Combatting "seasonal" settling in

[packocrayons]

I think Bruce nailed it. I build with a very open x brace, and the soundhole braces are weak. It appears I've been overbuilding the lower bout while simultaneously underbuilding the upper bout, causing sinking at the soundhole. Intonation appears to suffer which would further confirm this theory is correct. Now that I think about it logically, there's little reason to underbuild the upper bout as most of the sound would come from the large, unencumbered by holes area behind the bridge, trying to squeeze tone out of the waist is a waste (ha) of time.

I build with bolt-on necks. I'm doing an archtop and will be setting that neck, but as with most builders here, short of tradition, there's little reason to set a neck. I do a mortise/tenon (cumpiano style) and ensure it is tight to not allow any loss of sound transmission.

@redir - that's an interesting design, and I might have to try that. Spruce is _exceptionally_ strong in compression, so those soundhole braces will combat any attempt of the neck block to rotate inwards.

The brilliance on this forum continues to astound me. Thank you all for the very helpful insights.

[IndianHillMike]

Originally Posted by packocrayons

I build with bolt-on necks. I'm doing an archtop and will be setting that neck, but as with most builders here, short of tradition, there's little reason to set a neck. I do a mortise/tenon (cumpiano style) and ensure it is tight to not allow any loss of sound transmission.

Great! Sounds like you're figuring out the issues. And just in case our wires are getting slightly crossed, I'm talking about an entirely bolt on neck, including the fingerboard extension (bolts in the tenon and the fingerboard). It takes about 30 seconds for the neck to come off if it needs to be adjusted years down the line.

[Bruce Sexauer]

I go to some pain to overbuild the upper bout for the reason discussed, and also because I don't want "local" resonances in the upper bout that conflict with the cultivated performance of the lower bout. I kill the upper bout in both the top AND the back for this reason.

While a neck re-set on a dovetail guitar is indeed more challenging than a typical bolt on, it is not impossible, merely more time consuming. A great part of the expense is still incurred in shipping the guitar around, assuming it is warranty work. Screws/bolts are threaded devices, and popular wisdom of the ages holds that they will loosen over time due to vibration and humidity stresses, something a well fit dovetail will not do. No amount of beefing the structure between the sound hole and the neck will make a difference as far as the guitar folding across the sound-hole is concerned. In that regard, dovetail vs Bolt-on is moot. I do like to point out that since I started bracing to mitigate sound hole folding, I have only had to do a single reset, not counting geometry errors right out of the gate.

[MC5C]

I've built a number of guitars, and owned dozens, and I have never felt that I needed to do a neck reset (take the neck off, rework the joint, reinstall the neck) for anything like seasonal humidity changes. I've lived in southern Ontario, I now live in Nova Scotia, and the humidity changes are severe. What I do find is that, particularly on my archtops, I need to adjust the bridge height and action three or four times a year, at least in early winter when humidity has transitioned to quite low, and in spring. I can find I need to adjust the bridge a tenth or an eighth of an inch up or down, so that is quite a lot. I also have to adjust the truss rod at the same time, the necks will absolutely swell or shrink and the truss rod needs to be tweaked.

[IndianHillMike]

Something that I like to do with my entirely bolt-on necks is to use a belleville washer between the bolt head and block -- essentially a high tension conical spring. These help maintain a more constant tension on the bolts over changes in humidity and will ideally slow down any loosening over time. Luckily if/when the bolts do loosen, it just takes a little twist of an allen key to get things tight again.

And there might be something I'm misunderstanding about this, but I do think having a stiff upper transverse brace to help prevent the fingerboard from pressing down the upper part of the soundhole can only help (in addition I have a full 2.5mm pad under the entire soundhole area as well).

[Robin, Wales]

I have read this thread with interest. I was particularly drawn by Bruce description of the Martin style bracing being the culprit for future neck reset requirements. Often quoted on AGF is the "fact" that "every guitar will need a neck reset". To which my thoughts are "Well, the bloody design is wrong then!". But I'm not a luthier.

Interestingly, the Godin integrated neck design seems to be an attempt to solve the top S shape collapse issue Bruce mentions. I know that Art & Lutherie and Seagull are cheap guitars but I have had them living quite happily between 40% winter and 80% summer humidity, and the necks not moving at all in relation to the bodies of the guitars. Now a neck reset on these cheap guitars is all but impossible; however, as long as the original geometry is good then I'm not sure that they will ever need one?

[packocrayons]

Originally Posted by IndianHillMike

Great! Sounds like you're figuring out the issues. And just in case our wires are getting slightly crossed, I'm talking about an entirely bolt on neck, including the fingerboard extension (bolts in the tenon and the fingerboard). It takes about 30 seconds for the neck to come off if it needs to be adjusted years down the line.

Possibly another culprit, I float the fingerboard so that I can keep the top radius consistent. I find geometry easier to dial this way. That being said, we're in a thread about how I can't get geometry right.