Ok, with the tail cone fins fixed and foamed it was on to the booster fins. We had a couple of assembly challenges:
- Rail button placement
- Alignment of tail cone fins with forward fins
- Length of the rocket relative to the fin jig
- How to set internal fillets on the forward fins?
I'm sure there's different ways to solve these build issues. Here's how we tackled them:
We first fit the tail cone and booster sections together but not completely. There was enough room in the gap between the two sections to fix a 1515 rail button using a T nut embedded in wood through the tube wall. We did not epoxy the forward centering rings at this time.
When we fixed the tail cone fins using the fin jig we had also dry fit the forward fins in the booster section so they would be aligned. We placed tape across the seam between the tail cone and booster section which was then cut at the seam with a razor blade. By numbering each of the 3 sections of tape we had a way of realigning the airframe tubes for the final assembly.
We then ran a thin layer of epoxy around the tail cone connector tube pushed the sections together and made sure to align the tape markings. We placed the airframe back in the fin jig, dry fit a forward fin and clamped everything in place to ensure a straight and tight fit.
Because we had to widen the forward fin slots a space was left to run epoxy along the centering rings and airframe wall. So, we were able to make internal epoxy fillets without any additional drilling of holes.