Ask Terry McInturff anything that you want to...right here

Terry McInturff

45th Anniversary of guitar building!
Gold Supporting Member
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7,484
Yes that makes sense. Kind of like a big vs small cymbal or something like that maybe. I find these type of questions very interesting and it's feels a bit frustrating when you're a hobby builder with little to none experience of these kind of things. The ideal situation would be to be able to build a few guitars at the same time and try out different variations on the same theme to be able to tell the differences. Not really an option when building in your kitchen though... And every time I get the building itch again I want to try something different.

Another question: Do you feel there is a need to seal the wood inside the hollow guitar? I imagine that if you're having the wood at an ideal moisture level when building, why not seal it to prevent possible humidity problems ahead? A very thin sealer of course.

You have a very good sense about you, thanks for directing Q's my way.
Regarding sealing internal components on a hollow guitar; Ive never seen any disadvantage to doing so if the internals are exposed to easy access to the world via soundhole, f-hole, etc.

Now granted...there is no such thing as a finish film thickness that is sub .002" or less that presents any sort of "gas impermiable" barrier as regards H2O exchange....and you'd never want to use an "oil finish" for the job ever...but a light coat inside is a good idea. Real light but uniform.

As with all things "not vintage" there will be objections based upon the fact that there's never been a D-28 with a sealed interior....etc, ad nauseum.

Acoustic builders of deep experience please chime in.

I could go on but havent the time at present.
 

Terry McInturff

45th Anniversary of guitar building!
Gold Supporting Member
Messages
7,484
Hi Terry! I have read some of your posts here on the forum, so i thought I'd contact you hoping you could help me out with my case, since you seem to really know a lot about this... I'm currently having a one piece guitar built and it is pretty much done at this point... However, even though I have used carbon fiber reinforcements, I have run onto quite a few dead spots. Clamping the headstock took care of almost all of them, but it created a lot of neck dive, to a point where its really hard to play.

I did some research about it, and figured that I could try one of the two things:

1. Soak the neck in slow curing epoxy resin. A bit extreme, I know, but if what I read about dead spots is correct, it might alter the wood structure enough so that it the sound transition on the neck would be faster than the body, and thus, potentially avoiding the frequency cancellations which are causing the dead spots.

2. Remove the board, remove the carbon reinforcements, and put steel rods instead, to make the neck heavier. This would probably be similar to the headstock clamping, except that the weight would be equally spread across the neck, and thus, wouldn't cause so much neck dive, hopefully.

I know both of those seem a bit far fetched.. so any advice would really be welcome.

Thanks!! :)

I feel a bit guilty, because I am equally pleased that you have reached out to me for advice...and by the fact that I have negative things to say, regarding your Q. I am so sorry.

The two "remedies" that you propose are not only impractical, they bear witness to the fact that the neck design is LIKELY to be very flawed. Any neck that has probs that would bear consideration of your approaches should be thrown away. Im so sorry.

A note about the use of carbon fiber (or other) neck reinforcements...using such things is FAR FROM A GUARANTEE against future neck probs...yet I see lousy neck designs all of the time in which the "rails" are used for just that sort of guarantee; it does not work!!

The only proper use for rail-style neck reinforcements comes into play with a neck design that would operate fairly well without them. If you have built with "stressy wood"...or if the neck build design is flawed.. there is very little-to-nothing you can do to keep the neck from moving...in an unpredictable manner.

And as for carbon fiber rails, I stopped using them some time ago; my original TCM use of such things (circa 1982) has been copied by at least 2 builders well known to TPG and they have my blessings! Me...Ive moved on.
 

bladerunner

Member
Messages
2
I feel a bit guilty, because I am equally pleased that you have reached out to me for advice...and by the fact that I have negative things to say, regarding your Q. I am so sorry.

The two "remedies" that you propose are not only impractical, they bear witness to the fact that the neck design is LIKELY to be very flawed. Any neck that has probs that would bear consideration of your approaches should be thrown away. Im so sorry.

A note about the use of carbon fiber (or other) neck reinforcements...using such things is FAR FROM A GUARANTEE against future neck probs...yet I see lousy neck designs all of the time in which the "rails" are used for just that sort of guarantee; it does not work!!

The only proper use for rail-style neck reinforcements comes into play with a neck design that would operate fairly well without them. If you have built with "stressy wood"...or if the neck build design is flawed.. there is very little-to-nothing you can do to keep the neck from moving...in an unpredictable manner.

And as for carbon fiber rails, I stopped using them some time ago; my original TCM use of such things (circa 1982) has been copied by at least 2 builders well known to TPG and they have my blessings! Me...Ive moved on.

