Official Luthiers Forum!

Hi folks.
I have a question about flamenco guitar geometry.
I'm currently building guitar number three.

I'm wondering about neck angle.
Soundboard radius, if any.
Distance at the bridge between soundboard and strings.
How much soundboard flex are people getting at the bridge when the guitar is strung up.
Finally, How thick are other flamenco builders making their soundboards?

cheers,
Claire

Claire,
the thing i do to get the "right angle" is:
1.i build the guitar so that the nut side of the neck is about 2mm higher then that of the plane of the top.
2.i plane a slope into my fingerboard so that its about
   1.5mm thinner as it meets the soundhole.

of course numbers vary, but thats what ive been doing lately at the reccomendation of master luthier Boaz Elkayam, and R.E Brune's 1951 barbero plan supports this attitude too.

the old fashioned way of checking if the string to top distance is suitable is to see if a cigarette fits in there, if the fit is thight than its all good.
however, my impression is, that the more modern flamenco guitarists prefer a slightly higher action which keeps the buzzing down and supposedly contributes to a slightly warmer(more sustain?) sound.

so what i shoot for is such an angle that when i place a straight edge on top of my fretted FB i will end up with about a 5mm gap at the bridge position, or in other words, have the starightedge fall touch the bridge 2mm lower than its highest point.
i make my bridges 7mm tall.

i end up with tops at around 2mm thick.

a thing to consider is that the taller the bridge is the greater the torque is, therefore a taller bridge calls for a stronger(thicker?) soundboard.
and a low flamenco bridge calls for a less rigid(thinner?) top.

R.E Brune has a few very informative articles, i think they all appear in recent "GAL convention" issues of, well,the GAL magazine.

i have the magazines at university, once i m there ill check and let you know the exact issue numbers.

Udi.

Claire - I second everything Udi said. I also plane a little extra from the 12th fret to the soundhole on the underside, since the plane of the neck surface is at an angle to the plane of the top in the upper bout region.

I don't like planing the top of the fretboard very much, and instead have built a sanding jig with a replaceable shim that I tape the fretboard too and then pass under a sanding disk. I'm close to getting the geometry written up so that I can sand the long taper into the board before sanding the extra bit above the 12th fret, based on measurements off the guitar. I'll make that available when I get out from under the billion other writing tasks I seem to have right now. Here's the jig.

_________________
Jim Kirby
kirby@udel.edu

some worthy readings:
GAL #55 - Sabicas' 1951 Marcelo Barbero (R.E Brune).
GAL #79 - Eight concerns of highly successful guitar makers (R.E Brune).
GAL #48 - the guitar neck:its design and physics (Ervin Somogyi).

Udi.

Claire;
I've been repairing and making "flammers" for 30 years.
The neck angle is not(to)important if you arch the top !
WHY -because the arching causes the top in the bridge area to be higher than the the neck because of the arch!
Also a arch top will help with that hot "Flamenco" tone !
Why -because it's tighter because of the arch- !

I've had to repair more Spanish guitars because of NEGATIVE neck angle then any other repair!~
WHY-because the maker thought that the neck to top angle was neccessary !
Over time the top pulls up and the neck pulls up and the whole negative angle thought goes out the window -WHY
because the guitar becomes hard to play !!!!!!!!!
And the bridge has alot of stress also !

BUT if you arch the top it's not !
If you need any help - call me !

Mike Collins

_________________
Mike Collins

Mike,
how do you arch it? do you simply build in a hollowed out solera and press things into place? or do you pre-arch the braces like i assume you do on a steel string? and if so which braces do yo arch? and what interests me the most, whats the distance between the top and the strings at the saddle that YOU shot for?

Udi.