Fiberglassing Plywood Fins

I have a quick question about fiberglassing 1/4" plywood fins. How do you deal with the leading/trailing edge? The obvious answer seems to be to sand the leading and trailing edges in first, and then apply fiberglass. But then how do you get that smooth finish along the edges that don't have pressure applied to them? (my guess: A) Sand/fill, B) vacuum bag)

The other answer seems to be to apply the fiberglass to the flat non-profiled fin, and then sand to shape. Then there is no protection along the leading/trailing edge, the the fin as a whole is still stronger.

This is for an upscaled version of an Estes Ventris. I'm scaling it up to be 6' tall with a 54mm motor mount, 3" lower body, 4" payload. I'm also getting a 54 to 38mm adapter, so by design, it can take anything from a 38mm H to a 54mm L. I need to re-certify L1 (NAR membership has lapsed over 15 years and I can't seem to find my old number), and hope to cert L2 later on with the same rocket, if all goes well. That's why I want to re-enforce the fins - maximize "undamaged" flyability in case of a hard landing.

I plan to choose my motors so as to stay under Mach 1. No butt-kickers in this rocket.

Build thread forthcoming once it cools off enough for me to work in the garage for extended periods of time...

Thanks!

Sand first. I highly recommend reading some articles regarding fiber glassing model aircraft. There is a ton of useful information. Check glassing the wing at this site (for example):

https://www.modelairplanenews.com/workshop-tips-working-with-fiberglass-and-resin/

Titan II said:

Sand first. I highly recommend reading some articles regarding fiber glassing model aircraft. There is a ton of useful information. Check glassing the wing at this site (for example):

https://www.modelairplanenews.com/workshop-tips-working-with-fiberglass-and-resin/

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That looks helpful. I'll give it a try and will hopefully get some good results. I'll practice on scraps also, of course.

Or John Cokers video may help.

rharshberger said:

Or John Cokers video may help.

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I saw his other video on glassing a tube and plan to do that also. I just want a single wrap just to protect the tube from deployment dents.

I have a foodsaver, so looks like I can do the vacuum bag technique with fins. I also saw another video on applying glass to high power fins, but he didn't appear to have any sort of profile on the fins.

DanielLW said:

I also saw another video on applying glass to high power fins, but he didn't appear to have any sort of profile on the fins.

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You can vacuum bag even a profiled fin. Fiberglass cloth has enough stretch for gentle curves and shallow angles.

These survived just fine. Basic rounded edges done with a foodsaver. Simply waited til it was green and trimmed it with a knife. Sand after cured and surprisingly enough, it just works. The last pic took a hi t from what was probably a quick link and survived just fine. Transonic may be a whole different world.

And: No, I did not invent the technique. Seriously doubt you'll ever discover who did. May have been the Wright Brothers..

Mr. Coker has some excellent videos on the subject. Thank You John.