Progress has been made.
I remade the nosecone coupler and the joiner part with a new technique. The sacrificial female mold worked fine, but the balloons did not, I didn't have much compression, and the balloon for the coupler seeped air to the point of pulling the inner layer away from the rest of the layers at one end. My new method was to simply print a tapered male plug longer than the female mold. I laid up the fiberglass sleeves on it the same way as with the nosecone parts, but then shoved the female mold over it. The two parts taper locked together, and produced coupler parts with a consistent wall thickness, good inside finish, and a precisely controlled outer contour.
I also painted a layer of epoxy onto the main nosecone parts to fill the weave a bit and leave a better surface for sanding.
Then it was time for probably the most stressful part of the build. The heated post cure of the fiberglass parts. The oven I had access to doesn't have a super accurate dial, so I spent a ton of time yesterday tweaking the dial and then coming back 10 minutes later to see what the thermocouples read. The System 3000 resin has a very slow, gradual post cure regimen, I assume to ensure the parts don't warp. I finished up around 1 in the morning, and then pulled the parts out when I woke up this morning. I wasn't expecting the resin to change color this dramatically, but the parts are all exactly the same dimensions as when they went in, so I'm calling it a win. The drips are from the layer I painted on.
The printed fin can, and waterjet bulkhead parts also arrived today.
Overall the fin can is pretty good. The fit is very tight on the motor, but it does fit, so that shouldn't require too much sanding to adjust the fit. The surface finish is somewhat rough, but I think some wet sanding will smooth it up a lot. My one concern is that it looks like there was some warping of the fin tips. It looks like the fins are all in plane, and I just need to file the tips till the tip chord is flat, but the fin can does require a deeper inspection to make sure the fins aren't warped in a way that makes them crooked. If they are, then this won't be flying at Mudroc. If the fin can is good, then I'm still on track to fly on the 14th.
I do think that this fin can shape, with the swept fins and scalloped leading edges is somewhat uniquely susceptible to warping. If the fins weren't swept back, or there was a more conventional front end I think it could be printed with less risk of warping.
