View Full Version : Thickesses needed for Tenor Build

03-09-2009, 05:21 PM
Hey Gang,
I am right now in way cold Portland, OR.
I am a Electric Bass builder with a couple of acoustics built in the past. So I have a pile of sides and backs in mahogany, and a few spruce sound boards I would like to transform into some tenor Ukes. So I sketched a profile of a Tenor, More Small Gibson L0 looking, cobbed up a bracing design 3 fan brace, and now the fun part.
What is a good side and top thickness??
I used 0.085" for a Flamenco and a Parlor guitar I made for sides as they bent nicely.
I was thinking of building an all mahogany and 2 spuce tops. One with spuce bracing and one with a thinner top and spruce/carbon fiber braces.
What do you all use for kerfing??
Do you use the standard guitar top and back radius?? 25' and 15'??
Thanks for any input...

03-09-2009, 11:00 PM
Not getting a whole lot here, huh? I gotta admit, while this is the Luthier's Lounge, most of the member's I see post here are on the extreme ends, meaning, they are just starting, or they've already been there. Because of this, most of the suggestions for those just starting are similar, and pointed towards other resources.

That being said:
First off, if you're a Steel String builder, you'll have a tendency to overbuild - just something to be aware of.
More than likely, sides will be thicker than your top. You can keep the .085 for your sides.
Kerfed lining can be whatever you areadly use for your acoustics. I've used Basswood (very light) and Mahogany in the past. I'm liking Spanish Cedar right now.
Only a certain few use a radius on their tops - most factories are flat. Backs are tapered more than radiused. I've seen a few customs that use a radius dish, and I think there are (two) factories that use them as well. I throw a 15' on the back, which is almost unnoticable, but relevant. The 25' on the top won't hurt, but at 9" wide, that will be even less noticeable. I realize you're doing it more for affect, than effect.

I can almost guarantee that you'll need to put high tension strings to drive the top of your first build, because taking the top down below .080 may not sit well with you. I'd save the Mahogany top for last, but that's just me. I like all mahogany instruments, if they're built right. I think you can get away with more with the Spruce from a belly/bow standpoint.

Hope this helps.


03-10-2009, 07:03 AM
Gibson L0 style uke? That sounds pretty cool. I'd like to see that
I use 0.085" for my uke tops....they have all been mahogany or koa though. I figure by the time I sand out all my mistakes it ends up around 0.075 to 0.08 in the final product.

Moore Bettah Ukuleles
03-10-2009, 08:29 AM
This is how I thickness sand my koa, keeping in mind that each set of wood is approached differently depending upon that particular koa's response. I also only use nylgut or tynex strings. But these are my general numbers for my four string tenors; the numbers change obviously with more strings or different sizes. Because I work primarily with curly wood and do a lot of cutaways, my sides are sanded to .075". My backs tend to be closer to .080". My tops start out at .075 and get a bit thinner as the instrument gets closer to the finishing stage. I can take it pretty thin because I use a five fan bracing pattern and I also use quite a large carbon fiber bridge patch and radius the top. Edges of the lower bouts are taken down a bit more than the interior. I spend an enormous amount of time in proper thinning, scraping, sanding the top checking the deflection rate all through the process for maximum response. Something I learned from David Hurd (Kawika) and it's time well spent. Backs are built and shaped on a 15' radius dish, the dish being spun on a potters wheel for the proper shape. The tops are also radiussed but at 25' and not on a spherical dish but on a board that has a longitudinal radius instead. Because of my building process, for some reason my tops are always a bit steeper than intended, probably closer to 22'. I use toon for my kerfing and carbon reinforced Spanish cedar necks.
Again, PLEASE remember that these numbers are only starting places and only for koa. EVERY piece of koa I use is handled differently. You'll have to know the characteristics of your spruce and mahogany and treat it accordingly. I always have to stop and rethink when I add a spruce, cedar or redwood top.
DISCLAIMER: Your results will vary!
Good luck and hope this helps.

Pete Howlett
03-10-2009, 09:30 AM
1.9mm for backs and sides
1.7mm for fronts
Spanish Cedar kerfed lining
Spanish Cedar neck - no re-inforcement
22' radius to fronts, cedar bridge patch and only two 6mm x 12mm scalloped spruce fan braces.
12' radius to backs, cedar back bars

Seems to work for me...

04-26-2009, 08:58 PM
How big does the kerfing have to be to do purling inlays around the body? I am on my making 6th uke now and am wondering how wide the kerfing has to be to do a perfing around the top. I have done some wooden bindings using the stew-mac router bit with the biggest pilot i think it gives a .040 step. I am using mandolin kerfing now and don't think it will be wide enough on the top to give me enough support with a .125 purling cut on the top. Any sugestions.
Anchorage, Alaska