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Some thoughts on adhesives

Monte.C

Well-known member
#1
(I hope this is the best place for this posting)
(I'm sure there must be similar posts out there somewhere but I don't want to do a deep search... Here's my two cents.)

#1. It's ok for me to grumble about hot glue! This coming from a guy who has logged 1000 hours (at least) on CA and balsa and bass and birch ply. I'm new to planes but I used to design/build the slickest, sexiest RC speedboats, mostly offshore racing hulls.
#2. Hot glue is the best thing available for foamcore if you want an instant & strong bond.
#3. I've found that if you can afford the inconvenience of weighting your pieces down and waiting for the cure, Gorilla Glue is superior to hot glue - if you're the kind of builder that wants to go that way. There's no question that the finished weight is only a fraction of a hot glue connection. If done a certain way, the finished appearance can be super clean, where with hot glue even if you get rid of the ugly globs you still have shiny glue smears all over your precious model. That's perfectly fine for many of us. The most crazy builders like myself can't sleep at night when that happens.
#4. Some will say hot glue is best because it flexes and won't crack/shatter. Gorilla Glue isn't rock hard, it flexes too. It has much more plasticity than I thought it would. You'll see this if you trim off visible glue lines from your plane, and handle/pull/squish the trimmings. Also when you pull off the crustiness from the spout of the half used bottle. Let the scrap fully cure, then handle it. It moves and bends and folds as you wish. This is impact/cracking resistance.
#5. I've found that GG isn't the strongest when trying to bond to the silicone surface of my brown FT foamboard. (I think it's silicone.) If you're really careful with a blade you can sometimes peel away visible "trimmings" of glue from the surface without pulling away paper. Because of this, where strength is a significant factor I'll pierce the paper every 1/4" with a toothpick or cut very small windows through the paper along the joint to be glued, that won't be visible after gluing. This let's the GG bond into the cells of the foam, and into the edges of the paper so you still have all the strength advantages that the paper provides. And a foam-to-foam GG joint is infinitely stronger than the surrounding foam.

I'm one of those builders (I've heard there are others) who has found places where it's good to use GG along a joint with one or two spots of hot glue to tack it down to let the GG cure. This technique can be ideal for certain situations.

I'll get a bottle of medium CA in the mail in a couple days, supposed to be "100% foam safe," and I can't wait. I have a couple places on my current WW2 medium bomber build where this is just what I need. Not ultra strength-critical, but places where I want a near-instant but very clean joint. As with GG, I can pierce the paper to allow the adhesive to get in there with an internal structural bond. Who has had experience with foam-safe CA?

Who has thoughts? Opinions? Additions? Arguments? Seriously, I'm all ears. Thanks.
 

leaded50

Well-known member
#2
agree on much.. but :LOL:.... Globs ans smear can be removed though. Reason why i see hot glue best, is its more flexible than much, the foamboards flex a little it self, and together they stick better than many. Gorilla Glue i see as superb in some parts/places, other not, mainly i like it best where less flex isnt a question.
In a "sharper crack" hot glue seems keeps it better, without tearing foam beside the connection , that gorilla glue do.
Mainly reason for hot glue i would suppose most use for a faster build, without holding for a long time, or use as much taped long to get it cured.

I learned use both in a build, depending on what.
 

Monte.C

Well-known member
#3
agree on much.. but :LOL:.... Globs ans smear can be removed though. Reason why i see hot glue best, is its more flexible than much, the foamboards flex a little it self, and together they stick better than many. Gorilla Glue i see as superb in some parts/places, other not, mainly i like it best where less flex isnt a question.
In a "sharper crack" hot glue seems keeps it better, without tearing foam beside the connection , that gorilla glue do.
Mainly reason for hot glue i would suppose most use for a faster build, without holding for a long time, or use as much taped long to get it cured.

I learned use both in a build, depending on what.
Yes yes yes. Each adhesive in its proper place. You're absolutely right.
Especially if you'll be painting. All my airframes are still brown right now.:confused: I'd just go nuts if I had all the glue smears...
Hey you've got some good good looking planes there!
 

Merv

Well-known member
#5
I agree hot glue can be heavy. A lot depends on how much you use, I have found a thin bead is all that is necessary. One stick of hot glue can easily make a plane.
 

Monte.C

Well-known member
#8
Ok, three days later and I suppose I was a bit harsh on hot glue. (Chuckle.) It still frustrates the heck out of me, but each of these adhesives has its place, and for its convenience hot glue is super.
I'm really frustrated by the "one shot is all you get" nature of hot glue, and with only a couple short seconds to get it right.
I'm still clinging to old model building techniques, and now that I've discovered foam safe CA I'm finding good uses for it all over the place. Good stuff.
 

Hai-Lee

Old and Bold RC PILOT
#9
Ok, three days later and I suppose I was a bit harsh on hot glue. (Chuckle.) It still frustrates the heck out of me, but each of these adhesives has its place, and for its convenience hot glue is super.
I'm really frustrated by the "one shot is all you get" nature of hot glue, and with only a couple short seconds to get it right.
I'm still clinging to old model building techniques, and now that I've discovered foam safe CA I'm finding good uses for it all over the place. Good stuff.
My glue of choice is an American glue called Sullivans Clear Craft Glue! It glues the FB extremely well and does not swell or expand. I also use it for repairing retail foamies. It does work on wood as well though on hardwoods it is less effective.

Just what I use!

Have fun!
 

Monte.C

Well-known member
#10
My glue of choice is an American glue called Sullivans Clear Craft Glue! It glues the FB extremely well and does not swell or expand. I also use it for repairing retail foamies. It does work on wood as well though on hardwoods it is less effective.

Just what I use!

Have fun!
Hey I just came across your post "Part of what I do". Love. And dammit now I have to experiment with the Sullivans. Sounds like a great addition to the workbench. Thanks!
 
#11
I have had really good success with Gorilla glue on leading edges. The expansion helps to round them out if you trim away enough foam first. Be sure to seal the leading edge with tape beforehand.

I will use that there, and any wing creases and then clamp the joint together with hot glue on the spar and trailing edge.