spars of the right wing . This wing had both the front and rear spar attach brackets bolted into position so provided the reference for setting the incidence of the left wing. On the left wing the rear spar attach bracket had not been drilled to the spar so the incidence of the left wing could be set precisely the same as the right. This was done and the bracket clamped into position and then drilled through the bushes in the spar and bolted into its final location.

18th September 2010 - Fuselage back from storage

2010-09-19T18:44:00.002+01:00

Last week I set to and got the workshop clean and tidy so today I went and collected the fuselage from storage ready to mate the wings. I had intended to do this with the fuselage directly sitting on the drive and chocked up to get it exactly level so that it would be very solid to work on. However, I realised I was going to have to work underneath and that getting it in and out of the workshop was going to need two people so it seemed sensible to get it back on its wheels ready for starting work tomorrow. It hasn't been on wheels since it was primed and it looks much better than before in its smart white coat of paint.

17th August 2010 - The propeller arrives

2010-08-17T12:40:00.002+01:00

A propeller! I managed to find a perfect second hand 69" x 63" Sensenich wooden propeller off a Diamond DA20-C1. This has the correct SAE #1 mounting and 3/8" holes to fit my engine and propeller spacer. The pitch should give my target 150mph cruise at about 2450 rpm. This will be very much a cruise prop so I will have to see how take off distances work out. Worst case it should be possible to rework the prop to reduce the pitch by a couple of inches to improve static rpm.

12th August 2010 - Wing structure complete

2010-08-12T19:02:00.002+01:00

The workshop has disappeared under a layer of sawdust and wood shavings again but the wing structures for both wings are now complete and sanded ready for covering. The wingtips have come together well, carrying the profile of the main rib accurately as the wing tapers to the tip. You can just about see in the picture the way in which the top of the main spar stays flat throughout the wingtip but the lower edge tapers up. Next job is a major clean and tidy to create some room as I need to get the fuselage back from storage. I'm going to test mount the wings, finish the struts, and set the wing incidence before covering the wings. This will allow me to make any adjustments necessary as easily as possible. At the moment the rear spar attach bracket is not yet drilled to the spar on the right wing. This will give me a small amount of flexibility to set exactly the incidence of the two wings to be the same. Hopefully, all the measuring I did to make sure the spar spacings exactly match the fuselage will prove to be successful - we will see! It will probably be just into September before the next entry in the blog once I have retrieved the fuselage.

8th August 2010 - Wingtip spar caps and gussets

2010-08-08T17:09:00.001+01:00

The construction of the structure of the wings is nearly complete. The wingtip spar caps have been glued in place and the gussets completed for the left wingtip - just the right wingtip gussets to go. Then comes the sanding of the wingtips. The challenge will be to blend the curves together to get smooth surfaces for the wingskins to adhere to.

6th August 2010 - Wingtip frames complete

2010-08-06T19:34:00.000+01:00

Today I pinned, screwed, and glued the second wingtip frame together. Next job is to fit gussets to strengthen all the joints in the two wingtips and fit spar caps to the main spars and stub rear spars. Then it's back to sanding!

25th July 2010 - Tip ribs cut out

2010-07-25T12:37:00.001+01:00

I finished cutting two complete sets of wing tip ribs out of 12mm birch ply today. The picture shows one complete set plus the tip and tail ribs from the second wing. All the cutting was done with the CNC router using a 6.35 (1/4") cutter. The router was programmed for a 8m cut width so the machine does two passes at each height this ensures that the cut to final size is small and means that the finish and accuracy is superb. The program is set to leave 2.5mm thick holding tabs to hold the parts in place as the cut completes. It looks just like a model aeroplane kit (only bigger!) and removing the pieces is easy using a miniature saw blade in the Dremel. I've uploaded the coordinates of the ribs to the Yahoo Tailwind Group site if they are of use to anyone.

18th July 2010 - Wingtip test fit

2010-07-18T19:19:00.002+01:00

First job today was to calculate the dimensions for a stub rib rear section which forms the rear inside edge of the wingtip (top right of the picture). This is positioned 1" outboard from the last main rib to allow the aileron mass balance to fit between it and the wingtip to streamline it in normal flight. As before the dimensions for the stub rib were fed in the the CAD/CAM package and a test piece cut out on the router. Then it and the three tip ribs were located on the spars in their correct positions. A blank for the trailing edge was made by sawing along the diagonal of a 2" x 1" section of spruce to make two triangular sections. When angled at 45 degrees along the line of the wingtip trailing edge this section matches the wing section nicely and will need relatively little finish sanding. The ends of the trailing edge were cut to 45 degrees and the outer end pinned to the tip rib. Then the trailing edges of the two intermediate ribs and the stub rib were carefully marked and cut at the required angle. A piece of 3/8" spruce was cut to form the leading edge and the front of the ribs bevelled to match. The picture shows the wing tip assembled on the spars with just one panel pin in the tip rib the only thing holding it together.

Next job is to procure some 15mm birch ply, cut the final ribs for both wings, buy some Aerodux glue and then assemble and glue the two wingtips.

16th July 2010 - Wing tip ribs

2010-07-18T19:04:00.001+01:00

I've decided to make the wingtips from wood and have discussed and agreed this with my inspector. The plans do not give any information about the wing section as it tapers from the standard rib to the tip so I started by measuring the distance between the chord line of the main rib and the top and bottom at 10mm stations all along the profile. This was then input to a spreadsheet on the computer. Then I decided on the depth of the tip rib (determined by the height of the strobe/navigation light unit I've got to fit). The length of of the tip rib is given on the plans, together with the spar position in the rib. This allowed me to calculate length and depth of the two intermediate ribs. The profile of the main rib was then scaled for each of them to be the correct length and depth and the position and size of the cutouts for the main spar calculated. The profiles for the three tip ribs were then input into the CAD/CAM program and test ribs were cut out on some scrap 15mm ply (the same width as a main rib including the gusset) using the CNC router. The final ribs will be cut from 15mm birch ply but will have lightening holes cut out to significantly reduce weight.

