Graduated fingerboard relief and radius

[Bob Newby]

Here is an interesting article.

Michael McCarthy lives in California, where he plays jazz and hand crafts archtop guitars. In this article he discusses one of the
little-understood subtleties of designing and making fretted
instruments.

• Graduated Fingerboard Relief and Radius

Enjoy the read,

Bob

[Greg Mirken]

Well, I would question his basic premise here, that necks "pull up more on the treble side ... because there is more string tension there." A quick check of 5 different guitar string sets shows that the highest tension is on the A, D, and G strings, and that the B and high E have the lowest tension of all six strings.

[Bob Newby]

Hi Greg,

Feel free to post your comment on the article itself, and I am sure Michael will respond.

Best,

Bob

[Ned Knepp]

I wondered about that too Greg. I also have some reservations about his thoughts on the amplitude of a strings motion. From what I understand the direction of string vibration is pretty dependent upon the initial stroke. It seems to me that the strings tend to move more side to side than up and down so I would think that most of the compensation for the greater motion of lower strings would need to be in spacing between string, not distance from the fingerboard. Am I thinking wrong about this?

Ned

[Ned Knepp]

Interesting article, Bob, but I must say that you presenting it here then requesting that Greg make his comments on your site smacks a bit of Spamming to me. In my opinion it would be better to request permission from Frank before promoting your own site on his.

I'm not opposed to having more sites for Luthiers, I just think that a general announcement may have been a better approach.

Ned

[Bob Newby]

Stand down, please, Ned.

The only reason I suggested Greg may wish to comment where the article is posted is because the article's author is the expert, not me. If he has a question for the author, I am not in a position to function as the intermediary.

I must say that I reject your insinuation that this post constitutes spam. You, Greg, Frank Ford -- for whom I have the utmost regard -- and anybody else are free to register on the site in question -- just as you and I have registered here -- in order to openly participate in what each community has to offer. (Or am I missing something?)

Respectfully,

Bob

[Tim Mace]

I refer to Cumpiano's site all the time when I feel like he's got something related to whatever and even suggest on the the subject of this (radius,graduating) he got some how to ....I don't think Frank would mind at all.Surprised it was mentioned negatively.

[Ned Knepp]

Bob,
I have no issue with you having another site, something I think I stated clearly enough. I don't have any issue with you being here or even a post introducing your site. I just pointed out that the combination of you creating a post here which redirects the reader to your site followed by your invitation to the first responder to take his comments there, "smacks a bit of spamming to me". I didn’t say it was spam, but I believe it is leans that direction.

We have all, from time to time posted links to other sites some of those links were made by the owners of that site. In every case I can think of it was in answer to a question while it seems to me that the main point here is to generate interest in your new site. In my thinking this, pretty much amounts to an advertisement.

Can you see how I might think this as a bit like spam?

I didn't mind taking a look at your site. I found the article interesting and I look forward to more of the same. It is just that I would have looked at your site just as quickly if you had simply posted an announcement of its activation and wouldn't have though anything about it.

I have a lot of respect for Frank too and …. well, I would have done it differently.

Ned

[Russell Vance]

Always difficult these days to not "shoot the messenger"....what with the amount of agendas, perfidity and disguised commercial interest and spamming that goes on unfettered in the wider world, but, it was an interesting article and I read it that way.

Seems to me that it makes sense if the neck in question is subject to the forces presupposed (more force on the treble side of the board) and therein lies the issue for me: some necks twist this way undoubtably, but the majority do not.

Similarly, in the electric guitar world there is a proliferation of hybrid string configurations (light tops heavy bottoms, 10 - 52, 11- 54, 10 -70, different core to wrap ratios etc) which do not conform to this preposition or tend to ameliorate the effect. This is coupled with the widespread use of stiff maple necks and carbon fibre reinforced necks which also resist or negate the asymetrical twist in question.

This is not to be a naysayer, it simply says that this information, in it's unqualified form, is relatively useless and any attempt to implement it without determining the pathology of an individual stable neck is likely to cause a problem rather than fix it. But, obviously, for a neck that does have the problem of treble side twist this form of manual or machine manipulation would appear to be a useful tool in sorting the action. Good food for thought this article. Rusty.

[Jeff Highland]

Seems to me that even with his end result with string tension (1/64" differential)it would mean that if you gave the treble E 5 thou relief you end up with 20 thou on the low E
Way too much relief for my taste, you end up with high strings mid board and then climbing up out of the hollow as you get higher
If you did

[Ned Knepp]

Russell,
I've never worked on one but I was thinking about the double truss rod necks that some 12 string guitars have and wondering if this system would do what he was writing about?

Ned

[Russell Vance]

Yes, it was something that crossed my mind - however, to get a positive relief and a negative (tending) relief by way of a dual truss rod setup (like the demon Rickenbacker which use it for graduating the positive relief on their necks - a current thread) you would probably need to install double acting rods if you were starting out with a flat neck - this accounts for the fact that the neck is not spaghetti and will need to be forced to assume the gradient required. The weight and tone problems with having this much iron work in the neck becomes an issue.

However; if one was to construct a neck with positive relief in the quiescent state and then use two (side by side) one way rods to graduate the degree of (relative) negative relief you could achieve the same thing providing the neck was flexible enough. We have used a pre-stressed aluminum caul and carbon fiber reinforcements to dial in set relief when doing some necks, so that is doable relatively easily. The rest is a crap shoot but it would probably work.

Being an electric geetar sort of bloke, I probably haven't thought this through well, please feel free to tell me, and I'll probably blow the research and development money for this on beer anyway. Have a good weekend, Rusty.

[Ned Knepp]

I seem that I just don't know enough about this. I wasn't thinking that the rod would need to be double action rods or how much hardware that would put inside the neck. After reading your post I see that this would be a major pain to set up without something like your caul.

I have to admit that I'm intrigued by ideas like this but I can't see it having any real effect on me. I doubt I will ever have a CNC machine and I really doubt I could ever do this by hand.

Another thing that crossed my mind while reading the article was to wonder how susceptible this would be to environmental changes. I was think about a book I read which mentioned the problems exhibited by great violins as they are taken from place to place for concerts.

Thanks for adjusting my thinking on the double truss rod's, Rusty.

Ned