Fiberglass Over Expanding Foam?

I have a HPR that had a fin break off. I cut a small square out of the body tube to allow me to cut the fin off with my dremel tool. I have a new fin put in, and used expanding foam to fill the gap. I'm now planning on just tip-to-tip fiberglassing the rocket, and was hoping to just shape the foam to the body and apply the fiberglass right over it.

Anyone done this before?

Can the cut-out window not be replaced?

lvgdgts said:

Can the cut-out window not be replaced?

Click to expand...

Sure, just would be easier if I could skip that step.

Before you lay the glass over the foam, mix some microspheres with resin to make a slurry and apply it to the exposed foam surface with a squeegee.

Apply the glass over the foam surface before the slurry hardens.

Microspheres:
https://www.aircraftspruce.com/pages/cm/fillers/bubbles.php

Dump the West system out and try this:
https://www.aircraftspruce.com/catalog/cmpages/htr212resin.php

This is an impact resistant resin made by Resin Services. These are the guys that make the resins to meet Boeing specs.

Have your pieces of class cut and numbered before mixing the slurry. This will make application far easier.

One last thing, Bi-Directional glass will conform to compound surfaces far better than uni-directional. If there are no compound surfaces, uni is ok but it will not be a s strong as bid.

If you use Bid, and I hope you do, lay down at least two plies and cut then 45 deg from each other. This will give you the strongest joint / surface. For a fin going Mach, I?d put at least three ply of bid down.