11th July 2010 - Left wing structure finished

2010-07-18T18:49:00.001+01:00

Work is proceeding slowly and I'm also behind on blogging. The main structure of the left wing is now complete and glued up. However, this will be the last construction I can do with epoxy. I developed an allergy to epoxy when building the Vans resulting in contact dermatitis which became infected - nasty. This time I've been very careful to make sure my skin is covered and to wear gloves but I've still developed another bad reaction. Reading into the literature, it seems for anyone using epoxy the question is not if they will become allergic but when. Forced air breathing and full body suits seem to be the order of the day for professionals - hardly practical at home. So the rest of the construction will use a resorcinol based glue (Aerodux 500).

6th June 2010 - Propeller crush plate

2010-06-06T14:35:00.002+01:00

Over the last few days I have been slowly gluing up the left wing. So far the inner leading edge and the strengthening gussets, the aileron spar and gussets, and the main and rear upper spar caps have all been glued into place. In addition the bushings for the strut attach bracket bbolts have been glued into place and drilled and one of the 1/4" 12-ply plates glued and drilled. Remaining to do are the lower spar caps, the leading edge to the root rib, and the strut attach ply plate. Then it's time to sand......

While waiting for the glue to dry, I've used the CNC router with a special purpose aluminium cutting endmill to cut out a 1/2" thick propellor crush plate to match the SAE#1 propellor drive on the engine . In the bottom picture you can just see the holding tabs that keep the piece together as the mill cuts. The bolt holes are 3/8" diameter and are cut using the 1/4" mill bit using a special spiral descending cutting action. It still seems remarkable that a home made CNC router made out of MDF can cut to this accuracy. Total cost £7.00 for the piece of aluminium stock.

29th May 2010 - Left strut attach

2010-05-29T19:08:00.001+01:00

Work is getting in the way of building at the moment but I suppose it does pay for it. However, I did get a chance to make a bit of progress today. First job was to make the strut attach brackets for the left wing. For some reason I only made one pair originally (back in March 2008). The process for making one of these was first to bend a 9" length of 0.071" 4130 sheet into a U section using the bending brake - this takes considerable force! The legs of the U were originally about 1" long to give the brake a reasonable area to work on. Then the legs of the "U" were shortened to final size using the bandsaw. A smaller section of sheet material was then bent to fit snugly inside the end of the length and welded into place. This was repeated for the second bracket. Then a 3/8" hole was drilled in the end of each bracket. They were then bolted together and the second two holes match drilled through both brackets to ensure that the hole spacing was identical in each. Finally, the top of each bracket was curved where it fits against the outer wing rib.
Next job was to laminate 4 pieces of 1/16" birch 3-ply into the first of the 1/4" 12-ply plates which provide additional strengthening where the brackets bolt to the spar. This is done with epoxy without any filler and clamped tightly whilst the glue sets. The result is a plate considerably stronger than a commercial 1/4" material which would usually be 5-ply.

26th April 2010 - Basic assembly of the left wing

2010-04-26T14:28:00.001+01:00

Yesterday I positioned the left wing ribs onto the main and rear spars, drilled and screwed the inner leading edge and aileron spar into position and glued the spar root doublers and bushings into place. Today I drilled the main spar attach bracket to the spar. You can see the yellow swarf in the foreground that comes from drilling through the phenolic linen bushes - strange stuff!
I'm going to be busy over the next two to three weeks so not likely to make much progress but this will give me a chance to do some planning of the next steps as I want to make sure the wings align correctly to the fuselage before closing them up.

24th April 2010 - Left wing spars

2010-04-24T19:39:00.003+01:00

A couple of days ago I laminated the two sections of Douglas fir to make the main spar for the left wing. Today, now the glue is thoroughly set I cut the spar ends on both the main and rear spars using the CNC router. As before, holes were drilled with the router for bushing to take the mounting bolts. The lower picture shows the spars marked out for the rib positions. I've included a couple of videos of the CNC router in action for those of you who are interested.

19th April 2010 - Locating the ailerons and flaps

2010-04-19T19:38:00.000+01:00

I finished the sanding of the wing ready for covering today and then decided to match drill the ailerons and flaps to the wing structure before covering so that it would be easy to get the holes correctly aligned. I used two small pieces of 1/8" thick fibreglass top and bottom to represent the thickness of the wing skins (3/32") and the fabric covering and paint and two more pieces either side of the hinge to space the torque rod off the aileron spar. This 1/8" gap will allow room for the fabric covering of the control surfaces to wrap round their leading edges as well as provide clearance for the fabric covering the wing. The torque tube was clamped into position against the aileron spar and the hinges match drilled through the support blocks in the wing structure. The lower picture shows the aileron mass balance which in normal flght is in a slot flush between the wing and wing tip.

18th April 2010 - Sanding and more sanding

2010-04-18T17:28:00.000+01:00

This week time in the workshop has been spent sanding. The main spar caps, rear spar caps, inner leading edge, and aileron spar all needed sanding to final size to blend in with the ribs top and bottom. I made up a sanding block long enough to sand across four ribs at a time by cutting open a sanding belt and gluing it to a length of flat timber. Using this it was possible to blend in the joints without risking sanding dips into the timber between the ribs but it is slow progress and hard work. As at today the wing is complete except for the upper rear spar capsticks and upper aileron spar so I'm about 80% complete. The bottom picture shows the way the upper surface of the root rib and inner leading edge have been tapered to allow the skin to glue in place.

13th April 2010 - Root rib inner leading edge, aileron and flap mount blocks

2010-04-13T19:58:00.001+01:00

First job today was to pin and glue a section of timber between the leading edge of the root rib and the first main rib. This will act as the inner section of the leading edge for the first bay of the wing. Once shaped, it will be covered in the ply skin and then the outer section of the leading edge will butt join to it and overlap the skins. Next blocks of timber were cut to fit between ribs 1&2, 5&6, 9&10 and 12&13. These were glued into place and will be drilled through the wing skin to take the bolts that secure the flap and aileron hinges to the wing.

