Today we continued working on the cowling and the exhaust system.
While Dad handled the sanding and fitting of the cowling, I worked on setting up the exhaust system. First I assembled the support clamps, then applied anti-seize lubricant to the sleeve and ball fittings, then set it up underneath the engine.
With dad’s help we were able to mount the pipes onto the cylinders, doing up the hardware finger tight.
Using a roll of 3/4 inch electrical tape, I set the spacing correctly and installed the support clamps on the aft edge.
Dad did another round of filling today, as there is still a ways to go to achieve the alignment we need on the cowling air inlets. It’s amazing to watch him work, knowing just what’s needed to get the perfect fit and finish. At 79 years old he’s still putting in very long days, with no complaints.
With my dad back in town and helping with the cowling again, we made progress today on a few fronts. Dad worked on installing the top cowl air ramps, and started on the oil door, while I focused on the exhaust system.
Before the air ramps could be installed, we needed to address the alignment issues with the front of the cowling. In a couple of sessions, Dad applied filler to the edges of the air inlets, and trimmed the air ramps to fit.
Meanwhile, I installed the first section of the heating system, the heat t-fitting. I left the clamps loose for now, as it’s hard to tell if this will need to be finessed into position later. I then drilled out a couple of rivets, and installed the FF-00084 cover. After some puzzling, I realized that this stops the hot air from escaping the system when the passenger vent is closed, and the pilot vent is open.
Today I started on the exhaust system by cutting the scat tubing to length, and making up the flared-tube exhaust support fittings. No issues or challenges with this step, although I wonder how well these fittings will work. Hopefully they will grip the inside of the hose enough to hold on, I have read a few stories on vansairforce.net where these have let go. We’ll find out I guess.
Today I installed a new oil return line on the #2 cylinder (front left).
The original line from Lycoming interfered with the snorkel, which is a know issue with the EXP119 engine. Conveniently, Aircraft Specialty make a drop in replacement line for just this problem.
I removed the original line, and test-fit the new one. It worked great, but I couldn’t quite get a flush fit between the flared tube end and the fluid fitting on the engine. After some fiddling around I guessed that the problem was the fitting clocking not being exactly right for the new hose. I removed the fluid fitting, cleaned the threads, and reinstalled it (Loctite 567). Once I had close to the right torque, I slowly rotated the fitting while testing the fit of the flared tube. It was easy to check the alignment by just feeling how much resistance I had on the b nut. Once it fit freely, I stopped rotating the fluid fitting and torqued everything up.
Clearance from the snorkel is perfect.
Old line compared to new line. New line has the red seal on the endThe new line hugs the oil intake pipe, without contactingAnother angle, showing the author
Today I cut out the baffle seals and clecoed them in place. The seals come in a roll of rubber material, with the shapes pre-punched. It took a little time to cut out each shape with a razor, but it was easy to do. Each part is stamped with a label, and they are installed from part A to M.
The baffle seals press against the top cowling forming a seal, and forcing the airflow down through the cooling fins and into the ducting that cools engine components. Any gaps in the baffle seals means inefficient cooling and higher engine operating temperatures.
Based on some vans Air Force threads, I was ready for some of these seals to need to be switched, or flipped, or something. What I found was that if installed with the labels facing outside, everything fit just right. Except for part A, which appeared to be reversed. After a bit of deliberation, I decided it fit best with the label facing inwards. Once I have the cowling on, I guess I’ll find out!
The rubber roll with the baffle seals pre-punched and labeledBaffle seals clecoed into positionClecoed baffle seals. In the left foreground is part A which I installed with the label facing inboard
Tonight I shaped the left hand air ramp. This was trickier than the right hand side because the ramp is part of the air filter cover. Bending the ramp risks damaging or bending the cover. I practiced on a piece of scrap, and when that came out almost perfect I got started with the real piece. The first bend went well, and the second was going well also. However when I moved to the third bend line I noticed that the cover had developed an unwanted bend and a twist. I carefully worked the unwanted bend out, and carried on with the process.
The end result was acceptable, but not my finest work. I removed the paper template, match drilled the one screw hole, deburred, dimpled, and installed a nut plate.
With the part complete, I installed the air filter and cover, and verified everything fits correctly. Then I took it all apart again, as I’ll need to replace the oil return line.
Practice part. The curve is idealThe actual part. Not a great bend on this end, but it fits great.The aft end with a tighter radius. No cracks this timeAir filter and cover installed
Tonight I had only a few minutes, so I riveted the right air ramp into position and glued on the template for the left air ramp. I used a pop rivet in the aft-most, inboard hole, because access by squeezer was tight, and I didn’t want to use my rivet gun for fear of bending something.
This required sticking on a paper template, then, following a sequence of bends, shaping the piece until it conforms to relatively smooth curve. It’s a conical shape, so one end is a much tighter radius than the other. I managed to get the shape fairly close, but I ended up cracking the end with the most narrow radius. I stop drilled the crack, then filed out a relief notch to mitigate the risk of further cracks.
I then match drilled the holes into the baffling, and dimpled them. Dimpling the aft most holes was a little annoying because it was too far from the edge to use my squeezer. I used a pop-rivet dimpled instead, which doesn’t give great results, but good enough in this case.
The right air ramp with template glued onShaping the air ramp by gently tapping a block of wood against the various marks on the templateAfter shaping the air rampMatch drilling the air ramp to the bafflingMatch drillingMatch drilling the aft holes was almost impossible given the geometry, so I clecoed the ramp to the outside a drilled the aft most hole
The gasket for the fuel controller arrived today, so I went ahead and installed the fuel controller and final torqued the nuts.
Following the engine maintenance manual, I torqued the nuts to 17 foot pounds (204. Inch pounds). The manual assumes there is no adapter, which there is, but this seems like the right value for the size studs that I’m installing onto.
With that done, I worked on the alternate air installation.
The alt air is a backup air intake for emergency use if the aim air intake were to become blocked (ice, bird strike, etc). There is a door on the side of the snorkel that can be opened with a control inside the cockpit. The standard Vans design doesn’t allow the alt air to be closed once it’s opened, so you’d have to take the cowl off to reset it if it were ever pulled. That’s ok, but it means you can’t test the mechanism as part of a run-up before takeoff.
Of course someone had solved this problem and come up with an alternative door design that can open and close using the cockpit control. The only difference is the door itself, it mounts onto the standard location without any modifications. This is what I’m going to install.
I needed to buy a hole saw because I didn’t have anything big enough. The plans called for a hole that is 2 11/16 inches in diameter. The closest diameter I could find at harbor freight was 2 5/8, and when I drilled the hole, it came out slightly over-sized, which was perfect.
Some of the instructions are a bit confusing, but carefully reading and following the steps made sense eventually.
The inlet is glued into position using epoxy.
Fuel controller installed and final torquedPage 255 in the manual, explaining the torquing instructionsAfter cutting the hole, it was exactly the size I neededCleaned up holeDimpling the inlet The inlet final drilled and dimpledThe alternative door. Seems to be a good designGluing the inlet onto the side of the snorkelBecause of the geometry, and the nut plate, there’s a gap to fill around the edge of the flange
