couple of Qs...

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Well-Known Member
Sep 22, 2009
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OK guys, just a couple of quick questions:

*How much does epoxy weaken Kevlar (cord)? I epoxied it to the upper CR in my rocket... and then thought 'i wonder how much i just weekend that'... i should have thought about that b4, but oh well. i can always just cut it off and put the part that wasn't affected by the epoxy on without the epoxy this time.
*Can you satisfactorily thin epoxy (the 1-1 ratio syringe stuff) with rubbing alcohol, and use it for glassing? (i only need to do one 2" cone and don't want to really get into this yet... I’d rather use what i have right now since I’m currently in-debt to my mom, over rocket stuff of course!)
*and i'm sure there was something else... i'll think of it sooner or later. for now please just leme know what you think about these two things, mostly the kevlar b/c i want to glue that mount in the rocket and cant change it after that!:rolleyes:
For the first question, I don't think you weakened it at all. Many kits call for epoxying shock cords to things - PML has you epoxy the nylon strap to the motor tube. On alot of my kitbashes, I take a kevlar cord, tie it around the motor tube below the upper CR, and cover it with epoxy. You should be fine.

ok, thanx! i thought i had read some where that the epoxy can weaking Kevlar allot... mabye i didn't.
i know that pml has you epoxy their nylon straps to the mmt, i just did it myself actually, but this is somthing like 250lb kevlar cord and i thought there may be a problem. I drilled a hole in the upper CR, then i passed the cord thru it and put a knot in the end, i then coated the whole area w/epoxy. b/c the epoxy seems to have 'wicked' up some into the cord where its not atached to anything i thought there might be some problem... i guess not:D
if there is anything else some1 wants add to this please do, since i'm 'probobly' going to epoxy this in tonight, and then i can't make any changes!
That doesnt make sense, I mean people use epoxy and kevlar to strengthen their rockets so I would think it wouldnt harm it at all.
If you read the instuctions on aerotech kits they are very insistant about keeping glue away from shock cords becasue it weakens them - but they are talking about elastic...
yea, elastic does weaken when contacted with epoxy. But kevlar is ok
Second question regarding thinning epoxy with alcohol...Use 20 minute finishing epoxy from Bob Smith Industries, this flows nearly like water, and is suitable for glassing, no Alcohol thinning required. There are other epoxies suited for glassing but Bob Smith is where most of us begin. Then with a little more experience you can dig out the big "bucks" for the better quality epoxies (i.e. West Systems).
My first thought when I saw this thread was "a couple of Qs!?????" Oh... Questions... Not huge motors...:eek:

I would just get the finishing resin... YOu can get it from teh place you bought the glass. THat would work better in my opinion.

You are proabably fine with the shock cord. I always epoxy shock cords to stuff....:D Just dont do it with that elastic stuff... I hear it makes it very brittle.:eek: