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hot glue brittle in the cold

eagle4

New member
#1
Hey gang, yesterday I was out flying, and I noticed anything hot glued was coming lose. now this is fine if you notice it on the ground, like one of my planes, but the other one i found out when the motor mount came off mid flight, or after a flight that was a bit iffy, you notice that your control horns are only attached by the smallest amount, a tiny pull and they popped off. Just wondering if you've had similar problems with hot glue in the past? I've had gell type CA, silicone and epoxy recommended to me, just wondering what your thoughts are?
 

RoyBro

Senior Member
Mentor
#2
How cold was it yesterday in Montreal? I was able to fly yesterday in beautiful weather (in the 60s F), but today there's snow aplenty. It's supposed to ease off by Wednesday. I hope to be back in the air Saturday.

As for hot glue being affected by cold, I suppose it could have something to do with the surface to which it is attached. Are we talking foam planes, like the swappables? Is it possible that the surface to which the hot glue is attached is contracting due to the cold weather? If it is also smooth, that could be the issue. I can't imagine hot glue failing due to cold on my DTS foam planes, especially the firewall on the power pod.
 

Tritium

Amateur Extra Class K5TWM
#3
I learned a year and a half ago when building my first RC Powers Foamies. Gorilla Glue for motor mounts Hot glue for other places filleted with epoxy at regular intervals to hold during "cold or hot weather".

Thurmond
 

eagle4

New member
#4
all my planes are dollar store foam
it was hovering just above 0c where i was yesterday. i was having glue fail in a couple of different places, one was where a servo was glued down onto bare foam, another was a control horn which was glued onto a taped surface (yeah i know, not super secure, but still). for my motor mount for my Versa Wing, I have built up a triangle of foam from a few laminated pieces of foam, the bottom of that where it joined onto the plane came off, admitadly this was during a crash, but with the amount of glue joining foam to foam i'd have expected a stronger bond as the crash wasnt that bad at the back of my triangle of foam i have a piece of wood which the motor is screwed onto, this came off too, and i've had that attached for a long time, as i've kept the same triangle of foam for numerous different airframes without the need to replace the wood. (it was made originally for my F22, then my arrow then my sparrow) i just keep moving it from airframe to airframe, and previously have had no problem.
 
#5
Thanks for the advice Thurmond. I was wondering if Gorilla Glue or Epoxy would be preferable to hot glue for some critical areas. I've used hot glue for other projects and it does have some limitations on what it can effectively bind.
 

Craftydan

Hostage Taker of Quads
Moderator
Mentor
#6
Thanks for the advice Thurmond. I was wondering if Gorilla Glue or Epoxy would be preferable to hot glue for some critical areas. I've used hot glue for other projects and it does have some limitations on what it can effectively bind.
Depends on the part, but many of the FT builds have peices that are difficult to clamp evenly -- a requirment for GG or Epoxy. Most of the folded airfioils top that list. In thise cases, I take advantage of HG's speed to full strenght, but add a few spotwelds of GG (epoxy works too). it's there just to hold the joint if the HG ever decides to let go from heat.

from cool, however, I think Eagle (correct me if I'm wrong) is having problems at glue joints on non-porus surfaces. if the hot glue can melt into the paper/foam, once it gets cold it's still bonded. if it's mearly holding onto a surface using a very well fit surface tension, once it becomes too ridgid, it'll let go cleanly. It *might* also be pulling the paper away from the foam, because the glue joint was to the paper, not the foam underneath.

to deal with this:

- scuff up bonding surfaces on plastic peices (like servo sides or plastic control horns) a few scars on the surface will greatly improve bonding strenght at all temps

- cut away paper/tape at *critical* joints to bond to the foam underneath.

While the spotwelds compleatly work in high temp, you need to do these things to make sure the HG has a good all-temp bond first.
 

Foam Addict

Squirrel member
#7
Yes, hot glue and extreme packing tape as well. I lost an aileron on my bixler due to cold and a tape hinge. Anything below about 3 c and even the glue joints that Dan described often become brittle.
 
#11
Shouldn't foam safe ca + kicker work fairly well to hold stuff in place while the slow glue cures?

Edit: you might need a extra set of hands to use the kicker, while you hold the surfaces inplace.
 

Craftydan

Hostage Taker of Quads
Moderator
Mentor
#13
I hate winter.

Just an observation to sum it up.
Roger that!

It's already gotten down to the 60's(15-20C) here . . . Brrrrr . . .


Xerx,

In many cases, yes that will work, but it's a tradeoff between second degree burns or noxious fumes. Call me a sadist, but I lean toward burns in exchange for breathing. Others might choose differently . . .
 

.XxBensterxX.

Intermediate Hobbyist
#20
My bro recently got the CX4 blade heli. On his first flight he broke 3 blades and tryed epoxy on them. Ends up coming off in mid-air and crashing. He learned a great lesson. No epoxy on blades. Now hes waiting for more parts then just the blades