12th April 2010 - Strut attach bracket

2010-04-12T19:26:00.000+01:00

The outer bush for the strut attach bracket was first drilled through using a 3/8" hole in my jig block as a guide to make sure the hole was perpendicular. Then the other bush was match drilled about 1/4" deep to establish the hole location. The bracket was removed and this was then also drilled through using the jig block. This worked well to keep the spacing and alignment of the holes accurate and the bottom bracket fitted nicely over the bolts. Then the upper 1/4" thick 12-ply plate was glued to the spar. Once the glue was set the brackets could be bolted into position. The bushing material is very solid and it was possible to torque the bolts to the specified torque for a 3/8" bolt of 160 in/lb without compressing the wood of the spar.

11th April 2010 - Strut attach bolt bushes and corner blocks

2010-04-11T18:47:00.001+01:00

First job today was to mark the locations of the two strut attach bolts between ribs 7 and 8. Two 3/4" holes were then drilled to take the bushing material which itself will be drilled for the 3/8" bolts that fasten the strut attach brackets to the main spar. The bushing was then glued into place together with the rear 1/4" thick 12 ply plate. The 3/8" holes will then be drilled through the centre of the bushes and the rear ply plate. Then the front ply plate can be installed and finally the bolt holes drilled through it as well.
Then it was a case of gluing and pinning the corner blocks that strengthen the joints between the spars and the ribs, easy enough but took most of a day to complete - this must be the equivalent of dimpling when building in aluminium. This completes most of the wing structure, remaining jobs are to install the leading edge between the root rib and rib #2 and four blocks along the aileron spar to take the aileron and flap attach bolts. Then it's time to sand everything ready for the lower wing skin. The wing tip will not be constructed until after the lower skin is glued into place. I still haven't decided whether to do an all wooden wingtip or the original Wittman design which uses metal tubing to create the aerofoil shape.

10th April 2010 - Inner leading edge and aileron spar

2010-04-10T18:49:00.000+01:00

Two of the wood strips that I cut last week were marked up, drilled, and countersunk to attach them to the front and rear of the ribs. Then each rib was match drilled front and back with a guide hole to take #6 wood screws. The inner leading edge strip was then screwed and glued to the front of the ribs, then the aileron spar was screwed and glued to the rear of the ribs. Next triangular sections of wood with one right angle were cut to length to make corner blocks which will secure the ribs to the main spars and to the leading edge and aileron spars. Using a jig in the drill press to locate the triangular sections nose down, the blocks were then each drilled in two places to take panel pins which will secure them to the spars while the glue dries. I made enough blocks for both wings, the ones for the left wing are in the plastic bag in the foreground of the picture - lots of cutting and drilling.

9th April 2009 - The right wing root rib

2010-04-09T19:49:00.001+01:00

Just 30 minutes to give to the project today so I finished preparing the spar roots for the root rib and glued in place the rib and the upper spar caps between it and the first main rib. Now this is in place I can install the aileron spar and inner leading edge.

4th April 2010 - Right wing lower spar caps and spar attach brackets

2010-04-04T19:04:00.000+01:00

Today I drilled the spar roots for the spar attach brackets. First I drilled a piece of 3/4" thick aluminium with 3/16" and 1/4" holes using the drill press. This would then act as a guide to ensure the holes were drilled accurately through the spars. The the attach brackets were positioned over the line of the bushes glued into the spar and the holes drilled one at a time with a bolt inserted in each hole before drilling the next. The drill guide worked well and all of the holes came out accurately in line with the holes in the far side of the attach brackets.
Then the spar roots were notched to fit snugly into the root rib with the rear top section of the root rib aligned with the tops of the main ribs as per the plans.
The lower main and rear spar caps were glued into place between the ribs.
The strut attach is into the main spar between ribs 7 and 8. The LAA require that the holes for this are also bushed and that the spar is reinforced with 1/4" ply either side. Their specification for 12-ply material. As this doesn't seem to exist I cut 4 pieces of 1/16" birch three ply and epoxied these together alternating the grain direction, clamping them between layers of plastic to wait for the epoxy to set.

3rd March 2010 - Preparing the wing leading and trailing edges

2010-04-04T10:36:00.001+01:00

The first job today was to shape the sections of wood that will form the leading and trailing edges of the wing. The 3/8" thick stock material for the aileron spar and the inner section of the leading edge nose block had been supplied as 6" wide sheets so a combination of the bandsaw and the table saw were used to convert this to the sections needed. The aileron spar has an angle of 87 degrees on the lower edge and 80 degrees on the top edge. The inner nose block has an angle of 60 degrees on top and 79 degrees on the bottom. Angles up to 20 degrees can be cut on the bandsaw but above that the table saw is needed. After setting up the saw tables with fences and feather boards to hold the material test cuts were made on scrap material to adjust the sizes precisely. The final cuts were then made to exact size to butt precisely against the ribs and to require no further adjustment before gluing the skins in place. The aileron spar and inner nose block fit inside the wing skin. The outer nose blocks butt onto the front of the inner blocks and the edges of the skins. These were cut slightly over size and will be shaped by hand to form the leading edge shape. These were cut using the table saw from 1" x 2" stock. First this was resawn into two 7/16" x 2" sections and then the angles cut into the edges.
Then the 1/16" ply reinforcing plates were glued to the sides of the spar roots. The second and third pictures shos the wing mounts in place. The ply and spar bushes will be drilled to secure these in place. It is important that the mounts butt tightly against the ends of the spars as many flight loads are compressive and this tight fit provides additional strength to the joints.

2nd April 2010 - Right wing upper spar caps

2010-04-03T08:50:00.000+01:00

Now that I had a completed set of spars for the right wing I could start the main construction effort. First job was to thread the ribs onto the spars - easier said than done! The plans say to make the ribs a snug fit and they are. The only way I found to get them onto the spars was to tap the ribs an inch at a time, first along the main spar, and then along the rear spar. As the centre rib is 5ft from either end this took some time. However, after a couple of hours of gentle persuasion the ribs were in place and miraculously a wing appeared. Next lengths of 1/4" thick 1-1/4" and 1" wide spruce were cut to fit along the tops of the spars between the ribs. These were then epoxied into place to form the upper spar caps.
Finally today lengths of 3/4" linen phenolic rod were cut to fit in the holes in the spar roots and epoxied into place. This material is specifically designed to provide high-strength close-tolerance bolt holes in wooden spars and is available from ACS.

