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This fiberglassing method came from trying to flatten a set of warped
fins. I had tried, steaming and pressing but the warp always came back.
Also was tired of filling the grain on Quest/Estes balsa fins, the best I
had found for them was UPS shipping labels, they stuck well and are
strong, but this is just as quick, light and is stronger.
The first thing needed is a way to apply pressure, I have a 12 ton
hydraulic press, but it could be done with 8 big c-clamps (2 on each side)
or a $15.00 2 ton bottle jack under a car? The next piece is two strong
flat pieces of material, mine are Formica counter top scraps about 18
square. Foam rubber to distribute the pressure evenly and roll the glass
over the edges of the fin, and release film, I use backing film off of
window tint (because its free) others have used wax paper.
Trim and sand the fins the same way you normally would. Cut the
fiberglass with about 1/4 extra on all sides. Cut two pieces of foam
large enough for all the fins to fit with 1/2 between them on one piece
of foam. Cut a piece of release film bigger than the two pieces of foam.
Take one of the wood plates, center the foam on it and the release film,
test layout the fins to see how they will lineup.
Now mix up some finishing epoxy and paint it on the fins, smooth the
glass over both sides of all the fins. Arrange them on the release film
over the foam.
Fold the release film over the top of the fins. Add the second piece of
foam and the top wood plate.
Line every thing up and apply pressure, with the press I use maybe a
1/4 of its capacity crushing the foam completely over the fins.
Allow the epoxy to at least jell, if the fins were warped allow it to
cure. Relieve the pressure and remove the fins, trim and sand the edges
and you have flat, smooth and very strong fins.
I use this method for all of my rockets now. The first time I tried
this I used too much epoxy and had puddles pushed out of the foam and
cured in the release, now I use just enough to wet out the glass. For
small balsa fins I use one layer of .75 oz. Glass and thin the epoxy with
about 5 percent acetone so it is nice and runny, makes a very light and
very strong fins with less effort than the old sand and fill method.
My 24mm Fat Boy suffered a separation on an E-9 flight the airframe hit
the desert with a thump and bounced 6 up again, no damage due to one wrap
of .75 oz glass on the inside of the body tube (I only did it because the
nose cone fit loose) and on the fins.
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