classical guitar neck - luthier q

[Paul Barberton]

I am building a classical guitar using the Cumpiano/Natelson book,
Guitarmaking, as main reference. I was wondering, some guitarmakers
apparently make a trussrod for the classical guitar neck. I would prefer not
to put metal/carbon fibre in the guitar, but I thought some other hard wood
imbedded in the neck might help the stiffness. How important is it for the
sustain? Should I go ahead without a trussrod? Any advice would be much
appreciated.

Regards

--
Paul B

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[Chris Johnson]

Classical guitar necks usually don't have a trussrod.
The neck is meaty enough on a typical classical that there
really isn't any point to it and an adjustable truss
rod might not have the power to significantly adjust
the neck anyway.

So here's what you do:

You select the finest QUARTER SAWN wood you can find for the neck.
Make sure its grain is VERY vertical when you look at the endgrain.
You don't want any runout or twist in the piece and don't settle
for less than a blank that is truly quartersawn. Those growth
rings need to be vertical and consistently so for the best,
stiffest, most reliable neck.

Believe me, it makes a difference. You can pick up any guitar,
play it, yank on the neck a few times, and figure out if the
neck is flatsawn or quartersawn with just a little practice.
A quartersawn neck is much stiffer.

I build electrics with adjustable trussrods and I make only
quartersawn necks. When I'm done, the nut on the trussrod
is just tight enough to keep it from rattling. I've got
a guitar here that I built 13 years ago and I've never had
to adjust the truss rod at all. It's still just tight
enough that it won't rattle and no more.

CJ

[Dave Bernick]

As Chris mentioned, most classical necks do not have a trussrod. His
recomendations about wood selection are excellent. I've tried using
Mahogany, Cherry and Australian Lacewood. All work well - the Mahogany is
preferred..

Richard Schneider used to put a steel chunk/plate/rod in the neck - it's
purpose was to add mass to the neck, to improve sustain. This added mass had
to be counter balanced with a larger tailblock, for better balance of the
instrument. It works..

I have done experiments to see how a classical neck vibrates. It's primary
vibration mode is twisting - tortional, with the node up the centerline of
the neck. Some of this energy, of course, ends up as heat (not sound) and
negatively affects sustain. Richard's added mass lowers the resonant
frequency of the neck below any of the fundamental frequencies of the
guitar, and so..improves sustain.

I am now experimenting with a dual opposing, spiral wrapped carbon fiber
rod, in my classical necks. This is intended to stiffen the neck in the
tortional axis - hoping to minimize the parasitic damping affects of this
mode, without adding the extra mass. We'll see how it works..

dlb

"Paul Barberton" <pbarberton@y^a^h^o^o.com> wrote in message
news:9f342l$ff3$1...@ctb-nnrp2.saix.net...

[denisg]

Paul,
Take a heavy clamp and clamp it to the peghead to see what added mass
does to the acoustics. Then clamp the neck into a vise to see what
added stiffness does. In both cases compare to the normal condition.
Let me know what you think I am very interested in your unbiased
opinion.

Denis Grace

[Al Carruth]

I've found that a neck 'tuned' in it's first bending mode to the frequency of
the 'main air' resonance can give a 'fuller' bass response, with no loss of
sustain. Normally that mode is too low, but it can be raised if you make the
neck and head light. It also helps to put in a carbon fibre U channel rod.

I like to use those anyway on necks made of cedro: it's so soft that it can
move a bit more than I like. For mahogany necks it's not needed.

Alan Carruth / Luthier
http://www.alcarruthluthier.com

[David Schramm]

Paul,
No need for a truss rod. There is a way to make necks with spanish cedar
that are very stable, better then quarter sawn. For this method you do not
want to use quarter sawn wood! In fact 45-35 degree is what you want. The
neck is made from 3 pieces of wood if you look at the end grain it would
look like this /////////||||||\\\\\\\\\\ The fingerboard goes on top of
this. The center piece is the only one quartered and is only about 1/8th to
about 1/4" wide. To select the wood you have to do what John Gilbert calls
"Flipping the Wood". Too hard to explain, easier to show. This is his method
of building necks which John Gilbert taught me. Ebony has more movement then
cedar so
it will control the neck. The above method works with the movement of the
ebony in a positive way. In other words if it moves, it is in a favorable
fashion.

Regards,
Dave Schramm
http://schrammguitars.com

[Paul Barberton]

Many thanks to all for the advice.

Dennis Grace, I'll have to get back to you on the neck clamping experiment
over the weekend.

Regards,
--
Paul B

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