1st April 2010 - Right wing spars

2010-04-02T10:52:00.003+01:00

As the glue laminating the front spar was now properly set, I could create the root shapes for the spars and the tapers at the wingtips. Having built a computer controlled router I decided to use this to do the work. So I programmed the outlines of the four ends into Cambam which is CAM software with some limited 2.5D CAD capability. Then I positioned the first spar ready for the cut. Mach 3 software is used to control the machine. Good practice is to try the machine program with the cutter set above the workpiece so that you can observe the pattern without cutting the wood. Once I was satisfied with the program, the cutter height was set down and the program started for real. In fact on the first end of each spar there would be an opportunity to redo the cut in the event of problems as the stock material was long enough but this wouldn't be the case on the second end. In fact, the cuts all went well and the programs can be re-used for the second wing.
At the root ends I used the program to cut 3/4" holes where the bolts will go. These will be filled with some special bushing material epoxied in which will be final drilled to the finished size. This ensures that the bolts will not move in the wood and increases the strength of the joint by increasing the diameter of the hole in the wood.
I was particularly pleased with the wing tip taper cut on the main spar shown in the second picture. Trying to do this by hand would have been difficult and the router did a perfect job (last picture).
The cutter used is a 1/4" carbide cutter specifically designed for wood. I set the program to cut 1/8" deep at each pass, first cutting 1/16" outside the cut line and then at each depth cutting exactly up to the line. The linear rate of cut was set to 16" per minute. So to cut the full 1-1/4" depth of the main spar takes 20 passes - quite slow but a perfect result.
The holes were drilled with the same 1/4" cutter. The computer control moves the router bit in precise circles and the result is far better than could be achieved with any sort of wood drill and is of course perfectly vertical. Also the size can be adjusted to get just the right sort of fit to allow the bushing to be inserted and leave enough room for the glue layer.

30th March 2010 - Bevelling the rear spar

2010-03-30T19:29:00.007+01:00

This was a job I was worried about: two 11ft lengths of expensive hard-to-get wood that needed a 9.5 degree bevel along one edge. The options were to plane it, to cut it on the table saw, or to cut it on the bandsaw. I decided to use the bandsaw with a new 4TPI blade. The bandsaw was screwed to the workbench and the bandsaw table was set at the required angle. A jig was constructed to keep the stock in position as it passed the blade. A few test cuts were done on some scrap timber and then it was time to do it for real. Supports were set up for the timber both before and after the bandsaw so there would be no moment trying to lift one end away from the table then the timber positioned and the cut started. The timber was slowly fed through and a perfect cut resulted with the offcut maintaining exactly the same wedge shape and dimensions throughout. The second spar was then bevelled in the same way and I could breathe again! Now I can really make a start on the wing construction.

30th March 2010 - Laminating the Spar

2010-03-30T15:30:00.000+01:00

Finally progress!!!

I've been stalled since last year basically waiting for wood for the wing spars. It proved impossible in the UK to get the main spars in single pieces to a suitable quality so the LAA have authorised laminating two sections of Douglas Fir 2.5" * 1.25" to make the 5" * 1.25" main spar. The wood arrived last week and today was the first opportunity to get going. Douglas fir is a bit difficult to glue as it is resinous but I've used the West System epoxy with the slower 206 hardener according to their recommendations, First the surfaces to be glued were sanded with #80 sandpaper to create a key for the glue. The surfaces were then cleaned with acetone to remove grease and resin. Next the epoxy mix was brushed onto both surfaces. Finally, filler was added to more of the epoxy mix (6% by weight of 403 micro-fibres) and this was spread onto one of the surfaces. The two pieces were the aligned and clamped together gently to avoid squeezing out all the glue. 24 hours from now the bond should be cured but will continue to strengthen for the next week.

It has been difficult to get into the workshop over the last few months due to a combination of cold weather and work, but I have spent some time building a CNC router as shown in the second picture. This is based on the design shown on http://www.buildyourcnc.com/ and is amazingly accurate. The spindle is a conventional 1/2" router and you may be able to see the outline of my first test project ( a bird box) in the sacrificial top board. Lots of new things to learn with CNC, CAD and CAM software all required to produce a finished article. The router will cut aluminium and one of the designs done so far but only cut in MDF is a propellor crush plate.

17th November 2009 - Covering the rudder

2009-11-19T18:51:00.001Z

Since I'm now "fully" trained I though I'd better make a start on covering before I forget everything. The smallest piece to be covered is the rudder so that seemed like the place to start. I'm using the Stewart Systems covering process (http://www.stewartsystems.aero/) which has the advantage that the glue and all of the paints are water bourne which results in much reduced smell and hazard. The process is STC'd for use on most if not all certified fabric covered aircraft. Full details of the covering process including the manual are on the web site and there are also links to very helpful videos showing each stage. So it was a case of following through the steps I'd learned but using the Stewart glue. With such a small piece the result seems to be all rib covering tapes and finishing tapes but I'm reasonably pleased with the result and hopefully my inspector will be happy with the standard.

15th November 2009 - Overvoltage crowbar

2009-11-19T18:18:00.002Z

The alternator I'm using on the Tailwind is internally regulated and provides no protection to the aircraft circuits if it fails. The risk is that the alternator output voltage increases and damages the avionics and even the battery. The way round this is a crowbar overvoltage protection circuit - sounds crude and it is. Basically the circuit monitors the voltage on the supply wires and if it exceeds 16.2V shorts them out through the onboard thyristor. This trips the alternator field/alternator relay circuit breaker which disconnects the alternator from the battery and shuts off power to the alternator field. Many automotive style alternators will continue to generate even after the field supply is removed hence the need for a relay on the output. This is an emergency device which hopefully will not be needed as disconnecting an alternator when it is generating can result in further damage to it. A high power transient voltage suppressor will be wired across the alternator output to protect it if the crowbar operates.

