NECK

Preparations



Scale length
Fretboard
Step by step
Truss rod

Scale length.

The scale length of this guitar will be 27", with 24 frets. Other than guitars with a scale length of 25 1/2, 24, 24 9/16, 24 3/4, etc. I couldn't find any fretting tables of a 27". So, I had to do the calculating of the fret distances myself...

The mathematical formula for calculating the fret distances is called "18 rule". With Microsoft Excell, I made a spreadsheat to calculate the positions of the 24 frets, according to this "18 rule".



When marking the frets on the fretboard later, it's important to work relatively from the nut !! to minimize the unavoidable error. So when calculating it's important to know the nut-to-fret distances.

Fretboard

The wood used for the fretboard is Ebony.
The thickness of the fretboard will be 6 mm.


Drawn and rendered in Autodesk Mechanical Desktop 4.0


Neck

The neck of this guitar will be a three-piece laminate. Bubinga will be sandwiched between two pieces of Hard maple.
Dimensions of 1 piece: (L x W x H): (800x24x70) All dimensions are mm. If you laminate those 3 pieces together, you get a 'block' of: (800x72x70)mm. This allows for the full depth of the neck, and its angled (13) headstock.



STEP 1
Laminating the neck.

Drawn and rendered in Autodesk Mechanical Desktop 4.0

STEP 2
Cutting the 13 head angle with a bandsaw.

Drawn and rendered in Autodesk Mechanical Desktop 4.0

STEP 3
Routing the truss rod channel.
I will do this one first, because we still have a straight line to work with, and a flat ground.

STEP 4
Neck thickness (bandsawing)

Drawn and rendered in Autodesk Mechanical Desktop 4.0

Drawn and rendered in Autodesk Mechanical Desktop 4.0

STEP 5
The sides of the head are built up with small pieces of maple.

Drawn and rendered in Autodesk Mechanical Desktop 4.0

STEP 6
Cutting out the shape of the head with a coping saw.

Drawn and rendered in Autodesk Mechanical Desktop 4.0

STEP 7
Neck finishing

Drawn and rendered in Autodesk Mechanical Desktop 4.0


Truss rod

Also called "the back bone of your guitar".
For the moment, I'm considering to put a single action truss rod in the wizard-like neck...

Before I go any further, first a few words about the purpose of this guitar:
This guitar is especially made to be DOWNTUNED (a whole step).
Low to high: A D G C F A D
This explains also why I will make a 27" scaled neck.
Downtuning a guitar with a 25.5" neck makes the strings feel sloppy . Even with a .060 for the low A.

An increased scale length (27" <-> 25.5") causes an increase in string tension when tuned at standard tuning.
Increasing string gauge leads also to an increase in string tension.
DOWNTUNING your guitar causes a DECREASE in string tension. But that decreased string tension causes sloppy strings on a 25.5" scale guitar, and I don't like that.

So what can we do to get rid of those "sloppy" strings?
a) Heavier string gauges. (which I already did)
b) increasing the scale length. (from 25.5" to 27")
Numerical example:

NOTE*: The ABSOLUTE numbers in this table are not guaranteed to be correct. Since I only use the numbers to make a COMPARISON, there's no problem.

I used a string tension calculator to calculate the total amount of tension on the neck.

I made a comparison between a "normal tuned" guitar (1st table), and a "downtuned" guitar (2nd table).
As you can see, downtuning the same guitar (same scale length, same string gauges), results in 20 kilograms less stress on the neck !!

The neck (with truss rod) has to deal with 76 kilograms string tension. (This is 10 kilograms more than the same guitar with a 25.5" scale neck)

Keeping that in mind, we go back to the TRUSS ROD.

NOTE*: the neck will be reinforced with a 24 mm bubinga stripe.
I think I'm gonna use a single action, compression based, adjustable "standard" truss rod.

Longitudinal section of the neck
image drawed in AutoCAD 2000.


I know the existance of two way adjustables, HOT rod's, PBC tension free necks, etc., but I will try this one out with a traditional rod.

I made the truss rod myself, using the equipment of Lambert Aircraft Engineering (where I'm doing my thesis this year).


Custom made guitar by Jonathan. (GhesQi J)
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