AeroTech Fins and Adhesives

marvSRG · Jan 28, 2004

I know that in AeroTech kits, the rockets are constructed primarily with CA, and the fins are also glued to the "interlock" rings on the motor tube. The CA used in fin construction works very well with the much added strength of the interlock rings. But this is only in AeroTech kits. I plan on using some old AT fins that I had in a rocket that is constructed mainly of phenolic, cardboard, and plywood. Normally in such a rocket you would have plywood or fiberglass fins, and the rocket would be assembled with epoxy. But here is the problem: CA is the only adhesive that I know to work with plastic and cardboard/phenolic, and therefore it's the only thing I know to use in gluing these fins on. But although CA works very well, and is very strong, when it's used in fin attachment on a bird that doesn't have the AT fin attachment parts, and one that's intended to use low range HPR motors (mainly H's), I don't think that it is strong enough by itself...on AT kits the interlock tabs help tremendously, and to add, they fly mainly on midpower motors. But this is HPR with no AT parts. Any stronger adhesive reccomendations? I have tried epoxy, and it doesn't work that well, as epoxy really isn't formulated to adhere to plastics. With just a little strength, I could pop the fins off the rocket I tried that with...I'm just glad they held on for the flight. Any reccomendations??

Rocketjunkie · Jan 29, 2004

Rough up the gluing areas good with 60 or 80 grit sandpaper and use epoxy.

LarryH · Jan 29, 2004

The gel type epoxy(you know the stuff that comes in two cyringes?) works extremely well with plastic(not nylon, but most other plastics), in my own experience with the gel epoxy Ive never even had to rough up the surface before it would adhere. The downside to this is that it's fairly long cure... the stuff I have takes eight hours to fully cure, also it's very runny before it's cured, what I would do in your situation is glue the parts in place with CA, and then add gel epoxy fillets.... be forewarned however, this is the advice of a newbie to HPR, and for that matter it's free...... and worth every penny you paid for it!

marvSRG · Jan 29, 2004

Thanx for the replys so far. Larry, on my first attempt I tried the epoxy that comes in the two cyringes...but there are many brands that come that way. I was just using Devcon 5 minute...what brand and type were you using? I also agree with the CA first. That's what I was going to do anyways because it's really good for securing what you're working on before you put on the strong stuff. Thanks for the tips! And Tom, I'll try roughing it up a bit with sandpaper. I'm guessing this is allowing the epoxy to settle in the small holes and roughed out spots from the sanding, causing it to cling to that? Thanx again.

LarryH · Jan 29, 2004

Devcon high strength 2-ton epoxy is what I'm using, it has a full cure time of 8 hours, 30 minute working time and 2 hour handling time, It's possible that where you're going wrong is that you picked a quick cure epoxy, I've seen mention on this forum a few times that quick cure stuff will sometimes not bond correctly with certain materials.

Just out of curiosty how much pressure are you putting on the fins to get them to pop loose? I think if you pull on any rockets fin hard enough it's gonna come off, if you're getting the fin loose with just finger pressure then I'd say you have to look for something a little stronger..... again just my opinion, but it could be you're worried over nothing.

loopy · Jan 29, 2004

I can't remember the name of it, but I use an epoxy that comes in a dual syringe with blue plungers, typically. It's about a 15 minute working time, and about a 30 minute cure. I use it for all my fillets on my Aerotech kits, and have had no problem with adhesion to the fins, even without roughing them up first. I wish I could remember the name of it...it's readily available at Meijer...

Loopy

rbeckey · Jan 29, 2004

If the fins are through the tube to the motor mount, drill a row of small (1/16) holes in them near the root edge, and rough up the surface with 80 grit sand paper. I would suggest a long cure epoxy, like Bob Smith 2 hour. When you make the fillets the epoxy will flow through the holes and adhere to the roughened plastic quite well, forming a strong bond.