12th November 2009 - Fabric Covering Course

2009-11-19T18:00:00.002Z

I'm still waiting for the Douglas Fir needed for the wing spars so no progress on the wings but today I participated in a LAA course on fabric covering taught by Dave Almey at Skycraft. There were six of us on the course and each had a PA-25 pawnee horizontal stabiliser to cover. Dave showed us how to do each stage and then we tried it ourselves.
First the frame was glued and the fabric fixed to the first side. Rather than wait for this to set Dave produced another 6 stabilisers that had been glued by a previous course. These were then ironed to tension the fabric and the second side glued into place. This time the glue set during a short lunch break. Next a coat of dope was brushed on and then it was time to learn how to rib stitch. Dave said we had to do both ribs as the second one would be better - it was! Final job was to of glue in place tapes to cover the stitches and to protect the edges of the stabiliser. It was a very good course and having hands on experience under the supervision of someone who really knows how to do it provided the confidence to do it for real on the Tailwind - thanks Dave.

18th October 2009 - Ribs Completed

2009-10-20T12:03:00.000+01:00

Finally the last rib is glued, cleaned up, and final sized. Next job is to clean up the workshop which seems to have largely disappeared under a mountain of sawdust. The sacrificial board on the worktable will then be replaced with a new sheet of 9mm MDF and then the actual wing construction can start - BUT I'm still waiting on some Douglas Fir for the spars. The company cutting it for me had prettty much completed the job when a resin pocket appeared at the end of the cut length so it is back to waiting for some more lumber.

12th October 2009 - More Rib Progress

2009-10-12T10:32:00.001+01:00

It's difficult to say much interesting about building ribs or to take interesting pictures. However, the ribs for the right wing are now complete and there are just 6 remaining to make for the left wing - the end is getting closer.

4th October 2009 - Rib Progress

2009-10-04T19:08:00.001+01:00

Work continues making the wing ribs but the end seems in sight now. 15 ribs are now fully complete out of a total of 26. There are four variants: the root rib which is smaller and has the larger openings to allow the spar attach brackets to pass through, rib 2 which is a fully sheeted but has the same basic structure as the normal ribs, rib 13 which is also fully sheeted and also has a solid wood nose section 4" long to allow the wing tip to screw into it (if I decide to build the metal wingtip), and ribs 3 to 12 which are the standard open section ribs.

I have also now fully kitted the remaining ribs with the exception of the diagonals which are cut to fit in situ. The bottom picture shows the four sheets for the left wing ribs 2 and 13, bags containing all the rib uprights cut to length, and all the required gussets. At current rate of progress which seems to be two ribs every three days I should finally have all the ribs done in three weeks.

30th September 2009 - Identical ribs

2009-09-30T17:27:00.000+01:00

The production of ribs is underway again and I've also started the process of getting them precisely identical and perfectly matching the outline on the plan. First one of the ribs was sanded using a disc sander to final shape. This was then designated as the master. Using stub sections of front and rear spar the other ribs can then be located below the master. A trimming bit is then used in a bench mounted router to match each rib to the master. The picture shows the forward end of the lower rib being trimmed to match the master. The router cutter has a small bearing of exactly the same diameter as the cutter itself. The router is positioned to let this bearing ride on the master and the cutter then matches the profile of the new rib to the master. Using this approach the ribs can be matched perfectly ready for final installation on the spars. The use of the router table ensures that the sides of the ribs are perfectly at right angles to the faces. Moreover the process is very quick - a couple of minutes per rib yields the final result. The router is also very useful for trimming any excess gusset from round the edge of the rib. Run the bearing on the capstick and any overlap of the gusset or any glue is quickly removed.

29th September 2009 - Remote Compass

2009-09-30T17:13:00.002+01:00

Like all tubular metal aircraft, it is difficult in the Tailwind to find a site for a normal compass where it isn't influenced by the magnetic field from the airframe. This will probably be particularly the case for my build as I TIG welded the airframe and TIG is known for leaving steel magnetised. The solution is to have a remote compass situated in one of the wooden wings well away from the fuselage. Most modern electronic flight instruments (e.g. Dynon) have an option for a remote compass but they are expensive and I want to stick with the conventional panel layout. So, I decided to build my own remote compass. The picture shows the actual remote unit I've constructed; for reference the holes in the PCB are 0.1" apart so the entire unit is about 1" x 2.5" and weighs less than 1/2oz. Eventually it will be mounted in a small plastic box and screwed to one of the wing spars. The heart of the unit is an amazing chip from Honeywell - the HMC6343. This has in it 3 magnetometers to measure the earth's magnetic field and 3 accelerometers to measure gravity. These together allow the unit to not only report magnetic north irrespective of the orientation of the unit, but also to output the pitch and roll angles of the unit (and therefore the aircraft). The chip communicates using the I2C standard defined by Philips which uses a two wire serial bus. The four pin connector includes the serial bus wires together with a ground and 5V supply. It will be controlled by a microprocessor circuit installed behind the panel and the compass direction displayed on the display screen in the panel above the radios http://tailwindbuild.blogspot.com/2009/09/14th-september-2009-panel-painted-and.html and also on a separate dedicated 3 digit LED display - location to be determined. The actual orientation of the sensor is not important as calibration of the unit is extremely simple, first tell the chip whether it is on edge or flat, then point the aircraft in one known direction, compare the direction with the compass heading to calculate the deviation and program this into the chip, everything else it does itself and Honeywell guarantee less than 2 degrees of error between the compass output and the true heading with a repeatability error of less than 1/2 degree.

28th September 2009 - The Cowl arrives

2009-09-29T09:39:00.001+01:00

I've been away for a couple of weeks so no real progress on the build but today the cowling arrived from the US. I decided to go with the glass fibre cowling produced by Brian Alley at http://www.carbonfibercomposites.net/ and it's a beautiful piece of work. Very light but strong and lovely lines that blend the square front of the fuselage into the round disc behind the propeller spinner. This will now stay in it's shipping crate for a few months until I'm ready to assemble to the fuselage - hope it fits!

