to truss rod or not to truss rod?

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Paul Henneberry

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Hi All,
I'm coming to the end of building 4 long neck sopranos and I am now in two minds about fitting some carbon fibre into the necks. I know I should have planned ahead and that it would have been easier to do before I shaped the necks but I put it off. I haven't bothered on my previous regular length sopranos but now I've stretched them to 14 fret to the body and 14 3/4 scale length and I'm wondering if now is the time to take the plunge. There are two American black walnut ukes and one of each Koa and Tasmanian blackwood with the necks the same material as the bodies. They are of average profile I guess at about 13mm before the transition into the headstock and about 17mm before radiusing into the heal. The fretboard are already made out of mulga (which is very stiff) if it makes any difference. I've got some 3x15mm rectangular CF rod on hand and could jig up to do something like Sven did a few months ago if you guys think it is necessary.
cheers

Paul
 

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I'd agree with Sven. Remember, a uke is not a guitar. Necks are typically short enough to be of adequete stiffness, and the string tension is substantially less. Do it for bragging rights or to increase your skill set, but it's not really necessary.
 
Agree it's not really needed but ... it doesn't add much to cost or time and (if they're for sale) some customers perceive value in the added strength/rigidity.
Miguel
 
Thanks all,

I went into the project not intending to do it but then the doubts crept in. Thanks for setting me straight. As Habanera Hal suggested I might do it for the challenge on the next ones but won't bother on these. Is it Allen who floats the fret board slightly above the sound board by extending half of the CF into the fret board overhang and using it as a cantilever? I like that idea and I liked Sven's idea of the tapered inserts as well. I might have a play next time around. Attached is a picture of the Tasmanian blackwood bits laid together. Very pretty wood.

cheers
Paul
 

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Personally, much of my work is done to fit to metal, at a tolerance of about 0.003". This is not just at install, but also at the next time a setup is done. In another dimension, my pieces are checked every time at setup on a flat plate. If my pieces are not flat, I hear about it. IMO, Koa is not a stable wood like Mahogany or Spanish Cedar. Koa happens to be one of the woods that has been less predictable for me, in terms of retaining precision. Black walnut is not one of my favorite woods, but IIRC, it is more or less stable than Koa, depending on the exact cut of wood. In other words, similar, but different. I have seen Koa, that I thought was dead stable, shift with the rainy season, and then come back to flat when the humidity changes. This is just my experience. But..... If you are using Koa as a neck wood, I would absolutely use a piece of CF in the neck. If your Koa necks are absolutely the most 'boring' looking Koa Ever, and dead quartersawn, and the wood was cut more than 10-20 years ago, you might be okay without CF reinforcement.

I will not use Koa as a neck wood. Honduras Mahogany, or Spanish Cedar, and only with CF reinforcement. CF is inexpensive, quick, and easy to do. Why would I not do it? I have built one neck without CF reinforcement, not by my choice. It took a bow a couple of months later.


More important than the question of reinforcement, or not, IMO, is being patient with the wood. Any instruments I build, the neck blanks are roughed out, the top surface cut flat for reference, and then they sit. After at least a month, when it is time to build with them, they are checked for flat. This is based on years of watching wood move, slowly.
 
Paul Henneberry said:
Thanks all,

I went into the project not intending to do it but then the doubts crept in. Thanks for setting me straight. As Habanera Hal suggested I might do it for the challenge on the next ones but won't bother on these. Is it Allen who floats the fret board slightly above the sound board by extending half of the CF into the fret board overhang and using it as a cantilever? I like that idea and I liked Sven's idea of the tapered inserts as well. I might have a play next time around. Attached is a picture of the Tasmanian blackwood bits laid together. Very pretty wood.

cheers
Paul
Click to expand...

Allen may well do it that way, but I believe Rick Turner's the guy who first started espousing it.
 
