Hi,

I play a lot of stuff in open tunings DADEAD, DGDGGD etc, recently I decided my limited vocal range better might fit better if I tried Martin Carthy's trick of tuning it down to C (CACAAC etc). I got a set of heavy strings tuned it as above, the guitar sounds wonderful and my singing feels more relaxed.

Martin recommend that nothing heaver than medium strings is used on the guitar, does anyone know the mathematical calculation that will tell me the tension I am getting tuning heavies to C as compared to medium to E ?

Regards

Chris