"Words Mean What I Want Them to Mean"

[charles Tauber]

Originally Posted by arie

getting duller as i age, did i miss somewhere in this thread on what this amorphous shape should be called?

...there is no real name for this geometry.

Bingo!

Doesn't the word "curved" suffice? Or perhaps, "shaped".

Or, if one word seems insufficient, how about "curved shape", or "smooth curve" or "smooth curved shape". As long as you don't call it something it isn't.

I read, recently, on another thread, someone state that if you tune a string to pitch, under its own weight it will naturally assume the shape of a shallow parabola. It will not. (Hint: look up "catenary".) A parabola is a very specific, mathematically well-defined shape.

Years ago, a well-respected and well-known (then, anyway) guitar repairman wrote an article on the correct longitudinal profile to give a fingerboard when dressing a fingerboard so that when put under tension, the neck has the correct amount of relief. His starting point, upon which all further calculation was based, was that the strings vibrate in the shape of a parabolic curve. They do not. With that staring point he calculated to three decimal places the amount of fingerboard material that needs to be removed at each fret to achieve his desired result. The basic premise was wrong, particularly if working to three decimal places.

A parabola is a very specific, mathematically well-defined shape. It isn't whatever shape you want it to be. Innumeracy is to mathematics what illiteracy is to language. In this context, with apologies to Humpty Dumpty, "Shapes aren't whatever I want them to be."

I don't think there is anything further I can add to this discussion.

[arie]

Originally Posted by charles Tauber

Bingo!

Doesn't the word "curved" suffice? Or perhaps, "shaped".

Or, if one word seems insufficient, how about "curved shape", or "smooth curve" or "smooth curved shape". As long as you don't call it something it isn't.

I read, recently, on another thread, someone state that if you tune a string to pitch, under its own weight it will naturally assume the shape of a shallow parabola. It will not. (Hint: look up "catenary".) A parabola is a very specific, mathematically well-defined shape.

Years ago, a well-respected and well-known (then, anyway) guitar repairman wrote an article on the correct longitudinal profile to give a fingerboard when dressing a fingerboard so that when put under tension, the neck has the correct amount of relief. His starting point, upon which all further calculation was based, was that the strings vibrate in the shape of a parabolic curve. They do not. With that staring point he calculated to three decimal places the amount of fingerboard material that needs to be removed at each fret to achieve his desired result. The basic premise was wrong, particularly if working to three decimal places.

A parabola is a very specific, mathematically well-defined shape. It isn't whatever shape you want it to be. Innumeracy is to mathematics what illiteracy is to language. In this context, with apologies to Humpty Dumpty, "Shapes aren't whatever I want them to be."

I don't think there is anything further I can add to this discussion.

does it suffice? you're the OP right?

[LouieAtienza]

Virtually any curve can be defined by a mathematical formula. It may not be as neat as y = x*x.

[charles Tauber]

Originally Posted by LouieAtienza

Virtually any curve can be defined by a mathematical formula. It may not be as neat as y = x*x.

And, we'll call all of them "parabola", just 'cause there aren't names for most of them. Just like most words are spelled "smith", but pronounced differently as context dictates.

[LouieAtienza]

Originally Posted by charles Tauber

And, we'll call all of them "parabola", just 'cause there aren't names for most of them. Just like most words are spelled "smith", but pronounced differently as context dictates.

Easy there, bub! I'm just saying that the "intent" may have been to create a parabolic shape, even though it may not have, nor no mathematical means used to calculate the shape. Which is why I suggested "parabolic-like" to describe what we all seem to know is trying to be described.

There's plenty enough garbage on YouTube to be critical about. Why concentrate this crusade on one individual, who admits fault?

As to the video in question, I believe the creator makes it pretty clear here:

Originally Posted by Cambrian Guitars

Suffice to say I don't do my bracing like that any more!
I should take that old video down....it's embarrassing!
As the discussion in the video's comment section says, I agree that there's nothing parabolic about any of the curves....perhaps they should be called parabollocks curves? I got "caught up" in the marketing hyperbole, sorry. .

Cheers,
Dave Fifield

[charles Tauber]

Originally Posted by LouieAtienza

Why concentrate this crusade on one individual, who admits fault?

I would like to think that anyone reading the entirety of this thread would understand from the discussion that it isn't about a single individual.