15th September 2009 - Rib Rework

2009-09-16T17:48:00.003+01:00

As previously recorded I'd made a decision early in the build to final weld the fuselage, including the wing mounts, before starting on the wings so would have to make sure that the wings would fit the fuselage rather than the other way round. The key issue seemed to be to ensure the wing incidence (angle to the air) would be precisely the same on both sides. The root ribs have cut outs that precisely locate vertically the spar brackets that in turn bolt to the fuselage. and therefore set this incidence
http://tailwindbuild.blogspot.com/2008/10/8th-october-2008-right-wing-attach.html
So a few days ago I took the first completed root rib to where the fuselage is stored to measure up. Unfortunately, what I hadn't really considered is that not only does the vertical location of the wings need to be correct but the horizontal spacing between the brackets that bolt to the wing spars has also to match the fuselage very very precisely. In fact this spacing was correct on the left side of the fuselage but there was a difference of about 3/32" on the left side. When I then compared the spacing on a main rib I found that it was about 1/32" longer than the root rib/left side fuselage and so about 1/16" shorter than the right side fuselage. The good news was that the wing incidence was correct on both sides to within 0.1 of a degree - the limits of measuring accuracy.
So, in summary, the spacing of the spars on the plans for the ribs were about 1/32" different between the root rib and the main ribs and I'd built to the plans. Also I'd welded the fuselage brackets about 1/32" shorter than the main rib on the left side and 1/16" longer on the right side. These are small differences in welding terms but would mean that the wings would not bolt up correctly if the wings were constructed to the original spacing.
The solution was as follows:
The first root rib is correct on the left side of the aircraft so leave as is.
Modify the nine finished main ribs by removing 1/32" from the front of the rear spar slot and gluing a section of 1/32" ply to the rear of the slot (4 completed so far). Modify the main rib jig to match and then construct 3 additional ribs which will complete the requirement for the left wing.
Modify the root rib jig to construct the right wing root rib with an inter-spar spacing 3/32" longer than the left and build the right root rib (completed).
Then re-modify the main rib jig to match the right root rib and construct 12 right wing ribs.
Of course the external outline of all the ribs and therefore the wings will be precisely the same only the spacing of the spars internally will vary very slightly.
Perhaps I should after all have built the wings first, but logistically this would have been very difficult.

14th September 2009 - Panel Painted and Layout finalised

2009-09-16T16:59:00.005+01:00

I have to confess that I'm finding making ribs pretty boring, so a couple of days ago I painted the panel in it's final matt black and today installed the various instruments in it. Assuming my build sequence for the completed aircraft is correct, I should be able to install the panel complete with instruments and wiring without them having to be removed again so the photo gives a good impression of how the completed panel will look. From top to bottom, left to right the layout is as follows:
Starter engaged warning light
Mag switches (left and right)
Master/Alternator switch
Starter Push Button (NB, the mag switches have to be left impulse mag-on, right-off for this to operate)
Vacuum gauge
Tachometer
Hole for Trig TT21 Mode S transponder (mode S mandatory in Europe)
Pilot headphone sockets
Airspeed Indicator
Trio Autopilot
Artificial Horizon
Directional Gyro
Primer
Altimeter
Vertical Speed Indicator
Warning light Cluster (Low volts, Low Oil pressure, Carb temperature, Autopilot Engaged)
Information Display Unit (GPS Heading, GPS Groundspeed, Air Temperature, Carb Temperature, Bus Voltage, Battery Amps)
Garmin Apollo SL30 Nav Comm
Bendix King KMD150 GPS
Holes for Carb Heat, Throttle, Mixture
Oil Temperature and Pressure gauge
Intercom
Switches for: Strobes, Nav Lights, Auxilliary Fuel Pump, Spare for future requirement
Hole for CHT/EGT gauge
Fuel gauge
Pullable Breakers for alternator field and starter relay
Hole for Cabin Heat Control
Speaker On/Off switch
Chronometer: Time, Stopwatch, Flight-time
Emergency electrical power switch
Passenger headphone sockets
Spare 2-1/4" hole to be covered with panel blank pending any future requirement
12V Power Outlet

The intention of the panel design is to have good functionality but stay in keeping with the ethos of the aircraft and it's design date, hence the predominantly analogue instrumentation. The instrumentation also has to fit in with the physical requirements of the aircraft - particularly the depth limitations created by the fuel tank. I'm pleased with the way it has turned out but obviously the proof will be in flight.
Remember throughout the blog you can click on the pictures to see them enlarged.

10th September 2009 - Right Aileron and Flap completed

2009-09-10T19:30:00.000+01:00

A full day's work today although it doesn't really look like it. First job was to weld up three sections of 5/8" * 0.035" tubing to make the aileron mass balance horn. Then this was part filled with molten lead and tack welded to the front of the aileron torque tube to check for balance. A couple of iterations of adding lead and re-tacking saw the balance just slightly nose heavy to allow for the covering and paint. The aileron mass balance horn was then final welded in place. Unfortunately, when the test rib was checked it became clear that the weight would foul on the rear spar so it was cut off, shortened slighty, the top front edge curved, additional lead added to compensate and re-welded into place. It is still very close to the spar but should now clear OK. Next job was to mark on the bench the positions of all the wing ribs and position the flap and aileron over them. The positions of the hinges could then be marked and short sections of 1-3/8" diameter tubing sawn into quarter arcs and welded either side of the four hinges to locate them. Finally eight plates were cut out of 0.032" steel plate and welded round the hinges. The fabric will be glued to these to make a neat junction round the hinges. Some new T-88 epoxy also arrived today so it's back to rib making tomorrow.

9th September 2009 - Right Aileron and Flap continued

2009-09-09T19:24:00.000+01:00

Still no glue, so I carried on building the right aileron and flap. First 9 off 6" lengths of 3/8" * 0.035" tubing were welded to the torque tubes, 6 to the flap and 3 to the aileron, to act as ribs. Then the inboard end of the flap and outboard end of the aileron were constructed to length as per the plans and welded to the torque tubes. These are each made from two lengths of 3/8" steel channel. A string was then pulled tight between the ends and used to mark the final lengths of the ribs which were cut off using the angle grinder. The inboard end of the aileron and outboard end of the flap were then also constructed and welded into place sized and positioned to meet the string line. The tubular ribs were then flattened at the rear ends to fit inside the stainless steel "V" section trailing edge. Then the string line was used to ensure all of the ribs were precisely inline and small adjustments made where necessary, Finally the two sections of trailing edge were brazed onto the ribs. Next job is to weld into place locating plates for the hinges and covering support plates around them. Also the aileron has a mass balance welded to the front of the outboard end - details tomorrow.

