Multi-Glue Joint

[sam]

I've had this approach in mind for some time, but have never used it and don't know
if it's already in common practice - or if it would even work.

I had a peg box ready to glue to 'the' dulcimer, but had no ready surfaces on which to attach clamps.
I thought that by using a couple of drops of c/a or Permabond F in the centre of the mating surfaces,
surrounded by Titebond that I would have the structural and cosmetic benefits of the wood glue coupled with the
quick-holding/clamping properties of the other glues. The parts then could then be mated by hand, perhaps
with the aid of jigging tools, during the minute or two it takes the c/a or Permabond to set. That would act
as a clamp until the wood glue sets.

If the two adhesives could be kept segregated I'm wondering if this idea has any merit.


Sam

[Dominic]

Hey Sam, I've seen a custom shop PRS video where they use wood glue for the mitre on headstock binding then CA glue for the rest and they don't seem worry about them mixing. I've also read the ca sticks really well to protien based glues like hide or fish glue.
I can't visualise your gluing issue but there are always lots of tricks with different clamping techniques to get you out of a tight spot. Got a pic of what you are trying to do?
Cheers
Dom

[kiwigeo]

I cant see any sort of providing clamping pressure....certainly not the clamping pressure required to get a good joint with Titebond.

If the two pieces don't have an area where a clamp can take purchase then either temporarily glue on a block of wood to give the clamp something to hang on to. Use hide glue and then you can remove the block afterwards with a bit of heat. Alternately do what I do when gluing the neck shaft onto my lutes (its a scarf joint)......use a dirty big screw to apply clamping pressure to the joint.

[sam]

Maybe that's the bottom line: hand-pressure during initial set does not provide enough clamping pressure for
a satisfactory joint.

My assembly is a pegbox/scroll being joined to a dulcimer head block via butt joint. The mating area is 45mm X 35mm.

I'll have to research how to include photos in my posts.

I used an interesting method of 'softening' the sides for bending (40 years ago, btw). I had access to
a pressure vessel and a supply of anhydrous ammonia. The vessel was loaded with the walnut sides
and the lid was bolted on. It was evacuated then charged with the ammonia - at the residual
pressure in the supply tank. I don't remember the treatment time, but when they were removed, I could
tie them in a knot. This was a fascinating experiment, but an unnecessary overkill for instrument making.
The ammonia is also very hazardous and probably an environmental no-no these days.

[Paul B]

Bad idea, you're using one glue that doesn't shrink on drying, to hold everything together until the glue that will shrink on drying, goes off. Sounds messy and likely to make an ugly, uneven joint. Try it on some scrap and let us know.

[sam]

Hey Paul,

Your thinking is 100% in line with mine - using test pieces before jumping into the unknown on
one's project. It would be useful to then test those to destruction and compare results with ones normally
clamped and glued.

[Allen]

Some very notable small factory uke builders I know of use a drop of CA to the middle of the bridge, then spread PVA around the perimeter. Hand pressure to clamp for a few seconds, then away you go. They offer a life time warranty on the entire instrument, no matter how many owners you are down the line. Makes me think that they don't have any issues with the method.

I always size the binding rebate with hide glue when I use celluloid binding. Then glue in with CA. Sticks like the proverbial snot to a screen door.

[kiwigeo]

Sam I suggest you investigate my screw suggestion rather than muck around with glues. Attachment of the pegbox and body to the neck shaft on a lute present exactly the same problems you're dealing with...theyre all butt joints and using clamps is difficult. In both cases a screw is used to apply clamping pressure while glue sets.

[Paul B]

I think what I like least about this idea is that it takes away control from the builder. Glueing stuff together and then crossing your fingers and hoping it will all work out, is just the sort of situation most of us are trying to avoid. All of us have gone through the process (as newbs, and not so newb) of eagerly awaiting overnight while the glue sets up to see how it looked all sanded and prettied up. Only to be disappointed at the end result enough to start thinking about recovery. Happens to us all. Most of us learn from this, or ask the question from the rest of us.

Not saying you shouldn't post your ideas! Post away, but some of us who have been there before might say no, but not in a nasty way (I hope). Coming up with ideas like this is what this place is all about. Sometimes there are corkers that may need a little transwhatsification (for example, this idea might work really well with purfs! actually this one might be a goer!) So don't get stressed if you come up with an idea that gets stolen and turned into something more! It's just part of the process.

Keep the ideas coming!