Technical question about gauges and tension

[ccravens]

I have a question about string gauges and top tension. I am a non-scientific, non-technical person, as you will understand when you read my question.

I am attempting to string up a mandola (Flatiron - 17" scale) with octave pairs on the C, G and D strings. The manufacture recommended gauges are 49-32-21-12 for this instrument.

So I was considering stringing up the following set-up:
C - 49/25
G - 32/16
D - 21/11
A - 12/12

My question is: since 3 of the strings will be lighter than they would have been (had I kept the pairs unison), does that mean that my overall tension on the top will be less? And if so, does that mean that I might safely use a little heavier strings as a result?

Any info you can give would be appreciated.
Thanks in advance!

[pops1]

Tension depends on the core of the string not the finished gauge. On a Guitar the G string which is much smaller than the D< A< &E has more tension because of the core of the string and the note it is tuned to. If you don't need a heavier string because it sounds good and the string isn't too floppy then i would stay to the recommended gauges.

[Dave Cohen]

Tension depends on the core of the string not the finished gauge. On a Guitar the G string which is much smaller than the D< A< &E has more tension because of the core of the string and the note it is tuned to. If you don't need a heavier string because it sounds good and the string isn't too floppy then i would stay to the recommended gauges.

The tension of a stretched string depends on the mass, length, and frequency (i.e., of the open string). That mass includes the mass of the winding. It is true that the tension needed to break a string depends on the core wire, not the winding, but the relationship between the tension of a wound string and its' frequency depends on the length and the overall mass of the string, including the mass of the winding.

[jlatorre]

Do let us know what you decided to do, and how it turned out. I have a mandola that's due for restringing, and going to octave courses is very tempting.

[multidon]

There are some excellent online string tension calculators out there. I used to use Graham McDonalds quite a bit but now I use D'Addario's "String Tension Pro" more often. Spending some time there on your behalf, I found your octave string choices create a bit more tension than the recommended strings they are replacing. I got much closer matches by using .024w for the C, .015 for the G, and .010 for the D.

With your gauge choices you were actually creating more tension, not less, because of the notes you were tuning to at that scale length. Ideally, you want to match the tension of the original string before the substitution as closely as possible.

I would not go any heavier on the Flatiron as they are built on the light side.

[John Arnold]

It is true that the tension needed to break a string depends on the core wire, not the winding, but the relationship between the tension of a wound string and its' frequency depends on the length and the overall mass of the string, including the mass of the winding.

What the core diameter does affect is the longitudinal stiffness of the string. This has an effect on string bending, and on intonation.

[jmp]

My question is: since 3 of the strings will be lighter than they would have been (had I kept the pairs unison), does that mean that my overall tension on the top will be less? And if so, does that mean that I might safely use a little heavier strings as a result?

The basic answer I think you are looking for is: NO the overall tension on the top will not be less if you are choosing your string gauges correctly.

Why? Because the whole reason for using light gauge strings for higher frequencies, is so that the string tension is in the same range for all the strings...for a mandolin it looks like you want each string to be at around 25 lbs give or take a few lbs.

[Phil Goodson]

oops.