Newbie guitar repair questions - Yamaha acoustic

[vintshave]

Hello,

I have a Yamaha FG-441S which had a heavily slotted bridge. I ordered an ebony martin-style replacement bridge from stewmac and found that it does not have the same shape or pin slant as the original. This model (the fg)is the most "sold" guitar in history yet I cannot seem to find a replacement. Is there any way that I can get the Martin oversized bridge to work and to look good? It does not completely cover the one left by the Yamaha bridge.

I know that this is not an extremely valuable guitar, but I am using it to learn proper repair techniques and setup. In addition to the basic "how do I make it work "question, can you answer the following for me?

1) I took up a bit of the spruce top (not much) when I removed the bridge. How would I best fill in the divots (if I need to do it at all)? Could I use CA or even plastic wood?

2) I removed the pick guard because it was pretty beat up. Under it is a sticky mess. How should I remove this stuff?

3) There was a very, very thin centerline crack which I filled with CA glue. The crack is now sealed, however, the finish above it and to some extent, the sides of it, has CA on it. Would I need to sand and refinish the ENTIRE top for it to look right or is there a more localized approach that would look just as good and be less work?

Thanks so much!

[charles Tauber]

Originally Posted by vintshave

Is there any way that I can get the Martin oversized bridge to work and to look good? It does not completely cover the one left by the Yamaha bridge.

Probably not. The three things that matter most (i.e. show-stoppers) in a replacement bridge are as follows:

1. The pin holes line up
2. the saddle is in the right place relative to the pin holes
3. that it cover the area from the previous bridge

You may be able to fill things (holes, slots) and reposition them, but it may be easier to just make a replacement bridge using the old one as a template.

1) I took up a bit of the spruce top (not much) when I removed the bridge. How would I best fill in the divots (if I need to do it at all)? Could I use CA or even plastic wood?

Unless major pieces of the top are gone, leave it and reglue on top of what you have. Of course you'll need to remove the old glue to bare wood and end up with a flat surface to which to glue.

"Plastic wood" should not be used anywhere near any guitar, in my opinion: it is for construction, filling nail holes and stuff that will be painted and has no business being used in anything approximating fine woodworking. (Hobbyists everywhere will disagree.)

2) I removed the pick guard because it was pretty beat up. Under it is a sticky mess. How should I remove this stuff?

Depends upon the type of finish. You may be able to use lighter fluid or a product such as "Goo Gone", available at most hardware stores. Test it on the finish in an inconspicuous location.

3) Would I need to sand and refinish the ENTIRE top for it to look right or is there a more localized approach that would look just as good and be less work?

Most of the levelling can be done with a scraper or a razor blade used as a scraper. Final levelling can be done with fine sandpaper, 600 grit or finer. The gloss can be restored by using progressively finer sandpapers with or without following with rubbing compounds, such as those used in automotive applications.

You do not need to sand the entire top.

[vintshave]

Making a new bridge seems like a tremendous amount of work - particularly for a newbie. Is there any way that I can get this kind of replacement part? I have looked everywhere and replacement wood parts for Yamaha guitars don't seem to exist.

Alternatively, is there any way that I could repair the slotted original bridge? Could I build up the slots with CA glue until they are no longer slots? If so, would they be as strong as the original wood and not be "cut" by high-tension strings?

Thanks again.

[charles Tauber]

Start at the beginning.

What do you have, what is wrong with it and why do you want to change it?

Is the slotting of the bridge causing some specific problem? Is the action and intonation acceptable? Is there some other issue with the bridge that suggests that it needs replacement or repair?

I am using it to learn proper repair techniques and setup

My first rule of guitar repair is don't repair things that don't need repair. Or, in the vernacular, "If it ain't broke, don't fix it." The repair should not leave the instrument worse-off than before it was repaired.

[vintshave]

Good questions and ones that I probably should have considered before removing the bridge. Unfortunately I have already done so have applied some CA glue in an effort to fill in the slots. So given that I have probably already done it wrong, I might as well use this as an opportunity to learn something about guitar repair. In fact, I bought this instrument more or less to practice some techniques on before going and messing up something really nice ;-)

[charles Tauber]

Without pictures, I don't really know what you have.