Thank you so much for your honest answer. I have pretty much accepted that there is no way of fixing it, but if you don't mind, I would still like to ask some questions, just to get a better understanding:

1. If there really is no way out, how is it that clamping the headstock cured it almost enirely?

2. Knowing that graphite necks normaly aren't prone to dead spots because they are very stiff and hence vibrate at a higher frequency than the guitars playable range, wouldn't making the neck MUCH harder take care of it? This is how I came to idea of hardening it with epoxy, or steel rails.

3. Considering this is a one piece guitar, what would you suggest me to do? It really has a LOT of sustain on non dead-zoned notes (and I do mean a lot - some notes last over 20 seconds before decaying)... maybe remove the fretboard, cut the sides of the neck and "attach" the wings from another wood to it, kind of like the way neck through guitars are made? This option sounds to me like it could work... Last resort ofcourse, would be to turn into set neck... I don't know :(

Thank you so much for your time, and I really admire your work! I'm only regretting I didn't come to you in the first place and ordered from you.. Not that my luthier is bad, but obviously not as near as knowledgable as you.



Thanks!
 
Last edited:

Terry McInturff

45th Anniversary of guitar building!
Gold Supporting Member
Messages
7,484
1) adding mass vs stiffness are two different things
2) A neck that seems to require radical measures is simply not...at heart...apropriate for your needs.

Very sorry for the short response, its Sat night with my son, my little boy.
 

Terry McInturff

45th Anniversary of guitar building!
Gold Supporting Member
Messages
7,484
Terry, do you feel that bone vs a graphtec nut has any significant differences in tone and sustain? Also, what type of bridge do you prefer? Larger posts in the body of the guitar? Aluminum, titanium, brass, etc? Last, how much difference do the pots on the guitar really make between CTS and others? Including orange drop caps?

Many many thanks for the Q's but one at a time please..it is all that I can handle...

First Q...nut material...it is EASILY demonstrated that the nut material...tone-wise...is ONLY audible on the open strings. A good solid piece of bone will sound slightly brighter than the GraphTec......on the open strings. On fretted strings...zero difference.
 

Oz Hofstatter

Member
Messages
6,038
This is truly one of those really good Q's, many thanks, Oz.

As always, every single fellow TGP builder is invited..with open arms...to contribute to any of the TCM discussions; I'd love to see more participation along those lines, there has never been very much but lets see that change! :)

This will be a bit of a term-paper and so, bear with me.

On to the topic, whilst I roast a chicken for me and my boy. Let me begin by first defining some terms; most, but not all of these are to be found in the general "Luthier's Lexicon" of terms at this time.

1) The "Speaking Length" of the string
The speaking length of the string is that part of the string which is free to vibrate between the nut and the saddle, or between the fret and the saddle; important to note that the bridge saddle is always "in play".

2) "Scale Length"
The scale length of a guitar is most easily described as the distance between the nut and the mid-point of the bridge; the fret spacing is different for each scale length as well, and to use two easy examples, on a Les Paul of 24.625" scale that number represents an average distance betwixt nut/saddle and the fret positions are placed accordingly; whereas on a Stratocaster the longer scale of 25.5" dictates a longer distance nut/bridge saddle, and also a wider fret spacing.

3) True String Tension
The amount of force, measured in pounds and ounces, that's required to crank a given string..of a given gauge/type up to the desired pitch. The shorter the scale length, the shorter the speaking length of the string and hence..less true string tension. A LP requires less string tension than a Strat to bring the same string set into tune.

4) "Percieved" string tension
A TCM term that I use to describe the changes in percieved string tension...percieved by the player due to differences in break angle on various guitar configurations.

5) Break Angle
A term that I (and doubtless, others) use to describe the angle at which a string meets the nut from the tuner, and also the angle at which it meets the bridge saddle from the tailpiece, strung thru the body, etc.

6) "High Profile"...to..."Low Profile"

TCM terms I use to describe the general height above the top that the strings, pickups, bridge, and tailpiece end up being as a result of the neck angle.

7) Neck Angle (aka, "neck pitch")

This refers to how steeply the neck, as a whole, tilts back in relation to the flat plane of the top; using our two examples, a LP will have a neck that has a steeper neck angle than a Stratocaster does.

8) Headstock angle (aka "headstock pitch")

This refers to how steeply the headstock of the neck tilts back relative to the straight plane of the neck. Any cursory examination of LP-vs-Strat will show that the LP has the very notably steeper headstock angle of the two.

Let's take a break in order to review and to understand these definitions before I move on.


