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Laminated Bridge?
http://www.luthiersforum.com/forum/viewtopic.php?f=10101&t=35882		 Page 1 of 1
Author:  Bill Hodge [ Sat Mar 24, 2012 9:15 pm ]
Post subject:  Laminated Bridge?
I posted this a bit earlier, but had to rethink how I wanted to approach this question. I know a laminated bridge is doable for the sake of visual effect. I was wondering, for those of you who have done this, what your thoughts are on it? I'm thinking about laminating two thin layers on the bottom of a bridge using epoxy (or polyurethane glue) after I radius the bottom of it. I figure I can use the same block I use to sand the radius, for clamping the stack together thus maintaining the radius somewhat. I would still glue the bridge to the soundboard via my current method. Thoughts? Ideas? Yeahs? Nays? I welcome your input, but for the sake of gathering good information, please try and maintain the subject matter as best your able. beehive My thanks in advance to those who choose to participate.
Author:  Mike Lindstrom [ Sat Mar 24, 2012 10:53 pm ]
Post subject:  Re: Laminated Bridge?
What are you hoping to achieve? Is this for a visual effect or something functional?

Mike
Author:  Steve Saville [ Sun Mar 25, 2012 12:59 am ]
Post subject:  Re: Laminated Bridge?
I would use HHG or fish glue, not epoxy on all the joints. Why switch glues? The epoxy will fill the pore holes and the wood glue you use will not stick to those filled pores.
Author:  Steve Kinnaird [ Sun Mar 25, 2012 7:14 am ]
Post subject:  Re: Laminated Bridge?
Cold creep (a good name for a rock band--ooh, there I go violating your request) is your concern.
Will the stress eventually slide your bridge apart? Or at least shift it some?
Charles Fox gets around this by using very small threaded inserts in his bridges that hold the layers together mechanically. Very cool system, lots of work up front, but he gets those pretty little lines at the bottom edge of his bridges. I would think you should devise some method akin to his, where you "pin" those things together.

Steve
Author:  Bill Hodge [ Sun Mar 25, 2012 9:39 am ]
Post subject:  Re: Laminated Bridge?
Mike, not so much functional as visual effect. I really like the effect on Charles Fox's bridges, and though he described it to us when I asked during the SS course I took several years ago, I forgot specifics since I didn't take notes about it.

Steve S, I had considered HHG or fish glue but am concerned about separation if, say a guitar is left sitting on a stand with the hot sun beaming through a window on it in the midst of summer. But then, I suppose that would be a problem even with a non laminated bridge. The guitar I'm considering this for will be residing in South Texas. As far as pore leakage, the bottom 1/16th of an inch would be Gaboon Ebony, and the pores on that as you know are virtually invisible. Do you think the epoxy could seep through that thickness of such a dense wood?

Steve K, I didn't mean to imply humor was not welcome, :) I just know too much humor can drag things way off topic (I too have been guilty of that ;) ). So, cold creep, with epoxy? I had thought through the idea of screws, but I really, really hate the idea of screws on an acoustic bridge even if they're totally hidden. I know it has been and is being done. I do like your suggestion of pins (i.e. tapered dowels maybe) Certainly worth considering some experiments on.

BTW, I used to know some pretty cold creeps back in the 70's. :lol:

I do know Avalon Guitars has a laminated bridge design, and I don't think they use screws but I could be wrong.
Author:  woody b [ Sun Mar 25, 2012 11:31 am ]
Post subject:  Re: Laminated Bridge?
There's all different kinds of epoxy. I'm sure at least some of them will creep. Epoxy also adds damping......at least some epoxies. I don't know much about epoxy, or difference between types so I'm not much of an epoxy user.


I'd use powdered veneer resin. I think the proper name is urea formaldhyde glue. http://www.woodcraft.com/Family/2005350/ProGlue-Veneer-Bond-Dry-Resin.aspx
It doesn't creep, it dries super hard, no damping, and it's won't release with heat or moisture. Strong clamping is required, just like PU glue, but I believe you'd get a more invisible glue line. I use it for neck and tail blocks. If you want to pin the pieces like Steve suggested just hide a couple screws under pearl dots like Gibson used to do.
Author:  Bill Hodge [ Sun Mar 25, 2012 1:42 pm ]
Post subject:  Re: Laminated Bridge?
Thanks for that, Woody. Having been a custom fine furniture builder, I never even considered the veneer glues for use on solid wood guitars. But, I see validity and encouragement in your point and it makes total since to me. Especially since the Pro-Glue variety is the closest thing there is to actually welding wood together (or at least, so I've heard). Don't know why I never even took it into consideration. I use the West System 105 with 205 Hardener for laminating necks, neck blocks, and gluing on the fretboard for the past few years since being introduced to it by Charles Fox. Never have I had and problems with creep or delamination. It is what I was considering for laminating the bridge layers, but Steve Saville's thoughts have given me pause in considering that option. I suppose it's possible even on the densest of ebonies, that it could bleed through. I'm curious though, if the Pro-Glue could also bleed through the thinner layers (@ .062" +) because the carrying agent would be water. Thus, causing an issue with gluing the bridge to the soundboard with the LMI White similar to Steve's mention about the epoxy. Though I've known about Pro-Glue for veneers for some time. However, I've never had any experience with it. If your experience has been good overall, it certainly warrants some testing on my part.
Author:  woody b [ Sun Mar 25, 2012 3:49 pm ]
Post subject:  Re: Laminated Bridge?
I don't think Pro Glue would bleed, and cause adhesion problems. You can glue stuff to plywood, even plywood with really thin layers. It needs to be clamped several hours, but sets hard enough to keep from bleeding pretty quick. Epoxy takes alot longer to get hard enough to quit flowing, especially inside a joint. I suppose you could use LMI white for the lamination, but if you ever have to remove the bridge it will come off it 2 pieces. Same could be true for epoxy or even HHG. I had a neck block come loose when I was re-setting the neck on an old Martin. Someone had really used alot of glue on a previous re set, so it took alot of steam to get the neck off. It wasn't a big deal, but enough for me to start using Pro Glue for neck blocks. I've never used LMI white, but wouldn't hesitate to glue a 1/16" laminate on with Pro-Glue, then glue the assembly on with HHG. Pro glue is hard to clean up, so I'd glue the laminate on before shaping it or the bridge........if it isn't too late.
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