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
Today I worked on fitting the snorkel, completing a few more steps.
With the fuel controller covered in plastic, I placed the snorkel on the flange, and then assessed the alignment at the air filter end, where it attaches to the baffling. The instructions warn that small changes at the fuel control unit can have a large impact on the alignment at the baffling. While true, I found that I needed to take a uniform amount off the fuel control end to get the other end to line up. In total, it was about 3/8 of an inch longer than it needed to be, and after carefully sanding it down, the alignment worked out well. I had to disconnect the oil return line to complete this step, and continually bend it out of the way to avoid interference with the snorkel. I’m hoping that the replacement line I ordered will clear the snorkel, because I’m proceeding with fitting the snorkel before I have the new line in-hand.
Once everything fit, I drilled alignment holes in the air filter end of the snorkel, clecoed them, then marked out the excess snorkel to trim. Then I could take the whole assembly off the airplane and trim the snorkel. I used a hack saw to cut about half an inch off the end of the snorkel, then carefully filed it down until it was flush with the shelf on the air filter holder.
I could then install it back on the airplane, and mix up some epoxy glue to seal the gap between the snorkel and the air filter holder.
Marking the fuel controller end of the snorkel for trimmingChecking the alignment of the snorkel against the fuel controller flangeChecking the alignment of the air filter end of the snorkel with the baffling. The goal is to eliminate any side loading on the baffling, by trimming the opposite end of the snorkelSnorkel fit looks just about rightAfter drilling the alignment holesAfter trimming the snorkel and carefully filing it to be flushAfter sealing the gap around the snorkel with epoxy glue
