Strengthening fins

[captbk]

I was wanting to beef up my Doorknob fins and came across this super thin fiberglass sheet. It is easier to apply than cloth and it's smooth finish eliminates lots of sanding. I was wondering if anyone else has used this instead of paper.

 

[Lee]

I am interested to see if this works. I have 4 door knobs, have only flown one. Each flight results in fin damage. So far, I've papered, coated with CA, trimmed the bottom edge of the fins up about 20 degrees, and elongated the MMT to bear landing impact. Collectively these have all helped but are not the total solution.

 

[tsmith1315]

I was wanting to beef up my Doorknob fins and came across this super thin fiberglass sheet.

I'm very interested to know how flexible that is. I have a couple of transitions, and maybe fins, I expect to build using ribs/skins. Sound like it might be great for that.

I have some that's paper thin (0.003"), too thin for what I want, and haven't tried it as a balsa fin covering yet. Not sure if it can be sanded well enough for adhesion to a full fin surface at flight speeds. But it's a good electrical insulator between components in an AV bay.

 

[grapetang]

Electronic printed circuit boards (PCBs) are made from multiple layers of this (dyed green). At 0.015", it has a little flex though the thicker laminates are stiffer. I believe it's a thermoset and not a thermoplastic so it cannot be reshaped with heat. It can be sanded, filed, cut, drilled, machined, etc. By itself, the FR4 may be a little "soft" and can be scratched/cut or drilled through with an X-acto.

If the fins were made with 0.063" PCBs with or w/o the copper layers, the fins will be incredible strong but heavy.

It is epoxy/fiberglass so proper surface prep should get it to stick. It may not work for transitions unless the transitions have very large diameters. It almost seems like this material would work better for a thin fin core with balsa sides + paper skins.

Just my 2 cents!

 

[MidOH]

Neat vendor.

10 feet of 1/8" is $150. To put that in perspective, a Loc4 plywood fin set is $20.

10 feet of .060 (just under 1/16") is $125-ish.

10 feet of 1/4" is $260.

10 feet of 1/4" plywood is $100.
https://sigmfg.com/collections/plyw...ood-1-4-x-6-x-12-5-ply?variant=12308946550862
Might be a good idea to just switch completely to fiberglass fins. I scratch build a lot, and balsa keeps coming in warped. And plywood isn't exactly cheap. Laminating cereal boxes is ok for wee little rockets.

I see no reason why I can't bond fiberglass fins to a paper tube?

 

[heada]

https://www.launchlabrocketry.com/shop/p/vanderburndoorknob29mmupgradekit

 

[krislhull]

https://www.launchlabrocketry.com/shop/p/vanderburndoorknob29mmupgradekit

I will second this… I just built my Doorknob and used the Vanderburn upgrade kit. Makes for a rock solid bird. I am already planning on a second one with the Rocketry Works 38mm upgrade kit this time

 

[maverickrocketry]

blow up doll material?

 

[tsmith1315]

I was wanting to beef up my Doorknob fins and came across this super thin fiberglass sheet.

Have you tried this yet?