Chris_H said:
Personally, much of my work is done to fit to metal, at a tolerance of about 0.003". This is not just at install, but also at the next time a setup is done. In another dimension, my pieces are checked every time at setup on a flat plate. If my pieces are not flat, I hear about it. IMO, Koa is not a stable wood like Mahogany or Spanish Cedar. Koa happens to be one of the woods that has been less predictable for me, in terms of retaining precision. Black walnut is not one of my favorite woods, but IIRC, it is more or less stable than Koa, depending on the exact cut of wood. In other words, similar, but different. I have seen Koa, that I thought was dead stable, shift with the rainy season, and then come back to flat when the humidity changes. This is just my experience. But..... If you are using Koa as a neck wood, I would absolutely use a piece of CF in the neck. If your Koa necks are absolutely the most 'boring' looking Koa Ever, and dead quartersawn, and the wood was cut more than 10-20 years ago, you might be okay without CF reinforcement.

I will not use Koa as a neck wood. Honduras Mahogany, or Spanish Cedar, and only with CF reinforcement. CF is inexpensive, quick, and easy to do. Why would I not do it? I have built one neck without CF reinforcement, not by my choice. It took a bow a couple of months later.


More important than the question of reinforcement, or not, IMO, is being patient with the wood. Any instruments I build, the neck blanks are roughed out, the top surface cut flat for reference, and then they sit. After at least a month, when it is time to build with them, they are checked for flat. This is based on years of watching wood move, slowly.
Click to expand...

Agreed. I would never use koa as a neck wood. (I've even seen builders using curly koa!). I use a cf reinforcement rod not only for stability but also because I believe it enhances the sound. I want my necks as stiff as possible.
 
Moore Bettah Ukuleles said:
Agreed. I would never use koa as a neck wood. (I've even seen builders using curly koa!). I use a cf reinforcement rod not only for stability but also because I believe it enhances the sound. I want my necks as stiff as possible.
Click to expand...

Nosing in here...I've had a uke for 4 years that has a koa neck. I haven't noticed any bowing, and it's my player. Am I just lucky?
 
Thanks to all for your replies. Some for and some against but those for the need for reinforcement used bigger words and longer sentences so I erred on the side of caution and fitted some CF reinforcing rods. I cut some 15 x 3 rod down to 8 x 3 on a model makers table saw with a tungsten tip blade without any problems. For those that haven’t used this stuff it is amazingly (almost impossibly) rigid. I then routed two grooves in each neck and epoxied the rods in. The suitability of my neck timber was raised. I very much prefer the look of a uke or guitar where the exact colour of the body timber continues into the neck which for me means using the same wood. If that means always expecting the neck to deform and to need to use reinforcement so be it.
For those wondering what the holes in the centre of the neck are I screw the neck onto a 2 x 1 which I clamp in a vice for shaping. And the three white dots? I put a 1.6mm hole through the centre of the 3 x 4mm fret dot holes on the fretboard. I copy the holes onto the neck prior to gluing the shell dots in place. I then use 1.6mm styrene rod as dowels to locate the fretboard when the time comes to glue it to the neck. Tiny dowels and not ideally spaced but I don't get any slippage while gluing down the fretboards. On this occasion I expected the epoxy that I used to glue down the CF reinforcing rods to get into the locating holes and thought it would be easier to clean styrene out of the holes rather than epoxy.
As was suggested, better to be safe than sorry and it was a fairly easy task and I got to play with this amazing material.
Cheers
Paul
 

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I use .200" x .250" (5mm x 1/4" to make it more confusing) but i want to try some 3/8 x 3/8".
 
Beau Hannam Ukuleles said:
I use .200" x .250" (5mm x 1/4" to make it more confusing) but i want to try some 3/8 x 3/8".
Click to expand...
My supplier has that same size, which is the "StewMac" size. Of course Stew Mac sells the exact .200" router bit. Once the bit got dull, I decided to try a more "standard" size. And being the cheap guy that I am, 1/8" is about as cheap as it gets, and still effective.
 
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