Luthiers - is this possible?

[Moltesen]

I´m wondering if anyone has got any experience with building a 12-string with similar strings instead of octave strings on the first four strings - E to G. Could it be done with regular neck or would it require some kind of laminate to compensate for the xtra string tension?
Going for the big piano-ish sound - is this idea just plain stupid or has it been done before with fatal consequenses ?
Looking forward for some replies..

[Chris Rice]

I have a bajo sexto (the mexican instrument, not the Fender baritone) that I converted to a double strung acoustic 12 string many years ago. I generally tune it down around C. The concept comes from the mandocello, which is double strung in a similar pitch range.

This one has no truss rod and has been stable for close to ten years. On an electric with a thinner neck, I'd reinforce the neck with graphite and not worry about it.

You need an extra wide neck (1.75" minimum, I'd prefer 2") to handle the string excursion.
Custom bridge and pickups to handle the width.

I just made a video to give you an idea of what it does. Keep in mind this was a junk $100 instrument that I threw two sets of .012-.056 strings on, and that the strings are at least seven years old. Also, the frets are horribly worn brass and the bridge is not in the correct location to play in tune. The video doesn't convey the depth of tone very well, the guitar has a huge low end and subdued mids. I really like the notes behind the slide and the rattles of the slide, and stopped trying to eliminate the noises when I play this guitar.
http://www.youtube.com/watch?v=rkThZ4Qf8bk

I've never heard of anyone else doing this, but I'm interested.

[nmiller]

The sound might be similar to an octave mandolin, which has courses tuned in unison. It's hard to adjust for the different tuning, though.