gluing patch without taking top off

[Dr Rod]

Hi guys and gals

I need your advice on gluing a patch without taking the top off, which is what I have done in the past for bigger cracks.

This rib crack is small enough that I think I could fix it without taking the top off.

I have done this type of patch before by running a thread through the crack, which is attached to the middle of the wooden patch, then glue is applied and the thread is pulled and eventually cut.

are there any other options available?

please include how-to details or tricks, thanks.

[Schoolhouse]

In my experience, pulling a patch with string or thread has two drawbacks. First is the size of the hole for the string, second is the inability to get enough tension to level the crack. We use shop made clamps using a guitar tuner mounted on a block with a plexiglass bass. The patch has a hole drilled through it. Music wire ( we usually use .012 wire ) is fed through the crack and out the f hole . The wire is tied behind the patch with some sort of backing and the tail end is left long and taped to the outside of the bass. The patch is glued, the wire pulled to secure the patch against the inside of the crack. Working quickly wrap the wire around the tuner/windlass and tighten the wire. The patch will be pulled tight sandwiching the repaired area between the patch and leveling it against the plexiglass base of the clamp.
After the glue has dried, cut the wire outside the bass and pull the long tail and backing off the inside of the bass. It can be tricky, but very solid and almost invisible repairs can be made this way.
Tom

[tstone]

Schoolhouse, how do you keep glue from oozing up through the hole or out of the crack and gluing the plexiglass base of your clamp to the top?

[Schoolhouse]

Hot hide glue does not stick to plexiglass. The hole is very, very small.

[Dr Rod]

thank you so much Tom, that's very clever

I guess I gotta go shopping for plexi and find a guitar tuner

Originally Posted by Schoolhouse

In my experience, pulling a patch with string or thread has two drawbacks. First is the size of the hole for the string, second is the inability to get enough tension to level the crack. We use shop made clamps using a guitar tuner mounted on a block with a plexiglass bass. The patch has a hole drilled through it. Music wire ( we usually use .012 wire ) is fed through the crack and out the f hole . The wire is tied behind the patch with some sort of backing and the tail end is left long and taped to the outside of the bass. The patch is glued, the wire pulled to secure the patch against the inside of the crack. Working quickly wrap the wire around the tuner/windlass and tighten the wire. The patch will be pulled tight sandwiching the repaired area between the patch and leveling it against the plexiglass base of the clamp.
After the glue has dried, cut the wire outside the bass and pull the long tail and backing off the inside of the bass. It can be tricky, but very solid and almost invisible repairs can be made this way.
Tom

[vejesse]

How long is the crack? Where is it? Can the edges of the crack come together without drilling little holes in the rib and pulling a cleat through to align them? If they can, and you can access the spot through the F hole why not just edge glue the crack and use linen as the reinforcement? It's pretty tough to get a cleat to make close to perfect contact when you're working that way. And if it's not making close to perfect contact, it's not going to be any better than linen.

[Dr Rod]

thanks vejesse

the crack is in the lower bout, so it is accessible through the f holes

about 3 inches long

the edges are pretty aligned

how do you handle the glue-soaked linen?
what kind of linen is to be used?

Originally Posted by vejesse

How long is the crack? Where is it? Can the edges of the crack come together without drilling little holes in the rib and pulling a cleat through to align them? If they can, and you can access the spot through the F hole why not just edge glue the crack and use linen as the reinforcement? It's pretty tough to get a cleat to make close to perfect contact when you're working that way. And if it's not making close to perfect contact, it's not going to be any better than linen.

[vejesse]

When the first Don Teeter guitar repair book came out I think that type of repair became more popular. People like gadgets. I've got a carved public school bass in my shop now where someone used the pulled through cleats for a bunch of top cracks. Let's just say it was not a good outcome.

It's easier to fit a cleat to the inside of the ribs but even if you perfectly shape the cleat to fit the out side of the rib and then turn it around, the fit is never great. Then you're frantically trying to get things in place before the hide glue gels and the cleat rotates a bit. Don Teeter was using yellow glue so he could get away with it.

Using the linen is easy, dip the strips in hot glue and apply. But I've found a couple things to avoid. One is when you have a crack this is glued but under tension. Sometimes you have keep the clamps on while the linen dries, otherwise the moisture will pop the crack open. One other thing I've found is that you don't want to use a really wide linen strip in back of ribs with thin wood. The linen might distort the ribs as it dries and contracts. To avoid that I won't use linen strips more than 5/8" wide.