Official Luthiers Forum!

I have entered the 2012 Challenge build, part 2, and I am building a concert ukulele. However, I know next to nothing about building them. The uke will be all koa and I need to know approximately how thick to make the soundboard. I have it at .070" right now and it seems pretty stiff but I am used to working with dreadnought sized pieces of wood, not a concert uke sized piece.
Anybody have some info on soundboard thickness, bracing patterns and or brace dimensions? I would appreciate any help in those areas.

Tony

_________________
http://www.CostaGuitars.com
PMoMC

Have built abt 10 ukes .But I usually make miine under 2mm for softwood..070 seems pretty thin, but it all depends on the stiffness of the top.Without seeing it and tapping it ,hard to judge .Personally with such a thin top ., would brace it a tiny bit heavier i.e. insteead of 1/4in braces I might make them5/16in or abt 7.5mm instead of 6.5mm and a good sized bridge plate abt 2.mm or .095-100.

Thanks Ernie.
I will brace accordingly. It seemed to me that with the low string tension the soundboard should be thinner than what I would use on a guitar. How thin? But as I said, I know nothing about ukuleles!

_________________
http://www.CostaGuitars.com
PMoMC

When you go to brace it, put the braces and bridgeplate (if you use one) on the inside of the box. There, now you know everything I know about maing ukes.

_________________
Bryan Bear PMoMC

Take care of your feet, and your feet will take care of you.

Ummm....of course! Obviously I wouldn't put the braces on the outside. Sheesh...that would be silly! Now if you will excuse me I have to run out to the shop for a few.

_________________
http://www.CostaGuitars.com
PMoMC

Tony,

I used Hana Lima's plan set for a Spanish Tenor Uke. They have other plans. But I like Tenors. But, I did not like the depth of the Spanish uke. So I lessened that. Used a different neck block, stuck to the bracing plan. I love the roundness. The plans a VERY nice. I ordered one, made several copies for creating templates, etc.

I will say, learning how to bend Koa in small radii was interesting! I'll post a pic tonight.

Edit: Also, did not use a pinned bridge... used a standard loop through bridge (nylon guitar style)

Mike

[quote="Tony_in_NYC Ummm....of course! Obviously I wouldn't put the braces on the outside. Sheesh...that would be silly! Now if you will excuse me I have to run out to the shop for a few. [/quote]

If it is not a cutaway, you might be able to flip the plates over without planing off the braces. Unless you have already closed the box. . .

_________________
Bryan Bear PMoMC

Take care of your feet, and your feet will take care of you.

For a koa top you might go as thin as 1.5mm, depending on the stiffness of the wood. I have a Kumalae koa soprano from the '20s which weighs in at 220 grams (about 7 oz for you Imperialists). Still holding up after all this time.

If I were making a concert I'd aim for 1.8mm and then flex/think/scrape/repeat until the plate had some flex along the grain, but stopping before it became floppy across the grain. Back and sides a similar thickness.

1/4 inch bracing should be plenty, shaving down the sides but keeping the height. My sopranos have just a brace fore and aft of the soundhole plus a bridgeplate of soundboard cutoff, but I think most concert makers use three fans as well.

The important thing for a uke is to keep everything as light as possible; minimal linings, the thinnest possible finish. Otherwise you end up with a small, and very quiet, four-string guitar.

0.07" sounds about right for a concert....maybe a hair thinner but you can do that in the final sanding before finishing. I use two fan braces 3/16 to 1/4 wide by 1/4 tall. A transverse brace above and below the sound hold that are 5/16 by 5/16.

Tony:
I use 70 thou for all of my ukes. My present build is a 22" scale baritone with falcate bracing. The top is 70 thou and the back is about 80 thou. The back is 15 ft. radius as is the soundboard. This is more difficult to set-up but I believe that it gives a better sound. I am still trying to establish whether falcate bracing gives me the sound that I am after consistantly.

Good luck in the challange.

Bob

Thanks for the info everyone! I shall carry on!

_________________
http://www.CostaGuitars.com
PMoMC

Here's a pic waiting for bridge:

One more

What?? Who would put the braces on the outside?
That's crazy talk Bryan! I was only messing around.


Nice looking Ukes Mike.
Thanks for the info everyone. I am hobbling forward with the ukulele build. I installed the rosette last night and I might get a brace or two on tonight. The back is going to be one piece so I need to thin it a bunch and then brace it up as well. However, since I need to attach the neck first, I will not be worrying about that just yet.

_________________
http://www.CostaGuitars.com
PMoMC

Thank you Tony!

Sorry that my pics appear to dominate this thread! I posted them via Tapatalk and that's just how they came out. I guess the point was that the modified Hana Lima plans produce an excellent looking uke (IMHO ). I really struggled with this build, ruined two side sets before I got the bending procedure correct.

I will say that I have kept the neck & body separate during the process.

Mike

There, I fixed it for you!

_________________
Bryan Bear PMoMC

Take care of your feet, and your feet will take care of you.

Thanks Bryan!

_________________
http://www.CostaGuitars.com
PMoMC

No problem. If I cared more (or even just a little bit), I would head on over to your challenge thread and see if I can catch a glimpse of you patent pending-tone enhancing internal rosette.

_________________
Bryan Bear PMoMC

Take care of your feet, and your feet will take care of you.