West Systems G Flex for motor mount?

[RobertC]

I did a little searching around, and can’t find the exact answer I’m looking for in already existing threads, so I figured I’d just ask y’all. I’m building a 4” LOC Phoenix for my L1 certification and I just put the motor mount tube in it last night. I just switched from BSI 30 minute epoxy to West Systems G Flex thinking the West Systems stuff was better. But now that the stuff is dry, after it’s pretty much too late to do much about it, I had the thought to look and see what information I could find on it’s heat resistance. West Systems’ site says that it can handle temperatures up to 200 degrees Fahrenheit repeatedly, and that seems a bit low to me. I used it for the centering ring to MMT bond as well as the centering ring to body tube bond. I’m just wondering if anyone with more experience than me could contribute their thoughts on whether or not it will hold up with the heat from the motor casing. Thanks!

 

[Troy3003]

I'd definitely want a higher resistance to heat at the mmt itself. A flange mount engine retainer could be the answer but someone wiser than me could probably give a more definite answer.

 

[RobertC]

I'd definitely want a higher resistance to heat at the mmt itself. A flange mount engine retainer could be the answer but someone wiser than me could probably give a more definite answer.

A flange mount retainer hadn’t occurred to me. That’s a good idea, it would move some of the load out away from the motor. Another thing that occurred to me after writing the original post is that the rocket has a 54mm MMT, and when I ordered the rocket from LOC, I ordered a 38mm motor adapter with it. I could assemble the 38mm adapter with JB Weld and just fly it on 38mm motors. That would give me a little air gap in between the adapter MMT and the main MMT to help keep the heat away from the main MMT. I would still like to have the option to use 54mm motors one day, but that’s assuming that it comes back in one piece on the first shot I suppose. Thanks!

 

[Troy3003]

You may not have issues at all with the way you built it. I just am not real sure if the flex epoxy would break down quicker.

 

[Steve Shannon]

Your epoxy will be fine. The outside of the motor mount tube in the centering ring area really doesn’t get too hot or stay hot for too long for most motors. If you’re like most of us you’ll probably crash or lose the rocket long before the epoxy shows any sign of degradation.

 

[cwbullet]

Your epoxy will be fine. The outside of the motor mount tube in the centering ring area really doesn’t get too hot or stay hot for too long for most motors. If you’re like most of us you’ll probably crash or lose the rocket long before the epoxy shows any sine of degradation.

Isn't that the truth.

 

[RobertC]

For some reason I wasn’t getting notifications in my email about this thread. Thank you all for your input! Makes me feel a lot better about it. I still think I will pay more attention to the heat rating of the epoxy the next time, but these recent posts make me feel confident enough in it to hopefully attempt a flight on a 54mm motor one day.

 

[jd2cylman]

My L3 rocket has the fins glued on initially with West 5 minute (can't remember if it was the G-flex, or not), then West 105/205 with chopped carbon injected as internal fillets. Rocket Poxy external fillets. I've flown a M1939W, a m1560WT, and two N3300R motors in it and the fins are still as solid as the day I installed them.

 

[RobertC]

My L3 rocket has the fins glued on initially with West 5 minute (can't remember if it was the G-flex, or not), then West 105/205 with chopped carbon injected as internal fillets. Rocket Poxy external fillets. I've flown a M1939W, a m1560WT, and two N3300R motors in it and the fins are still as solid as the day I installed them.

That’s pretty impressive. Maybe I was worrying about it a bit too much. I believe West System’s website says that the g-flex performed a little better than 105, and for my external fillets, I’m going to use something else as well. Thanks for the reply!