Starting up with max high string tuning, in order to reach A4, the scale needs to be shorter than approximately 24", else you'll hit the max tensile breaking point of the steel alloy..
Low tunings will require extended long scales, a simply a matter of the needed mass in the string for vibrating at whichever frequency.
Most players over at ss.org feels 27" is sorta the minimum scale for a low F#.Many are using 080, 085 or 090, and 28" - 30" is getting more common these days, simply for avoiding such gauges.
My 8-stringer is a Schecter Riot 8 ltd, and the mere 26.5" isn't suitable for standard E (with a low F#), so I tune ordinary fourth G2# - F4#, simply because this works without special fat lows or cheese slisers high ends ;) My low is an Ernie Ball bass 075 string, high is a D'Addario 008, which I can with sortof so-so ease bend to G4# without breaking it.
My view on fifth tuning is that fanned frets / multiscale is needed, else the strings will simply vary too much in gauges.
I have the feeling you may want the fifth for fretless, which will of cause eliminate the need for bending, and as such circumvent high string breakage to some extend. You'll still need to observe the max tensile strength, though.
In the ss.org Extended Range Guitars forum, check the two threads: "The A4 and beyond thread" and "String gauges and inharmonicity". Have fun ;( /van Per Boysen wrote:
The more I play fifths tuned string instruments (like the Cello and the Stick) the more I like it and I'm curious about if it would even be possible to tune a six stringed guitar in fifths? What I mean is that if starting by the low E the highest string would have to be awfully thin, as it would have to be tuned to Eb... oh my gosh, almost one octave higher than the normally tuned guitar's high E string! That just can't work. But if starting even lower at the bottom? From experimenting with down-tuning normal guitars I know that you can tune at C on the bass string without loosing too much good tone. Anyway, let's say we string up a guitar like a cello: C-G-D-A-E; as my five stringed cello goes. Adding a sixth string on a guitar would mean tuned to B - that is B one octave higher than the B string on a normal fourths tuned guitar. Something tells me that string will break every ten minutes :-) The more I'm thinking about it the more it seems to make sense to tun the fifths tuned guitar's highest string one octave lower, in the C based cello tuning that would imply (for 1st string) the same B note that a normal guitar has as 2nd. Then that string could be used for cluster and close voicing chord work. Imagining a guitar tuning going (low to high) C1 G1 D2 A2 E3 B2. That would definitely work as far as mechanics go. The A2 string and above should plain to allow glissando bending. When thinking about how chords and scales work out on such a fretboard it seems even better than the traditional guitar tuning. The key question here is how does such a tuning affect the feel and resonance of a normal electric guitar? So, has anyone tried it? Greetings from Sweden Per Boysen www.perboysen.com http://www.youtube.com/perboysen
-- rgds, van Sinn