Epoxy Putty Recommendation for TTW Fin Fillets

My cuts through-the-wall on a 6" dia. Blue Tube weren't so precise, and I have up to a 1/8" gap between the 1/4" thick wood fins and the body tube. I've used Loctite Epoxy Putty Stick before, but I don't like the 5 minute work time.

What is your recommendation for an epoxy putty that won't sag too much into the fin/tube joint, and also gives me a longer work time for the fin fillets than 5 minutes? Weight of the putty really isn't an issue, as I'm already quite a bit overstable. Thanks!

Mike Momenee
TRA#12430 L3

Apogee sells "Fixit epoxy clay" here:
https://www.apogeerockets.com/Build...y_Clay?zenid=b4e28786172c3f040ecd42462f47dd28
It has a one to three hour cure time, and a little alcohol on your favorite tool will give you nice fillets.

You might be able to find it cheaper elsewhere....

I know that I type slow, but eight minutes to post a link and type two sentences?

Thanks fellas. Fixit Epoxy Clay is leading 2-0. Never used it, but I'll be ordering some from Santa.

Mike Momenee
TRA#12430 L3

Personally I'd just use RocketPoxy. With 45 min cure or so it reaches a putty state. Use it to fill gaps. Then go in with a next mix and about 20 min cure and pour the real fillets with the same stuff.

Using clay for the entire fillet will be a sanding nightmare. I'd use it as little as possible if at all, and epoxy fillets over whatever fix you do.

Id personally epoxy the roots in using a fin jig to hold them in proper place, then tape the outside and fillet the inside with epoxy, then fillet the outside with epoxy normally

I'd go with the Rocket Poxy...I've been meaning to use it sometime, here is the forum thread, look at post #64

https://www.rocketryforum.com/showthread.php?68818-WildMan-Sport-build-instructions-thread/page3

I'd be tempted to forget the clay and just lay a piece of 3oz glass cloth over the gap and slather it with any suitable layup epoxy (West, Aeropoxy, US Composites). Then fillet as usual - RocketPoxy is a common choice. The clay is a PITA to sand, and I think things will end up stronger if you glass the joint.

I just used rocket proxy the first time on a 3" fiberglass Tomahawk. I had drilled holes in the fin slots to give access for internal fillets.

The Rocket Poxy covers the holes and made beautiful fillets all in one shot. No sagging what some ever. This stuff is my new favorite. The kit I got from Wildman a year back included several colors of dye too. Amazing that a few drops of black in 20 ml was all that was needed.

In the end, no sanding and no painting required, just awesome glossy black fillets.

Yea forget the fixit epoxy clay, it's pretty brittle. Rocketpoxy is what I'd use too.

US Composites 635 Medium 3:1, mixed with enough colloidal silica to make a peanut butter consistency. Used it on every single build to date without any issues whatsoever.

Aeropoxy 6279 epoxy structural epoxy. Very thick and strong

I have, and therefore use, a lot of West 105/205. For this application, I would mix a batch and let it setup to near peanut butter (or use silica 405) and fill the gaps then fillet as normal.

Another vote for RocketPoxy. Easy to mix, easy to use. Forget the clay stuff... it doesn't seep into the crevices, and sanding it is a nightmare.

Thanks again, fellas.

Mike Momenee
TRA#12430 L3

Whenever I use thickened epoxy I brush the area first with freshly mixed unthickened epoxy so it can penetrate and bond. Then I apply the thickened epoxy to the area. I believe the unthickened epoxy allows a good transition.


Steve Shannon

30 minute epoxy with fine sanding dust from my belt sander mixed in has worked good for me.

Steve Shannon said:

Whenever I use thickened epoxy I brush the area first with freshly mixed unthickened epoxy so it can penetrate and bond. Then I apply the thickened epoxy to the area. I believe the unthickened epoxy allows a good transition.

Click to expand...

I've seen this recommended in several of the epoxy systems, painting laminating epoxy on before laying down the heavier stuff.

Good tip, I had forgotten!

System Three line of products are outstanding. I use the Epoxy putty and paste on the supersonic classroom demo rocket that broke Mach 1.35 - pretty solid stuff. Easy to sand and takes primer/paint easily.