Replies to This Discussion

Permalink Reply by Tom T on March 5, 2019 at 1:31pm

Surprising to hear that a Maple neck with fret board is bowing. What kind of string tension are you running?

If you are playing slide, a slight bow is acceptable as long as it doesn't cause tuning problems. If you are fingering notes, bowing could make playing a lot more difficult.

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Permalink Reply by Brent Kasl on March 5, 2019 at 2:02pm

.042

.034

.026

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Permalink Reply by Tom T on March 6, 2019 at 9:58am

I think you could go a good bit smaller with your string selection and reduce tension.

Check out the Gitty string sets for 3 stringers tuned to DAD or GDG. Strings in the range of 0.030, 0,022 and 0.012 are fairly common and that would significantly reduce total tension on the neck.Check out Gitty to see what's available.

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Permalink Reply by François on March 6, 2019 at 11:57am

Had a similar problem with using guitar strings on a pie tin banjo that had a plywood neck. So I ended-up using some banjo strings. Since I caught the problem early, the neck returned to it's original shape and everything was fixed.

The worst thing that can happen to the instrument is a twisted neck. If that's the case, I don't know if there's really a way to fix it other than removing material...

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Permalink Reply by Timothy Hunter on March 7, 2019 at 12:43am

is the neck actually bowed? or is the neck just tilting up under tension? how big a block did you use inside the CBG? as Tom T said thinner strings will definitely help with the tension.

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Permalink Reply by Tom T on March 7, 2019 at 2:48am

I've found that string tensions of between 16 and 20 lbs are very playable with either slide or fingering. For D3-A3-D4 tuning strings with diameters of 0.027, 0.017 and 0.012 will give approximately 20 lbs of tension on a 25 inch scale guitar.

0.025, 0.016 and 0.011 will produce tension of approximately 17 lbs on a 25" scale.

These string tensions are significantly less than those currently installed"

0.042" = 50 lbs tension

0.034" = 70 lbs tension

0.025" = 70 lbs tension

These tensions may not be representative of what Brent actually has on his guitar since he may be tuned to something other than D3 A3 D4. Still, it should be noted that lighter string tensions are very playable and easy on the neck.

These days, I usually take my desired tuning and desired scale length to calculate what strings I need to give me the 16~20 lb range. I do this before I begin the build so I can order the specific strings I need. Several online sites sell individual strings and it may cost you a buck or two more for a custom set, but I think it's worth it.

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Permalink Reply by Brent Kasl on March 8, 2019 at 9:49am

I'll try it

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Permalink Reply by Taffy Evans on March 9, 2019 at 1:45pm

Hi, all the above suggestions are a good way out of your problem. But I would be more proactive and look at the cause of the problem, why are my necks bowing with the light pull of only  3 strings.

i would hate to build a guitar for somebody and have to tell the customer they can only use certain gauge of strings and limited tunings.

I would look at the cause. Neck dimensions, stiffness and grain orientation. 

Taff.

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Permalink Reply by Timothy Hunter on March 9, 2019 at 6:34pm

i think the main clue is this "then secured inside the box with blocks" i think the side of the box was twisting under tension because he then goes on to say "Lately I have been reinforcing the neck with material that runs the inside length of the box then extending about 2.5-3" and haven't seen any bowing problems"

i dont think the original blocks were big enough to support the neck tension with the large strings.

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Permalink Reply by Del Puckett on March 9, 2019 at 6:50pm

I have built over two hundred CBG's using every type and style of neckwood imaginable...and....  I have yet to have a neck bow on me.  True that I only build three string CBG's and typically tune down to EBE.  

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Permalink Reply by Paul Craig on March 11, 2019 at 7:32am

Maple is usually hard enough to handle the string pressure for a 3 string guitar as is several other types of wood even without a trussrod. I'm wondering about the construction of the guitar(how it's braced). What scale are you using? What tuning?

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Permalink Reply by Taffy Evans on March 11, 2019 at 2:08pm

Hi Brent, I may have misunderstood your opening comments.

You say you had bowing neck problems and fixed them. My earlier answer suggested looking for the problem to avoid it happening again, which it seams you had already done. 

When you said "bowing neck" this normally conjures up a vision, to me, of the fretted area or fingerboard area bowing up. It appears to me now that you may have been referring to the "neck extension" into the body/box bowing. Is this the case?

I would normally consider the "neck" as the part that sticks out from the body, not what's inside as a support, as also used  in some banjoes and resonator guitars. 

To answer your question though, the height of the strings over the body - if not too low - will not have any detrimental effect. More important is the height of the stings over the frets, as that will effect playability, tuning etc.  I cant imagine your strings being higher over the body than those on a violin, mandolin or even an acoustic guitar.........are they???

Most guitars would have a slight bow - relief - either built in or adjusted in by a truss rod, to help with buzz free fretting.

Taff

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