I'm actually super stoked about the fin bases and they took me a while to get dialed in. It's mostly done with a cnc router. Long process short, I carve out a pocket on one side of my piece of wood, fill it in with casting resin mixed with milled glass and cabosil, sand it flat, flip and carve matching pocket on opposite side, fill again with casting resin mixture, and finally cut both sides of the complete fin and base. It's a significantly longer process than is probably required, but it gives the best results.
I made a base mold that I used for my first few fins. I routed a mortise into a 2x4 slightly bigger than a normal fin base. Then I carefully cut along one side of the mortise to make a split mold. Seal up the edges with tape or plastic wrap and clamp the halves together. Dump in a thick resin mixture and place your fin in as straight as possible. Impatiently let it cure because you are so stoked on your new fin. There is a lot more hand shaping and sanding to get the base to fit into a box this way, but it is a very easy way to make a base. If you aren't into mixing your own resin concoctions, I've had a lot of success using automotive filler like as long as you use the ones with fiberglass mixed in.
You can also check out wavewasters on YouTube he had a video for making silicone fin base molds and an accurate jig for setting fin cant. I hope this helps!
Thanks, how do you get your fin base out of the mortise? Doesn't it stick?
It's a split mold and I use tape or plastic wrap to "seal" the mold so it doesn't stick. Tape is by far the better solution, but plastic wrap works well in a pinch. They also make mold release you can buy, but I've never used it. Check the older threads because chipfish and plusoneshaper had several threads discussing base molds for fins. Everyone seems to have their own pefered way. A wooden split mold is definitely on the low tech end of some that people here have made.
I'm pretty sure they make a mold release that is an aerosol spray can as well. Have seen the stuff at a supplier.
That which can be assorted without evidence was read in an illegal magazine.
1/8th" G-10 + 3 layers of 1/8th Aircraft ply to get a 1/2" thick at the base.
The same here. Today I bagged this twin fin. Carbon + 2 x 4oz + plywood and 2 x 3mm g10.
Some brilliant creativity going on in this thread. Nice work guys!