moving the neck forward

[dejkon]

I have the Manuel Reyes flamenco guitar plans drawn by Tom Blackshear. In the notes it says to move the neck forward 2mm to get the correct action what does that mean?

[schramm_guitars]

I think he means that the neck lifts at the nut about 2mm to create a forward neck angle. Visualize a straight line from the soundboard to the nut, then 2mm up at the nut creating a downward slope towards the soundboard. In order for this to be correct the thickness of the fingerboard, fret height, desired action and desired saddle string height all have to fall into place.

There are no guitar making books available today that explain neck angle properly which is one of the reasons I wrote and published my guitar making CD Roms.

When building a guitar the first things you need to know is how high you want the strings at the saddle, your action, fingerboard thickness and fret height. The rest of the guitar is built around these dimensions. If not your just guessing and hoping your neck angle will be correct...which it won't.


For example, let's say you want the following:

10mm saddle string height (SSH)
3mm first string action (SA)
5mm fretboard thickness (FBT)
1mm fret height (FH)

Firat I make a dummy fretboard block that is about 20cm long and about 5cm wide. The thickness is calculated by adding the FBT and FH, 5mm + 1mm=6mm.

Next I need to calculate the proper neck angle I need to know where my straight edge is going to be at the saddle when it is placed on top of the frets only. This is calculated by taking the desired SSH and subtracting two times the desired action, 3mm(SA) x 2= 6mm; 10mm SSH - 6 SAx2= 4mm.

So now I make a gauge block that is 4mm thick and about 50mm long and about 10mm wide and place it at the saddle location. The dummy fretboard is placed on the neck and a straight edge is placed on top of that. The neck angle is adjusted so that the straight edge should just touch the gauge block. At this stage I lock in the neck angle. If I'm using the Spanish method I now glue the back on with the center strip adjusted so that it hits the foot and locks this angle in place.

I actually add about 0.010 to the gauge block to compensate for the string pull.

Pretty simple basic lutherie. Perfect neck angle every time.

[dejkon]

I still dont understand how you assemble the neck to the top, sides, then back and get it to maintain that angle.

[dejkon]

Tom Blackshear also talked about a slight concaving that occurs between the 12th fret and the bridge. So the top and sides go on as usual then you force that angle with the back seam against the foot of the heelblock. Which would also in turn begin to create the concaving of the soundboard.

[schramm_guitars]

There is minimal concaving of the top. Moving the neck at the heel 1/32" has a major effect on the string height at the saddle. Sometimes as much as several millimeters.