8th September 2009 - Right Aileron and Flap

2009-09-08T20:09:00.001+01:00

It has been a frustrating few days as when I'd finished the first tube of T-88 epoxy I found that the second tube had gone hard so I was unable to make any progress on the ribs. Today, I'm still waiting for fresh glue to arrive so I cleared the worktable and decided to make a start on the ailerons and flaps. I'd constructed the torque tubes back in August last year http://tailwindbuild.blogspot.com/2008/08/8h-august-2008-flap-and-aileron.html so first job was to make the hinges which need to be in place on the torque tubes before the ribs are added. First I added a dummy aileron spar and dummy sections of skin to the rear of one of the ribs. This then gave the spacing and angles for the 0.071" thick 4130 steel plates that will bolt through the wing to secure the ailerons and flaps. The hinge itself is 1-3/8" diameter 0.058" thick 4130 tube which is a good fit around the 1-1/4" diameter torque rods. The 4 hinges for the right wing were constructed in a single piece and then sawn up. The plates were both welded to the tubing and also brazed as it seems pretty important that they don't fail! A 3/16" hole was drilled through the top of the tubing to allow the joint to be oiled. The second picture shows the profile of the weld and the fillet of braze metal. Then, with the hinges installed, the torque tubes were clamped to the bench ensuring that they were exactly straight and level. Finally a jig was made to hold the ribs (3/8" tubing) at right angles to the torque tubes and aligned with the centre line.

1st September 2009 - 2nd root rib

2009-09-02T17:32:00.000+01:00

I constructed the 2nd root rib today - seen in the jig before gluing. The problem with this type of jig is that the jig blocks can not be glued to the board as there is a piece of plastic sheet protecting the plan from the glue. This means that when fixing and removing the ribs the nails holding the jig blocks can tend to loosen allowing them to move. OK for two-off root ribs but not for 24 identical main ribs.

31st August 2009 - Ribs and rework

2009-08-31T19:11:00.000+01:00

It's been slow progress over the last few days but there are now 7 ribs completely finished and one with glue setting before the gussets are installed on the second side. I've also made a jig for the two root ribs and the first root rib has been constructed, glued, and is setting in it. For the root rib jig I've just pinned blocks of wood to locate the rib structure to a piece of polythene over the full size plan as there only two ribs to make so the jig does not need to be too durable.
I was intending to have a first go at covering starting with the rudder which is the smallest and simplest structure but when working out how to fix the fabric I realised that it was going to be difficult to get a good seal round the rudder horn. In order to give somewhere to glue I welded a small plate either side of the front rudder spar round the horn similar to those installed previously around the hinges. Then this needed the priming touching up where it had been sanded or burnt off so it's another seven days for the paint to completely harden before this is ready to cover.

23rd August 2009 - Priming Complete

2009-08-25T10:04:00.000+01:00

Finally the priming is completed, actually the priming itself isn't too bad but cleaning the parts with the Deoxidine is fairly unpleasant. This is basically a phosphoric acid solution which dissolves the aluminium oxide and etches into the aluminium. It does produce a very clean surface for the paint to adhere to but smells terrible and is messy to use particularly on big structures like the fuel tank and combing.

Painting is not my strong point and I usually end up with the surface covered in runs and marks but this time I've invested in a new type of paint gun - LVLP. This stands for low volume, low pressure. Low pressure has been around for some time and has the advantage that the overspray is greatly reduced. Low volume means that the amount of air used is also greatly reduced. I'm spraying using a 1.5HP 50 litre compressor which is not sufficient for conventional guns but works fine with the LVLP gun which uses only 6.5cfm at 22psi. The gun is, predictably, Chinese made but a beautiful piece of engineering and good value - http://www.auarita.com

The rib making has taken something of a back seat recently so still only 4 complete and 1 half done.

19th August 2009 - More ribs and primer

2009-08-21T09:15:00.003+01:00

The process of making ribs continues slowly, four complete and one gluing. Similarly the priming seems endless especially as I left out the fuel tank and the panel from the list last time. However, the end is getting nearer. All items except the combing and the fuel tank have been cleaned and at least partially painted so another couple of days should see the priming complete. The primer takes 7 days to completely set so once all the priming is complete I can then start applying top coat to those items where it is needed and that have had the requisite drying time. This is a subset of the items where they are visible or where the better wear resistance of the top coat is useful.

16th August 2009 - Ribs and primer

2009-08-16T19:41:00.000+01:00

The first rib was completed today other than tidying up the edges which will wait until all the ribs are complete so that they can be done together to ensure they have exactly the same profile. The second rib was built in the jig and the gussets stapled to the first side. Then it was back to priming. I think my estimate of 2/3rds done yesterday was overly optimistic - perhaps it's 2/3rds now. I still have the stringers, the seat bottoms, the seat backs, the coming, the cowl cheeks and the baggage compartment floor to clean and paint and one side of the doors and outer floor panel to paint.

15th August 2009 - Rib gussets

2009-08-15T19:57:00.001+01:00

Yesterday I carried on with the priming in the morning and went for a fly in my RV9A in the afternoon. Today it was more priming to start with - I think I'm about 2/3rds of the way through. Then I sorted out an approach to cutting the rib gussets from the 1/16" mahogany plywood called for in the plans. The 8' x 4' sheets of ply are very unwieldy to work with so I cut a small piece off and made the first set of gussets as per the full size rib plan. Then I laid these out on the plywood and established that a 5" x 13" piece was sufficient to make a half set (one side of the rib). I then cut five 13" strips off the main sheet which should be enough for 45 sets ( I need 44). The tip rib and the root rib are fully sheeted and there are 11 standard ribs in between each side. The master set of gussets were then used to draw round and the 5" strip with the outlines cut off. The gussets were then cut out on the bandsaw using a fine tooth blade running at medium speed. Rather than mass produce these I think I will make two sets each day to cater for the one daily rib. Finally I glued up the first rib using staples to hold the gussets in place while the glue sets. As per LAA requirements I also made a test piece with the batch of glue which will be inspected (destructively) by my LAA inspector to satisfy himself that the glue batch is satisfactory. I'm using T88 epoxy for gluing the ribs.

