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What are the advantages of reinforceing the neck block with carbon rods like we see in so many configurations? Is it so you can make a lighter neck block and still keep it solid, or does it produce a stronger neck block regardless of what you may do otherwise (like top/bottom extensions)?

Well, a bunch of people have read this and passed on responding, probably because like me they are not sure quite what you are asking. Are you talking about buttress systems where the neck block is braced against the guitar waist? These are intended to keep the neck block from rotating or collapsing into the body, removing the need for later neck resets. Or are you talking about a different thing?

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Jim Kirby
kirby@udel.edu

Sorry for being unclear, yes that is what I am talking about. Was not quite sure what it is called.

I'm guessing they should be pretty effective. I've never tried it. They are a reasonably low-mass addition to the guitar, and I can't see any good reason not to try one out. Perhaps they offer some leeway in going lighter on top braces, in order to build a more lively guitar? I have no experience that allows me to say.

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Jim Kirby
kirby@udel.edu

How about those relatively simple cantilevered neck blocks Martin uses these days? I'm not entirely sure what they do but I've been imitating them. Seems like it would give more stability and support there, maybe even transfer some vibrations and aid in sustain(?). There are so many variations of neck blocks it seems dumbfounding.

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"Preoccupation with an effect gives it power and enhances the error"
from "Your Owner's Manual" by Burt Hotchkiss.

Edward: No experience at using this type of set-up but I will give you my take on them.The string tension on the guitar trys to rotate the top of the neck block inward toward the sound hole.This is very subtle and slow acting in most cases but over time(years) some distortion will happen and raise the action of the guitar.The buttress system fights against this and helps to prevent this distortion.
Tom

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A person who has never made a mistake has never made anything!!!

I have used my own system of tubes derived from Larson's Prairie State "tone tube". I run them from the neck block to buttresses near the end block and feel it does help. My neck blocks are probably a bit heavier than normal blocks, but then I was never overly concerned about weight in my instruments. A few grams this way or that doesn't bother me.
I really don't think that you can make the bracing lighter, or the top thinner because of the tubes, but it's possible that there is some contribution tone wise to the instrument. What that could be I don't want to speculate on, but suffice to say that I use them in all instruments and do like them.
There is of course, the rotational aspect of using the tubes. As Tom said, it is a very slow acting force, but I feel that the tubes help to counteract that rotation.

The martin cantilevered neck block is not for a buttress effect . The block design is to be for a clamping cawl. I cut the things off when I use a martin block.

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John Hall
blues creek guitars
Authorized CF Martin Repair
Co President of ASIA
You Don't know what you don't know until you know it

i'm kinda in favour with the somogyi method at this point. small spanish style foot going up to a fretboard support and butting into the utg. the utg then runs unscalloped straight into the kerfing. small side supports re-enforce the utg ends at the kerfing and run down to the kerfing that attaches the back. very, very, solid.

the graphite tube style ala mcknight works well also. to each his own as some use less support and some use more.

i was able to play a mid 70's guild a while back -a D40 i think (the bluegrass special?) and it had a massive neck block. the thing must have been 4 to 5 inches wide. the guitar felt very good and solid.

Ok, the theory sounds good, thanks for the replies. Now I have some questions about putting this into practice on a current build.

I want to make a neck/body join that is strictly bolted, no mortise or anything, and the fretboard extension is independent from the top. Will making a buttress like this sufficiently support this area? Is there anything else special I would want to do?

In a system like this, where would you want to position the buttress? From the top of the neck block running to the bottom of the waist, and then from the bottom of the waist to the top of the tail block?

At the join at the waist I presume it would be best to have a small block or dowel sort of thing running vertical against the side from top to bottom. Does anyone else see a problem in assembling this (if I have made myself clear so you can visualize it)? Maybe insert the braces into the neck/tail blocks first and then slide the waist block down into position and glue?

Here's the way I do it.

If you elevate the fingerboard very much above the top, you increase the leverage on the heel enough so that extra reinforcement is required or the heel will flex over time. There are a number of ways to get that reinforcement. I use a large maple spline buried in the heel. I think Rick Turner uses a steel rod welded at a right angle to the truss rod. McPherson does something like that too, I believe. And I think Laurent Brondel mentioned using a CF tube.

Here's some of what I do, which is an adaptation of stuff that Rick Turner and Mike Doolin have published. www.chassonguitars.com/design.html

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http://www.chassonguitars.com

And this is how I do it. This is actually a 00-28, and thusly the carbon fibre rods are fairly slender. The short scale and light strings should not be a serious threat in the long term.
FWIW
Mike

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The Biggest Little City, Nevada
www.hammondguitars.com
I love building guitars!