Bow Glues

[willie]

I would agree with most of what mike and pat have mentioned as important, and would like to add a bit more, as epoxy and glue discussions come up frequently.

within  the so called boat builder formulations, system three, and possibly others, you can read the tech sheets online to see what the mechanical properties are.

straight epoxy resin is plenty strong enough, and formulas that cure quicker tend to be weaker, so there is a trade to consider when choosing by cure time.

Additives do not really add strength, they reduce strength while adding other qualities that improve gap filling, so one again, a good fit with a runnier epoxy excels. Keeping glue joints flat really helps. The slower curing, (but stronger), resins just need better gap control, as there is a longer time for it to run before it sets up.

Silica is a common additive to control viscosity, makes a harder finished product, gives it the glass like quality some desire, but makes the cured resin more brittle than straight resin without. Not sure if that is what some users call "stronger"

other additives (plastics?), reduce strengths but add tool ability and/or flexibility of the cured matrix, making easy to sand fillers etc.

the more fillers, the harder it is to mix well. poor mixing also reduces ultimate strength and cure time.

[BowEd]

Can't say more then whats already been said.I'm in the smooth on group.Seen it used many many times.Used it myself many times.No problems.Like bubby said it does not need a hot box.24 hour cure is all too.Long pot life of 2 hours to adjust things if many laminations are wanted.I've used it 6 months from purchase with no problems.Do what it says on the can.
I like tite bond 3 for snake skins and other thin backings.

[gfugal]

I'm wondering about the temperature strengths. The only reason I was hesitant about smooth on is because I heard that if you don't hot-box it initially then it will be a weaker bond at higher temperatures (the exact temp I'm unsure probably well over 120°)? Without the hot-box it should still be full strength at temperatures bellow that unknown temp. Here's the question: if it's exposed to high temps after curing, let's say 150° in a closed car on a hot summer day, will it permanently weaken the bond or only temporary? I doubt anyone is ever going to shoot a bow when it's hotter than 120° outside so if it isn't a permanent weakening then it should be a moot point. I don't know if anyone has the answer to that, but I'm going to assume that it doesn't, as due to the anecdotal testimonies in its favor. I've personally have never used it so I can't say.

Really I don't think there is a superior glue. It's just a matter of preference. If it works then it works. It just depends on the conditions you have. There's no good or bad just works or doesn't work for the conditions.

[gutpile]

I used smooth on last boo bow ...gap filling no hot box required to set....worked fine...gut

[PatM]

Epoxies do generally cure better at higher temperatures and then withstand that higher temperature if later exposed to it. I believe Smooth-on is one of those. 

Epoxy can actually be post cured at a higher temp but I would think it needs to be supported while that takes place.

The benefit to G2 and Gel magic is that they cure at room temp AND have high heat resistance without being heated during the cure or post cured.  Gel Magic also improves with post curing.

I'm also told that G2 boasts higher mechanical properties over Smooth-on but the latter clearly has all the properties a bowyer is looking for. You just may be able access a comparable epoxy more readily depending on your location.

[BowEd]

gfugal....I think the danger the specifics say about smooth on was well over 200 degrees if just 24 hour cured with a 1A to 1B ratio.Quite high really.Now that's when the bow is braced too at these temperatures.Un braced not so.No danger.If left to cool down before bracing it is in no danger of delamination.If mixed that way it can be cured faster in the hotbox at 150 degrees for 6 hours.Left to cool to room temperarure it can be braced.If mixed with a 2A to 1B ratio left to cure 24 hours it can still be post cured later for 2 hours at 250 degrees to enhance it's qualities and heat tolerances also of which I don't know it's limits there though.Possibly talking with a rep that info can be found.
That's my interpretation of it.The fellas I shoot with that shoot FG bows are aware of this.They do not leave it strung in a cab on a hot day.Laying outside in the sun no problem though.Bottom line is high heat will not debond it while unbraced.Braced possibly.
The mechanical properties and modulus compression and tension properties are way beyond what wood is.It's specific gravity is just over 1.1So it is dense.
I use a putty knife to size my surfaces with a thin layer.Just the way I've seen it done by my friends.Warming the material prior to sizing is helpful.Warming mixed smooth on prior does loosen it up also.Making sure it is a shiny layer prior to putting laminations together and is done saturating the surface.I want a very thin line for a glue line.Almost invisible if mating of material is done properly.As thin as a sheet of paper or thinner.That's less than 10/1000's of an inch or less.Using in the range of 60 to 70 pounds of pressure is what my friends use.