Mike Dexter - Posted - 03/18/2010:  04:28:24

On my next Banjo building project i want to extend the fingerboard over the head. Does this effect the 'geometary' of fixing the arm to the hoop as in the normal way? I would imagine that one would just have to fix the arm slightly higher up the hoop---an i correct in thinking this? What clearance would you give the F/B over the Head?

Your views appreciated.

beegee - Posted - 03/18/2010:  05:03:32

The neck angle may also change to allow for bridge height whne you raise the neck up to allow for the thickness of the fingerboard. The fingerboard needs only to clear the top of the tone chamber minimally, maybe 1/16". Don't forget to check the clearance for the tension hoop. With a fingerboard extension, you'll have to remove the neck to replace the head.

desert rose - Posted - 03/18/2010:  06:10:15

It will change the geometry significantly.

Normal bluegrass banjos have the strings clear the head by no more than .100" and often much less when the string is fretted at the 22 fret.

You will have to make the neck angle basically 0 to allow the fretboard to extend over the head, and count on a tall bridge

Its been done, Gibson made banjos in the prewar days with fretboard extensions over the head. Tsumura book has some very good pictures

Scott

BrittDLD1 - Posted - 03/18/2010:  09:42:50

Hi Mike--

Be aware that many (not all) of the 1920's and '30s extended fingerboards
had a flat blade of metal (preferably steel) hidden in the layers under the
extension -- to support it, as it "flew" above the head.

Without that metal blade -- there is a tendency for the extension to crack at
one of the frets slots. (A fretless neck -- like a violin, wouldn't have the same
problem with crack propagation at the notches.)

The neck can CAN be fitted at a more modern steeper angle, if desired...
The cantelevered extension simply has to be built to transfer the stress properly.
(But that is more difficult to do, on a wide and shallow tongue of wood... A few
shallow, tapered vertical splines would help.)

My guess is that a blade of carbon-fiber laminate might even be better than
stainless steel. Perhaps a piece of ribbed aluminum extrusion would work. Better
yet... mimic that aluminum extrusion with a flat sheet of carbon-fiber and some
vertcal carbon-fiber ribs bonded below it, on edge.

Enjoy the process!


Best
Ed Britt

Edited by - BrittDLD1 on 03/18/2010 09:52:28