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Hi folks, I am trying to get some thoughts on an issue I am having with the elusive and troubling neck movement.

First some backround:
This is a 12 string with .080-.015 strings tune down to B although lately I've tuned it down to Bb.

It has 2 carbon fiber rods as well as a truss rod.

It is a new build and is 6 months old, it is not kept in the case, the humidity is usually around 35 but the weather down here in Georgia is starting to cool down at night.

Last specific, I didn't have the heel cap glued on when I fit the neck and there wasn't contact all the way across the bottom base of the heel but the contact points of the sides/cheeks was very tight (less than .002). When the cap was glued it did not fit flush.

So my questions are, of all the culprits: Weather, string tension , glue failure,etc. or a combination.

How much does the cheek contact of the heel effect the overall stability of the joint?
If the glueing of these contact points is over a French polish (very thin) finish,does that hinder seriously the bond?

I did compare the string tension of baritone strings at a lower tuning compared to medium light guage at standard tuning and feel I am not increasing the tension enough to warrant such a problem in the short amount of time.

And lastly, it is affecting the action as now I have serious buzzing at the 2nd fret.
Just wondering if a neck reset is the only option, how can I avoid this if indeed it is somehow my design failure.
Thanks for any thoughts.

That little gap is multiplied about two in terms of action at the 12th fret. Is this a dovetail joint? If so the dovetail itself should hold the neck on the rims, and the glue only needs to be in the joint not the heel to the rims. I am not the best repair person, but if this happened on my guitar I would pull the neck and refit the dovetail.

If it is a bolt on tighten the back bolt.

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http://www.Harvestmoonguitars.com

Thanks John, that is why I am confused because the dovetail was tight, no gaps all the way down the heel with a .002 feeler gauge. I honestly and regrettably can't remember if I used titebond or hide glue but if it was hide, maybe it failed from being too thick.

If it's a dovetail, you can't really blame glue failure. The dovetail joint itself is supposed to do 100% of the work holding the heel to the shoulders, and all the glue is there for is to keep it from sliding apart upward.

Looks to me like the dovetail was not as tight as it initially appeared - not uncommon, as dovetail fit can be a deceiving element with a fair learning curve to be able to accurately gauge the fit throughout the joint.

No way around it if you want to do it right. Time to steam it apart, clean, shim, and refit the dovetail.

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Eschew obfuscation, espouse elucidation.

I'd guess your dovetail was loose from the get go, but the glue was keeping it in place, and has now either creeped or moved from RH.

The fix requires pulling the neck and shimming the tail of the dovetail. Just a small square 1/4 x 1/4" is all that's needed.

I do not set too many dovetail joints but when I do while setting the neck I chalk the mortise. Then set the neck and check where there is contact on the tenon cheeks. I want contact along the entire tenon. While setting the neck I will only remove wood that has chalk on it. When I do it correctly when the neck is even with the top I have full contact along both tenons.

I was taught if set properly you should be able to string up a guitar with no glue in the joint.

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http://www.Harvestmoonguitars.com

Yup.