The first question is why were the slots there. Were they caused by wear or purposely put there by someone? The usual reason they are purposely put there, particularly on a Yamaha, is that there isn't enough saddle projecting out of the top of the bridge. Slots are then added to increase the angle that the strings break over the saddle, increasing the downward force exerted by the strings on the saddle. If you fill the slots, you may revert back to the problem that was addressed by slotting the bridge.

The usual cause of not having enough saddle projecting from the bridge is that the neck angle has changed and is in need of a neck reset. This was the first thing to check prior to ripping the bridge off. Regardless, that question still needs to be answered: does it need a neck reset? Is that what lead to slotting the bridge?

Without knowing that, there is no basis on which to proceed, no way of knowing what action needs to be taken, what needs to be "fixed".

[vintshave]

What pictures would be best for me to take and at what angles?

Also, I think that the neck reset issue is borderline. A straight edge run across the frets will JUST bump into the top of the bridge if I am pressing it down into the top as best I can. So I don't think that this is an issue of a guitar crying for a reset.

Also, I have been hearing that Yamaha uses marine glue. I don't know if this is true, but if it is, does it make any sort of clean removal of glued joints impossible?

[charles Tauber]

Originally Posted by vintshave

What pictures would be best for me to take and at what angles?

At this point, probably the top and bottom of the bridge - showing the slots you want to fill and the gluing surface of the bottom - and the top where the bridge needs to be attached, showing the gluing surface and the pieces missing.

[vintshave]

Thank you very much for your comments and advice. It really helps when you are starting out (even at the age of 49) to know that there are people out there willing to give their valuable time.

Financially, this guitar isn't worth the time I'm spending on it, but it is good enough and I got it at a reasonable enough price ($75) where I both want to see it playable again but would not be devastated if I really messed it up. The crack you see in the top photo is completely sealed. I used ultra-thin CA to fill and seal it. It was not all the way through the wood. I had taped around the crack, but that CA glue seems to be able to get under it (an argument for hide glue) or at least, better tape. I sanded down around the crack and wet sanded up to 2000 grit. I pronounced it "good enough" for a first effort and turned my attention to the bridge. I don't think that the guitar absolutely needed a neck reset (although it was close). A straight edge along the frets just grazed the top of the bridge when it was in place.

Whatever glue Yamaha used I don't think it was the "serviceable" variety. I heated both the spatula and the bridge itself quite a bit and felt very little softening. I have since heard that they may be using Marine Glue, which is a good explanation why wet heat wouldn't budge it. In any case, that's my story and the link to the pics are below. Thanks in advance for your help!.

https://plus.google.com/photos/11515...MiU8tXhy8SM-QE

[charles Tauber]

Originally Posted by vintshave

The crack you see in the top photo is completely sealed. I used ultra-thin CA to fill and seal it. It was not all the way through the wood.

Based on the photos, I suggest that not only did the crack go the full thickness of the wood, but was also "open". It appears to be the center seam of the top having failed. The most likely cause is shrinkage due to dryness. Probably, the appropriate measure was to start by hydrating the guitar to see if the gap would close fully or partially, prior to gluing. Generally, the approach to crack repair is to close the crack, if possible, glue, then reinforce from the interior, rather than fill an open crack with glue, creating a black line of adhesive.

I would probably have used an aliphatic resin (yellow) glue to glue the crack. Others might have used CA glue. Given the open-ness of the crack, ultra-thin was not called for and using a more viscous version would have reduced the amount that bled under the tape.


I see nothing out of the ordinary regarding the bridge slots. I would not have touched them unless there was some specific problem they were causing.

The amount of top wood that was attached to the bottom of the bridge when the bridge was removed is of no concern - it is insignificant.

As manufactured, a rim of finish was left underneath the bridge that needs to be removed, the gluing surface of the top needs to be prepared as does the bottom surface of the bridge. My preferred tool for preparing the gluing surfaces of top and bridge is a cabinet scraper and/or a chisel used mostly as a scraper. If you don't have or are unfamiliar with a cabinet scraper, I suggest buying one ($10 or so) and learning to sharpen and use it. A chisel can also be used as a scraper when the blade of the chisel is held more-or-less vertically and dragged across the work leading with the back face of the chisel.

