eight string tenor specs

gspears

gspears

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A friend of mine is wanting an eight string tenor. I am looking for information regarding the nut and bridge/saddle width. Also the minimum or average headstock length that is needed. I will most likely use Grover V97 tuners. But I am open to use other tuners to space space and weight. Also string spacing between the pairs and other sets. Any help would be appreciated.
 
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8-string ukes have kind of gone out of favor here in Hawaii. I used to make a number of them, but it's been a few years since the last one. Necks really are not any different in size between 4, 6, and 8 strings here in Hawaii. Neck widths are also not very standardized. At the nut, necks are often 36-38mm wide, with the strings 2mm or so inside of that. String spacing, outside to outside at the saddle is often around 45-46mm. Spacing between strings in the pair is 3.5-4mm. Closer and they will rattle against each other. Wider and they will be difficult to fret together. For tuners, most of us would use mandolin 4 on a plate ones. The more expensive Grove 309 sets work well. Don't use the V-97's. Get your tuners and case before you do your building and make sure your headstock will fit in the case.
 
I build them with 40mm wide nuts instead of my standard 36mm for a 4 string instrument.

I give the octave pairs 3mm on center spacing and the unision pairs 2.5mm on center spacing.

Also you have to pay attention to the shape of your peg head and the string path. I prefer using a slotted head stock as it removes the possibility of the strings riding across the post of another. This is a possibility on the gG or aa sets.

To get the most compact peg head you can us mandolin tuners, or the Gotoh Stealth tuners.
 
I'm ready to trim the neck. Before I do, does anyone have thoughts of the neck width at the 12 fret? I have taken the advise from Allen and Bob and increased the neck width at the nut. Just not sure if I should use the same dimensions down through the neck. I usually use the dimensions in the Hana Lima book for the width of my neck at 12th fret.
 
I show 1 3/4" or ~ 45mm at the 12th fret. These dimensions are not written in stone. This is for a standard 4 string tenor, not necessarily for your 8 string. Use for reference.
 
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Draw out your string spacing at both nut and saddle at full size and add 4mm to each side. That will give you your dimensions.

I do this with every variation of instrument I build.
 
I'm curious to know if builders do anything different than a standard tenor in terms of bracing or soundboard thickness.
 
You've doubled the tension, so if you are building on the edge in terms of soundboard bracing, then you will want to compensate in either thickness or bracing.

If you are familiar with the cube rule of doubling a materials thickness increasing it's stiffness 8 fold then you can see it wouldn't take much.
 
I think Jake pretty much did for the 8 and 6 string.... probably not a bad thing because they were great to make but an ultimate challenge in so many areas. I cut my 'ukulele teeth' on them an was pretty relieved when they fell out of fashion so to speak. It's the 5 strings that are the killers though!
 
As I said in an earlier post, here in Hawaii 4, 6, and 8 string necks are all the same size. No difference in width in a factory Kamaka neck in the past, and they set the standard. If you start changing the neck width, people have trouble playing them when they switch instruments. It's amazing how much a mm here or there can throw you off. You want the neck, and the feel of the fretted notes, to be the same. Kamaka's have remarkably tight spacing, but it works. I don't have an actual 8-string of theirs here now, but I do have plenty of broken bridges. The outside string spread on their bridge is about 43mm. That said, when I made 8-strings I did widen the outside spread at the bridge to 45mm. Widening the bridge holes is not as noticeable as widening the nut.
 
Good News Then. Thanks Bob! As an amateur, I just want to be sure on the design so it doesn't end up as expensive firewood! :cool: Thank you all for the input. I will not be building many 8 strings I'm sure. But it is exciting to try something different. A couple years ago I built the Hana Lima Kasha braced baritone design. It turned out great! one of the best sounding uke's I've made.
 
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