Cherokee-M Construction - Fin lamination
June 23 - 29, 2003:
The goal here was to smooth out the external fillets to give the carbon cloth a nice even surface to lay down against. The external fillets on the fin-body tube joint was made with Aeropoxy (R2032 Resin and PH3660 hardener) thickened with West Systems 404 high-density filler and reinforced with kevlar pulp. The basic shape was there, but the surface was still pretty rough. I took down the worst of the sharp peaks with a file, but this stuff is so tough that a file wasn't going much deeper (sandpaper is right out). And anyway, the point isn't to reduce the size of the fillets by filing them away, the point is to fill in any voids and pits to produce an even surface for the laminating cloth to adhere to.
What I did was spread a layer of Superfil, a lightweight, low density, epoxy-based filler, on top of the epoxy and kevlar fillets. When the Superfil had cured, it was easy to sand it down even with the top of the original kevlar fillets. This leaves the full strength of the kevlar fillets with Superfil in the low spots to give a nice even surface for the laminating cloth to lay down against.
Finished fillets:
Close up of finished fillets. The epoxy-kevlar structural fillets are yellow, the Superfil is blue:
