Cabin heat feed, ignition mount start

This is another two-day post; yesterday I was mostly busy working on Helio stuff, but I did get some time in the shop in the evening. The first thing I was working on was making the hole in the right rear baffle that will feed air to the exhaust heat muff, and thence into the cabin. I used the provided flange part to outline the required hole, and marked the center. Unfortunately, because of the bends in the baffle here, I couldn’t use my trusty hole cutter, but I was able to use the largest of my knockout punch set to make a starting hole that was only about 1/8” undersize. Then I just opened the hole up to my outline with a Dremel cutting bit.

Next I clamped the flange in place and drilled the four rivet holes, followed by some fine-tuning of the hole. At this point I was ready to rivet the piece in place…or so I thought. There’s a provide piece of metal screen that’s to be trapped between the flange and the baffle, I guess to prevent debris (like insects) from entering the cabin in-flight. The plans call for tank sealant to be used in between the flange and baffle, I assume to keep the joint well-sealed. I was planning on using some good old RTV, but…turns out I don’t have any. I think now I remember that the last time I needed RTV, I had to poke a hole in the side of my tube because it was so dried up.

So I just set this aside for now, and moved on to starting on the real fun fabrication work: the case top mount for the ignition coil pack. I busted out the angle I bought for this purpose, did a bunch of measuring, marking, and laying out, and got to work. After drilling the two bolt holes, I outlined the material I needed to remove from the vertical flange. This is necessary both to ensure the mount fits well against the case, as well as to provide an aperture for the fuel injector line to go through. After all, the whole reason for this custom mount is to work around that line.

After all that layout work was the usual dance of drilling holes, rough cutting with the bandsaw, refining the shape with a cutter in the Dremel, and straightening things up with the file. Then it was time for the big event: a test fit on the engine. It lines up nicely and provides good space underneath for the injector line, so it looks like it’ll achieve its purpose:


Of course this is only one of the two mount pieces; I’ll need to make essentially a mirror image that will go on the other side of the case. There will also be more trimming to be done – these pieces are intentionally oversize, and once I get the location of the coil pack right, I should be able to remove a good bit more material. I’ve also got to think of how I’ll adapt a brace on the backside of this piece for the rear baffles.

But hey, things are going well so far. I’m thinking that from here, I’ll finish the coil mount, get the coil in place, then set the baffles aside and start working on fitting the cowl. That way I’ll get my look at whether the cowl properly clears the coil pack – it’s still possible I might have to relocate the coil elsewhere, though I sure hope not.

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