Thanks a lot Terry!!!!
Cheers,
Oz
 

Terry McInturff

45th Anniversary of guitar building!
Gold Supporting Member
Messages
7,484
You are welcome Oz...I'll get to work on the answer to your Q's real soon...I thought it best to define the relevant terms first,
 

Luke Gibson

Silver Supporting Member
Messages
1,213
Terry, quick question regarding Quarter Sawn vs Rift Sawn mahogany necks. Is there any possible difference in tone using one or the other for a neck? ...or would the natural variances of wood cause more differences in tone then the actual "cut" of the wood?

The reason I ask is because I read on the LPF that the "best sounding vintage LP's" had either rift sawn or partially flat sawn necks, not quarter sawn.... Thanks!!!
 

Terry McInturff

45th Anniversary of guitar building!
Gold Supporting Member
Messages
7,484
Terry, quick question regarding Quarter Sawn vs Rift Sawn mahogany necks. Is there any possible difference in tone using one or the other for a neck? ...or would the natural variances of wood cause more differences in tone then the actual "cut" of the wood?

The reason I ask is because I read on the LPF that the "best sounding vintage LP's" had either rift sawn or partially flat sawn necks, not quarter sawn.... Thanks!!!

In the '50's Gibson specified quartersawn wood, as they had done for decades. If there was a minor variation in the cut...away from vertical grain...they always seemed to place this short portion at the headstock; the neck shafts always seemed to be straight grained. Ive never seen a flatsawn vintage Gibson neck of mahogany....and this would be a very poor idea.

As for the quote you mention...I dont see how such comments can have any validity unless the person making that statement had played numerous examples right up next to each other, thru the same rig, in the same situation.

I can only voice my own opinion of course!
 

Luke Gibson

Silver Supporting Member
Messages
1,213
Thank you for your time and opinion! :bow


In the '50's Gibson specified quartersawn wood, as they had done for decades. If there was a minor variation in the cut...away from vertical grain...they always seemed to place this short portion at the headstock; the neck shafts always seemed to be straight grained. Ive never seen a flatsawn vintage Gibson neck of mahogany....and this would be a very poor idea.

As for the quote you mention...I dont see how such comments can have any validity unless the person making that statement had played numerous examples right up next to each other, thru the same rig, in the same situation.

I can only voice my own opinion of course!
 

Glowing Tubes

Gold Supporting Member
Messages
8,637
Hey Terry,
Cool thread, thanks for taking e time to do this.

I have a la carbonita type tele with two filtertrons in it that was built for me.
The neck pickup is somewhat louder than the bridge pickup and there is no way to adjust the pickup height of either one due to the way they mount into the body of the guitar. Is my only option to raise the screws in the bridge pickup? I'd like to lower the neck pickup actually but it won't go lower.
I wish I could lower both of them to be honest. :FM

RC
 

Deed_Poll

Member
Messages
3,088
Hi Terry,

This thread is great!

I was wondering if you had an opinion on freeze drying blanks / billets, before shaping of course, to remove moisture content as a means of decreasing weight and improving stability. I remember a luthier friend of mine showing me an amazing 80+ year old piece of figured mahogany (thin, for back / sides) that unfortunately had split in several places and couldn't be used (other than as a lamtop or pretty wall decoration!).

I've done a little research into freeze drying machines, which are manly used to preserve food, and the general figures seem to be that they bring moisture content down to about 1%-3%. I understand that even after kiln drying woods, moisture content is around 15%-20%, and this moisture gradually dries out over the years and decades.

Would moisture content this low (~3%) present problems with the wood assimilating too much moisture content from the air through screw holes, etc. and warping? And would you expect to hear any sonic differences compared with a body / neck of comparable weight with higher moisture content?

The application would be a solid body guitar. I'm thinking about getting some mahogany to a food company for the treatment, and sending that on to USA Custom Guitars for CNC shaping. Sound like a wild idea?

Thanks a lot!
 

garyrogue

Gold Supporting Member
Messages
1,083
Not sure if the freeze part is needed, just vacuum. But Terry will have to answer the rest.
Terry thanks for starting this thread and sharing.
Gary
 

Deed_Poll

Member
Messages
3,088
Not sure if the freeze part is needed, just vacuum. But Terry will have to answer the rest.
Terry thanks for starting this thread and sharing.
Gary

Hi Gary,
As I understand it, the freezing is required to bring the moisture to below the triple point (below which it cannot be both liquid water and solid ice), I think to guarantee that the moisture immediately passes from a solid to a gas as the vacuum reduces the pressure. I think in vegetables this needs to be done fairly rapidly in an industrial machine to prevent large ice crystals from forming and ruining the texture of the food- I don't want a big rubbery guitar neck after all!

:)
 

Terry McInturff

45th Anniversary of guitar building!
Gold Supporting Member
Messages
7,484
Hey Terry,
Cool thread, thanks for taking e time to do this.

