soundboard thickness

Tom Landman · April 2006

In Vintage Guitars, Vol. 8 (the Selmer/Maccaferri edition), there is a comparison of several dimensions of a 1950 Selmer (#808) and a 1991 Dupont MD30. The average top thicknesses are listed as 2.2mm for the Selmer and 2.1mm for the Dupont.

Ken Bloom · April 2006

All of this is very interesting. If I were to follow the practice I've done in the past, my inclination would be to make the top around .100" under the bridge and then taper it out to around .075 at the edges. This is the sort of graduation guideline I've done on bouzoukis with stressed tops and it worked very well. Anyone know if this appraoch has been tried with this particular design?

sockeye · April 2006

David Hodson told me in an email that the old Maccaferris had tops around 2.5mm thick on the models with the resonators and that after the resonator was taken out of the design, the top thickness went down to 1.5mm. Seems to me (I'll have to look for the email) that he said his (Hodson's) tops are 1.8mm & that the measurements are taken from Fapy's Selmer, which is David's inspiration...

Craig Bumgarner · April 2006

FWIIW: There is an article in Fall 2002 Guitarmaker magazine by Shelley Park on Selmer top construction. It is not long on details but covers the process from start to finish. In the article she states: "The tops can then be milled to their final thickness, which ranges from 3mm to 2.8mm depending on the stiffness and response of each particular plate."

I was reading a book on classical guitar builders last week and one of the builders had devised methods of measuring the deflection of tops under fixed loads. The article was not detailed, but it appears the top was suspended on the edges and a weight applied to the bridge area. The test may have applied to the both the unglued halves as well as the joined top in its final dimension. It also appears the plates were tested with the grain and across the grain separately. The deflection under the weight was measured by a dial indicator and logged. Though a single test like this is not likely to quantify all the variables, it is clearly better than nothing, especially if you have yet to work out the data via the more subjective methods of tap tone and flexing the top in ones hands.

Craig

Ken Bloom · April 2006

One of the more intriquing aspects of this whole discussion to me is that all of this seems to center on the soundboard being the same thickness throughout. My experience with other plucked instruments, balalaikas, bouzoukis, guitars,etc. is that the best of them most often have graduated tops. They are thickest under the bridge and then taper down to the sides. This type of guitar seems to seek a balance between the thickness of the top and height of the arch, depending on the arch for much of the strength, if I understand this all correctly. My question here would be, is a graduated soundboard ever used? Anyone ever try it?

Josh Hegg · April 2006

What I have seen happen since the Selmer plan is the top has pretty much stayed the same – Thin thru-out. The thing that has changed is the bracing. Not so much the placement but the amount of wood taken away from the bracing. The modern builder is really thinning the braces down. The braces I built are to the Selmer plans and after looking at a Park, (new) Favino, Dupont and other builders the bracing is very thin. Selmer bracing uses much more wood over all for the brace.

Cheers,
Josh

Ken Bloom · April 2006

Thanks Josh for the insight. After reading all these responses and the thread in the History part of this forum about whether or not it's worth it to have a Selmer, I'm inclined to go with bracing as per the plan and graduate the top, making it about .100" directly under the bridge and then tapering out to around .070 or so. Considering all that's been said, I think I would need to go down to .090 very quickly and have a substantial outer portion at the .070" dimension. I'll probably make the back a uniform thickness. If anyone has an opinion about this approach I would sure like to hear it.

Digger · May 2006

Interesting thread and indeed the first I've seen on top thickness for this style of guitar. I'm not far from stringing up my first Petit Bouche.

I followed the Charle plan for strutting and as there were no specific measurements for thickness of the top and I have no experience with these guitars I picked 2.2mm as a random starting point. You can't beat the scientific approach to guitar-making, can you?

Still, after reading the thread 2.2 seems as good as anything else for now.

I quite like a thicker top, I have to say. They seem to take a lot longer to play in but if it's a good top I've found it to be worth the wait.

My real reason for being here is to ask if someone would be kind enough to direct me to a thread I've seen that gives a nice step by step guide to carving a bridge. I've been punting around for ten minutes or so and can't find the damn thing

Thanks lads.