Saturday, July 18, 2009

Progress galore

Alright so I masked off the fins and applied the black high-temp epoxy fillets:
I had a scare while preparing the epoxy. It's approaching its shelf life of 6 months and the curative is yellowing. According to Dave Triano the resin:curative ratio is critical so he provides the former in a white cup and the latter in a syringe. I began to squeeze the syringe into the cup but the plunger stuck then slipped and splashed a bunch out onto my work space. I'm grateful that it splashed back and not into my eyes! Always wear goggles, kiddies. Since the system was aging I guessed the failure mechanism would be unintended polymerization so I chose to roll the dice and assume the ratio would work. This expensive 500F Tg resin appears to have cured correctly as the Kevlar pulp-augmented fillets seem incredibly strong.
I then cut a piece of Kevlar/carbon fiber hybrid fabric to just fit inside the perimeter of each fin and bridge the body tube. I also cut a slighly larger piece of 6 oz carbon fiber cloth to extend just beyond the first piece. I mixed up a 50g batch of Aeropoxy and added a bit of colloidal silica to prevent it from running down the fins as it cured. I also added 3 wt. % white epoxy-compatible pigment as a visibility aid. Here's the third pair of fabric layers laid up and curing:
Once I finish the fourth fin pair surface I'll post-cure in my oven to maximize strength and temperature resistance. Then begins the fun process of filling, priming, sanding, priming, and painting. Wish me luck.