Day off and weather not conducive to painting… well, then, start another rocket instead, right?
I started on Patrioony today. Aside from the shape of the fins and some weight I’ll have to add to the nose it’ll be mostly a standard Baby Bertha build right up until the finish paint goes on, so no need to go into a lot of details here.
But I’m doing a couple of things differently. Unlike the standard Patriot, this will have the fins offset a little past the tail of the body tube — not, obviously, sticking as far back as the standard Baby Bertha fins, but they’re back there. So I’m papering the fins, for added strength if nothing else.
Also, I’m using Kevlar for the body end of the shock cord. It’ll attach to elastic just before the end of the body tube. I’m using Chris Michielssen’s removable Kevlar technique with one slight modification:At the front centering ring, the guide straw is placed near the outer edge of the ring. This should help the Kevlar stay more clear of the ejection charge. On the other hand, to avoid a 90 degree kink in the Kevlar that could put a lot of stress on the rear centering ring, the guide straw slants in to the inner edge there. Other than that it’s the same setup, with the Kevlar tied around the motor mount behind the rear centering ring.
One potential problem with moving the front end of the guide straw to (near) the outer edge: it could get clogged by adhesive when the motor mount is installed. To prevent that I took a length of painter’s tape, stuck down one end over the guide straw end, and folded the rest in half to make a handle. As for the Kevlar I fed it back through the motor mount tube to keep it out of the way for installation:As soon as I pushed the motor mount into place I pulled the tape loose. Then I set the tube on its front end, partly to apply a fillet to the rear centering ring and partly to discourage epoxy from running into the guide straw at the front:
So that’s curing, the fins are curing and being pressed flat, and I’m done for tonight.