A collection of information on the subject of mandolin making that I have gleaned from the web, been told by people or found out on my own.
Where possible I have attributed the info to where I found it.

Tone

Gilchrist mandolin tone
Gilchrist builds different styles of mandolins depending on the woods he uses. This is what he said himself
"at one extreme is Red Spruce and Rock Maple, at the other extreme is Engelmann Spruce or European Spruce and a soft Maple such as European Maple. Red Spruce and Rock Maple makes a bright clear sounding mandolin with a very strong attack, characteristics the bluegrass players like.
Engelmann and a Soft Maple have a mellow, bassier sound that the classical players prefer (Gilchrist C style). Gilchrist also changes the resonant frequency of the soundbox to make a warmer or a brighter sounding instrument. Reducing the resonant frequency either by increasing the volume or reducing the surface area of the soundholes will produce a warmer tonal quality.

Ray Dearstone tunes the front plate 1 full tone lower than the back. He normally tunes the front to C and the back to D. When using harder wood he has used C# for the front and D# for the back. This interval produces uniformaly good instruments.

Higher arching produces a brighter sound. My first F5 copy has its arching 2mm higher than normal (16mm from memory) this instrument is quite bright.

Carbon fibre neck stiffening
To stiffen a neck it is hard to beat a "proper" carbon fibre pultrusion. For size, the bar should be as deep as possible, but the stiffness is less sensitive to the width of the bar. I use a 4mm thick by 16mm deep pultrusion and taper it's depth just enought to allow the neck to be carved to the right shape without running into it. Proper pultrusions are better than just stuffing in as much fibre as possible and soaking it in resin because a pultrusion has a much high ratio of carbonfibre to resin and it is the fibre that does the work. BTW refering to carbon fibre as "graphite" is incorrect as the 2 materials are completely different (it has just as much in common with charcoal -or coal for that matter) Of course if you use a graphite rod and the neck bends you can always cut off the peghead, sharpen the end and use it as an interesting pencil(G)

Tone differencec between F5 and F4 instruments (round sound hole and F holes)

The soundholes on old Gibson A models and F2s and F4s are ellipses of ellipticity about 0.6, with area about 2.9 sq. in. The area of the two f-holes together on A-50s,A-5Ls, and F-5s, F-12s, etc., is about 3.8 - 4.0 sq. in. That puts the Helmholtz resonance and the lowest plate resonance closer together, whereas in the oval hole models with the smaller soundhole area, the Helmholtz resonance and the plate fundamental don't couple too well. That is part of the "characteristic sound" of oval hole mandolins.

Mandola scale lengths - Don Lashcombe

The American "Mandola" (following the Gibson tradition) is more fully named "Tenor Mandola" and is tuned the same as a Viola. The European classical "Mandola" (following the tradition extending back to the origins of the mandolin family intruments in Naples) is more fully named "Octave Mandola" and is tuned like a Mandolin except an octave lower. Just to be confusing, there is an an "Octave Mandolin" in America/UK tuned this way.

In *very* rough terms, the scale lengths (nut-to-bridge) are:

• Mandolin 13-14 inches g d' a' e"
• Tenor Mandola 15-17 inches c g d' a'
• Octave Mandola 17-18 inches G d a e'
• Octave Mandolin 19-21 inches G d a e'
• Mandocello 24-26 inches C G d a
• Guitar 24-26 inches E A d g b e'

String Tension by Donald Lashomb
The tension of any string at a given pitch (say G=196Hz) is determined strictly by the length of the string and the mass-per-unit-length of that string. The length is, of course, fixed by the nut-to-bridge distance (or fret-to-bridge distance for fretted notes .. I'll get to that). It matters not what the string is made of, how big its diameter or the particulars of its construction; all that matters is how heavy it is *per inch* = ie. its mass-per-unit-length. So a large diameter string made of less dense material (nylon) will have the same tension as a small diameter string made of hi-density material (steel). Here's the formula:

         # Tension of a string
         #
         #           (2FL)^2*m'
         #       T = ----------
         #               g'
         #
         #       F = the Frequency of the string
         #       T = Tension of the string in lbs
         #       g'= gravitational constant ( 32.2 ft/sec^2 * 12 in/ft )
         #       L = Length of the string in inches
         #       m'= unit mass of the string in lbs/in