I have a la carbonita type tele with two filtertrons in it that was built for me.
The neck pickup is somewhat louder than the bridge pickup and there is no way to adjust the pickup height of either one due to the way they mount into the body of the guitar. Is my only option to raise the screws in the bridge pickup? I'd like to lower the neck pickup actually but it won't go lower.
I wish I could lower both of them to be honest. :FM

RC

Thanks for your question sir.

Its hard for me to comment without knowing more about the way that the pups are mounted into the guitar; Im assuming that they can be removed, in order to route the pickup cavities deeper? Or, perhaps there are springs underneath them that could be shortened..or removed...or in the case of the bridge pup, lengthened?

It would be very unusual to not be able to remove the pups and modify some aspect in order to allow for lowering the pickups. However....if this simply cannot be done, you are right...raising the poles on the pickup would be your only option. Best of luck!
 

Terry McInturff

45th Anniversary of guitar building!
Gold Supporting Member
Messages
7,484
Hi Terry,

This thread is great!

I was wondering if you had an opinion on freeze drying blanks / billets, before shaping of course, to remove moisture content as a means of decreasing weight and improving stability. I remember a luthier friend of mine showing me an amazing 80+ year old piece of figured mahogany (thin, for back / sides) that unfortunately had split in several places and couldn't be used (other than as a lamtop or pretty wall decoration!).

I've done a little research into freeze drying machines, which are manly used to preserve food, and the general figures seem to be that they bring moisture content down to about 1%-3%. I understand that even after kiln drying woods, moisture content is around 15%-20%, and this moisture gradually dries out over the years and decades.

Would moisture content this low (~3%) present problems with the wood assimilating too much moisture content from the air through screw holes, etc. and warping? And would you expect to hear any sonic differences compared with a body / neck of comparable weight with higher moisture content?

The application would be a solid body guitar. I'm thinking about getting some mahogany to a food company for the treatment, and sending that on to USA Custom Guitars for CNC shaping. Sound like a wild idea?

Thanks a lot!


Its a very interesting Q, and new to me as well. Many thanks for asking.

1) No guitar builder of any experience would ever use wood that was over 8% moisture content; typically we see 6%-8%, with 8% being the upper limit of acceptably dry.

2)Its easy to take a body billet that is 12%-15% and dry it down to the acceptable range, and this can be done at home (pm me for details)

3) I have no knowledge of freeze drying wood, but the concept worries me a bit; I am suspicious that such a procedure would result in damage to the wood in the form of cracks...big ones, tiny ones...hidden ones even. If a piece of mahogany is brought from 15% down to 8% or lower quickly, this could shock the wood and cracking could easily occur. I wouldnt do it.

4) Because the wood will want to re-absorb moisture, depending upon the finish film this will happen, to a degree, sooner or later. This will cause dimensional changes in the wood and problems can result. Its a nice idea to have 3 % moisture content, but in the real world this is drier than is needed.

5) The majority of KD mahogany Ive worked with arrived to me at 8%, altho I always check every bit of it before use.
 

Deed_Poll

Member
Messages
3,088
Terry,

Thanks so much for your detailed response. I think you're right to urge caution! And given that it appears I have remembered my figures wrong, it seems like a lot of effort / risk just to get another couple of percent out of the wood.

I still might try it, but I fear you might be right about cracks forming in the wood. In order to prevent this as much as possible, I will have to freeze it very rapidly in an industrial machine like they use for strawberries on cereal. This is the process Birdseye patented, and minimises the formation of large ice crystals which could drive the wood apart.

Big thanks again for your insight!

Dan
 

Terry McInturff

45th Anniversary of guitar building!
Gold Supporting Member
Messages
7,484
Terry,

Thanks so much for your detailed response. I think you're right to urge caution! And given that it appears I have remembered my figures wrong, it seems like a lot of effort / risk just to get another couple of percent out of the wood.

I still might try it, but I fear you might be right about cracks forming in the wood. In order to prevent this as much as possible, I will have to freeze it very rapidly in an industrial machine like they use for strawberries on cereal. This is the process Birdseye patented, and minimises the formation of large ice crystals which could drive the wood apart.

Big thanks again for your insight!

Dan

You are welcome Dan! What is the moisture content of the wood right now?
 

burningyen

Member
Messages
15,161
I still might try it, but I fear you might be right about cracks forming in the wood. In order to prevent this as much as possible, I will have to freeze it very rapidly in an industrial machine like they use for strawberries on cereal. This is the process Birdseye patented, and minimises the formation of large ice crystals which could drive the wood apart.
The question is do cracks form from ice crystals driving cells apart, or do they form from different parts shrinking at different rates, leading to pulling apart/separation.
 




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