In my experience, there is no practical way to use sandpaper to remove the glue on the top where the bridge is glued. Sandpaper CAN be used on the bottom of the bridge, but sandpaper has the natural tendency to dome surfaces - not what you want. Mostly, I'd use the back of a chisel as a scraper for the top and a scraper for the bridge. There is some technique involved to produce a flat surface without tearing the #$^% out of the softwood top.

With both surfaces flattened, I'd hold the bridge where it needs to go and trace around it carefully with a scalpel type knife cutting just through the finish. Then remove the excess that is beneath the bridge. To hold the bridge in position while scribing around the bridge, I use two 3/16" machine screws with appropriate wing nuts and washers. One screw goes in each of the first and sixth bridge pin hole and the nuts and washers tightened from the inside to hold the bridge down and in place. (I use the same screws, nuts and washers along with two cauls for actually clamping the bridge during gluing. One caul fits the bridge plate and goes inside the guitar, the other cut to the contour of the bridge and sits on top of the bridge. The screws go through the "sandwich" of outside caul, bridge, top, inside caul, even when scribing the finish. Of course the cauls need to have holes drilled appropriately to accommodate the two screws. Don't forget to wax the surface of the inside caul that goes against the inside of the top - or use a sheet of wax paper.)

For gluing the bridge, I'd use yellow glue, maybe hot hide glue if you want the challenge.

That should get you started.

[redir]

A good trick that I use for hydrating a guitar like that is to leave the guitar in your bathroom after a shower for a couple hours. You don't want the thing to be soaking wet but placed in a small room with high humidity. Put it in the case with a humidifier between 'treatments'. Do that over the course of a week or two to see if that crack closes. In this case I would also build cork lined cauls to the shape of your lower bouts to squeeze the top together with long clamps for gluing up. Then glue in cleats about an inch apart on the inside to sure up the joint.

[charles Tauber]

Originally Posted by redir

A good trick that I use for hydrating a guitar like that is to leave the guitar in your bathroom after a shower for a couple hours. You don't want the thing to be soaking wet but placed in a small room with high humidity. Put it in the case with a humidifier between 'treatments'. Do that over the course of a week or two to see if that crack closes. In this case I would also build cork lined cauls to the shape of your lower bouts to squeeze the top together with long clamps for gluing up. Then glue in cleats about an inch apart on the inside to sure up the joint.

Agreed, but now that it is full of dried CA glue, chances of success are probably limited, which is part of the reason I didn't go into any of that.

[vintshave]

Originally Posted by charles Tauber

Based on the photos, I suggest that not only did the crack go the full thickness of the wood, but was also "open". It appears to be the center seam of the top having failed. The most likely cause is shrinkage due to dryness. Probably, the appropriate measure was to start by hydrating the guitar to see if the gap would close fully or partially, prior to gluing. Generally, the approach to crack repair is to close the crack, if possible, glue, then reinforce from the interior, rather than fill an open crack with glue, creating a black line of adhesive.

I would probably have used an aliphatic resin (yellow) glue to glue the crack. Others might have used CA glue. Given the open-ness of the crack, ultra-thin was not called for and using a more viscous version would have reduced the amount that bled under the tape.


I see nothing out of the ordinary regarding the bridge slots. I would not have touched them unless there was some specific problem they were causing.

The amount of top wood that was attached to the bottom of the bridge when the bridge was removed is of no concern - it is insignificant.

As manufactured, a rim of finish was left underneath the bridge that needs to be removed, the gluing surface of the top needs to be prepared as does the bottom surface of the bridge. My preferred tool for preparing the gluing surfaces of top and bridge is a cabinet scraper and/or a chisel used mostly as a scraper. If you don't have or are unfamiliar with a cabinet scraper, I suggest buying one ($10 or so) and learning to sharpen and use it. A chisel can also be used as a scraper when the blade of the chisel is held more-or-less vertically and dragged across the work leading with the back face of the chisel.

