Type of glue for bookmatch top

Valie

Hi there, I've allways been using Alcolin glue for my building projects but I've noticed that a few days after spraying there is a visible line on the joint.I suspect that the stresses in the wood is expanding etc. I was thinking of using epoxy for the bookmatch top (Bird's eye Maple)@ Allan - will it work or should I invest in hide glue. Is it available in SA? and at what cost.

AlanRatcliffe

Yes, epoxy will work well and wont be prone to moisture (cold glue) or heat (hide glue). I usually use and recommend Epidermix 352, made by ABE. Never had a glued joint come loose using it. It's locally made and it's commonly found in many hardware stores.

Manfred-Klose

I've got a Question :

I've a got PRS dvd where the guys do a factory tour of their workshop and show how they make their guitars, when they glue the 2 pieces of wood together to create a solid piece of bodywood, the luthier mentions something that they use a "radio frequency glue".

What is radio frequency glue? does keep unwanted EMI out?

Valie

Thanx for the info. Thats what I love about this forum.Thers'e always help close by and listening to the MP3's you guys made sure that I will stick to my day job for a long time.You all sound great.

AlanRatcliffe

Manfred Klose wrote What is radio frequency glue? does keep unwanted EMI out?

It's a type of hot glue that you heat with radio waves in the frequency of 2 to 30 megacycles. You clamp the two pieces of wood together with the glue in between and plate electrodes on either side then apply the RF. The nice thing is it heats up the wood and glue uniformly, unlike steam and other methods.

Manfred-Klose

Would it be practical to use such a glue?

Is it only PRS using this stuff, or do all the others guitar makers also use it?

It would probably be hard to find locally, a while back i went searching for conductive paint,no luck.
Everthing points back to Stewmac.com

AlanRatcliffe

I don't know which guitarmakers are using it, but it's become quite common in the woodworking world. Relatively large equipment outlay though, so I think mostly it will be some of the bigger builders.

Bob-Dubery

Alan Ratcliffe wrote
Manfred Klose wrote What is radio frequency glue? does keep unwanted EMI out?
It's a type of hot glue that you heat with radio waves in the frequency of 2 to 30 megacycles. You clamp the two pieces of wood together with the glue in between and plate electrodes on either side then apply the RF. The nice thing is it heats up the wood and glue uniformly, unlike steam and other methods.

Isn't there a danger with all these new-fangled glues? Namely that they glue too well and cannot be undone?

With good steel-string acoustic guitars a neck reset is going to be a necessity at some point. And when that time comes you don't want the neck glued so solidly that it can't be steamed loose.

AlanRatcliffe

That's the beauty of RF glue - it can easily be reheated in the same manner for removal. A lot easier and more efficient than steaming a neck joint loose. The inside of the wood heats up at exactly the same rate as the outside, so you don't have to wait for the wood to heat all the way to the glue.

Gearhead

Valie wrote Hi there, I've allways been using Alcolin glue for my building projects but I've noticed that a few days after spraying there is a visible line on the joint.I suspect that the stresses in the wood is expanding etc.

This could very well not only be the glue. The stresses in the wood you mention can come from two things you both control yourself:
- stability of the pieces you are joining;
- straightness of the pieces you are joining.

The way I think you should work is time-consuming but will not leave any stress in the wood:
- buy wood long before you start building and store it in a place that gets no liquid water but plenty of outside air;
- when you start the guitar, do not plane the wood to size right away. Leave yourself 5-10% of the final dimension firstly;
- leave the wood to adjust to its new size for a while (more is better, 2x more < 2x better) before taking off some more;
- after the last thickness step, rout the sides you are joining square to the top and straight. This will decrease the joining force tremendously;
- apply the joining force through the middle of the wood and evenly across the face.

It will be tough to prove, but I'm convinced that not having residual stresses inside a guitar will help it sound better as well.

On epoxy - I like the hard-curing stuff but some kinds cure but never become hard. Although the hard kind is brittle when too thick and does not fill well, it should not have to. The softer kind imho has no advantages over other kinds of glue - that are a lot easier to work with.