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Bubble behind bridge = high action

Posted: Mon May 10, 2021 3:16 pm
by thepezident
I have a Martin Dreadnaught Junior that has developed high action.
I noticed that it also has a slight hump behind the bridge.

I gave the neck a little tweak and its helped but ultimately...I think the hump is the problem.
I keep in in the basement...sometimes in its soft shell case..sometimes hanging up.
It lives in Pennsylvania and in the summer I run a dehumidifier in the basement.

A friend said to put wood across the top and bottom and clamp the wood.
Insert a steamer or dab a damp cloth under the bridge (from inside) and SLOWLY tighten the clamps over the course of a few days.

whaddya guys think?

And what should I do going forward?

Re: Bubble behind bridge = high action

Posted: Mon May 10, 2021 3:16 pm
by thepezident
front page bump

Re: Bubble behind bridge = high action

Posted: Mon May 10, 2021 3:23 pm
by mickey
I think there is a factory very close to you that can give you better advice than all of us combined. :D

Re: Bubble behind bridge = high action

Posted: Mon May 10, 2021 3:39 pm
by thepezident
mickey wrote: Mon May 10, 2021 3:23 pm I think there is a factory very close to you that can give you better advice than all of us combined. :D
I was about 500 yards from that factory yesterday while visiting my mom....

Re: Bubble behind bridge = high action

Posted: Mon May 10, 2021 4:20 pm
by toomanycats
thepezident wrote: Mon May 10, 2021 3:39 pm
mickey wrote: Mon May 10, 2021 3:23 pm I think there is a factory very close to you that can give you better advice than all of us combined. :D
I was about 500 yards from that factory yesterday while visiting my mom....
I'd definitely be doing some dumpster diving if I lived near a guitar factory.

Re: Bubble behind bridge = high action

Posted: Mon May 10, 2021 4:28 pm
by BatUtilityBelt
Don't take this advice without a luthier's opinion on a nice guitar (I am no luthier). But I once addressed this on a guitar I got for almost free - bought it with the notorious hump and subsequent raised bridge. For several days I would put a warm cup of water with a sponge in it inside the guitar, and put a large board (larger than the width of the lower bout) with a weight on it across the lower bout to weigh it down. I figured the sides of the guitar would keep the lower bout from going any further than flat. This worked great on a cheap guitar, I think it took less than a week. Strung to standard, the hump has not come back over several years. No clue if it would work on a nice solid top guitar.

Re: Bubble behind bridge = high action

Posted: Tue May 11, 2021 12:22 am
by Mossman
Keeping a guitar in a basement is never a good idea. A while back, I had a friend who brought me his Martin D-15 to rescue, which he had kept on a stand in his entertainment room in the basement of his house. You'd think it would be pretty safe in there. His basement was completely finished, and it didn't seem damp, or any more humid than the rest of his house, but the neck had bowed so badly, I wasn't sure if it could be corrected without the use of clamps and steam. I managed to set it right by gradually adjusting the truss rod over a period of a couple of weeks... I got it playing really well, but I don't know how much travel that rod had left by the end of it all. :?

I've never had to deal with a hump in the top of an acoustic, so whatever I could suggest about that probably shouldn't be listened to... :D

Except to suggest you have a chat with Martin about it.

Re: Bubble behind bridge = high action

Posted: Tue May 11, 2021 6:47 am
by Floridian FX
https://www.stewmac.com/luthier-tools-a ... octor.html

I have the brass pin mount version that I put on a 1976 J45 that had a severe hump/raised bridge. I have had it installed for about a year and a half and it has solved the hump problem.

Re: Bubble behind bridge = high action

Posted: Tue May 11, 2021 2:25 pm
by thepezident
thanks guys...
This is a $500 guitar
Not chump change by any means....at least for me...

I'm gonna try the weighted wood and a damp sponge