Newbie needs Yamaha acoustic repair advice

[John H Tischler]

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!

[Hesh Breakstone]

Hi John and welcome to FRETS!

It would be helpful to us if you posted a pic or two of the gutiar top in the bridge location and of the bridge too, top and bottom.

What most of us do when we need to replace a bridge is simply make a new one.  It's not difficult and you can practice a bit making bridges from pieces of a 2 X 4 if you wish to.  As you already have determined a Martin bridge foot print and pin hole spacing won't work for you so in this instance it's likely that making a new bridge is the only alternative.  The saddle slot is often cut after the new bridge in glued in place so as to get the saddle scale length correct.

As for your other questions please see below:

1)  This is why I would like to see a picture of the damaged top and original bridge bottom.  Often when a bridge takes wood fibers with it upon removal we tend to try to replace these fibers, divots if we can carefully mine them with a very sharp chisel off the bottom of the bridge.  It's important to have as much wood-to-wood contact under a highly stressed bridge as possible.  Although there is no set rule of thumb for how much wood-to-wood contact is the minimum I tend to use the 80% rule meaning that my glue choice will change if I don't have at least an 80% contact area.  In addition f*ctories are notorious for not removing enough finish under bridges on new guitars so often it's the case that if we carefully scribe and remove additional finish getting very... close to the perimeter of the bridge foot print, the part that will show if we go too far, we can actually increase the quality of the glue joint over the f*ctories original work.

We use hot hide glue for bridge reglues unless the top is excessively damaged and the instrument is not valuable in terms of preserving it's sonic qualities or out right value.  As much as I hate to even offer this at times when a top has heavy damage, the instrument is not valuable in any way, and the client simply wants it put back together to hang on a wall epoxy can be used.  Even then we will use a quality epoxy such as West Systems and proper epoxy application methodologies where you wet both surfaces and then thicken the rest of the epoxy and apply it as the third/middle layer prior to clamping.  But... epoxy is only for special situations and again we only use quality epoxies.  By quality I am also referring to an epoxy that will release with heat. 

In Lutherie the glues that we use are "serviceable" meaning they can be released with heat and/or moisture.  Reversibility permits the instrument to be serviced in the future if need be.

As such CA sucks... is evil... and has only limited uses in Lutherie but still important uses.  We simply won't use it in any application that needs to be serviceable.

2)  Naphtha and a little elbow grease and it will clean up nicely.  Naphtha will not harm the finish.

3)  Step one in our shop before addressing a crack is to wash one's hands....  Clean hands prevent dirt from one's fingers from contaminating the future glue joint of a crack which will show forever more if we do get dirt in there.

CA was a bad choice but no worries this is how we all learn.  Instead what we might have done was rehumidify the gutiar or use excessive humidification to close the crack and then glue it together with a serviceable glue such as hot hide glue, Titebond original (only - the other Titebonds are not suitable for Lutherie).

A picture of the crack would be helpful too.  CA is often used to "drop fill" where we use thin CA without accelerator and then with a combination of scraping with a safed razor blade, sanding with 2000 and up wet paper, and rubbing out with compounds and finally buffing often one can greatly improve the repair to look pretty good.  But again let's see what you have before we start making suggestions.

[Joshua Levin-Epstein]

John,

You may be able to wash off the excess CA with acetone, but acetone will damage many finishes. If the neck of the guitar has the same finish as the body, take off one of the tuning machines and put a dab of acetone where it won't be seen when the machine is replaced. If the finish gets soft, you're back to removing the excess mechanically.

I've had Asian instruments in my shop that were entirely impervious to acetone, so you may luck out.

 

Joshua

[George Roberts]

I wish there were a "thank you" button like they have on Mandolin Cafe.  Hesh, you have once again supplied superb information in a concise, and well reasoned manner.

[John H Tischler]

Hesh, 

Thank you very much (and the rest of you too) 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 pics are below.  Thanks in advance for your help!.

[Christian Johnson]

Japanese mystery glue.  You are going to have to scrape it off.  I'd invest in a good quality German or Swedish scraper from a wood working supply house.  Mine is a Bahco and it's invaluable for removing glue and finish.

[Jeffrey L. Suits]

I'd check the neckset of this guitar, before I went any further; "heavily slotted bridge", sounds like someone's already desperately tried to get the action cown.