Maximum number of plates used in top construction?

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Jason Brown
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Maximum number of plates used in top construction?

Post by Jason Brown »

What is the maximum number of plates I can use in constructing a top? I'm taking a building lecture and the instructor told the class that 2 is the max, due to the forces the top is exposed to. What if I only have 6" plates that I can glue up, then what?

Clay Schaeffer
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Re: Maximum number of plates used in top construction?

Post by Clay Schaeffer »

Adding "wings" is sometimes done by using the wood from the waist area to increase the width of the lower bout. I'm not sure why your instructor said what he said, but even well known builders (Torres) used tops with multiple pieces.

Trevor Gore
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Re: Maximum number of plates used in top construction?

Post by Trevor Gore »

One guitar I made had a five piece top (no centre joint) and a four piece back; no issues. Both Smallman and Torres have used multi-piece tops, but that's about all that those two guys had in common!! A well made glue joint is stronger than the wood. Sounds like your lecturer could do with a refresher course.

Rodger Knox
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Re: Maximum number of plates used in top construction?

Post by Rodger Knox »

Jason Brown wrote:What is the maximum number of plates I can use in constructing a top? I'm taking a building lecture and the instructor told the class that 2 is the max, due to the forces the top is exposed to. What if I only have 6" plates that I can glue up, then what?
The forces to which the top is exposed must certainly be the pressures of the marketplace. :lol:

A well executed glue joint is at least as strong as the adjacent wood, so ultimate strength is not a constraint on the number of glue joints in a top. I suspect that the longitudinal and transverse stiffness might be affected if taken to the extreme of more than 5 or 6 joints, i.e. 6 or 7 piece tops, but that could be a good thing.
A man hears what he wants to hear, and disreguards the rest. Paul Simon

Jens Moller
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Re: Maximum number of plates used in top construction?

Post by Jens Moller »

Of course, there is the Yamaha bamboo guitar - where the top is made of hundreds of strips.

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Chuck Morrison
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Re: Maximum number of plates used in top construction?

Post by Chuck Morrison »

I've built several guitars that had "wings" within an inch of the outer edge of the lower bout to make use of great (but not wide enough) wood. From what I can tell, that did not impact the sound or formation of the expected modes of vibration. It should be noted that while something may sound pretty good, or at least "like a guitar", what goes on in the modes can be quite different and show up if you test for it.

I also built a guitar with 3 top sections; a center piece of spruce surrounded by two pieces of redwood. The Chladni patterns showed that the spruce vibrated in distinct isolation from the redwood. There were very few patterns that crossed the glue joint(s). The eventual owner liked the sound a lot and I liked the eventual sound as well. However, the main top monopole was isolated to the spruce portion and a number of very non-standard patterns were observed. Play-in was interesting as the two woods seemed to respond to the stress differently. There were weeks it sounded very strange. Once it settled the sound was even and fairly impressive.

I'm fairly sure that it was the difference in the woods that caused this isolation, not the mere presence of a glue joint, although I have heard some say that just a joint will have that affect. I have not built an evenly spaced 4 or 5 piece top to test that out.

Douglas Ingram
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Re: Maximum number of plates used in top construction?

Post by Douglas Ingram »

I've built some tops from 6-8 slices of White Cedar. White Cedar does not typically grow to large trees which can provide excellent tonewood pieces, so piecing together the best pieces is much easier than finding it in larger pieces.

The guitars turned out just fine, the joints if well done are near invisible, and you would need very sophisticated testing to determine if there is any difference from 2 piece tops. Oh, BTW, I build classical guitars.

The top requires proper bracing due to the forces that it is exposed to, not a minimum number of pieces in the plate.
I may be crazy...but I'm not insane.

Chuck Tweedy
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Re: Maximum number of plates used in top construction?

Post by Chuck Tweedy »

The top requires proper bracing due to the forces that it is exposed to, not a minimum number of pieces in the plate.
Great point! That is the direct (and correct!) counter-point to the instructor's claim.
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Miguel Bernardo
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Re: Maximum number of plates used in top construction?

Post by Miguel Bernardo »

Hi, Romanillos actually prefers to have a top made of 3 or more pieces and have perfect quartering all over it, than a two piece top with almost perfect quartering. who am i to question him?

Tom West
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Re: Maximum number of plates used in top construction?

Post by Tom West »

I may be off base here but I think John Arnold did an experimental top with something like 8 or so strips and basically concluded there was not much if any differance between it and a normal 2 plate top. If good matches can be made multi strip tops will make better use of our dwindling supply of soundboard material.
Tom
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Miguel Bernardo
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Re: Maximum number of plates used in top construction?

Post by Miguel Bernardo »

IIRC, Trevor Gore made a guitar with a 5 piece top of radiata pine(!!!) - he said it worked out well.

Trevor Gore
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Re: Maximum number of plates used in top construction?

Post by Trevor Gore »

Miguel Bernardo wrote:IIRC, Trevor Gore made a guitar with a 5 piece top of radiata pine(!!!) - he said it worked out well.
I guess that would be this one, Miguel.

Bob Hammond
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Re: Maximum number of plates used in top construction?

Post by Bob Hammond »

If memory is correct, when making up a 4 piece top, using offcuts from the waist to make up the width of the lower bout, then the offcut pieces must be exchanged to the other side, and then flipped over, so that the chayotance of the offcuts matches the main halves. Did I get that right? It means that the pieces are arranged so that the reflective glistening of the glued-on wings matches the main pieces after a finish is applied. Whether the exchange & flip is done or not, I'd suggest careful jointing and the use of hide glue. The hide glue will look much like a natural grain line, and it won't cause problems with finishing.

I'm sure that this is discussed in some archived library thread.

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