30 minute epoxy okay for through wall fins to engine tube?

[Tom]

Title pretty much says it all.

I am working on an Estes "Star Orbiter". It has through the body tube wall fins that get glued directly to the engine tube. I am just a little worried about the heat. Don't really know how hot the outside of the engine tube gets.

Or is JB Weld in order?

BTW it is for F motors (and maybe more).

 

[Titan II]

30 is fine.

 

[Tom]

Good, lol it would take 2 or 3 days for jbweld. I have to set the fins one at a time.

 

[Bat-mite]

I never use JB Weld on anything except the retainer body to the MMT.

Make sure all surfaces you want to bond are sanded!

 

[markg]

I am working on an Estes "Star Orbiter". It has through the body tube wall fins that get glued directly to the engine tube. I am just a little worried about the heat. Don't really know how hot the outside of the engine tube gets.

For wood fins and cardboard MMT, wood glue works. I use Titebond on all my cardboard rockets, including a 3" cardboard one with a 38MMT that flies on Loki 38mm G motors. 30 min epoxy would be fine as well.

cheers - mark

 

[dr wogz]

Tom,

The longer the cure time of the epoxy, the more time it has to seep into the cracks, crannies & crevasses to get a good bond. The downside, is that this also allows more time for it to ooze & flow out of the areas you want it in.. And, while 30 minute is "set" in 30 minutes, it isn't fully cured for at least 12-24 hrs..

Orient it so that it stays put / pools where you want it. I will do a set of fins a night, so a 4 fin rocket will take 4 nights.. (And an additional 4 night for internal fillets..)

I'll 2nd Mark's comment, that for wood & paper (and this size rocket) wood glue is suffice.

I either case, make sure the surface is well sanded & scuffed up. The rougher the 2 mating surfaces, the better the glue will do its job.

Save the JB weld for metal connections, and where you want / need high temp resistance. (Yes, the motors get hot, but it's only for a very short time..)

 

[neil_w]

I'm mostly using BSI 15 minute these days rather than 30 minute. The quicker cure time is immensely helpful, but I still think I'm getting good strength in my LPR/small MPR applications. Also, BSI rates its 15 minute variety as its most flexible, which seems generally beneficial.

 

[Nytrunner]

30 minute will be fine for the Star Orbiter. (my chunky L1 in the pic below used only 5 minute, and a corner of the fin will snap off before the fin comes out.

Echoing the above, I use wood glue on cardboard/plywood rockets now, including my chunky L2 (also below)

 

[Tom]

Interesting that some of you chose wood glue over epoxy. Thanks!

I had already done the epoxy though, worked well except I flubbed the fillets today

That's another thread....

 

[neil_w]

Although I commented about epoxy (which I use for some things, sometimes), I too would be using wood glue for a paper-and-wood rocket.

 

[jqavins]

Interesting that some of you chose wood glue over epoxy.

Many of us overbuilt. An E30's maximum thrust, for example, is 11 pounds, so during thrust no part of a rocket powered by one will see more than 11 pounds force. If you had attached these fins with wood glue then hung 11 pound weights from them, would they stay in place? You bet they would! A tough landing can subject a fin to higher forces; frankly I'd rather the glue joint fail than the wood; a joint that's less than bullet proof protects the wood, like the fuse in electrical device protects the wires.

 

[Tom]

I was mainly concerned about the heat and it's impact on the adhesive. I guess the engine tubes don't get that hot after all?

Or does wood glue stand up just fine to moderate heat?

 

[neil_w]

What seems to get hottest are long-burn reloads. @mbeels lent me an F20 reload and that was quite toasty after the flight. BP motors don't get very hot, nor do typical SU motors in my experience. And wood glue *does* stand up to moderate heat just fine.

 

[mbeels]

Yes, I either 30 minute epoxy or wood glue would be just fine. As neil_w said, wood glue tolerates heat quite well.

@mbeels lent me an F20 reload and that was quite toasty after the flight.

(F12 actually) Yeah, the metal casings of reloadables conduct heat well and get HOT!

 

[jqavins]

Where the thick rolled paper tubes of BP motors don't.

 

[Tom]

Thanks for the feedback everyone.

I ordered another Star Orbiter since I botched the fillets on the last one. This time I will use wood glue for most everything except setting the motor tube, and the plastic retainer.

I prefer the ease of use and clean up with wood glue.

Thanks again.

 

[Nytrunner]

ah, the metal casings of reloadables conduct heat well and get HOT!

\But for motor certification they can't exceed a certain temperature threshold. I don't recall that limit, but it's lo enough for our glue needs

 

[Steve Shannon]

\But for motor certification they can't exceed a certain temperature threshold. I don't recall that limit, but it's lo enough for our glue needs

Exactly! And that’s the surface temperature of the case. It still has to transfer through the MMT.