Eight String Ukulele

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Dave Gentner
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Joined: Thu Feb 02, 2012 12:25 pm

Eight String Ukulele

Post by Dave Gentner »

I've been asked to build an eight string tenor ukulele. I've made several regular tenors already. Any suggestions as to what precautions I should take to allow for the additional tension? Do I just increase the height of the fan braces, or do I add more?
Alain Lambert
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Joined: Sat Jan 07, 2012 7:18 pm
Location: Trois-Rivieres, Quebec

Re: Eight String Ukulele

Post by Alain Lambert »

I have no answer for you, but I am curious, are the strings still nylon? I imagine that pairs of nylon would require a larger spacing at the nut than pairs of steel strings.
If strings are nylon, the pull on the top would be about double, close to a classical guitar according to Kawika http://www.ukuleles.com/Technology/strings.html. As the brace strength goes with the square of the height, a 10% increase in height would be sufficient. As I said, I never build one ( but you just gave me the desire to!) so take this for what it is worth!
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Bob Matthews
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Re: Eight String Ukulele

Post by Bob Matthews »

I made one a few months ago and you can read about it here http://bobmatthewsguitars.co.uk/index.p ... ks-ukulele

Any questions, just fire away.

Bob
Alain Lambert
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Location: Trois-Rivieres, Quebec

Re: Eight String Ukulele

Post by Alain Lambert »

Thank you Bob, very nice instrument.
Would you have dimensions for the top bracing, nut spacing, and neck width?
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Bob Matthews
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Re: Eight String Ukulele

Post by Bob Matthews »

Hi Alain

The top braces started out at 1/4" x 1/2" and the utb 1/4" x 5/8".
The nut width is 40.5mm and the spacing at the bridge is 46mm (same as at the 12th fret).
I set the outer strings 3.5 mm from the fretboard edge and 2.5mm between the pairs.

HTH

Bob
Dave Gentner
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Joined: Thu Feb 02, 2012 12:25 pm

Re: Eight String Ukulele

Post by Dave Gentner »

Wow Bob, that's really nice. So you didn't add any additional braces. You just increased the fans from 3/8" to 1/2" and the tbs from 3/8" to 5/8". Tell us about the soundhole braces. I usually don't put braces there but instead glue a square patch the same thickness as the top around the soundhole going from utb to ltb. How thick did your top end up? The Uke I'm building koa top, back and sides. My tops are usually around .070". Thanks for the info.
Alain Lambert
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Location: Trois-Rivieres, Quebec

Re: Eight String Ukulele

Post by Alain Lambert »

Bob Matthews wrote:2.5mm between the pairs.
Is that 2.5 mm center to center or between edges of the strings?
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Bob Matthews
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Re: Eight String Ukulele

Post by Bob Matthews »

Dave, for the soundhole braces I just went with my acoustic guitar making experience and made them - imo - strong enough to resist the future possibility of any soundhole collapse due to string tension.
My top on this one was .090" thinned to .085 around the perimeter of the lower bout, but in all honesty, I believe I could have gone even thinner as the uke comfortably holds the 8 string tension. Originally I finished the top with the same two part lacquer I used on the back and sides but after stringing up I didn't get the response and sound I was looking for, so I stripped the top and then French polished it - which made quite a remarkable difference.

Alain, yes I used 2.5 mm centre to centre and have no problems with the strings touching each other even when strummed hard.

Bob
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Alan Peterson
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Re: Eight String Ukulele

Post by Alan Peterson »

The Tahitian Uke is an eight-string animal. Prob'ly not what your client asked for or is expecting, but it's worth looking at.

There are plenty of webpages, but the photos at http://www.boraborarealtor.com/tahitianukulele.html are really cool.
Alan Peterson
Name in Anagram Form: "Resonant Peal"
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