Acoustic Guitar Construction

The cause of the crack along the pick guard is two fold and was probably there before the low humidity magnified it. First, it is the result of a shrinking PG and second the low humidity. It WILL NOT go away without removing the PG and closing it up with humidity or moisture (I have occasionally put a drop or two of water directly in the crack and used my soldering iron and cotton cloth to "steam" it closed. The PG will noticeably continue to shrink once it is removed from the top and will need a new PG to cover the visible area where the old PG shrunk. I've repaired a hundred of these like this (both types of cracks BTW). Way to many 70's Martin have this problem. Martin used a solvent to "melt" the bottom of the PG to adhere to the raw wood and as it ages and shrinks it pulls the wood with it.

Sorry guys but I wouldn't come within a mile of that nitro finish with CA it will mess it up big time.

First, I use tape to mark the gap locations (along the side and both ends) then humidify the guitar. Place a Dampit or 2 (I have 2 for such occasions) inside the body and be sure the sound hole is closed off, let it sit overnight and check it in the morning, continue this until the gaps are closed up (will likely take a couple days to a week, sometimes longer). Once closed use HHG to glue the cracks. If you have a jack you can gently open the crack and apply the HHG. I use a small suction cup to force the HHG into the crack. Don't worry about getting the HHG off the finish, it will clean up just fine with warm water when your done. Once the glue is in there remove the jack and let the HHG do its thing as it cools it has its own clamping action. Wait until the glue is dry on the outside to clean it up, i use warm water and a cotton cloth. It will dissolve the glue on top and not hurt the glue in the crack. Depending on how big those cracks are you may want to add cleats on the inside.

I thought this video was somewhere. You may or may not need a splint like Ken and Dan said.

http://www.stewmac.com/How-To/Online_Re ... r_top.html

Thank you all - a lot of great info. I'm working to get the humidity brought back up first and then will talk with him to see what he wants done.

Once again this forum has proven how generous people can be with information and encouragement - thank you.

We won't send the bill until after Christmas :-)

Quick update. My friend wants the shrinking pick guard on the D-28 fixed so the first step is to remove it, and let the top relax.

A warm lamp softened what adhesive was left, and the plastic came off easily. You can see from the photos that the shrinking pick guard was pushing the top down pretty significantly, and a crack was starting on both sides. Its been off about two days, and the top is already flattening out a little.

I'm now debating whether to follow in the footsteps of Frank Ford, and apply nitro lacquer to bring the finish up to level before applying the new pick guard, or if I should follow Dan Erlewine's method of just sealing the surface under the pick guard before replacing. If just sealing, I'd use shellac, not superglue.

http://www.frets.com/FretsPages/Luthier ... dfill.html

http://www.stewmac.com/How-To/Online_Re ... guard.html

I think its shrunk too much to warrant reusing the old one.
http://www.frets.com/FretsPages/Luthier ... guard.html

The CA has the added benefit of adding crack resistance. You'll want to use a slightly oversize replacement.