Hi everyone , This is a Martin with an aluminium soundboard , the bridges on these tend to let go . This one has been reglued 3 times , taking care to scuff the metal and using hi strength epoxy . Im in Australia so returning to factory is not an option . Any ideas ?
How quickly was the epoxy applied and the bridge attached and clamped up after the top was scarified?
I am an absolute amateur when working with Aluminum and I am no metallurgist, so take what I say with a grain of salt, but I've always heard that when gluing to aluminum, the laminations must be glued, in-place, and clamped up within 30 seconds of scarifying (scuffing) the aluminum. The reason being that aluminum is incredibly quick to react with oxygen and by the time a minute or two has elapsed the surface will have oxidized.
How do you scuff the aluminium?. I have successfully built a guitar body of aluminium using epoxy to glue wood to metal. I used a stainless steel wire brush to scuff the aluminium as stainless is supposed to not contaminate the gluing surface. I mixed the glue first and then scuffed the area to be glued. The glue went on immediately after the scuffing. The idea that you want the glue on the metal before it has a chance to oxidise is spot on. I guess that the idea is that glue sticks to the metal better than the oxide does.
Hi Todd , Im are of that , I actually had a pool of alcohol over the bridge area as I abraded it , then rubbed glue over it as this evaporated . I was very careful . I am wondering if there is a glue used in the building game or industry ?
I never heard of a Martin with an aluminum soundboard. You sure it’s not HPL (high pressure laminate)? A man made material that Martin uses for some entry level guitars.
I don't know for sure, but I'd bet Martin uses thick [gel] cyanoacrylate like they use on the HPL soundboards.
Bolts would work...
Martin X has an .032 Aluminum sheet bonded to wood, see the patent.
The picture is a billet cnc machined soundboard, Totally different sound.
Yes there are (2) 4-40 screws thru the aluminum with locknuts under.
The local store sold one 8 or 10 years ago. The bridge came off shortly after. The local store repaired it with wood glue. When it came off again fairly soon, the owner brought it to me (his son originally wanted it because it was 'cool looking'). I didn't scuff anything but did clean off a good bit of glue. I lightly clamped it back on with medium viscosity super glue. I still see it being played from time to time. IMO, it still sounds strange but is passable plugged in. Bridge is still there. YMMV. Good luck.
I recall from my previous learning that "mechanical fasteners are used where an adhesive is not suitable". Now, I suppose one could say that the manufacturer knows what they are doing and that an adhesive they use should work, but experience and reality attacks prove otherwize, especially in the case of gluing dissimilar stuff.
Overarching this is the observation "the bridges on these tend to let go" which makes the solution to the problem not include: doing the same thing over an over again and expecting a different outcome. Glued and screwed/bolted in a tidy fashion for me.
the glue to use is CA from 3M. that is what martin used on those along with the composit top guitars belive it or not! crazy right? just make sure everything is CLEAN CLEAN CLEAN. good luck