soundboard thickness

Elliot · May 2006

Digger wrote:

Thanks Jack, but that's not it. What I saw was a step by step guide with pictures/diagrams. Pictures are always a big plus for me

Could this be it? - scroll down to find the bridge articles.

http://www.frets.com/FRETSPages/pagelist.html

Digger · May 2006

Nope, not that one either, Elliot.

It was this one:
http://launch.groups.yahoo.com/group/gy ... ent/files/

I could have sworn I'd seen it here. Still, there you go.

Thanks anyway.

murrayatuptown · January 2014

Is this thread populated by builders? I'm not sure whether to start a fresh question or leave it here as I think it's relevant to the current discussion. If not, I guess someone will say so...

I'm curious if anyone can tell me if there is any knowledge out there about Chladni plate tuning for gypsy style guitar tops. Thus far, everything I read about tap tones is very subjective...preference for dryness vs wetness ,and not specific tap tones, just long ring...

I am very slowly accumulating books, plans, parts, & wood & might first replace the top and neck on an acoustic guitar I was given that needs major repairs, an I thought why not go in this direction? If that results in something better than a pile of kindling, next project might start from scratch...I've got a set of Michael Collins oval hole Selmer/Maccaferri plans.

Thank you

Murray Leshner
Holland MI

murrayatuptown · January 2014

Back-comment on the top stiffness/deflection topic...Roger Siminoff's tap tuning book (and probably website) discuss a fixture for stiffness/deflection as well as the intent behind this vs. audible testing.

I can't explain it well enough, but it sounds like there is some crossover between the two approaches, with the wood mechanical measurements being oriented toward repeatability in a commercial batch construction environment...I think it relies on having proven finished pieces that were built 'by ear', then 'characterized' by deflection measurements, and this data used for the next batch of tops/backs. I'm not sure it's as predictable without a known-good set to start with.

My statement(s) here are based entirely on reading, not experience...an 'armchair luthier'...

Buco · January 2014

murrayatuptown wrote: »

Is this thread populated by builders? I'm not sure whether to start a fresh question or leave it here as I think it's relevant to the current discussion. If not, I guess someone will say so...

I would suggest that you start a new thread as this forum is frequented by some of the best builders of the genre and I'm sure you'd start an interesting conversation. You'll probably get some answers either way but I think it would serve you better to start fresh.

Buco

Al Watsky · January 2014

These guitars also have similarities to classical guitars , in particular the thickness of the tops. Some of these have tops that are as little as 1.5mm thick. Its pretty fun actually. Nice light guitars with steel strings.

Craig Bumgarner · January 2014

Top (soundboard) thickness, now there's a mine field. So many factors go into this. It is really more about the stiffness and the weight of the top. This will vary considerably with various woods and even as much as 200% within species. Thickness is just so tangible, we grab that thinking we have something significant. Thickness is much easier to measure than stiffness or even finished mass. And of course, the entire top assembly with the braces, pliage, liners, etc. is what is really important.

Deflection testing will get you in the ball park, allowing you to thin bracing and top to norms. I use a 1kg bag of lead sinkers and a metric dial indicator that measure to .001mm. Deflections of 0.10mm and 0.15mm at the bridge area of finished, strung up manouche guitars is common. Deflection testing PLUS the mass of the finished, installed top assembly with bridge, will give you a pretty good idea of the dynamic capacity of the top assembly. If you are interested in the details of this, the book(s) by Trevor Gore and Gerard Gillet cover it extensively.

That said, some generalizations can be made. In guitars I have measured (over 50 to date), most of the spruce tops with Selmer style bracing (4-5 major, 4 minor braces) ranged from 2.4mm to 2.8mm range. 2.5mm is most common. Cedar tops run thicker as do tops with fewer braces as can be expected. Three brace guitars often run 3.0mm in spruce and 3.6mm in cedar.

Finally, I don't personally think top thickness is critical to the sound. Everything else being equal 0.2mm either way isn't going to make much different, at least until you get all the other factors in line. Getting the overall stiffness right and the best stiffness to weight ratio you can get are what really matter. The advice I hear experienced luthiers give to beginners is to use target thicknesses to get in the ball park at first, but keep thinking about stiffness, weight and bracing design as you develop your skills. 2.5mm in a spruce top is a very good place to start.

Oh, and trying to judge the quality of a guitar by its top thickness is pretty meaningless. The best guitars I have ever heard have run everywhere from 2.2mm to 3.6mm. A guitar's sonic quality is much more than top thickness.

Al Watsky · January 2014

My main concern with top thickness has do do with durability and longevity. I have seen recently guitars that have dangerously thin tops that sound great but that have a disturbing tendency to crack, very easily. A thin top has a lot going for it , its sensitive and loud but often has a short optimal life.
Its OK with me, I'll repair them, they will look fine and play well but most likely will break again in another location.
Ka-ching !
I've seen many thinly constructed guitars over the last 30 years. There were several builders of classical guitars builders in Spain that were the flavor of the month in the 90's who pushed their tops down to 1.5 mm or there a bouts.
Even when they didn't crack the often failed unless they were treated like new born infants.
Be careful builders ! We want your guitars to last for a hundred years, not a hundred days !
:rofl: