Double Neck 12 String

[Rick Gentry]

Howdy.
What do you more experienced men imagine the bracing and genreral construction of this guitar to be like? Wouldn't the tension be about 250 pounds? Would a soundpost be a practical addition?

[Rick Gentry]

It is a custom shop Martin that was hanging at the NAMM show in LA. Definitely a one off.

It's funny, since becoming fascinated with it, I have found a lot of Martin acoustic necks on Ebay, and have been pondering what the case might look like.

[Tim Mace]

Sound posts defeat acoustic properties of anything but violin family IMO....but it's been done.Fender tried some crappy device
in the 60's I believe.About an inch in diameter.It looked like a spacer between top ans back as i recall.God awful gawdy.

[Rick Gentry]

Do you think that a 1/4" stainless steel rod would work? Or would hollow be better? This instrument would have a pickup of course, so any lack of harmonic tingle could be massaged by signal processing.

[Ned Knepp]

Rick,
"To each his own:, but I wouldn't be particularly interested in an acoustic guitar that forced me to use signal processing to produce a decent sound. To me it just doesn't make any sense to go to the trouble of building an acoustic that MUST be plugged in. That's not to say that a pickup system wouldn't be nice, I just don't want an acoustic that is dependent upon one.

I think Rory is right that carbon fiber would do the trick without adding much in the way of weight or acoustic damping.

Ned

[FRANK]

LOOK AT BREAD LOVE GUITARS SIMILAR TYPE PUSHING FROM THE BUT BLOCK TO THE BRIDGE

[Rory]

Kinda suprised-wood, metal dowels, etc....nobody mentioning possibility of carbon fiber for this application? What about laminating carbon fiber into the top braces and also using solid carbon fiber rods as buttresses in the body to distribute the load? I saw some interesting pictures on the net (cant recall where) of a guy using carbon fiber buttreses in the guitar- they extended from the neck block to a point down the body where the sides meet the back. Looked convincing to me anyway? I've been using carbon fiber in necks (2 pieces either side of the truss rod) and also laminating it into the top braces of x-braced 8 string flat top bouzoukis. I pretty sure I could put two bricks under my last neck I did and jump up & down on it with no issue (but maybe I wont..)-the stuff is very stiff and strong. I've seen double neck octave mando/ mandos that had 16 strings still holding up playable after a long time. Carbon fiber would keep the weight down, be very stiff and remain stable over time-or am I missing something?

Rory

[Ned Knepp]

I've seen some carbon fiber laminated bracing but I don't really know much about how it is done. The little bit that I've worked with carbon fiber, I used epoxy to glue it in place. Maybe a laminate of spruce and CF epoxied together but then I wouldn't know if the standard luthier glues would hold the bracing well enough with part of the surface area being CF. I just don't know enough about it.

Maybe part of the reason Martin built this is to show off how strong the "A" frame bracing system is. Does anyone know if it is strong enough to handle this kind of tension?

Ned