[murrmac123]

Originally Posted by charles Tauber

That is one issue, yes. There is nothing "parabolic" about the longitudinal shape or the cross-sectional profile.

Charles, I am as pedantic as the next man when it comes to misuse of the English language, but I have to say that at some point, clarity and brevity has to take precedence.

I totally agree that there is nothing "parabolic" about the longitudinal shape, but as far as the cross-section is concerned ..can you come up with a better and snappier one word description of what the profile is?

The fact that the curve of the cross section might not totally satisfy any mathematical equation is irrelevant IMO. Everybody knows what a parabola looks like ...there is an infinite number of parabolas (parabolae?) so as long as the cross section of the brace looks like a parabola, then there is no harm done by calling it a parabolic brace.

It's much like the "semihemispherical" shaping of fret ends, which technically is a misnomer ...but everybody knows what is meant by the term ...it is simply a shorthand way of describing the softening of the facets.

So let it be with "parabolic" bracing ( with the caveat that it applies to the cross section, and not to the longitudinal profile ).

[charles Tauber]

Originally Posted by murrmac123

So let it be with "parabolic" bracing ( with the caveat that it applies to the cross section, and not to the longitudinal profile ).

Let it be so.

And so it was written.



Seems time for me to step away from the keyboard for a while. "Thanks for all the fish."

[LouieAtienza]

Originally Posted by charles Tauber

I would like to think that anyone reading the entirety of this thread would understand from the discussion that it isn't about a single individual.

You're the one that posted the link to the specific video! A video that happens to be 5 years old. I totally agree that the shape created is not an exact parabola, though that might have been the aim or goal. Maybe I'll draw a set of braces in CAD and cut and shape them on the CNC. Then I'll be the only person on Earth to truly claim to have parabolic bracing!

I can think of other "sacred cows" of lutherie being hogwash, such as a compund radius fretboard being a conical section, or using the same radius dish to shape braces and glue them to the back... why worry about what somebody calls what they do? There's no intent of fraud or deceit.

Now, taking a plywood piece, bending it into a side, and calling it laminated, or better yet, layered... That irks me because lay people are still confused into thinking they're getting sides and backs made in the same fasion as Somogyi or Smallman.

[Jim.S]

Where are the photos of these heelless necks that have been mentioned, give us a look. It has always sat with me as a great idea.

Jim

[LouieAtienza]

Originally Posted by Jim.S

Where are the photos of these heelless necks that have been mentioned, give us a look. It has always sat with me as a great idea.

Jim

I have to dig them out of my old computer. Just procrastinating getting a hard drive enclosure so I can transfer the files to my laptop. And then upload to photobucket (I have posted pics in this forum before...)

[redir]

If I remember correctly from past posts Charles is an Engineer. In a former life as a geologist I remember very well having to work with engineers. Some how I still manage to have all the hair in my head!

[Howard Klepper]

Originally Posted by arie

getting duller as i age, did i miss somewhere in this thread on what this amorphous shape should be called?

We have some perfectly good words in English for this job. "Arched" will do nicely. "Paraboloid" for those who wish to sound techie without making a false claim.

[Ned Milburn]

Originally Posted by murrmac123

It's much like the "semihemispherical" shaping of fret ends, which technically is a misnomer ...but everybody knows what is meant by the term ...

FWIW, I have NO idea what semihemispherical shaping of fret ends means... *baffled*

@ redir

I love that quip about semantics - "still not enough coffee". This is where pragmatism eclipses both optimism and pessimism. Thanks!!

Now to make another pot of java!!

[Howard Klepper]

Originally Posted by redir

Whats wrong with shaping braces like that? Semantics set aside. Seems to me that having strength in the middle of the span where it is weakest tapering out to the rim where it is strongest makes sense to me. I don't do my back bracing like that but I don't see anything wrong with it either.

It is dandy if you are building a bridge, and want sufficient support along its whole length without using excess material. For a structure intended to vibrate and pump air effectively at certain frequencies, the picture is very different. I'm talking only about the longitudinal curve here.

The beam theory applied by structural engineers is relevant to guitar bracing. But guitar bracing plays both a structural and a musical role. Treating it a solely as a support structure for load bearing is an error. The job of a guitar top or back is not the job of a floor.