foam fins

[ericm541]

Are there techniques to fiberglass dense foam to create a rigid fin? Also maybe epoxying foam onto wood or fiberglass fin to shape then fiberglass?

 

[boatgeek]

You can definitely make a thicker, lighter fin by glassing over foam. If you're making something really big, you can use a combo of a sheet of plywood as a core, foam over that, and glass over the foam. Any way you do it, the technique is basically the same as if you were doing tip to tip or reinforcing sheet stock. Get the foam substrate to the shape you want, then glass over to suit.

 

[ericm541]

That's fantastic, what type of foam would be the best? I was told you can get dense foam insulation at home depot that would work.

 

[ECayemberg]

I've done foam core fins several times....J through P powered. Lighter, but more work than straight G-10 or plywood.

One such example, though it looks like Photobucket killed the images: https://www.rocketryforum.com/threads/no-thunder-a-little-bit-different.44833/ These, and a few others I made, used Gatorfoam as the core. For higher power, a layer or two of glass or carbon on the skins is helpful. I prefer to edge all foam fins with a strip of wood...spruce, pine, oak, or equivalent.

 

[AeroAggie]

Are there techniques to fiberglass dense foam to create a rigid fin? Also maybe epoxying foam onto wood or fiberglass fin to shape then fiberglass?

There are dozens of ways to make composite sandwich structure. John Coker has a pretty good tutorial that uses balsa for a core, but you can substitute foam for balsa in this example. https://www.jcrocket.com/nike-custom-fin.shtml

Blue foam from the box stores is perfectly suitable for a core material, though a little on the heavy side. It cuts easily with saws or hot wire, and is fairly easy to sand.