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Is this an indictment or a vindication of the process? 1974 was a long time ago.

Ok, I am confused. I thought the normal process WAS a lap joint.

Lap joint;
I mean a cut in each brace -for half of it's height.
WOOD TO WOOD
Fit & glued it's so much stronger !
mike

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Mike Collins

Is anybody using anything other than a lap joint?

I think we're off the rails a little bit.

Mike C, I think everyone is using a lap joint. Even with a lap joint, most folks cap it somehow. Some decide to cap with cloth some with a wood cap (apparently some do both ).

FWIW, I've been doing the cloth since I started trimming the peaks of the braces at the lap up really close to the intersection. Basically doing what is described in the Gore book, but I don't go all the way. There is still 5mm or so in each direction of the intersection where I don't peak the braces.

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I guess I've been doing this so long I can't communicate to newbies.
Start learning how to work the wood-joints-thickness by hand.
Try making guitars before thickness sanders-store bought jigs-power tools
designed for instrument making only.

A joint that was made so BOTH braces were cut to make a SOLID joint once glued.
NO need for a patch-unless your a smoker!
Mc

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Mike Collins

Thanks, Mike. Yes, we are talking about the same thing. I just didn't realize you were saying that if the lap is sufficiently tight you recommend foregoing any patch or cap. What I do is thickness the brace stock to .265 and then cut the notches for the lap joint with a 1/4" spiral bit. Then, run them through the sander until they are a tight fit. I think Lance posted this approach a long time ago. I spend to much time searching the archives here.

Thanks for your feedback. It's good to hear it from the pros!

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Well if you can't figure it out then pfft to you, Mike.

Amazon has a large selection of gun cleaning patches from 3/4" round to a couple of inches square. Any suggestions on what to order? I have been using wood as a cover, but might try using a thin slice of wood and the cloth. Thanks, Bob

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I disagree with Mike Collins. Even a tight half-lap joint is putting the glue lines in the open part of the joint facing into the box under a tension load, and that's just not good practice. For one thing, most glues, even Titebond, have fairly low shock resistance, so that a bit of a knock on the top can start failure in a glue line that is already under significant load from bridge torque. I used to see the results pretty regularly back when I did repairs, in the form of braces that were splitting out along the center from the base of the open side. Reinforcing it takes all of about two minutes; why not do it?

Agreed, not to mention that the mechanics of a lap joint necessitates gluing end grain to long grain which is iffy at the best of times.
I am considering a small buttress fitted on 2 opposite sides or maybe all the way around the lap.

B

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My memory is so good, sometimes I remember things that never happened.

my joints have never failed
100's of guitars I've made use it.
Remember one brace is glued to the top all along it's length.
One is notched into that one.
Mike

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Mike Collins

I bought a linen pillowcase on Etsy for $6. I think it shipped to me from Estonia. That will last me for years.

do you really think a glued cloth patch will help????????

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Mike Collins

Yes, a glued cloth patch will help. I've used them a number of times on repairs of braces that have cracked at the joint, and they hold well; I never had one come loose afterward. A wood patch is far better, though, IMO.

Having worked on old parlor guitars that have been restrung with steel strings I've noticed that the place the top fails is between the bridge and soundhole. The X braced guitar concentrates the reinforcement in this area, and is one reason that Martin guitars originally meant for gut strings when strung with light gage steel survive better than most. Since the forces in this area are trying to push the top down and open the joint on one side of the X it makes sense to me to cap that brace in some fashion. I think of the glue soaked patch as a low tech form of "fiber reinforced plastic". The wood patch creates sort of a through mortise which again will be able to resist the forces acting on the top in that area. The little slip of wood is no trouble to fit to the top if the brace and I think adds a lot to the strength of the joint.

I don’t know you and I’m not familiar with your workmanship, but I’m sure your guitars are very high quality instruments if you have 100 plus under your belt. However, Martin probably has hundreds of thousands and they use a lap joint with a reinforcement cloth. I’ll go with Martin.

