A video I stumbled onto. How to make foam cored molded fins.
Don’t know if you’ve seen this series of videos. Its something I’ve been meaning to get around to.
THANKS Mako! I’ll be using your method soon!
I designed parts for small séries utility véhicule using this tech some years ago. Allow to make compressive foam résistant with médium to low density easily than with syntactic foam. Some molded Windsurf and know paddel boards from starboards, the tough ones, are made like this for long time. Nsp too use foaming glass reinforced resin. It´s an effective way to go for some sandwich skin. I use it with success those last years. Still searching the best way to go.
I’m sure some folks will be surprised to learn that high density foam fins came on the scene about 1960 +/-. They appeared on major label customs, as well as the ever present popouts of the day. In 1959 Velzy&Jacobs were even making balsa boards with hollow glass fins, made in a clamshell mold. Yes, they leaked. You’d see boards with several inches of water sloshing around inside the hollow fin, sticking out of the trunk of guys surf cars. Surf racks had not yet come into vogue.
Been there, its a bit fiddly and its difficult to get all the tiny air bubbles out, and rear-fins are a bit diffdifficult workiworking with a double mold.
My best advice for side fins is to use a pane of glass to put on top when the resin is curing, this gives a flat surface and you can use ryv silicon as the shrinkage of the resin wont distort the fin.
I found the whole process quite annoying but maybe thats just me. It would be far better using a vacim chamber too to eliminate the bubbles. However i did get some half decent fins from my experiments. But in the end not worth the hassle.
Sorry for the typos, using my phone to post! Im sure you can work out what i was trying to say.