I've made 'bout a dozen and a half solid-body six-stringers with no truss rods and no problems. HOWEVER, my necks are short scale (23"), made with quartersawn oak, cherry or maple, and I use .009 gauge strings. I always check the natural curvature of the wood before starting, too, and let that help counteract string pull. With that combination of factors, normally, string tension creates just the right amount of relief. The only problem I've ever had, believe it or not, was a bit of backbow (!!), which was rectified with heavier gauge strings! Now, I don't try to make the necks super thin either; they're a little on the fat side at about 7/8" thick (or a tad less) at the first fret.
I did make one guitar for use with .011's, in which I put parallel carbon fiber rods from Stew-Mac. No problem handling the additional pressure... If anything, the neck's TOO straight under pressure! Those carbon fiber rods really do stiffen up a neck, but they are pretty dang expensive (like $15 apiece, if I recall).
Bottom line, you CAN make a 6-string guitar without a truss rod. A few of these are over two years old, get played a lot, and haven't shown any signs of instability.
P.S. The threaded rod you mentioned functions as a standard, compression-style truss rod. It's not a matter of stiffness or deflection; rather, when tightened, it compresses the rear of the neck, thus opposing the pull of string tension. To work, it's got to be anchored at the ends.
Stewart-Macdonald sells these "square tube" rods similar to what Martin used to use; you just chisel or route a channel into your neck and epoxy them in there; then glue the fingerboard on.
This same sort of material is usually offered at hardware stores, it may be a bit cheaper there.
Thanks Mark for the tips but don't mention any stores as i'm in ireland and its hard enough to get a cigar box to start with in saying that i really appreciate your tip thank you
I have only gone up to four strings, using standard 1 X 2 hardware-store oak for the neck with a 1/4 X 2" fretboard; absolutely no neck bending or warpage.
Going up to six string adds a lot of tension; I believe a standard steel acoustic set pulls about 120 pounds if I remember correctly.
In that case some sort of reinforcement might not be a bad idea. Martin for many years used a simple piece of rectangular stock; not adjustable in any way. I believe that Stew-Mac sells carbon-fiber braces as well.
I have heard of people using things like allthread (threaded rod), but it's round and not very stiff in terms of deflection.
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I did make one guitar for use with .011's, in which I put parallel carbon fiber rods from Stew-Mac. No problem handling the additional pressure... If anything, the neck's TOO straight under pressure! Those carbon fiber rods really do stiffen up a neck, but they are pretty dang expensive (like $15 apiece, if I recall).
Bottom line, you CAN make a 6-string guitar without a truss rod. A few of these are over two years old, get played a lot, and haven't shown any signs of instability.
P.S. The threaded rod you mentioned functions as a standard, compression-style truss rod. It's not a matter of stiffness or deflection; rather, when tightened, it compresses the rear of the neck, thus opposing the pull of string tension. To work, it's got to be anchored at the ends.
This same sort of material is usually offered at hardware stores, it may be a bit cheaper there.
http://www.stewmac.com/shop/Truss_rods/Non-adjustable_truss_rod/Mar...
Going up to six string adds a lot of tension; I believe a standard steel acoustic set pulls about 120 pounds if I remember correctly.
In that case some sort of reinforcement might not be a bad idea. Martin for many years used a simple piece of rectangular stock; not adjustable in any way. I believe that Stew-Mac sells carbon-fiber braces as well.
I have heard of people using things like allthread (threaded rod), but it's round and not very stiff in terms of deflection.