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Bracing sliding around when gluing them
http://www.luthiersforum.com/forum/viewtopic.php?f=10101&t=19083		 Page 1 of 2
Author:  Tai Fu [ Mon Oct 06, 2008 12:23 am ]
Post subject:  Bracing sliding around when gluing them
It's really frustrating when the brace slides around as I glue it. No matter what kind of clamp I use (Stewmac Mini cam clamp, C clamp, spring clamps) the brace always wants to slide around a little. Does the brace have to be on like to .001 inch or can it be off by a little bit? The thing that sucks about hide glue is that there are only about 15 seconds before it gels and by that time any correction will be too late.
Author:  Rod True [ Mon Oct 06, 2008 12:50 am ]
Post subject:  Re: Bracing sliding around when gluing them
Actually, that's really the beauty of hide glue. Get the brace set in place (within 1/64-1/32" is fine) hold it for about 5-10 secs, the glue grabs enough to hold it in place than grab the clamps and clamp it down. It gels but is not hard of course and you can clamp down the brace.
Author:  TonyFrancis [ Mon Oct 06, 2008 12:54 am ]
Post subject:  Re: Bracing sliding around when gluing them
-
Author:  Arnt Rian [ Mon Oct 06, 2008 7:12 am ]
Post subject:  Re: Bracing sliding around when gluing them
Another alternative is liquid fish glue, which is so tacky ;) that braces which are glued with it won't slide around on you. It's open time is very generous, unfortunately so is the cure time (about 12 hours). It is otherwise similar to hide glue.
Author:  Tai Fu [ Mon Oct 06, 2008 9:27 am ]
Post subject:  Re: Bracing sliding around when gluing them
Thanks, also on the back I just finished bracing, it curled slightly backward where there's a concave radius that is 90 degree to the braces when I laid a straight edge on the side without braces. I suspect it's from the moisture of the glue and stuff. I can straighten it out if I put forces on it (like when glued to the side) but how much movement is acceptable with guitar wood? I took the back and put it under weight to hopefully help it bend back to a flat.
Author:  Pat Foster [ Mon Oct 06, 2008 12:23 pm ]
Post subject:  Re: Bracing sliding around when gluing them
When gluing the X-brace with HHG, I also heat the top, the braces also, and I do one leg of the X-brace at a time. Much easier for me this way.

It's really important to put on the notch-up brace first. [headinwall]
Author:  Bruce Dickey [ Tue Oct 07, 2008 12:57 pm ]
Post subject:  Re: Bracing sliding around when gluing them
Pat Foster wrote:
.

It's really important to put on the notch-up brace first. [headinwall]


:D
Author:  Terence Kennedy [ Tue Oct 07, 2008 1:42 pm ]
Post subject:  Re: Bracing sliding around when gluing them
Another recommendation for HHG to ease brace displacement. I also glue one limb of the X at a time. If you dry clamp with the X assembled and mark carefully it's worked fine. I've been laying my heating blanket out on the workbench and setting it to around 150 and just laying the braces on it while I get things ready. I've had plenty of time to get things set. The bridge plate was always my biggest problem with sliding before.
Terry
Author:  Mike Collins [ Tue Oct 07, 2008 2:14 pm ]
Post subject:  Re: Bracing sliding around when gluing them
One thing that's extremely important is NOT to use to much glue!!
You do NOT need to spread it on both gluing surfaces-you do NOT need a thick layer either.
Ouze out(large amounts) is a warning of to much glue!!!

Try some experiments with waste wood-gluing up pieces and get a feel for how much glue you need-if a light coat tacks and the pieces do NOT move -you got it right!
[:Y:]
Mike
Author:  Howard Klepper [ Tue Oct 07, 2008 2:17 pm ]
Post subject:  Re: Bracing sliding around when gluing them
Unless your religion requires you to use hide glue :geek: , you will probably find it a lot easier to use LMI's white instrument makers glue.

If you clamp hide glue after it has gelled, you won't get the best bond, because there is a limit to how much the gel can be compressed. That's partly why they give hide glue a number for gel strength.
Author:  Rod True [ Tue Oct 07, 2008 9:54 pm ]
Post subject:  Re: Bracing sliding around when gluing them
Now have you ever thought of taking that partially gelled squeze out and putting it back in the jar or bottle? Would that be a bad thing?
Author:  Tai Fu [ Wed Oct 08, 2008 8:42 pm ]
Post subject:  Re: Bracing sliding around when gluing them
Here's an update:

I managed to clear out my "go bar deck" (the laser printer is useless now) and I made some go bar with some hardwood trim they use on walls. So now I have 2 tone bars glued on at the same time.
Author:  Rod True [ Wed Oct 08, 2008 8:48 pm ]
Post subject:  Re: Bracing sliding around when gluing them
That's the idea. One question though? Are your braces arched on the bottom? You are clamping on a flat surface underneath them.
Author:  Tai Fu [ Wed Oct 08, 2008 8:54 pm ]
Post subject:  Re: Bracing sliding around when gluing them
Rod True wrote:
That's the idea. One question though? Are your braces arched on the bottom? You are clamping on a flat surface underneath them.



