Acoustic repair.

[Bulletr0k]

Note: Tis is an acoustic Guitar, but I need help repairing it anyway, it's the bridge.


Now, this guitar is/was my sisters, and she never really used it. Thus, it's dusty, untouched, and as used as the day we bought it from the thrift store.

The problem is, aside from a few scratches and a lot of dust, is the bridge. It seems, in theory, that since the strings had a lot of tension from not knowing how to tune, so the bridge has come off of the body some, at a slight angle, maybe a few mm. from the body. I was wondering how i could fix it.


A very important diagram showing what the guitar has.

Edit: The nut fell off when I was taking off the old strings. Joy.

[202dy]

Generally speaking, the bridge should be removed and re-glued. Here is a quick overview.

The bridge is removed with either heat or with force. With heat, the guitar top is masked off with foil covered card board and heat is applied via infra red or halogen lamps. Alternatively, silicon heaters can be used. As the glue heats, a palette knife is inserted in the gap and used to work the bridge off. It is a good idea to score the perimeter of the bridge with a razor, like an Exacto knife. A chisel and mallet can be used to knock the bridge off. The strike line is the headstock side of the bridge. The trick is to strike the glue line rather than the bridge. Work from one end to the other giving sharp raps to the chisel.

When the bridge is on the bench, clean up begins. The bottom of the bridge is scraped clean as is the area of the top where the bridge resides. Wood to wood contact is paramount. It is not unusual for the bridges on inexpensive instruments to be glued to lacquer. This is not a good connection. When this is the situation, the lacquer on the top needs to be scraped off. Razor blade scrapers work especially well for this, although so luthiers will use a Dremel in a router base to rout the lacquer off.

Reglueing requires making cauls to match the shape of the bridge top. The cauls should be padded with either cork or leather. Some techs will use "friendly plastic" to get the fit right. Another large caul is used inside the guitar to allow the clamps to clear the braces. Otherwise the clamps will dent the wood. Others uses speciallized clamping rigs. The clamps need to have at least a six inch throat to reach the bridge. Luthiery supply houses carry quite a few different designs. Check them out on line. White, yellow, or hide glue are the adhesives of choice for this task. White glue has the longest open time, about seven minutes at seventy degrees. Apply glue to both pieces and clamp. Tighten the clamps enough to get good squeeze out, but not so much so as to starve the joint. A dish of warm water and pieces of cloth or paper toweling are used to clean the top of the glue that squeezes out from the joint. This process takes seven to ten minutes.

Technically, the clamps can come off in an hour or two. Or you can leave them on all night. Once the glue sets, it doesn't matter, but a lot of people prefer to leave them on. Final clean up occurs the next day. It is not unusual to run a small drill bit through the pin holes to clear them of glue.

If you do not have good woodworking skills, are not seriously handy, or are not willing to purchase some specialty tools take this repair to a tech.

[Nelson Guitars]

Well said. Especially the part about having good wood working skills. There are many ways to screw up a bridge replacement.

I always find the advice that Frank Ford gives over at frets.com to be spot on if you need help with this sort of thing. Hope it's OK to say that here. It's not a forum site and chock full of information and years of experience.

Oh by the way. It's OK that the nut fell out. It's supposed to do that. Held in by string tension. Please don't glue it in.

Greg N

[202dy]

Originally Posted by Nelson Guitars

Well said. Especially the part about having good wood working skills. There are many ways to screw up a bridge replacement.

I always find the advice that Frank Ford gives over at frets.com to be spot on if you need help with this sort of thing. Hope it's OK to say that here. It's not a forum site and chock full of information and years of experience.

Oh by the way. It's OK that the nut fell out. It's supposed to do that. Held in by string tension. Please don't glue it in.

Greg N

Frank Ford is one of the top men in the field. It is not only o.k. to mention frets.com, it is a highly recommended resource.

[Bett]

Is it just the bridge that came off? We have an acoustic guitar and the bridge has pulled part way off, but it's taken part of the body with it. The soundboard has cracked behind the bridge for some reason (I think it may be missing a brace on the inside under the bridge). My mother said two people have told her it can't be fixed, though I refuse to believe that. It's not an expensive guitar, I think we got it for free, but it looks nice. Maybe someday it'll get properly fixed (I made a removable string holder that keeps most of the tension off the bridge as an experiment).

