Build/paint progress and simulation refinements

I've made quite a bit of progress on EM-SEM-FITY in the last few days. I applied car primer to the booster section and found a few more rough areas. I allowed this to dry then sanded down the remaining asperities. Tonight I applied the final coat of primer and that's drying now. Tomorrow I'll spray the booster and part of the nose cone glossy white and allow them to dry/cure overnight. Then on Thursday I'll apply the vinyl decal and at least one layer of clear coat to seal the decal and maximize gloss overall.

Now rewinding back to last night I fully assembled the rocket including an M1939 reload to determine an optimal amount of nose weight to yield a static stability margin of 1.65. This turned out to be 25 oz of led and epoxy in the nose tip. I butted the nose cone against the wall as the center of pressure and center of gravity are measured and reported from the nose tip. The wall makes it easier to use a tape measure:

Here's the technique I've always used to determine the amount of lead shot required for good stability. This allows easy addition of shot to the bag and the position provides and accurate static moment:

In addition to ensuring an optimal amount of nose weight I also recorded center of gravity and overall mass measurements that allowed me to further refine my RockSim design and simulations. That program does a pretty good job of calculating starting points for component mass and center of gravity but you really need to override both with measured values to generate the best simulations.

Here I've built a bulkhead for the nose cone, fit it into the shoulder, and applied 15 minute West Systems epoxy thickened with colloidal silica. This increases viscosity and prevents the epoxy from running down gaps around the disc while curing:

Tomorrow I'll add a single wrap of carbon fiber/epoxy to the inside of the shoulder to strengthen it and render the bulkhead impossible to extract.