These are pre-shaped and arched stewmac braces... so yes they are arched in the bottom. I copied and cut the arch onto a piece of plywood so in the future I can buy pre-shaped braces from LMI and arch them myself.
Author:  Rod True [ Wed Oct 08, 2008 9:10 pm ]
Post subject:  Re: Bracing sliding around when gluing them
So your clamping the arched braces onto a flat surface? What do you think that will do to the arch in the brace?
Author:  Tai Fu [ Wed Oct 08, 2008 9:36 pm ]
Post subject:  Re: Bracing sliding around when gluing them
Rod True wrote:
So your clamping the arched braces onto a flat surface? What do you think that will do to the arch in the brace?


The instructions that came with the braces and stewmac kit instructions says to clamp it to a flat surface and when released the top will conform to the arch. So far it has.
Author:  Rod True [ Wed Oct 08, 2008 9:46 pm ]
Post subject:  Re: Bracing sliding around when gluing them
Yes, it will do that but there will also be some stress on the glue joint as the brace was forced flat when glued now it pulls up on the top plate and the glue joint is stressed because of this. It's probably not much but it is there. It also won't be as arched as it was before gluing it to the plate. Depending on the strength of the glue joint, over time that stress may cause the joint to separate. This is why we use a radius dish to glue the braces on. That way there is no stress in the brace, just a bit of stress in the top or back plate.
Author:  George L [ Thu Oct 09, 2008 11:43 am ]
Post subject:  Re: Bracing sliding around when gluing them
Rahimiiii,
I use clamped guide blocks as described above. As a rookie, I've found this to be very helpful in that it helps keep the braces in their proper alignment while I focus my attention on getting even clamping pressure.

Radius dishes are optimal, but there are other cheap and easy ways of getting the radius into your top and back plates before gluing the braces to them as well. One method I have used is to stack 3"x5" note cards in a staggered progression to match the arch of the braces. It's hard to visualize when written, but here's a link to text and pictures that explain this technique pretty clearly:

http://www.kennethmichaelguitars.com/contourtool.html

It's not pretty, but can get the job done.

Best,
George :-)
Author:  Pat Foster [ Thu Oct 09, 2008 12:24 pm ]
Post subject:  Re: Bracing sliding around when gluing them
With all the respect for you that I can muster, Rod, I have to disagree. The amount of stress put on the top of a typical flattop guitar to make it conform to 25 or 30 ft radiused braces is negligible compared to the stress from the string pull after the guitar is strung up. I don't think clamping flat is a problem, even long term.

Pat
Author:  ncovey [ Thu Oct 09, 2008 12:56 pm ]
Post subject:  Re: Bracing sliding around when gluing them
Lots of strong points and techniques regarding bracing placement and proper gluing, sliding around etc.
I agree with Howard in the use hhg, also the tension and pressure exerted by stringing to pitch far out way the slight negative stresses created by clamping flat otherwise radiused braces.
One thing I find helpful in setting a brace and holding it still for clamping is to apply small drop of CA in one or two spots on the brace, just a tiny drop held firmly for a couple seconds usually will lock the brace in place long enough to get the clamps set.
Author:  Tai Fu [ Thu Oct 09, 2008 7:28 pm ]
Post subject:  Re: Bracing sliding around when gluing them
ncovey wrote:
Lots of strong points and techniques regarding bracing placement and proper gluing, sliding around etc.
I agree with Howard in the use hhg, also the tension and pressure exerted by stringing to pitch far out way the slight negative stresses created by clamping flat otherwise radiused braces.
One thing I find helpful in setting a brace and holding it still for clamping is to apply small drop of CA in one or two spots on the brace, just a tiny drop held firmly for a couple seconds usually will lock the brace in place long enough to get the clamps set.



I'll try that next time, thanks for the advise. I used to do that in my rocket building days (gluing fins to a body without any clamps) but I was concerned about CA glue ruining the bond or something...
Author:  Chris Paulick [ Thu Oct 09, 2008 8:24 pm ]
Post subject:  Re: Bracing sliding around when gluing them
I'm new to gluing up braces with a go bar deck and HG but I put my go bars on about every inch or so. I just glued on the X brace the other day and put the intersection go bar on first and then some where near the center of the rays and then the ends and then filled the gaps. I used a 4 oz. squeeze bottle that floats in my Rival Hot Pot Express (much cheaper then a glue pot, $20 or less I think) to apply the glue down the brace and placed it. Pretty much, well just like John Mayes does in his video. It's pretty fast and faster then messing with a brush. For what it's worth. :|
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