29th July 2009 - Off to the sandblasters

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

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

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.

21st July 2009 - Firewall Supports

The heaviest item on the firewall is the battery. This will be an Odyssey PC680. This is a drycell 12 Volt 16 Ah Battery capable of 680 Cranking Amps for 5 Seconds. The advantage of the drycell technology is that there is no acid to spill and the battery can even be installed on it's side if required. The PC680 weighs less than 15 pounds, about 7lbs less than a typical aircraft battery, but still needs proper support to mount on the firewall. Two lengths of 5/8" * 0.028" ID tubing were welded vertically between the firewall diagonal and the top firewall cross member. Four tabs were then welded to the diagonals and drilled to mount the battery case which is the standard Vans case for the PC680. Above these two additional tabs were welded and drilled to mount the master relay and starter relay. Towards the bottom left of the diagonal an additional tab was welded and drilled to 5/8" to take the gascolator firewall mounting. This is a special bulkhead fitting available from ACS designed to mount the gascolator solidly on the firewall. The incoming fuel line is connected to a AN6 male tube fitting on the cabin side. The gascolator is screwed directly onto the 1/4" male pipe thread on the engine side. No other support is needed. The gascolator will be at the lowest point in the fuel system designed to trap any water in the fuel and act as a fuel filter.

18th July 2009 - Stripping the airframe

No work was possible yesterday as it was too rainy to get the fuselage out of the workshop to work on it. The weather was somewhat better today so the first job was to layout the various components pictured in the previous entry on the firewall and mark their positions. Then, the rest of the day was spent removing the engine, gear, engine mount, firewall,and all of the baggage compartment structure. The fuselage is now stripped right back to the welded frame ready for sand blasting and painting after any additional firewall supports are welded into place.
The firewall itself will be drilled as required and then the exact locations of the supporting structure can be established.

16th July 2009 - Baggage Compartment Complete

I spent time yesterday and today fitting the baggage compartment sidewalls, roof, and rear panel into place and drilling the support angles to fit 44 spire clips which take the mounting screws. The side, rear and roof panels will eventually be covered in cloth or vinyl fabric, the floor will be carpeted.
Next job is to layout and drill the firewall and build any required supporting structure. The second picture shows the items that mount to the firewall. Top left to bottom right they are:
Battery box
Master Solenoid
Starter Solenoid
Fusible link mount for alternator protection fuse
Brake reservoir
Vacuum regulator (vacuum air filter missing from picture but also to be mounted)
Sensor manifold for oil pressure and fuel pressure
Cabin air control box
Electric fuel pump
Gascolator (fuel filter and drain valve)
Gascolator mount

In addition firewall penetrations are required for:
Primer Lines
Power Cabling
Sensor Cabling
Throttle Control
Mixture Control
Carburettor Heat Control

13th July 2009 - Baggage Compartment Floor nutplates

I only got a couple of hours in the workshop today but installed 16 nutplates in the lower baggage compartment angles to fasten the floor into place. Once screwed into place the floor , with the siffeners, seems reasonably strong without adding too much weight.

12th July 2009 - Baggage Compartment Floor

The baggage compartment floor is a piece of 0.050" aluminium sheet cut to size and stiffened with two lengths of "J" angle (left over from the lengths used as stiffeners in the Vans RV9A fuselage). These were cut to length, match drilled, dimpled and riveted to the sheet using 20 flush 3/32" rivets each. The sheet was then inserted into the angles which support it and 16 holes match drilled. Tomorrow the holes will be drilled to final size and nutplates riveted onto the angles to screw the baggage compartment floor into place but allow it to be easily removed for maintenance and inspection.

10th July 2009 - Fresh Air Vents

I'm trying to build the Tailwind to a budget of £12,000 complete and flying so without cutting any corners I am trying to find cheap and elegant solutions to the various parts of the build. Installing a standard fresh air system with car-style vents could cost anything from £75-£150 depending on whether plastic or aluminium vents were used. However Vans Aircraft have designed a fresh air vent kit for the rear seats of the RV10 which they also sell for installation in other Vans aircraft and if it's good enough for the RV10...
At $18 for a pair of vents this provides a cheap and neat solution to getting fresh air into the cockpit. The pictures show the left hand vent installed in the cowl cheek just forward of the front door post. When closed the 1.5" x 2.5" vent closes completely flush with the outer skin and when open should direct a nice stream of fresh air into the cockpit without too much drag. Of course it helps that I've got a full set of riveting tools left over from building my RV9A!

9th July 2009 - Back to work mounting the engine

It was good to get back to work today after 6 weeks off. First job was to collect the engine from the shop where the shock load inspection had been completed. No damage found and all new bearings in the bottom end so the engine should be good to go once the aircraft is completed. I asked the shop not to paint the short engine following the inspection as I'll do this once the cylinders are all installed.
The plans for the engine mount warn of two issues, first to ensure that the bottom supports do not foul on the sump and second to ensure that the top diagonal tie bars do not foul on the vacuum pump (if fitted). This is all very well but as the mount can't be test fit until complete I just followed the dimensions in the plans exactly.
The good news was that the sump is well clear. The bad news was that the top diagonal tie bars did get in the way of both the pump itself and the pump drive. To solve this the short section of the tie bar starting at the right top engine mount and linking towards the top left fuselage mount was cut out completely and the full length tie bar linking to the top right fuselage mount was cut from the left top engine mount. With the engine in place it was then possible to re-make the short section and put a small angle in the long brace to clear the pump. The new short section was then tack welded into place with the engine installed and the left engine mount joint remade. Next the engine was removed and as much as possible of the new joints final welded leaving short sections on the underside to be completed when the engine mount is next removed from the fuselage. Finally the engine was re-installed and the vacuum pump now fits as shown in the last picture. If I was doing this again I think the best approach would be to leave off these top diagonal tie bars completely, fit the engine and then tack them into place ensuring clearance.