Why not the wood reinforcement strip? There really is no downside to this approach and it does a lot more than the cloth patch.

I don’t know you and I’m not familiar with your workmanship, but I’m sure your guitars are very high quality instruments if you have 100 plus under your belt. However, Martin probably has hundreds of thousands and they use a lap joint with a reinforcement cloth. I’ll go with Martin.[/quote]

good-

I've also repaired many with dry torn patches.

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Mike Collins

Mike Collins wrote:
"I've also repaired many with dry torn patches."

It's well known that hide glue deteriorates with exposure to air. I've seen old Neapolitan mandolins, with the bowl was lined with paper or cloth, that had the lining flapping loose because the glue had broken down. At that point it's not doing anything except getting in the way of a repair. Cloth without glue holding it doesn't do much.

When I use cloth side tapes I shellac them to protect the glue from the air. I'd do that with a patch on the X crossing as well if I could.

With a wood patch the glue is covered up, and won't break down any faster than any other glue on the instrument.

the shellac is a great way to protect a patch Alan.
I hope your sharing this helps with those who use a patch.

Mike

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Mike Collins

Epoxy might be an even better way to create a patch that won't come loose from humidity breaking down the glue.

The advantage of HHG with this, particularly when you're adding a patch to an existing guitar, is that the moisture of the glue softens the patch so that it will conform to the contours of the brace crossing nicely. With no moisture epoxy would not do that. It's also relatively easy to handle HHG and massage the piece into place with your fingers: epoxy is too sticky and remains so, while the HHG gels after a bit. Epoxy does help with the 'drape' of fiberglass cloth, and on new work you could use that. It's still likely to be a mess, though, unless you vacuum bag it, and even then...

IMO a cloth patch is most useful as a repair: I've used them several times. The brace that has split out is glued up with whatever glue you like, using a post and an outside clamp over the top to make sure the joint is tight. Then you put on a patch, making sure it laps down the side of the brace over the split line. It's hard to get any shellac in on that patch without making a mess, so you might regard this as a 'temporary' repair, but that still should be good for the next 30-50 years, so it's not that temporary. For new work I much prefer the wood cap over the top of the joint.

"the moisture of the glue softens the patch so that it will conform to the contours of the brace crossing nicely. With no moisture epoxy would not do that"

Some epoxies have the ability to "wet out" cloth and wood pretty nicely. When laminating sides I first dry the veneer to remove as much moisture as possible and then wet it out with epoxy and bend and clamp it over the form with no heat involved. If the epoxy didn't soften the veneer I think there would be major problems. YMMV

I had the opportunity today to put some numbers on the contribution a wood patch or cap on the x-brace joint can make to top stiffness. A couple guitars ago, I started measuring the deflection of the top before, during, and after carving the braces to see what I can learn about the magnitude of the effects of carving on a given top and for comparison between guitars. On the guitar I'm building now, I measured the top deflection after gluing the braces on, but before doing any carving. To my surprise, the deflection (0.044") was just about the same as the deflection on the tops of the last two guitars after their braces were fully carved. Then I realized I had not put the usual wood cap on the x-brace joint yet. So I made a cap and glued it on and re-measured the deflection. It was 0.029" which is close to the values of the other two guitars before brace carving and with x-brace caps on. After carving all the top braces (scalloped x-braces) to my satisfaction, the final deflection was 0.049". So the difference in top stiffness between uncarved braces with and without a wood cap was pretty close to the same as the difference in stiffness between the uncarved braces with a cap and the fully carved braces with a cap. Put another way, the effect on the top stiffness of leaving the cap off was about the same as the effect of fully carving the x-braces, tone bars, and finger braces. That seems like a pretty substantial effect on top stiffness and I was surprised that the effect was that large. I wonder how much a cloth patch would increase the stiffness.

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