Given how bad the cowl fit is and how many times I'm likely going to need to take it on and off, I think making a jig to help reliably get it on the crankshaft centerline will pay off. The manufactured jigs for this purpose are machined metal ones. I'm sure they're nice, but for a one time use, I'm not about to spend $400 on one! Basically, the way the jig works is once you get the top and lower cowls somewhat matched up, you drill and cleco a round disc to the nose bowl to create a consistent reference point. Basically, like this:
I'm not sure what I'll make the disc out of. Probably either just a nice flat piece of plywood or a sheet of hard plastic.
With that in place, you can work with the cowl halves separately (you have to work with them individually to get them trimmed to match the fuselage). The second part of the jig is a spacer that bolts to the prop flange of the engine. It has a tube extending from the center that the disc can then slide over as a reference every time you take the cowl on and off for measuring. That means you get the cowl in the same position every time. Without the jig, you have to measure, prop up and clamp the cowls every time you move them.This is the $400 jig. Looks beautiful, but seem like overkill for what it does.
I don't know if it'll work or not, but I drew up a similar jig in CAD and am going to 3D print it. $10 in filament to save $400 seems worth the attempt! I have a scrap 1" dowel that I'll stick into the center hole for my locator pin that will mate with the disc that clecos to the cowl. The big question to be answered is did I get the depth of the spacer correct? The normal prop spacer is 2.25", but then I had to take into account the spinner backplate and how it sets, plus leaving about 1/4" between it and the cowl. That ended up requiring the spacer to be 1.4375" thick (so that when the disc slides in place and up against the spacer, the cowl is sitting in a location that will ultimately be 1/4" behind the spinner). Time will tell if I got that right.
