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  #21  
Old 10-20-2015, 10:13 AM
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Quote:
Originally Posted by luke strawwalker

Double glue joints for attaching fins are as fast as using CA, and stronger than the materials... the fin will disintegrate or the tube delaminate, but the glue joint itself will remain intact... I've seen it myself. Once the glue joint is stronger than the materials it's joining, there's really no point in going stronger... LOL

Later! OL JR: )


Good point to bring up. I have been using double glue joints on fins since reading about it a couple years ago. It is amazing how quickly the fin grabs and does not need to be held by hand to keep it from leaning to one side or the other.
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  #22  
Old 10-20-2015, 10:17 AM
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Quote:
Originally Posted by luke strawwalker
Quite true...

Someone was telling me here while back about some guy that used to do tons of fiberglass layups for HPR, just practically bathed in the stuff, never gave it a second thought...

Until one day he developed sensitivity allergies to it, and then had to give it all up because it got to him so bad...

So, be careful... might not be today or tomorrow, but eventually....

Later! OL JR


That might go back to the days of r.m.r -- I recall a guy named Dangerous Dave. Sadly, I guess a fitting nickname. I never recall hearing how things ended up for Dave, health-wise. I started wearing nitrile gloves right after I heard about his health problems.
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  #23  
Old 10-20-2015, 10:47 AM
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Quote:
Originally Posted by UlteriorModem
A 19mm it let go on a C65, ejection charge did it I think.



Curiouser and curiouser. I don't think a C6-5 can generate enough heat for long enough to soften a joint under normal circumstances using any of the glues being discussed in this thread.
Admittedly, I've never used 5 minute epoxy but other posters seem to be unanimous in condemning it.
What else happened during the flight ? Did the whole motor mount eject ?
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  #24  
Old 10-20-2015, 11:51 AM
Rex R Rex R is offline
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a Quest engine might. I've seen their labels start turning brown from heat.
Rex
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  #25  
Old 10-20-2015, 07:21 PM
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Quote:
Originally Posted by LeeR
Good point to bring up. I have been using double glue joints on fins since reading about it a couple years ago. It is amazing how quickly the fin grabs and does not need to be held by hand to keep it from leaning to one side or the other.


And no need for fancy and expensive fin jigs and other gimmicks to hold everything while slobbery yellow glue runs everywhere before it tacks up... LOL

Later! OL JR
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  #26  
Old 10-20-2015, 07:22 PM
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Quote:
Originally Posted by Rex R
a Quest engine might. I've seen their labels start turning brown from heat.
Rex


+1... and nearly burned through as well...

Later! OL JR
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  #27  
Old 10-20-2015, 07:57 PM
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The motors could soften the glue over the extended time of descent and recovery, but not during powered flight/ejection when max strength is needed.
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  #28  
Old 11-16-2015, 08:59 AM
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I sincerely wish I had seen this thread before I installed a motor mount in my current scratch-build with 5-minute epoxy. Fortunately, in my case the MM is held in with 4 centering rings and a balsa transition, so collectively I would hope it'll hold together.

That said, I am now going to apply a Titebond fillet on the front ring (should be fun, 11" from the end of the BT) and a 30-minute epoxy fillet on the aft ring.

I only used epoxy in the first place because of the CA applied to the inside of the ends of the BTs. Oh well.

I wish any normal hardware store carried any of the slower-setting epoxies. 5-minute varieties were all I could find anywhere. Ultimately ordered some from Amazon.
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  #29  
Old 11-16-2015, 09:34 AM
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Just remembered something that hasn't been mentioned about using slow curing epoxy for a MMT's placement inside the body tube.

Make sure that the mount is supported in its final position so that it doesn't slip inside (or out) before it cures.

I've seen couplers do this too. I've applied epoxy, slid in the part, then set it aside, upright, to work on the next thing. Next thing I notice is that it's sliding down inside the tube. So far, I've managed to catch it and pull the part back to its intended position before it set, but if the placement is critical, it could be a problem if not caught early enough.
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  #30  
Old 11-16-2015, 09:42 AM
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Quote:
Originally Posted by K'Tesh
Make sure that the mount is supported in its final position so that it doesn't slip inside (or out) before it cures.

I like to think "of course I would have thought of that, duh". Knowing how reality works, though, I say "thank you for that tip!" I can only imagine the choice words that would be uttered upon coming back and seeing the MM having slid out of position (out of the rocket would be bad; *into* the rocket would be unspeakably bad.)

Choice. Words.
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