Carbon fiber rod needed for basswood neck?

[Brushwood]

I’m having a new rosewood fretboard (choosing this instead of ebony ‘cause I’m thinking rosewood might help a bit with warming up the sound?) with new frets put on a mid 1930’s Kay Kraft Deluxe round hole archtop guitar. It’s replacing a worn pearwood fretboard. The neck’s made from basswood and is bowed and my guitar repair person is suggesting that after the neck is straightened the strength of the new fretboard will be enough to keep the neck from bowing again in the future.
I understand that basswood’s a very soft wood and I’m concerned the fretboard alone technique could be taking a risk. I’m wondering if I should politely insist that one or even two carbon fiber rods be added in the repair. Btw, I’m also thinking to ask to have a truss rod installed because it’s a 25 3/4” scale length and I’d like to tune it down 1/2 or even a full step while adding a capo to the 1st or second fret to make it a shorter scaled guitar. I normally tune down at least 1/2 step anyway on my other guitars. Any advice would be appreciated on the carbon fiber rods or truss rod addition or even a combination of both.
Thanks!

[Fathand]

Necks that have warped and been straightened sometimes warp again. Since you are replacing the fretboard it's a perfect time to reinforce it. You could use carbon fibre or a piece of 1/8" x 1/2" aluminum or even steel. These wouldn't show if you're trying to keep it looking original.

2 way truss rods are pretty easy to install, cheap, and only use about a 1/4" x 3/8" slot, that would be my choice.

[Howard Klepper]

Your instincts are right. At least a pair of carbon rods or an adjustable truss rod. Both would be even better. Your repair guy sounds inexperienced; it's okay to tell him what you want.

It's more likely to be poplar than basswood, but either one is among the weaker hardwoods.

[Brushwood]

Originally Posted by Howard Klepper

Your instincts are right. At least a pair of carbon rods or an adjustable truss rod. Both would be even better. Your repair guy sounds inexperienced; it's okay to tell him what you want.

It's more likely to be poplar than basswood, but either one is among the weaker hardwoods.

Thank you for your advice and info Howard. Here’s a photo taken from a “history of guitars” book describing some of the specs of my K2 Deluxe where it mentions the basswood neck on the lower right.
IMG_1679236690.713294.jpg

[Brushwood]

Originally Posted by Fathand

Necks that have warped and been straightened sometimes warp again. Since you are replacing the fretboard it's a perfect time to reinforce it. You could use carbon fibre or a piece of 1/8" x 1/2" aluminum or even steel. These wouldn't show if you're trying to keep it looking original.



2 way truss rods are pretty easy to install, cheap, and only use about a 1/4" x 3/8" slot, that would be my choice.

Thank you for your input. I’m not too concerned about keeping it looking too original as I’d just like it more playable. I’m mulling all this over.

[Howard Klepper]

Originally Posted by Brushwood

Thank you for your advice and info Howard. Here’s a photo taken from a “history of guitars” book describing some of the specs of my K2 Deluxe where it mentions the basswood neck on the lower right.
Attachment 89192

Interesting, but I wonder what their source is (e.g., factory records?). Other sources (https://www.snathanieladams.com/2019...-guitars.html; https://guitar.com/features/the-unto...f-kay-guitars/) say Kay used mostly poplar, plus some mahogany and maple, with no mention of them ever using basswood. Poplar could be confused with basswood if someone didn't make a very close examination.

[John Arnold]

In checking modulus of elasticity (stiffness) specs on the Wood Database, I was surprised to learn that basswood and Honduran mahogany are essentially the same, while yellow-poplar is a bit stiffer. In any event, reinforcement is generally a good idea.

[keith.rogers]

Without seeing the neck or guitar, I'd be concerned about routing too much away in the "break" area of the headstock/neck to support an adjustable rod, especially if you're already concerned about the wood. (I'm assuming a "soundhole" or body-end (under the fingerboard extension/overstand) adjustment is not an option.

There are some low profile type rods that you might look at, but if it's giving you some jitters, you might consider doing what I did on an old Kay (parlor) that worked well. In a video I saw from the S-M folks, a CF rod was inserted inside a Martin steel "box-type" [non-adjustable] truss rod. I put one of those in and the previously bowed neck held up quite well.

I would have some thoughts about using ebony vs. rosewood though. I, personally, don't think there's a big difference in sound between the two, but good ebony is noticeably stiffer than rosewood.

[Rudy4]

A fretboard, regardsless of wood or thickness will not prevent a neck from flexing under string pressure.

I did a similar job on a Kaycraft guitar and fitted a a length of 2024-T4 aircraft aluminum bar stock into a slot cut into the neck. The finished neck was fitted with a new ebony board and remained straight, other than the planned amount of relief, under string tension.

I've done this on a number of instruments in the past, using 1/4" thick 2024-T4 and cutting the bar in a long taper from 3/8" at the nut to 5/8" close to the heel. I normally route a a tapered channel, fit the bar, and glue a cap over the bar which is finished flush to the neck before the fretboard is added.




The bad part of the Kaycraft retrofit job was it still used the curved neck heel mated to a curved block and retained with a bolt once the neck angle was determined, one of Kaycraft's not so well-thought-out innovations. It sounds great on paper, but that joint is just nasty as far as being able to lock it into a stable position. Hopefully your Kaycraft doesn't have the wonky adjustable neck.

[keith.rogers]

Originally Posted by Rudy4

A fretboard, regardsless of wood or thickness will not prevent a neck from flexing under string pressure.
...

What? Maybe I'm misunderstanding what you are typing here, and, slotted, without frets, sure, but the neck+fretboard (material and thickness)+frets+truss (type/material/installation/etc.) rod (if one) all play a part in the straightness, or not, of the neck under tension. There is, after all, a reason some bowed necks that do not have adjustable truss rods can be corrected using compression fretting on the finger/fretboard, i.e., with frets that have an oversize tang.

[Rudy4]

Originally Posted by keith.rogers

What? Maybe I'm misunderstanding what you are typing here, and, slotted, without frets, sure, but the neck+fretboard (material and thickness)+frets+truss (type/material/installation/etc.) rod (if one) all play a part in the straightness, or not, of the neck under tension. There is, after all, a reason some bowed necks that do not have adjustable truss rods can be corrected using compression fretting on the finger/fretboard, i.e., with frets that have an oversize tang.

Yes, every part of a completed neck "plays a part". If you've ever had a pre-fretted board in hand then you know how easy it is to bend.

The board itself does not serve as an adequate structural component to prevent forward bow.

Do remember that the OP is looking at the board as a way to prevent forward bow on a "basswood" neck.

As far as compression fretting goes, yes it can be used to force a neck back to a more desirable amount to relief but I personally consider it a kludge method of correcting a problem that would have been better addressed by utilizing proper construction methods. There are any number of methods used to correct problems that work at least temporarily. Tons of repair folks use those methods and its often based on how much time and effort you want to put into an instrument based on its overall value. No problem with that, and its a consideration on the OP's case with the KayKraft.

I'll base my knowledge on what I picked up from Irving Sloane MANY years ago regarding neck reinforcement. "If you can bend it by hand it will not provide the ability to prevent a neck from bending under the force of string tension".

To further ruffle feathers, I'm not a big fan of skimpy CF strips for the same reason. Paul Reed Smith was adding a 3/4" square CG rod in his high end acoustic guitar necks because he didn't feel that the usual strips worked for that purpose.