[Bulletr0k]

As far as i can tell, it's just the bridge. After taking off the strings, I can see it more clearly and hopefully can repair it. The nut came off too, but that should be an easier repair.

[Nelson Guitars]

By the way, without opening up the whole "best glue" debate this is exactly the sort of application where hot hide glue shines. If the original installation was done with HHG then you would be able to de-bond this with moist heat, clean both surfaces with hot water and have perfect surfaces to glue together again. Anything else and you will be gluing to wood fibers that are already saturated with old dry glue so the new glue will not be able to perform to its greatest ability.

Once you have the bridge removed try to clean the visible glue off with a clean rag and hot water (150 degrees F) If the glue softens and turns to Jello then likely it is HHG. If not then your best option is to sand down to bare wood being careful not to round over the edges of the bridge bottom. On the guitar top, mask off the areas around the bridge and scrape or sand the surface as best you can trying to remove the old glue. Patience is key here since you don't want to damage the adjacent finish or remove too much of the top.

Good luck.

Greg N

[202dy]

Originally Posted by Bett

Is it just the bridge that came off? We have an acoustic guitar and the bridge has pulled part way off, but it's taken part of the body with it. The soundboard has cracked behind the bridge for some reason (I think it may be missing a brace on the inside under the bridge). My mother said two people have told her it can't be fixed, though I refuse to believe that. It's not an expensive guitar, I think we got it for free, but it looks nice. Maybe someday it'll get properly fixed (I made a removable string holder that keeps most of the tension off the bridge as an experiment).

It is typical that the bridge will pull loose from the top.

When the top cracks behind the bridge the repair is more difficult to perform. It would be extremely unusual for a brace to be missing. The X brace runs directly under the bridge. It is built of two long pieces of spruce that traverse the guitar body diagonally and cross between the sound hole and the bridge. Underneath the bridge, nestled between the arms of the X is the bridge pad or plate. It is a flat piece of spruce roughly the same thickness as the top. The pad stiffens and reinforces the top at the bridge in an effort to eliminate bridge rotation. On inexpensive guitars the pad can be plywood which bends and offers little reinforcement. It would also be unusual for the pad to be missing. The larger the pad the stiffer the top. But some folks claim that a large pad makes the top less responsive. When the top cracks, it is usually at the end block edge of the bridge plate.

The guitar can be repaired. Typically, this will be a bridge pad replacement. The existing pad is removed and replaced with a larger one. The lacquer is touched up and the bridge is replaced, sometimes with an oversize one. It is expensive and time consuming. Sometimes a spruce pad can be laminated to the existing one but if it is plywood it is usually not a successful repair. If the guitar is inexpensive it might not be cost effective to do this.

[Bett]

Yeah, I think it was the bridge plate that the guitar seemed to be missing. I tried to feel for it but there was nothing in the area it should be in between the cross braces. It could be I missed it at the time. I really don't know anything about that guitar though. I think there's a blank sticker on the inside, but besides that I haven't seen any markings. It could have been something cheaply made. Anyway, it probably won't get fixed any time soon since we have 2 other acoustics and don't really need another to play. It's just sitting in the basement right now with it's clamp-on bridge/string holder and 4 pieces of wire since I couldn't find anything else for it.

[202dy]

Originally Posted by Bett

Yeah, I think it was the bridge plate that the guitar seemed to be missing. I tried to feel for it but there was nothing in the area it should be in between the cross braces. It could be I missed it at the time. I really don't know anything about that guitar though. I think there's a blank sticker on the inside, but besides that I haven't seen any markings. It could have been something cheaply made. Anyway, it probably won't get fixed any time soon since we have 2 other acoustics and don't really need another to play. It's just sitting in the basement right now with it's clamp-on bridge/string holder and 4 pieces of wire since I couldn't find anything else for it.

If it is a no name, laminated guitar the price of the repair will probably exceed the value of the instrument by a three to five times. If that is the case, this one is a loser. Salvage the parts and use the rest for kindling. If there is any solid wood that can be saved for patch work.

[Bett]

I wouldn't chop it up (my mom wouldn't let me anyway, it's hers) but we are saving it. It has a nice headstock and tuners on it. Maybe someday I'll try to fix it, even just as a learning experience.