Large Fin Construction

Getting ready to build some really big fins for the Balls project. 24" root, 24" span & 12" tip length. Max speed around 400 MPH.

I'd like to keep them as light as possible and don't want to spend a lot of money as I'm pretty sure they'll end up being single use fins.

I'm currently thinking about a grid of 1/4" birch plywood spars, filling it all with foam, then wrapping the whole thing in 1/16" G10. Gonna make a rough air-foil shape out of it to give the structure as much rigidity as possible.

Any recommendations or ideas are very welcome.

Thank you!

Peter

What about sheet foam, fiberglassed/kevlared/carbon fibered?

blackbrandt said:

What about sheet foam, fiberglassed/kevlared/carbon fibered?

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+1. I'd think about a foam core with a glass overlay. How much sweep do you have? The more the better. I guess the better question is what shape are they?

Here's a quick sketch of the fin profile. These will be surface mounted, bolted to a welded steel frame, so the root has to be pretty strong. Other than that they just have to last for the ride.