13th August 2009 - Fuselage Painted

2009-08-14T08:21:00.000+01:00

I collected the fuselage from being sandblasted and primed today. The company I used is called AirBlast and work out of a disused airfield at Gosfield. They were recommended because they have experience with the sort of thin wall tubing used in aircraft - too much enthusiasm with the grit gun can blow holes in thin tubing!

The airframe now looks smart and clean in it's coat of white epoxy primer and will temporarily be stored in the hangar at the airfield where my LAA inspector is chief engineer.

12th August 2009 - Starting the wing rib production line

2009-08-12T19:12:00.000+01:00

Actually the production line really started a couple of days ago when I sealed up one end of a piece of plastic pipe and filled it with hot water to soak overnight the first two 1/2" x 1/4" spruce strips that form the top and bottom structure of the ribs. Yesterday these were then clamped to wooden formers to form the bends which shape the nose section of the ribs and allowed to dry overnight. At the same time the next pair of strips were put in to soak. So today I had a pair of dry shaped strips that could be inserted into the wing rib jig, a pair drying in the former, and put the next pair into soak. The rib construction jig is a piece of MDF onto which the outline of the rib was copied from the full size wing rib plan. This was done by fastening the plan to the board and then pricking through the outline and internal structure with a compass point. Then small blocks of wood were pinned and glued to the board around the outlines of the various rib structures. Finally, at each point at which the rib structures are glued, 3/4" holes were drilled through the MDF so that the glue used to make the rib won't also bond it to the jig.
With the top and bottom strips in place, the internal strips could then be cut to length and fitted. The seven upright strips and front and back blocks were then mass produced (24 of each) to cater for the full requirement. This was done using the bandsaw with its mitre guide to cut the correct angles top and bottom. Finally, two off of the 5 diagonal braces were produced. These have to be finished individually using the disc sander so each day I will use the extra set as a template for that days rib. Next job is to fabricate the gussets that glue over the joints to support them. 48 each of these needed (one either side of the 24 ribs) so I'll try and find a convenient way of mass producing them as well.

11th August 2009 - Priming the aluminium parts

2009-08-12T18:44:00.001+01:00

The fuselage and empennage are ready to pick up having been sandblasted and primed with Epibond epoxy primer. That's a job for later in the week so today I made a start on priming the aluminium parts. My system is as follows:
First each part is immersed in a solution of Deoxidine 624 and scrubbed with a scotchbrite pad. Deoxidine 624 is a liquid cleaner for aluminium and its alloys to remove oils and oxides prior to painting or anodising.
Then each part is washed with clean water and hung up to dry making sure not to touch them with anything that might result in contamination (e.g. bare hands).
Finally once completely dry the parts are laid out on a mesh table and sprayed with the Epibond. This takes 7 days to fully harden so each part will then be stored for at least that long before topcoating with Ranthane polyurethane where applicable.
Surprisingly, unless I've miscounted, there are 53 separate aluminium parts that need spraying including large panels such as the floors, doors, and cowl cheeks. This is going to take some time to complete and is weather dependent as I will be spraying outside. Anyway at least I've made a start with 12 of the smaller parts cleaned and spayed on one side. This will be a background job at the same time as building the wing ribs - see tomorrow's post.

29th July 2009 - Off to the sandblasters

2009-07-29T12:56:00.001+01:00

No it's not a new attempt to make a flying car! Today I loaded the airframe onto the roof of the car, put all the various loose bits like rudders and elevators in the boot and headed off to the company who are going to sandblast and paint the airframe. Its amazing how light the complete airframe is considering that its completely made of steel. With my wife's help it was easy to lift onto the car and secure it safely. I decided to get the painting done professionally as the Epibond epoxy primer is pretty unpleasant stuff and I haven't got the appropiate breathing equipment to allow you to spray without inhaling the fumes. So next time the airframe is pictured it should be looking very smart in it's white primer coat. The fabric glue is designed to stick directly to the primer and I will only top coat areas that are exposed to view in the cockpit.

24th July 2009 - Fuselage Welding Complete

2009-07-24T17:33:00.006+01:00

First job today was to fabricate and weld into place an upright between the lower firewall cross member and the firewall diagonal. Two tabs were then welded to this to take the electric fuel pump mountings. Next a tab was fabricated and installed on the diagonal to mount the vacuum regulator and finally a mount was fabricated to attach the vacuum filter also on the diagonal.

The two pictures, taken with the firewall itself omitted, show the various firewall components mounted in place with the exception of the cabin air control and brake fluid reservoir which mount directly to the firewall without welded supports.
As can be seen in the second picture the engine mount sits neatly over the solenoids, battery and gascolator. I'm going to redo the tube from the tank to the fuel pump using a 45 degree fitting to shorten the route and reduce the bends needed in the tube.

Hopefully that is now all the welding on the fuselage complete. I've completed all the necessary items on my list http://tailwindbuild.blogspot.com/2009/03/25th-march-2009-list.html so next job is to get the fuselage sandblasted ready for priming. The question then will be whether to start on the construction of the wings or carry on and cover the fuselage. I have managed to find a source of Douglas Fir for the wing spars so will use these rather than Spruce as this gives an important improvement in the strength of the spar attachments. There probably won't be many updates over the next two or three weeks while I get the sandblasting organised but hopefully by mid-August things should be underway again.

22nd July 2009 - Firewall Day 2

2009-07-22T20:05:00.006+01:00

The first job today was to install nutplates on the tabs installed yesterday to support the battery and relays. Then the firewall was fitted to the fuselage and the fuel tank installed to allow the other components to be located. The auxiliary fuel pump was located between the tank and the gascolator ensuring that the connecting tubing descended over it's complete length. The tubing sections are 3/8" soft aluminium with standard 37 degree ends manufactured to connect them. The fuel pump is mounted on rubber isolating bushes to reduce noise. Supporting tabs for the fuel pump will be on the agenda for tomorrow. Next a stiffening panel made out of 0.063" thick 2024-T3 aluminium was riveted to the firewall to support the brake reservoir. A 2" hole was drilled for the cabin hot air inlet and the air selector screwed to the firewall - this will eventually be sealed in place with firewall cement. A 7/8" hole was drilled in the firewall to take the vacuum regulator, again a support tab is needed for this. Finally a bracket was fabricated to support the vacuum filter. This also needs welding to the fuselage structure.