Composite Fin Can

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This is the first layer of carbon fiber on the "can" part of the fin can. I laid up two wraps of 6.4 oz fiberglass cloth, then this layer of carbon fiber.

Two more wraps of fiberglass cloth were followed by a final layer of the 5.7 oz carbon cloth.

I allowed the "can" to cure overnight, then sanded it with 100 grit paper to rough up the surface. The fin cores are 1/4" birch plywood. I used the same fin alignment setup used for the Prelude rocket. Each fin was tacked in place with epoxy, allowed to set, then the next fin was tacked in place.

Once all the fins were tacked in place, I filleted the joints.

I'm applying four layers of cloth "tip to tip" on each fin surface. You can see each layer in the above photo. This went significantly better than I expected. The carbon cloth is not as flexible as the glass, but it laid down and wetted out very nicely. I allowed the epoxy to gel, then heat cured it at 180 degrees F. for two hours. Heat curing does two things, it increases the finished strength of the composite and it increases the temperature resistance. Not to mention it speeds up the curing process!

Here is the first set of fins after a rough trim of the excess. With two fins only half done, it's already very strong.

The lay-up of glass and carbon fiber is done. I've done a little light sanding, but I need to putty, prime and do a lot more sanding before it's done.

Here's a shot of the aft end. There are 10 layers total (4 carbon fiber and 6 fiberglass) between the fins of 5.7 ounce carbon fiber and 6 ounce fiberglass, resulting in a material thickness of .08". The fins have 4 layers on each side for 8 layers total (4 carbon fiber and 4 fiberglass). At this point the fin can weighs just under 750 grams.