27th August 2014 - Baffled by baffles: day 1

The Vans baffle kit arrived today so I could make a start fitting it. Vans only do a kit for a dynafocal mount O-320 engine and I'm using a straight mount O-235-C2C so I expected that some "fettling" would be needed. The first obvious problem was that the mounting holes where the side baffles bolt onto the cylinders were in completely the wrong place although the cut-outs for the rocker covers were thankfully completely accurate. So cover plates for the incorrect holes were fabricated and riveted into place. Then correctly placed holes were drilled and the doublers  and strengthening angles riveted into place. Next the rear left baffle was test fit. This needed many-many iterations of trimming to fit round the parallel engine mount. Finally a good fit was achieved and it was riveted to the rear left-side baffle.
There is a mounting bracket, just visible in the picture, screwed to the rear two top engine join bolts. This also required much adjustment to fit on the bolts and clear the engine crankcase but eventually it was in place and the left rear baffle was match drilled and clecoed to it. This will be bolted up when the baffles are finally installed.
The right rear baffle was easier to get fitted snugly around the engine. It will need a spacer to rivet it to the rear-right-side baffle but that is a job for tomorrow. 8 hours work on the baffles so far!

21st August 2014 - Exhaust system complete

The extra 45-degree section of exhaust arrived today together with a 6' length of 2" scat tubing (this stuff is so expensive!). This allowed me to finalise the exhaust, seal all the joints with exhaust putty and clamp everything up with heavy duty clamps. Then the scat tubing was cut to provide links between; the carb air box and the air muff, the air muff and the cabin heat valve on the firewall, and the air muff and a flange which will be riveted to the baffles to get a source of fresh air. This pretty much completes the engine install apart from the baffles. The other little jobs are just to route the engine breather, plumb the vacuum pump, and connect the fuel pump pressure relief overflow.
No pictures, but I have also been working on tidying up the joint between the lower and upper parts of the cowl. As delivered the step overlap is not deep enough to get a smooth transition so additional fibreglass has been bonded onto the lower cowl to build it up. Next job will be to blend everything together with copious amounts of filler.

19th August 2014 - Cabin and Carb Heat Muff - part 2

The 2" holesaw that I had ordered arrived today so I was able to drill three holes in the heat muff. Three lengths of 2" aluminium tubing were cut and welded into the holes. This completes the heat muff. 2" scat tubing will be used to plumb up the air intake (bottom right), the cabin heat (bottom left) and the carburettor heat (top left).

18th August 2014 - Left exhaust pipe, oil filler door

The exhaust system is now complete pending arrival of one extra 45 degree bend and some heavy duty clamps for the overlap joints.
The left system is constructed the same as the right except that the bend which angles the exhaust inwards and down is a 60 degree angle rather than 45 as the cylinders on this side of the engine are further to the rear of the engine. For final assembly I'll use a jointing paste on the overlap joints.
With the exhaust complete, I used the extra time today to cut out the oil filler door flap from the upper cowl. The removed section was riveted to a section of hinge and this and some stainless steel strip was riveted to the cowl to mount the door and provide a lip for it to sit on. A hole was then drilled through the door and the strip and a catch installed. I still need to  fibreglass the strips onto the cowl to provide extra support and get rid of any gaps.

16th August 2014 - Cabin and Carb Heat muff: part 1

The straight section of pipe on the right exhaust is the only place that will take a sensibly-sized cabin and carburettor heat muff.
A 8" length of 4" diameter aluminium tubing was used as the outside of the muff. Two end plates were cut using the CNC router from 16SWG 6061-T6 aluminium sheet to fit the ends of the 4" tube and with  2" holes asymmetrically placed to position the heat muff clear of the lower cowl.
1.5" lengths of 2" aluminium tubing were welded into the holes. The forward one was positioned inside the muff to allow it to slide forward as far as possible on the exhaust pipe. The rear one is on the outside and once welded slots were cut into it to allow it to be clamped to the exhaust pipe using a worm drive jubilee clamp.
Then the end plates were welded onto the 4" pipe to complete the muff hot air box. Next step is to cut an inlet hole for the fresh air supply and two outlets; one for the cabin heat and one for the carburettor heat. These will have short lengths of 2" aluminium tube welded into place to take the 2" high temperature scat tubing which will be used to plumb everything up.

15th August 2014 - Right side Exhaust fabricated

I've decided to build a 2-pipe exhaust system with cylinders 1 and 3 feeding into one tailpipe and 2 and 4 into the other. This isn't as efficient as a crossflow system (1 & 2, 3 & 4). However,it is much easier to construct. The system is made from the mild-steel custom exhaust build parts available from jetex.co.uk.
As a start, I bought 2-each of 1m straight , 90 degree bend, 60 degree bend, 45 degree bend, and 30 degree bend.
Then it was a case of slowly fitting and cutting the sections in an iterative fashion until a route was established that cleared the cowls and routed out of the slot in the bottom of the lower cowl.
In the event I used a 90 degree bend off cylinder 1 connected to a 45 degree bend to angle the exhaust in and down. A 30 degree bend was used from cylinder 3 which was fit and welded to a machined hole cut in the 45 degree bend (took over a couple of hours to get a matching hole and end-profile). Next a section of straight pipe was welded on. This will take the hot air box for the cabin and carburettor heaters. Finally another 45 degree was used to create the tailpipe angling the exhaust down and away from the fabric under the fuselage.
I still need to make a support for the rear of the exhaust. This has to be connected to the engine rather than the airframe so that as the engine moves on the mount it doesn't stress the exhaust.
The routing for the left side will be similar but because the 2 and 4 cylinders are more to the rear a sharper angle will be needed before the straight pipe and this will also be shorter. I think this means that worst case I will need to buy two extra 45 degree bends, best case is just one more.

14th August 2014 - Spats and brakes

The Tailwind has taken something of a back seat recently however, finally some progress.
Some time ago I bought a pair of second hand Vans' spats. These are the original non-pressure-recovery versions. These were drilled for fastening to some sort of mount on the inner side of the wheel and onto the axle nut on the outside. The challenge then was to fabricate some sort of mounting bracket and fasten it to the airframe in some way.
Before I could start I needed to find some way of jacking up the wheel so I could work on the axle. I found a bit of spare steel tubing of about the same diameter as the undercarriage leg. This was cut in half and some scrap plate welded on and drilled so it could be clamped to the leg. Then a bit of angle iron was welded on at an angle so that a car jack could be used to lift the wheel. This works well but marks the paint so I will have to line the inside with some rubber.
The spat mounting plate needed to be kept clear of the brake disc so 1/2"-long spacers were cut out of some steel tubing. The 1/4" bolts that secured the brake mounts were then replaced with longer ones to take the spacers. A bit of scrap aluminium was then progressively cut to fit the bolts and clear the brake caliper. The wheel was then replaced and  the spat test fit. Holes were drilled in the mounting plate and the spat clecoed into place. This was then repeated for the second gear leg. The spats were positioned so that they were horizontal with the aircraft in normal flying pitch.
The development mounting plates were then removed and a final version drawn up on the computer in Cambam. Then the CNC router was used to cut final versions out of some 2mm 6061-T6 aluminium sheet.  Nut-plates were riveted into place for the spat mounting screws and the plates mounted in place. They will have to come off again to be painted.
AN822-4D right angle fittings were installed in the top of the brake calipers . Finally, some 1/4" soft aluminium tubing was bent and cut to make the brake pipe. The ends were flared, making sure that the AN nuts and sleeves were in place first. The brake pipe will be taped to the rear of the undercarriage leg and covered by the leg spat. The loop of pipe is to ensure that flexing of the leg will not break it.