I am starting this thread from my office, but hope to post a few pictures as I get started this evening.
We have been using small cupped C-5 fins and also Scimitar 451's. The Scimitar's are only available in a natural composite and it feels like those are milled fiberglass suspended in epoxy or polyester. They are exceptionally heavy.
I want to lighten the fin up, without decreasing the stiffness, so I intend to use a relatively hard epoxy and mix in some Cabosil with the milled fibers, to lighten the total mass up.
Cabosil is fumed silicon dioxide. It's my understanding that due to its inert nature, it has been used in food such as kethcup as well as in shampoo and some cosmetics. When mixed into resin, Cabosil functions as a resin thickener amongst other things. For my purposes, Cabosil, by volume, is about 1/20th the weight of the milled fibers...it's my hope that I can reduce weight without sacrificing stiffness, by reducing some of the milled fiber content and replacing it with Cabosil.
Getting back to the build, the first part will be to create a RTV Urethane mold - as first mentioned by Lakewake Mark. The result, after pour, will be an exact duplicate of the original fin, only using different materials.
RTV in the RTV Urethane stands for Room Temperature Vulcanizing. I will make a two part pour mold, rather than a glove mold (brushed on) as I did when making the high density rail foam mold.
A quick overview of the project:
1) Build a small box to hold the RTV Urethane
2) Build up the bottom of the box 1/2 way with Clay. This is important as we will remove the clay and turn the box over, to pour the second half of the mold.
3) Inset the fin to be molded in the clay, sealing the underside by pressing it into the clay.
4) Liberally apply mold release to all surfaces.
5) Mix and pour the RTV Urethane into the top of the open box and completely cover the fin being molded.
6) Wait
The RTV Urethane takes 48 hours to cure well enough to handle. Handling it too soon will distort the mold.
7) Turn the box over and remove the clay. The open cavity is now ready for pouring the second half of the mold.
8) Liberally apply mold release
9) Mix and pour the RTV Urethane into the top of the open box (which is the bottom turned upside down) and completely cover the fin being molded.
10) Wait some more.
Once the RTV Urethane has completely cured, it can be removed from the box and the fin taken out.
Clamping the two mold half's together will then form a cavity that can be filled with the resin/ cabosil/milled fiber mixture. Also, I may fill some of the core of the fin with a slightly shaped piece of corecell, which will be encased within the epoxy/fiber/cabosil mixture.
Pictures at 11
Ok, I won't stay awake that late, BUT later.
Hybrid Mode
