X brace crack repair

[Larry Pederson]

I’ve gotten an early ‘60s D-18 that’s in nice original condition except that it probably had one traumatic   accident. I got it intending to repair several side and back cracks to make it into a “player” guitar. I am planning to leave the 1” long lower bout top dent and the lower bout side dent with a couple missing pieces of finished mahogany near the top dent. I’ll repair the minor cracking around the dents but the dents are beyond my ability to repair and finish. No problem so far.

Then I spotted the X-brace crack … hmmm. You can see in the photos it travels from the center of the X to the small brace farthest from the center.  The crack is through the width of the brace traveling along the grain. There is a very minor crack in the brace on the opposite side of the X intersection with the problem brace that should be easy to deal with.

I’m looking for suggestions to effectively deliver glue (probably Titebond) into as much of the crack to securely repair this damage. I was planning to wedge the crack open a bit farther and use a disposable plastic bulb pipette with the fine end to deliver the glue. The viscosity of Titebond is a problem. Can I dilute it so it flows in and out of the pipette tip easily (1/4 H2O?)? Or is a disposable syringe with large gauge needle a better tool? Glue will still need to be diluted to flow out the needle without too much effort.

This guitar was built with hide glue. Is this the time to make some up and learn to use it? Are there non-soluble solids that would have to be filtered for hide glue to be usable in this instance?

Is something like Superglue gel a good way to go for a really permanent fix?

I have 3 Stewmac brace repair jacks ready to apply once I figure out the glue and the glue delivery issue. I tried a forum search but didn’t find any prior discussions that dealt with my problem.

I strung this guitar up before I bought it, and it’s a very “strong performer” with the tone and volume of a really fine sounding non-scalloped bracing D-18 of the ‘50s and early ‘60s. And that’s with a screwed up brace. It can only improve if I do the repair properly.

I will really appreciate the input of anyone with experience dealing successfully with a problem like mine.

[Mark A. Kane]

Just did one of these but the crack was longer and open a little more. My fix was generally as follows:

Blue painters tape on either side of the bracing, and anywhere else glue might drip (though I'm not overly concerned, as I clean it anyway, post-repair).

I use 3-4 blunted and dulled (on the belt sander) X-acto blades as wedges in the crack, positioned for easy removal. 

I work Titebond (undiluted) into the crack, using my fingers to force it in, working quickly. I'll follow up with a small palette knife in the crack, if possible. Then, more glue with my fingers.

Pull out the wedges (use a big rare earth magnet to assist), wipe everything down with a wet washcloth (doesn't come apart like paper towels).

I prepare (in advance) and test-fit small go-bars (6-8, depending) from popsicle sticks and coffee stirrers (smouched from Starbucks). Install the go-bars, wipe up the squeeze-out and have a cup of tea.

I find the go-bars easier to work around than the jacks (though I own several jacks, and they obviously come in handy in other situations). The key is to test-fit. I'll often notch the ends to fit a particular brace-shape, then number them so I'm not fumbling around when the glue is calling.

[Mark McLean]

I think Mark just gave the ideal rundown on this repair.  Nice ideas for sourcing disposable in-guitar go bars!  I definitely wouldn't go with hide glue because you need a lot more time than it would allow before grabbing.  Titebond would be my choice. 

[Larry Pederson]

Thanks for clarifying the best choice and the very fine tips and detail on getting it done well. I feel confident I can get the ol' D-18 back in action soon with all cracks sealed up nicely. Thanks again to both Marks!

[LARRY KLOSE]

Does anyone have any opinions about using LMI Luthier's Glue for this repair instead of Titebond?  Better, worse, the same?

Larry

[Hesh Breakstone]

Titebond is fine.  The reason why this is not a good opportunity to start getting your HHG chops down is the open time for HHG is only 15 seconds or so without preheating.  So you have to ask yourself after doing dry runs (not the gastrointestinal version...) if you can have the glue where you want it and the clamps/jacks in place in 15 - 20 seconds time.  My answer would be no so I would use Titebond.

Another approach would be to with one hand on the top of the bridge and the other hand in the sound hole to pump the top, flexing the brace crack open and using your finger on the first pass to pack the crack with glue.  Repeat with a small feeler gauge in your sound hole hand and using the feeler gauge push glue into the crack while pumping the top.  

I would then use a couple of 5" reach sound hole clamps (C clamps) with a piece of leather taped to the lower contact point and a caul on top of the guitar to prevent damage to clamp.  Two clamps should do it.

We have and use video cameras in the sound hole and we also have and use enough hypodermic needles to keep a room of junkies happy (or dead...) for a very long time.  I'm trying to get Dave to design and engineer a little robot that runs around in the sound hole painting glue and holding things in place but that one is going to take some time... :)  Besides the robot might get uppity and want a living wage....

[David Farmer]

This is the position I like to have a guitar in for an X brace crack. The brace is perfectly horizontal and the top is tilted slightly towards the floor. This let's me apply a small puddle of glue on the high side of the brace crack and it sits there with out dripping or running anywhere while I flex the crack open and closed and gravity caries it into the crack and out the other side. Put a small puddle over the tight end of the crack first. That allows plenty of time to work it in. after you have good glue penetration at the tight end, put some glue on the wider end and it will rip right through to the other side quickly.

