MIMF

I removed the bridge on an acoustic guitar, because the old one was broken.
I used heat, and some proper bridge removal knives, but there was still some tearout on the guitar top. It's not terrible, but not good either.
I'm going to make a new bridge with just a bit larger footprint than the old, because in my opinion the old one had too little material ahead (nut side) of the saddle. I believe this is why it failed, cracking on both ends of the saddle slot.
I will remove the finish and clean up the whole area under the new bridge so the glue is on wood.

To get back to my problem: Do I have to fill the area where the wood is missing with something?
Or, will the hide glue itself fill the gap?

I will take a picture and post it later today.

Hide glue does not fill gaps. Splice in some spruce.

If I recall, Frank Ford showed his method on frets.com

Pat

Here are some pictures of the guitar.

First I'll show the cracks in the bridge, that caused the repair.
The other side is the same.


And here is what the top looks like now.
I believe this bridge was glued on top of the finish. I may be wrong, but it sure looks like that is what happened.



Here's a couple of pics where I have a separation knife in some of the splinters, and under the finish.

Thats a plywood top. You have gone though the top ply in several spots. This is not good.

The reason the bridge cracked in the first place is not because the saddle slot was too close to the front of the bridge. It cracked because the slot went completely though the bridge which is not recommended.

Due to the plywood top, and the missing wood, this might be a situation where you should glue the new bridge on with epoxy which will help to fill the voids and keep the top from further delamination.

But you should scrape the full foot print of the bridge to remove the old glue and finish. You want the new bridge to make contact with the wood as much as possible.

Also, you do not need a larger bridge. Just get the finish removed along the back edge. The 1/4" overlap there is what likely caused the bridge to peel up because this is where the greatest peeling force is located.

Thanks for posting these pics Gordon. I knew that some manufacturers glued their bridges directly to the finish, and I always wondered what would happen of they needed removal.
That looks like a pretty bad job by the original maker. The rear edge of at least one wing was never in contact at all.
I also winder if you used enough heat - or if there is any hope of getting one of these off without damage like that.
You will certainly have to do some top repair to make a new bridge mate properly. And I would recommend routing off any remaining finish from the top, under the new footprint.

Q: What is the maker of the instrument?

Thanks for the replies. This is a Washburn guitar.
Actually the old bridge was not lfting at the rear. The reason I was removing it is the cracks. The saddle was leaning forward badly.
I think the bridge was glued on top of the finish.
I think I will attempt the repair Barry mentioned.

There is only about 1/8 inch of wood in front of the saddle slot. I think that maybe a contributing factor also.

The photo shows that the finish extended about 1/4" under the back edge of the bridge. The other shiny stuff looks like the old glue. But either way it needs to be scraped down.

Here is the bridge outline cleaned up.
I clamped 2 straight edges to the guitar and used my Dremel to rout about 1/64 out.

Looks like you routed through the first layer of plywood exposing the second layer. I am not sure that was a good move. This may or may not cause delamination further into the top.

At this point, I would advise going back to hot hide glue for the bridge attachment.

Yes Barry, I did go through the first layer. I had to, to get somewhere even close to level.
I am cutting the new bridge out now, and will post pics later.
It is to the point where I either glue a very thin layer of spruce in, and cover it with the new bridge, or shape the bridge perfectly for the very shallow rout.
Advice?

Applying a layer of spruce only adds another glue joint which is not a benefit, except it would raise the bridge up to the level of the top so that if you ever need to remove the bridge in the future it would be possible. But at this point I would just make the bridge and glue it in and hope for the best. It will probably be OK.

Thanks Barry. This guitar is obviously a cheapie. I will advise the lady who owns it, that this will be the last time the bridge will be able to be replaced.
I don't think it's the end of the world, as long as she can play it for a while.

And she is my friend, so this is a very inexpensive repair for her.

I've been quite a few of these types of repairs for a local music store and it looks like you've done about what I would recommend. Many of the new Chinese made guitars are using a catalyzed finish which is very hard to remove and most leave between 1/8 and 1/4' of finish under the edge of the bridge to look good. This frequently causes the bridges to fail. They are also using some form of glue which is non soluable and very hard to remove. Using the dremel is about the best you can do in that circumstance and it's better to loose all or part of a layer of plywood but create a solid, flat wood surface to glue to.

I agree that there is little value in adding layer of veneer to re-create the original thickness of the plywood as long as the depth is not too great. 1/64 should be fine. If you needed to add wood to raise it, then you might consider using epoxy to add the veneer layer, but use hide glue or titebond to glue the bridge on. That way the bridge can be removed later if need be but the veneer layer would stay in place.

Thanks for your input Chris.
When I was removing the bridge, it seemed to take a lot of heat, and still didn't loosen up the way others have in the past.
As I have started putting this back together, I realized what was going on.
The original bridge saddle slot was cut too deep, right through, to allow room for the unusually thick under saddle pickup strip.
The strip is about 1/8 thick. By the time you get the strip in, there is not much depth left for the bridge saddle.
When I sized the new bridge, I measured it at 5/16 thick. I cut the slot 15/64 deep. That leaves a bit less than 1/8 for the saddle.
I'm going to try leaving the pickup in, and seeing how the saddle sits. If it wants to lean forward too much I will suggest leaving the pickup out and inactive.
My friend is not playing in front of people anyway.

If you run into another one of these, you might try a different approach. For an inexpensive guitar like that I would have reglued the cracks on the bridge and glued in the saddle to restore strength. Although glued in saddles are a pita to remove, using an organic based glue (hide, titebond, etc) vinegar will soften them in the event the saddle needs to be pulled in the future. Gluing in a well fitted saddle would have added enough strength and saved pulling the bridge. Some will not agree with me on this, but even Martin glued in some saddles.

I spoke with another repairman at a local music shop.
This guy works at a shop in my city that deals in acoustic instruments almost exclusively.
He's been there for a long time and is well respected.

Firstly, he told me that he wouldn't do this repair on a cheap guitar. He would advise simply spending the money on a new one.
Having said that, he then told me that in the past when doing a bridge like this he has of course used heat and knives.
But when he ran into a difficult bridge like this one, he has routed the bridge off.

I can see this working. Set up some blocks to guide the bit, and simply take small layers off, stopping when almost level with the guitar top surface.
Use a sanding block to finish.

Opinions?

That is a common technique.

"Firstly, he told me that he wouldn't do this repair on a cheap guitar. He would advise simply spending the money on a new one."

That is something to always keep in mind, and a reason to do the repair in an expedient but effective manner.

Given that it's a cheap guitar and the bridge isn't going to be replaced a second time, I'd epoxy it on. solid, strong, won't creep and fills gaps great.