In my experience, there is no practical way to use sandpaper to remove the glue on the top where the bridge is glued. Sandpaper CAN be used on the bottom of the bridge, but sandpaper has the natural tendency to dome surfaces - not what you want. Mostly, I'd use the back of a chisel as a scraper for the top and a scraper for the bridge. There is some technique involved to produce a flat surface without tearing the #$^% out of the softwood top.

With both surfaces flattened, I'd hold the bridge where it needs to go and trace around it carefully with a scalpel type knife cutting just through the finish. Then remove the excess that is beneath the bridge. To hold the bridge in position while scribing around the bridge, I use two 3/16" machine screws with appropriate wing nuts and washers. One screw goes in each of the first and sixth bridge pin hole and the nuts and washers tightened from the inside to hold the bridge down and in place. (I use the same screws, nuts and washers along with two cauls for actually clamping the bridge during gluing. One caul fits the bridge plate and goes inside the guitar, the other cut to the contour of the bridge and sits on top of the bridge. The screws go through the "sandwich" of outside caul, bridge, top, inside caul, even when scribing the finish. Of course the cauls need to have holes drilled appropriately to accommodate the two screws. Don't forget to wax the surface of the inside caul that goes against the inside of the top - or use a sheet of wax paper.)

For gluing the bridge, I'd use yellow glue, maybe hot hide glue if you want the challenge.

That should get you started.

First of all, thanks for the detailed advice. I found that I could not implement the scraper advice for doing the bottom of the bridge. Whatever epoxy they used on it sticks to the wood so well that I started notice gouges in the wood from that method (it gives me a greater appreciation of why luthiers hate epoxies and CA glues). So I abandoned that in favor of sanding the glue off. However, understanding what you said about "doming" I used self-adhesive 220 on a granite block that was engineered to .0005" flatness and got the result I wanted.

I am in a greater jam on the guitar top. Scraping with a chisel doesn't seem to help get it any flatter. If anything, it seems to create more hills and valleys. And the spaces where spruce was gauged out...can I safely glue the bridge over these areas with little/no effect on the sound or must I fill them in completely with spruce bits and glue?

Lastly, how can you be certain that you are gluing the bridge in exactly the right place? It seems that being off by even a little is as good as being off by a mile.

[redir]

Oh I should probably read better. If it's filled with CA that's a problem.

[charles Tauber]

Originally Posted by vintshave

it gives me a greater appreciation of why luthiers hate epoxies and CA glues

I don't think that luthiers hate epoxies or CA glues. They have their appropriate uses, as do the glues.

understanding what you said about "doming" I used self-adhesive 220 on a granite block that was engineered to .0005" flatness and got the result I wanted.

If you hold the bridge up to a strong light and place a straight-edge along at various locations along the length and then width of the bottom of the bridge there shouldn't be any light visible between the straight-edge and the bridge. Particularly, there shouldn't be any light as you approach the edges of the bottom of the bridge.

Scraping with a chisel doesn't seem to help get it any flatter. If anything, it seems to create more hills and valleys.

I did explicitly say, "There is some technique involved to produce a flat surface without tearing the #$^% out of the softwood top." Now you know, first-hand, what I meant. Ditto for a scraper. That was contained in my statement, "If you don't have or are unfamiliar with a cabinet scraper, I suggest...learning to sharpen and use it." What you have experienced is the first step in "learning to sharpen and use it". You now know how not to use it in this application. A scraper will exaggerate hills and valleys if used parallel to the hills and valleys. Used perpendicular to the hills and valleys it will lop off their tops producing a flat surface. For a gluey mess, start by removing some of the excess using the chisel as a chisel.

And the spaces where spruce was gauged out...can I safely glue the bridge over these areas with little/no effect on the sound or must I fill them in completely with spruce bits and glue?

Unless there are large chunks of top-wood missing you don't need to worry about them; you can ignore small divots. However, for there to be a good glue joint, the old glue must be removed back to bare wood. And the gluing surface needs to be "flat" (other than the small divots).

Lastly, how can you be certain that you are gluing the bridge in exactly the right place? It seems that being off by even a little is as good as being off by a mile.

I use the screws, as I described. Simple, dead-accurate, no shifting during gluing.

If you don't like that, a few strips of masking tape can also be used around the perimeter of the bridge to help prevent it from sliding around while gluing. But, that isn't as effective.