First time builder - Rocketpoxy alternative?

The Rocketry Forum

Help Support The Rocketry Forum:

This site may earn a commission from merchant affiliate links, including eBay, Amazon, and others.
No. Completely different. Rocketpoxy is the easiest epoxy to use that I've tried. JB Weld is one of the hardest, I only use it for motor retainers because it is heat resistant.

Hi @DaHabes and anyone else who wishes to respond,

But is BSI a substitute for RocketPoxy? I hope so. I would order RocketPoxy. Since it is out of stock, however, I cannot.

Stanley
 
This is for any brand epoxy. 5 minute is the weakest, will become brittle over time and does not soak into wood as well as the longer working times will. Finishing resin is thin, great for doing glass work. 30 minute is kind of all around usage. You add additives to make any epoxy thicker, but it will weaken the glue. I do not like any of these for fillets, but they will still work.
 
Is there a consensus of opinion on this important issue? Is JB Weld a good substitute for RocketPoxy?

I have decided to go with BSI — mentioned above in Post #2 — which I find out stands for Bob Smith Industries. I can get it on Amazon.
I think the best alternative is West Systems six10. It is thixotropic (stays in place) and really easy to use.
 
Epoxy that is best for composite matrix, i.e. in fiberglass, carbon fabric, etc. will be more rigid than what's best for gluing. With glue, a little flexibility increases the peel strength. I think stuff like West 105 is enough of a compromise that it can work well for laminating, but also as glue with the right fillers in it. I've built a couple of boats with Raka and I think it's pretty good stuff and possibly very similar to West. Both companies have some specialty epoxies which are different. Raka is cheaper but does not have the extensive collection of information and advice that West has.

Some epoxies will hold up to high temperatures better than the regular West or Raka, particularly after post-curing, where they are subjected to somewhat elevated temperatures. Regular West and, I presume, Raka, can soften in a closed car on a hot, sunny day. That's why so many homebuilt composite airplanes are white.

Glue only has to be as strong as what it's holding together, so I think there's a place for the 5 minute stuff. I think some 5 minute epoxies hold up better than others, but I don't remember which ones. I try to use slow epoxies for most things.
 
Sir, I have BSI in 15minute and 30 minute, JB weld, West Systems 105, West Systems Six10 thixotropic, big bong 5 minute and 30 minute with the mixer nozzles like @Hobie1dog g uses, and plain ol' 5 minute epoxy.

Anything will work within reason. The slower the cure, generally the better the bond, but there is much more to it.

The bonding surfaces prep, matters at least as much if not more than the epoxy itself.

If you go to west systems website you can sign up for and read old E-issues of their magazine on how and what to use their products for and when.

If you search out @JohnCoker www.jcrocket.com you will learn a ton. That dude is sharp as a tack.

This place is full of extremely intelligent, interesting people, almost all of whom are kind and helpful as well.

Don't be afraid to ask questions.
If you want heavy education, search the L3 build thread. It is full of peoples builds for their L3 projects,
with years and years of experience, laid out so you can see how and why they are successful.

The type of epoxy does matter, but technique matters much more, (5 minute stuff breaks pretty easy take a skip on it, except for little fiddly stuff)
 
I once ran across some 5 minute epoxy that was quite strong, but I don't think I've seen anything else like that since. It held the bridge of my glasses together for weeks after a flaky hockey incident.

I should think even the biggest bong I've ever seen would be a fairly low stress application. Do Asian companies have hilarious names and trademarks as some kind of of marketing gimmick? If so, does it work?
 
This is for any brand epoxy. 5 minute is the weakest, will become brittle over time and does not soak into wood as well as the longer working times will. Finishing resin is thin, great for doing glass work. 30 minute is kind of all around usage. You add additives to make any epoxy thicker, but it will weaken the glue. I do not like any of these for fillets, but they will still work.
Somewhere in my "Epoxy Resins" book is a table of additives and the resultant strength. I *think* that aluminum oxide was one that increased the strength. IIRC fumed silica---Cab-o-Sil---doesn't weaken epoxy significantly, but it has to be mixed in *very* thoroughly. Either use slow epoxy or mix the cab-o-sil into the resin first, then add hardener.

And it's moot regardless. Almost any epoxy is much stronger than is needed for rocketry. Exceptions: most 5-minute epoxies don't soak in much before they gel. And for an extreme project, say a min-dia M, go to the people who have done it successfully and use their suggestions.
 
Just found it. Granted this book is almost as old as me, but...Shear strength of epoxy without filler, 2760 psi. With 100 parts aluminum oxide to each 100 parts resin at 25C, shear strength was 3750 psi. At 105C the unfilled resin was 450psi, the filled was 1650psi, almost four times the shear strength(!).

A different table gave modulus of rupture(?) in psi. Unfilled epoxy was 18kpsi. With fillers silica (sand) 16.8kpsi, flint powder (different sand, but purer)17.6kpsi, quartz (even purer sand) 14kpsi, kryolite 15kpsi, portland cement 14kpsi, and atomized aluminum 14-15kpsi. There were other fillers that were worse but I have no idea what Surfex MM or albalith is, and no one is interested in asbestos filler anyway.:eek: FWIW every tested filler reduced shrinkage from the unfilled resin. To be expected as the filler itself won't shrink.

Also FWIW any metal filler will reduce shrinkage and increase thermal conductivity, if that's of interest.

Point is that yes, 14kpsi is less than 18kpsi, but in the scheme of most rocketry that's unlikely to be significant.
 
I have to agree 100%

I also just purchased a gallon kit of U.S. Composites laminating epoxy. So far, I have had good results. Less expensive than West Systems or Aeropoxy PR2032 for same amount of resin and comparable quality. I still like Aeropoxy ES6209 for structural work, as well as Hysol EA-9462. JB Weld for attaching motor retainers, though I just installed a motor retainer with the Hysol and we'll see how that holds up.
 
I also just purchased a gallon kit of U.S. Composites laminating epoxy. So far, I have had good results.
I've had good results using U.S. Composites epoxy as well. Although, I do/did prefer the ease and convenience of using Rocketpoxy and waiting a few minutes for the desired thickness over adding thickening agents to laminating epoxy.
 
Back
Top