How thin can you go?

Some questions for you long-time uke builders: How thin can you take a hardwood top on a soprano uke, e.g. koa or mango? And do you alter/add bracing to adjust for that? And does that depend on the stiffness of the top? At this time, I am working on my third soprano, a curly mango top, and am in the range of 0.059-0.058" thickness on the top. My previous soprano had a koa top, c. 0.065" thickness and the center single brace, and it's nice, but I still want to push the limits a bit. Comments? (I'd prefer polite ones, thank you)

If you want to start putting some lattice bracing, then you could easily go to 1.0mm thick. This is what some of Greg Smallman's Classical guitars are built to. But that is a whole new kettle of fish.

Instrument building (particularly with the smaller, stringed instruments) is a balance between building it lightly enough, and building it robustly enough. I think we all know that.

If you want to push the limits, why not experiment, and then let us know how it works out? I'd be interested to see how you get on.

John Colter.

I have thought of the lattice bracing, as well as whether to/not to add a bridge patch. Plus, slightly doming the top. I realize with the short scale, the small vibrating plate and the small resonant volume make the soprano probably the trickiest to build well. I will report back as I proceed, and appreciate any input and guidance. Thanks!
Don Mostrom

The most amazing, and alarming, instrument I ever handled, was a scaled-down lute, smaller than a soprano uke. It was an exhibition piece - a vanity project, really. The builder was very experienced and skillful, and he reduced everything to the same scale. The result was a beautiful thing that felt as though it was made from parchment. It was playable, but had to be handled with great care.

I believe it did not last long.

JC.

I recently built an all padauk uke, and to compensate for the stiffer/heavier/denser soundboard, I made it a bit thinner, 1.5mm, which was undoubtedly made thinner yet, what with the final sanding on the assembled body, and then I ended up having to strip the whole thing and refinish with a shellac seal coat due to adhesion issues over the epoxy grain filling I applied to the bare padauk, which entailed another round of finish sanding. I've just completed it this last week and strung it up with some Aquila nylgut, and the strings haven't entirely settled in, but it seems to me that when played loudly, it sounds a little muddy, like there's too much vibration going on, and I've wondered if the top isn't simply too thin.

Top thickness, arching and bracing all need to work together. The key for me is how the top moves or deflects. How that is achieved is a function of how those three points are addressed. I start with the top radius as that adds a great degree of stiffness. Then I look at top thickness. Personally. I do not care for the tone of very thin tops. Finally I will adjust the bracing to achieve the deflection I desire.
Depending in the wood being used I think you are in the right range of thickness for a soprano. But you are talking about two totally different woods. Mango can be very soft and floppy, requiring the necessity for a thicker top. With koa it depends on the particular board as it's range of stiffness can be highly variable. Don't forget to consider the type and thickness of the finish used as it can greatly affect the tone, especially on very thin top instruments.

Hey Chuck, when you talk about deflection, are you talking about how the soundboard bends, and when you do, are you talking about how it bends with the grain or against it, or both? Thinking about with or against is a little confusing to me, so here's an image of what I mean, along with some suppositions on my part. http://i.imgur.com/9ByI6ZQ.png. Also, it would seem that what you know about deflection in relation to arch and bracing comes from lots of experience? It would be hard to quantify how much (or how robust) bracing needs to be in order to impart x amount of deflection.

"It would seem that what you know about deflection in relation to arch and bracing comes from lots of experience? It would be hard to quantify how much (or how robust) bracing needs to be in order to impart x amount of deflection."

IMHO it's an art, not a science.

JC.

Deflection mapping is based on proven known good instruments that you've built. So in that manner yes, experience and building many instruments is important. Make good records of everything you build and when you get an uke that knocks your socks off it will be easier to duplicate. The art part comes from knowing when and how much to deviate from your mapping and your records. Every uke and every set of wood is different. I wish experience could be taught but it can't and IMO there's no better teacher.

Amen to that.