Franklin says you can dilute tight bond 5-10 percent with water by volume without affecting strength.

That said, I kind of hate to see it used on an instrument originally built w/ hide. Are you hell bent on doing this one yourself? I agree this is definitely not the place to start learning hide. Tightbond is a one shot deal. If it came into my shop and The Tight bond had failed to hold it, I would  groan when I saw it.

[Hesh Breakstone]

You know David that must be a universal thing, that Luthier groan.... when we see the ravages of what happens when someone does hack work.... :)  Colorful language is standard fare in our shop too...  We're not judgmental.... :)  You should hear what I am known to say when I see a lifted bridge that some yahoo squirted super glue under.....

Good going using gravity to your advantage!

Regarding diluting Titebond.  Lately I have been gluing cracks a bit differently with great results.  After rehumidifying I've been rubbing in watered down Titebond as a sizing and then rubbing in full strength Titebond.  I find that the wetting with the thin stuff helps the thick stuff wick or migrate into a tightly closed crack which is the goal.

By the way your shop looks pretty clean!!!

[Dave Richard]

Speaking of Luthier's Groan....I used to say, luthery and repair isn't rocket science, but one must be thoughtful and careful. But after seeing so many appalling and inept 'repairs', I've decided...it must be rocket science!

[Larry Pederson]

There's plenty of science in good guitar repair ... like the "slight" dilution of Titebond lowering the viscosity and surface tension allowing better penetration of the glue into very tight spaces. It seems to me that some glue is better than no glue, especially at the narrow end of the crack I'm dealing with. That diluted glue still dries completely and adds strength in a gap previously filled with air. So I'm inclined to apply that slightly diluted Titebond to the narrow end of the crack.

I'd be more inclined to turn this guitar over to a repair person I know and trust if the cracked brace weren't so easily accessible and easy to apply pressure to. The cracked piece is perfectly aligned with the rest of the brace. I know I can apply Titebond to the whole length of both sides of the crack and I can apply careful even pressure to rejoin the loose piece. It could be that it's repaired more effectively and reliably than what I'm hearing the limitations of using hide glue could accomplish short of some heroically timed sequence of glue application and pressure to the brace.

I'd be more inclined to have that trusted repair person work on this guitar too if it had more collector appeal and value. It's a working class D-18 made very precisely and solidly in the old Martin factory in the manner of the pre-war Martins, but cursed with the heavier bracing and played lots to entertain whoever owned it. There are tens of thousands of fine guitars from Martin in better condition out there.  However, the indented damage to the edge of the top and the splintered damage to the side I mentioned earlier means, I believe, this will never be a collector's item in my lifetime. I'm going to fix it to solid "player" condition for flatpicking old time fiddle tunes. I think the sound of this guitar will be right there with the best of the very fine modern guitar builders, and the only thing lacking will be my skill in playing it. My son can worry about justifying my use of Titebond on the brace repair and other cracks I'll be tackling if it should become a collector's item ... hopefully in the distant future  : ]

Thanks to everyone for all the input and discussion on my repair problem. You effectively kept me from using a staple gun or screws to get that sucker to stay put. I really do sympathize with you pros out there when you get stuck correcting the moronic things some people try. Thanks for the benefit of your experience and I'll be more aware about using gravity as my friend in future repairs!

[Howard Klepper]

I cannot see the point of using screw jacks or jack posts (what I think people mean by "go-bars" here) where you can get long cam clamps on the brace through the sound hole.

Using a jack or post requires an outside clamp if you are going to get any significant pressure and not crack the top.

IMO the best glue for a cracked brace is Titebond Original Extend.  Since it is not redoing an original joint, a "period correct" glue ought not to be expected.

[Carl Mesrobian]

My philosophy on this, as well as on upright bass repair is "if it was originally wood, use whatever you have to - if it's a joint, use hot hide glue". I've used epoxy on cracked blocks and mask off to prevent it from running into a joint that has hide glue :)

[David Farmer]

Tightbond extend has more resistance to high heat after it cures in addition to more open time. I agree it is a better glue.

I also don't understand the discussion of posts and jacks. The easiest aspect of this crack is that it can be clamped through the sound hole. In case my photo is misleading, the cam clamp is holding the crack flexed open for applying glue, not clamping against a post or jack.

I am not pushing for hide glue use out of some period correct fanaticism but out of practicality. This guitars value may never go up much, but because it is a 60's Martin, if it is not damaged further or has good repairs going forward, it wont' loose value further and that is worth something.

Howard with all your experience, if you fixed this crack with extend, I'm sure it would be a slam dunk. Fixed forever. I'm just trying to caution against the Stated idea that," some glue (Tightbond) is better than no glue".

 Unlike so many instruments, this guitar will still be worth fixing a second time, If a Tightbond attempt by someone without the experience to insure a good outcome needs re- fixing, the cost of having it done well the first time will seem like a deal passed by.

Hesh, I guess I caught the good corner of my shop.