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Crack repair suggestions?
http://w-ww.luthiersforum.com/forum/viewtopic.php?f=10101&t=16285		 Page 1 of 1
Author:  Steve Brown [ Thu Mar 06, 2008 8:37 pm ]
Post subject:  Crack repair suggestions?
Anyone have any good tips on repairing cracks in a top? There are three thin cracks along the grain in the lower bout of a 1961 Gibson LG-3.

Steve Brown
Author:  bluescreek [ Fri Mar 07, 2008 7:54 am ]
Post subject:  Re: Crack repair suggestions?
Old gibbys like martin had their each historic cracks. Martin from the pickguard that opened along the pickguard to the bridge.
Gibson , that also was a shrinkage issue but can also loosen the top brace as well. The martin is easier , pull the guard and ad water . there are times when this doesn't work and you need to do something a little different. These cracks need to have wood added to them. Stew mac sells a knife that is designed for this but I suggest this method.
Hopefully you have an old top. If you don't you can take some spruce with similar graining and stain to match the old top. Spray a little finish on it. This repair will show but it will be a ery stable job. I use my inlay tool and a straight edge. I will cut about 3/4 through the top. I blow out the crack and then mask off with tape. I usually use a 1/16 or 3/32 cutter . This gives me a nice clean slot. I then cut a piece off the top trying to use the best grain match I have and sand to .005 less that the cut depth. Here I like to use HHG but I have used tite bond , and elmers. Carefully dry fit , add glue. With HHG you can make it a little wet and it lows in . regardless clean tight edges are important. If you are stripping the top , then you can let the wood proud and sand down. Be sure to match the run out direction.
A plastic wallpaper edge roller helps to set the patch to depth if you are doing a finish to finish repair.
let me know how you make out
john hall
blues creek guitars
Author:  David Collins [ Fri Mar 07, 2008 8:07 am ]
Post subject:  Re: Crack repair suggestions?
A crack is not just a crack. There's simple dryness cracks, some that will close back up nicely and others that won't. There's cracks that have been open for 30 years and cracks that popped up last week. There's cracks from shrinking pickguards, cracks from shifting necks and shoulders, cracks in a warped belly behind the bridge, cracks that cross braces or bridge plate.

What kind of cracks do you have?
Author:  Hesh [ Fri Mar 07, 2008 8:48 am ]
Post subject:  Re: Crack repair suggestions?
Image
Author:  Jody [ Fri Mar 07, 2008 8:57 am ]
Post subject:  Re: Crack repair suggestions?
LOL Hesh, thats the best technique I have seen for that type of crack.. being in construction I see WAY too many ! with that application , I would be ( almost ) certain the crack would not reappear ! LOL too funny! Jody
Author:  WaddyThomson [ Fri Mar 07, 2008 10:07 am ]
Post subject:  Re: Crack repair suggestions?
laughing6-hehe laughing6-hehe laughing6-hehe laughing6-hehe laughing6-hehe
Author:  Michael Dale Payne [ Fri Mar 07, 2008 12:31 pm ]
Post subject:  Re: Crack repair suggestions?
With a good crack repair knife clean the crack out and clean the edges to a relatively straight line and smooth edges. This usually only entails a single pass of the knife through the crack. fabricate a wedge the length of the crack of the species of wood to match the top. This wedge must be in the proper grain orientation and the small end of the wedge needs to fit through the crack and the tapered sides of the wedge must be smooth and clean of burrs and dents. I also taper the ends to a point on the wedge. Fill the crack with hot hide glue, fish glue or a wood glue like Titebond or LMI white glue. Places the properly sized wedge in to the crack and carefully push sown til the wedge is in good contact with both edges of the crack. Allow to dry for a couple hour s and scrape the wedge flush with the inside and out side of the top. Practice this on some scrap a couple times first. This will create a near invisible repair. However a vintage instrument has acquired patina to the wood this will be difficult to match exact and if the top has not been stained in the finish process I prefer not to try to hide this repair by attempting to stain the wedge. I have used a tea bath on the wedge to darken it prior to installation a few times with good results.


With just a little practice this is a pretty easy repair
Author:  Howard Klepper [ Fri Mar 07, 2008 12:34 pm ]
Post subject:  Re: Crack repair suggestions?
David Collins wrote:
A crack is not just a crack. There's simple dryness cracks, some that will close back up nicely and others that won't. There's cracks that have been open for 30 years and cracks that popped up last week. There's cracks from shrinking pickguards, cracks from shifting necks and shoulders, cracks in a warped belly behind the bridge, cracks that cross braces or bridge plate.

What kind of cracks do you have?


What David said.
Author:  Evan Gluck [ Fri Mar 07, 2008 12:46 pm ]
Post subject:  Re: Crack repair suggestions?
What Howard said (about what David said). Can you post a photo? Might be of some use.
Best, Evan
Author:  Bruce Dickey [ Fri Mar 07, 2008 1:15 pm ]
Post subject:  Re: Crack repair suggestions?
Don't tell Chas. Freeborn, but I just fixed four huge cracks in a Baby Taylor. My guess was dry and hot conditions caused them, that and poor construction techniques.

I humidified it for three days right over a huge humidifier with twin blowers. That helped a bunch.

Then I made a tone bar to span the lower bout. Babies of this vintage have only a bridge plate and that's it in the complete lower bout, no kidding. So all the major cracks were in this area. The side to side scalloped tone bar tied most of it back together.

I used little binding size sticks cut to length to prop up the tone bar internally and later removed them. They flexed into place, mini-gobars if you will.

Then I moved to cleating the remaining cracks, backing them up with spruce cleats, also glued using mini-gobars internally.

I was playing the little Taylor this morning, it is really sweet, now. So repairs to the top are a little like building a ship-in-a-bottle. Through the soundhole is actually a great access port.

I would have loved to clamp everything and considered making clamps to fit each repair. But after sleeping on it, came up with the mini-gobar idea, which worked marvelously. That sort-of reminded me of installing a sound-post in a violin through the F-hole.

Sometimes repairs just require you THINKING a bit, to come up with plausible solutions to the problem. Good luck. Pics bud, we need pics.....

EDIT: Oh yeah, I forgot that I did use a side to side Bar Clamp to close the major gaps as I glued internally....
Author:  Steve Brown [ Fri Mar 07, 2008 7:53 pm ]
Post subject:  Re: Crack repair suggestions?
This guitar has all the typical Gibson issues. The pick guard shrinking cracked the top where it abuts the fingerboard extention and the sound hole . The traverse brace is pulled loose about an inch and the X brace broke loose at tore the line patch. I found this exact damage described in "Guitar Player Repair Guide". I removed the pickguard with very little damage to the top. These will close. I did a dryfit to test them. The cracks that I'm unsure of are less obvious. The Center line and two parallel cracks below the bridge in the lower bout appear closed. I can't move one side of the crack but the finish is cracked. One more is wider and will move. I plan to work titebond in it with my finger as John Hall suggested and a couple of patches on the inside. On the tight ones I'm tempted to use thin super glue. Comments?

Steve Brown
Author:  Frei [ Fri Mar 07, 2008 8:18 pm ]
Post subject:  Re: Crack repair suggestions?
I repaired a top crack using a small V gouge and glue. The V gouge cuts a perfect notch in both the scrap and the top and matching is fairly easy.
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