More coil mount work, getting ready for cowl fitting

Tonight I picked up where I left off with the coil pack mount. Since the first piece from last night fit up nicely, I used it as a pattern for making its mirror-image mate. Drilling the two bolts holes and roughing out the cuts went pretty quickly, but it took a little more work than that. Turns out the case casting is slightly different on the left side, and I needed to remove a little more material to get it to fit nice and flush on the case.

Once I got both pieces bolted in place, it was time to set the coil pack on top and evaluate the fit. One concern I had after last night was whether these two pieces of angle would actually provide a large enough mount pad for the coil pack. After the test fit, I think this is going to be fine, though there’s not a lot of extra space. I could make this a little better by adding some washers or spacers between the brackets and the case, but doing that would make this a lot more annoying to install or remove. I’ll have to evaluate the actual edge distance on these bolts to make a decision here.

The other thing to evaluate here is the clearance between the coil pack and the cowl. In an attempt to get a first approximation of this, I once again draped the cowl over the top of the engine and firewall. I found that the cowl would rest on the coil before it contacted the flywheel, which isn’t necessarily a bad thing. After all, the cowling isn’t supposed to contact the flywheel, but the unanswered question here was what the right position for the cowl nose ought to be. Both the vertical and longitudinal positions here can make a good bit of difference in clearance with the coil pack.

So I decided that this was a good time to do some of the prep work for fitting the cowl. The nose of the cowl gets its position set relative to the prop spinner backplate, so that backplate needs to be in place for this. In the case of a CS prop like what I have, the backplate attaches to the prop itself, which means that I need the prop in place to fit the cowl. So I got to work breaking out the prop and spinner, installing the backplate, and finally actually hanging the prop.

Installing the prop is a bit of a slog, though that slog is balanced out by, well, by the fact that I’m installing the prop, which is sort of a cool milestone. The thing is that the six prop bolts are captive inside the prop hub, and the arrangement means that each bolt can be turned about one flat at a time with a wrench. Additionally, the bolts need to be tightened gradually and equally, to pull the prop squarely onto the crank flange. What this means is that I did a lot of walking from one side of the prop to the other and back. All told I think I spent 40 minutes tightening those bolts.

I haven’t done a real recheck of clearance with the coil – I also need to rig up something at the front of the engine to support the cowl nose at the proper height – but I did lay it back on top just to help get some “hey, it looks even more like an airplane” photos:

Fun fact: you may notice some mud dauber nests on the prop blades. At least those are easy to clean off, right now they’re making my nice carbon fiber blades look not as good as they’re supposed to.

So there we are. I need to get some hardware to rig the from cowl support, and also install the forward top skin, but I’m in a decent spot to start thinking about laying out the first big trim cut on the upper cowl.

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