jb weld vs epoxy vs others

[watermelonman]

I have an anodized aluminum part that specifically mentioned JB Weld for adhering to a body tube. Any reason to use JB Weld over this?
https://imgur.com/DFUdx5j

What about across the rest of the rocket build, any reason to prefer or not use the 5m epoxy I currently have? Also, what about CA? I barely know what it is except by acronym.

 

[DizWolf]

I'm assuming it's an aeropack. In which case you'll want to use JB weld for the heat resistance.

As for the build, it depends on materials, and stresses/speeds you expect. There are many opinions on this. I like using Aeropoxy ES 6209 for many builds. It's great on fiberglass and bluetube. I use it on cardboard and wood, but really wood glue is lighter and makes a joint that's likely to be stronger than the tube/wood. Proline 4500 is great for fillets and cures faster than the aeropoxy I use. Rocketpoxy is also great for many applications. I'm not as familiar with it, but west systems also gets great reviews.

5minute epoxy will work just fine for many rockets. It just doesn't have as high a strength as some other epoxys, and once you start buying it in quarts and gallons the options really open up for specialized properties.

 

[watermelonman]

Yes! Well not an Aero Pack, but it is a motor retainer of sorts. Thanks for the recommendation; I did not realize that JB Weld had higher heat tolerance. I will pick some up tomorrow and likely use the 5 Minute Epoxy for the rest of the rocket.

When you say this epoxy does not have as high of a strength, what sort of magnitude are we talking about? I assume mid power and L1 rockets would be fine. What about L2 or the L3 monsters?

 

[DizWolf]

There are guys that have used wood glue or 5 minute glue for L3's. All depends on how you use it. Large rockets are actually less likely to see high stress in some cases.

Each glue is different, but I find most 5 min/hobby shop epoxies to cure fairly brittle. Aeropoxy not only holds more stress, but has a little bit of flex to it.

Here's an excellent comparison John Coker did: https://www.jcrocket.com/adhesives.shtml

My L1 was done with a mismatch of 5 minute and 30 minute epoxies. Been on 16 flights over 3 years and still holding together.

 

[JeromeK99]

I wouldn't use 5 min epoxy for that application. As stated above it is a bit brittle and over time it might not hold up a well as other varieties. A 30min hobby epoxy should do the trick just fine and be usable for most of your other epoxy gluing needs. JB Weld is just plain overkill. Better heat resistance? Sure, I'll give you that... but what about your cardboard motor tubes? Wouldn't they be subject to the same heat? They are not bursting into flames from normal flights. What about fiberglass tubes? I've seen body tubes melt from sitting in the sun too long at a launch. Now the flame of a rocket motor even BP can burn a hole in a steel plate! But your retainer isn't in the line of fire. For big motors, you need to raise the rocket up on the guide and perhaps not use a flat plate that is perpendicular to the guide.

You can definitely use JB Weld. I'm not saying don't. I'm just calling "BS" on the absolute need to.


Jerome

 

[DizWolf]

The retainer is metal and holding the metal case. It will hold heat better than cardboard. It's a good idea to use high temp epoxy on them, and aeropack recommends it.

Can you use other epoxys? Probably, but it may not hold up as long. I used it on retainers, not entire builds.

 

[watermelonman]

I picked up some JB Weld from Home Depot today. I plan to use it on the metal retainer, 5 minute on the other mixed material joints, and simple wood glue for any cardboard to cardboard connections that might remain. Does that seem like a good plan? I do not yet have any 30 minute or aeropoxy though I would get some if it made a big difference.

 

[DizWolf]

Sounds like a good plan.

If if keep building, bulk epoxy like quarts of aeropoxy actually SAVE you money over the cheap stuff.

 

[4kids49]

I picked up some JB Weld from Home Depot today. I plan to use it on the metal retainer, 5 minute on the other mixed material joints, and simple wood glue for any cardboard to cardboard connections that might remain. Does that seem like a good plan? I do not yet have any 30 minute or aeropoxy though I would get some if it made a big difference.

I use JB Weld on my retainers. Keep this in mind. Whatever you use on cardboard, the cardboard is the weakest link. I had a JB Welded Aeropack retainer on a cardboard motor tube blown off in an over pressure event. The cardboard gave way, and all of the JB Weld was still stuck to the retainer. This probably saved my rocket from worse destruction.