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The discussion got me to wondering: how many of you reinforce the center seam of the top? I mean other than the usual braces. Some recommend little diamonds of spruce placed in those areas between the braces (that are otherwise unsupported). So--any of you guys do that? If so, how large do you make your supports?
SteveSteve Kinnaird38372.862349537

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Ive been seriously considering a pair of small matching material diamonds.. I Dont do anything now..

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Lance@LuthiersForum.com

Interesting--the subject line wouldn't let me fill in the whole line. Which should read: "A question based on Paul Schulte's question". That just makes a bit more sense.

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From Nacogdoches...the oldest town in Texas.

http://www.stephenkinnaird.com

On my last 6 or so guitars I have use 1/2" square diamonds. two behind the tonebars and one if there is room between the tonebars and the bridge plate. I made a 00 size guitar and during the finish process I was experimenting with a UV lamp to hurry the finish cure. I put it the manufacturers specified distance from the guitar and used less than the specified exposure time. When I checked it the finish had bubbled up and the seam had started coming apart on the top. I got the top satisfactorily reglued (My daughter got that one as a birthday present)and decided 1st, not to use UV anymore and 2nd, to use the small diamond patches under the top. After they are glued on I use a chisel and from the center of each, shave them till they taper into the top at the edge of each. I really don't think they dampen the top much at all but since the grain runs across the top they may help keep things together a little longer in adverse humidity conditions.

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I don’t do anything extra to support the center seem on my guitars. However I am using a symmetrical lattice bracing pattern which may make a bit of a difference. It means that besides my main X brace I have 2 smaller X braces crossing the center seem. I have not had any troubles so far.

Josh

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Josh House

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I use the 1/2" square centre seam supports, a la cumpiano. One of my shipments from Rivolta had a carrier board that was essentially top-grade, stiff material, except it had massive, long knots (ie branches) running through it in 3 places. Perfect for slicing up back centre seam reinforcements and diamonds, and so I've got enough cut to last many a guitar now.

John, do you glue the diamonds with the grain running parallel with the top grain, or opposed?

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Lance@LuthiersForum.com

My bracing pattern is such that one of the "tone bars" runs down the center of the top and covers that joint. I am hoping that does the trick. I do believe that some kind of reinforcement of this joint is a great idea.

JohnJohn Kinnaird38373.3131597222

Lance, I glue them on with grain perpendicular to the top grain.

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Hey Everyone,

Does it have to be a diamond? Could it be a small circle or thin straight strip? Or....?

jeff

Steve,
I haven't heard of anyone doing that for many years.
I knew a great old Luthier in the 60's who used to do just that. Little diamond shaped pieces. He would place them near the bridge area. He said it was a small insurance policy.
It never affected the sound of his guitars in any adverse way.
You brought back some old memories!!!
Thanks, walterK

John....

UV? Are you using a uv-cure polyester, or are you using a IR (infra-red) heat lamp?

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Jeff, MIne are actually squares that are cut 45? to the grain. They are glued on with the grain side to side and so that one of the corners points to the bridge.But as long as they are not too large (mine are .5" squares) they could be circles or whatever.

Don, This particular time and the only time I tried this, it was target coatings USL. I had read in their forum that using UV lights could speed curing. It didn't work out for me so I didn't try again. I'm not in that big a hurry. I had to strip the whole thng and start over but it turned out great in the end.

Correction: Don, Perhaps I'm confused it may have been infra-red. I'll have to check on that.John How38373.6184143519

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Fess up. You know it just might be a bonus, even in the tone department. Think of stiffening the top a bit more at the center, and having it more flexible at the perimeter. (The analogy of the speaker cone.) Braces are tallest at the mid point, and thinnest at the edges....
Perhaps these small patches--within reason--should not be viewed as a detriment to tone at all. I like John H's idea of 1/2" diamonds. And of course my bro's idea of a brace running right down the seam. (Only you wouldn't catch me doing that in one of MY guitars! )

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From Nacogdoches...the oldest town in Texas.

http://www.stephenkinnaird.com

My little patches are so small .5" sq and usually cut from scraps of the top I'm working on so not very thick and then feathered from the center out. Not much wood left when I'm done so I don't think there is much harm done. On the other hand there's not much wood left to help out either. I'm just hoping it helps keep the seam from moving.

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