First off, my name is Mark and I am new here. I am not a luthier, I am just a guy trying to pick up some skills and hope to be able to build guitars in the future. I wanted to start with some repairs since I am pretty familiar with setting up acoustic guitars and doing minor tasks like fret leveling, intonation, shaping new saddles and nuts. I picked up a Seagull SM12 on Ebay with a cracked bridge and the soundboard caving inward.

I know that a lot of 12 string guitars have problems with the string tension pulling the bridge area upward so I thought it was just the belly bulging up and I would be able to use a Bridge Doctor, but after receiving the guitar I noticed that the top is actually caving in more than I thought between the neck and bridge.

There is a hairline crack running from the bridge out toward the kerfing and bends up to the waist. At the waist the crack goes from a finish crack to a full open break in the top. See Image

Looking down at the guitar in playing position the top dips from the fretboard to the bridge and then it slightly bulges up from the bridge to the tail. Here's an image

Looking at the guitar from the tail to the headstock you can see the top is caved in at the waist.

The top is also cracked at the glue joint all the way from the tail to the bottom of the soundhole. This crack moves when I push it so it's also a clean break al the way through.


The bridge also has a crack forming all the way through the back 6 string holes. This looks like it could be glued and clamped. 


Other than that the guitar is in pretty good condition. The neck is straight and strong, and the back and sides look great. I bought this guitar for cheap so I am not afraid to really dig into it. I am really looking for some experience. If you need any more information or pics from me please let me know.




Tags: belly, bulging, caving, cracks, in, top

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I should look into that. I was looking at getting all the supplies from LMI. Is that a good place to get tonewoods from? Any bad experiences there?


LMII complaints here..


I thought I'd bump this post up, as since yesterday I also have a Seagull SM 12 spruce, in about the same condition as yours. There are no cracks in the top, but the bridge was lifting (I've already removed it completly, and "stolen" the tuners for another 12-String I had lying around), and the top is caved in between the soundhole and the neckblock. And behind the bridge is a huge bulge in the top. As well as that, it seems that the top had started to split on the centre seam sometime in the past: This has been "repaired" by an unknown expert (!), with a piece of plywood (see pics)

When I get round to repairing it, I think a complete new top is going to be the best bet, maybe with thicker braces and a thicker bridge plate this time to better deal with the string tension from 12 strings?



go on Grahame and make that top...unless you've got some youth serum.How will you debulge it?I really prefer

you go ahead w/the new top though.BTW I'm full of advice and rarely use it myself.Turn that bulge into a positive.

Maybe it's supposed to be there.I'd also be tempted to plug it up and use a tailpiece setup! I like the elasticity they

can achieve on a 12er.


Cool! Please try to take pics if you can of the process so i can see what you did. As i am getting into it, i am not sure how to match Seagull's compound radius on the top so i was going to change it to a 30ft radius. My fear in doing that is lowering the heel block too much and then the bolt on neck would have a bigger gap between the top plate and the fingerboard.

Do you think this will be an issue?


I am also not very happy with the kerfing on the top so I think I will also replace that. The bottom kerfing looks great, but there are gaps missing on the top. Do you guys have any tips on removing kerfing?

You could make your own solid (no kerf) strips out of mahog.or other wood.I did it on a mandola I made.I like that because you don't knock out kerfed ares when fitting braces and it looks neat except it's hard to see under the top.

If you plan it right you can make corrections at the neck & tail blocks.Perhaps thicker top in places?Read some of the notes on Cumpiano's site.The most interesting to me was how you can put an angle on the neckblock to acheive a better match neck to body.Not advising you to do this w/o grasping the effect.

I don't mind a little free extension above the top since it's a bolt on plus you can see how the instrument

reacts to climate by watching the F/B.You don't ant to wind up w/ the old hump at the neck to body.


Just to update you guys. I pulled all the binding off the top, removed the neck, and removed the top. It's easy to see that the braces are really thin towards the kerfing. It also looks like the kerfing needs to be replaced because there are a few gaps where they put a few filler pieces in where the kerfing they had wasn't long enough to go around the whole guitar. Also there is glue squeeze out all over the place on the top. I assume they figure no one sees that when the guitar is together. Anyway here's a few pics with the top off.


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