6 hours.
First thing was finishing up drilling the top cowl hinges, then it was on to the cowl itself.
I finished measuring the line 2″ back from the firewall all the way around the fuselage. My original plan was to just mark the ends of the lines with red electrical tape, which you can see in this photo, but after some thought, it turned out to be a stupid idea. Electrical tape flexes like crazy, and a closer examination from a different angle showed the tape line to be wavier than an acidhead’s dorm room. What I did have was a flexible plastic ruler, which allowed me to mark the ends of the 2″ lines all the way around and still conform to the shape of the fuselage. Once I had a good line, I laid the edge of the red tape on it, which gave me a tactile cue for measuring back onto the cowl itself. 2″ back from the red tape is where the edge of the firewall is, so that got marked on the cowl, and the same process repeated, but this time with masking tape. Masking tape flexes less, and doesn’t seem to bother the fiberglass cutter on the Dremel too much.
Here’s the Pepto-pink cowl with the tape line marked, ready to have the extra bit trimmed off the end. I had to clamp a couple of blocks to the bench to keep it from jumping around, but once that was set up, I cut off the overhang on the cowl. There wasn’t much. With 1/4″ of clearance between the spinner and the front of the cowl, there was just about that much overhang from the cowl aft of the firewall edge. Once the cowl was marked, I put the hinges back on
This is right after trimming off the excess. What followed this was a lot of iterations of sanding and shaping, trying to keep the 1/4″ of clearance up front, but maintain a nice even 1/32 gap all along the cowl edge. You leave this gap for paint. If you don’t, when you put the parts back toghether, the thickness of the paint makes them not fit anymore, and the paint gets chipped, and nobody wants that.
The 1/4″ gap up front is pretty important. The engine is on rubber mounts, so it’s going to flex a little when it starts and shuts down, so you want to keep the spinner clear of the cowl. In this shot, it’s still a little high, I want to have the spinner about 1/16″ to 1/8″ above the cowl to account for when the engine sags after the first few hours of flight. I guess the rubber mounts do this. Go fig.
Apparently, the pink cowl is thinner than the old green cowl Van’s used to provide. The plans have you putting .032 shims between the hinges and the firewall because the old cowl used to stick up significantly. The pink one, or at least this one, required no shims at all. It’s either flush with the top deck skin or just slightly above it, just enough to catch a fingernail on. That can be sanded flush without thinning the material significantly.
All in all, a non-suck day.
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