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Last winter I made a commissioned 12 string for a customer from Hawaii. He picked it up in person in June and was delighted with it. I strung it with D'Addario Silk and Steel light strings because I like the warmer tone, and the ease of playability. I figured the lower tension would also be a positive for a 12 string. I had it strung up for two weeks prior to the customer's arrival and it didn't move at all. Neck had about .004 relief at the 5th fret and the action was 3/32" bass side and 2/32" treble with the rod snug.

I got a call last week from him saying the action was very high and the guitar needed a neck reset. While we were talking, he admitted that his humidity control had been intermittent, and also that during a record heat and humidity wave, the guitar was subjected to temps in the 90's and near 100% humidity for a week while he was out of town and the power went off. Needless to say, this voids the warranty. I had gone over the absolute need for climate control with him, verbally and in writing. He agreed to ship the guitar back to me for inspection.

When I received it, it did show signs of over-humidification: The top and back are slightly over-domed, the center seam has telegraphed through the lacquer, the nut is no longer flush with the sides of the neck, and the Maple neck stringers can be felt due to the Mahogany swelling more than the Maple. The neck relief is at .012 at the 5th fret and the action is 4/32" both sides. The body geometry seems fine, no rotation of the bridge or neck block that I can see.

The neck relief is what concerns me. I made the neck to my standard 6 string specs except for the 1 7/8" nut width. It has a sound hole adjustable 3/16" truss rod. All my 6 string necks have held more or less dead flat with the rod loose, so I didn't have any misgivings about using the same rod in the 12 string neck. All my research into 12 strings (this was my first) focused on bracing and top thickness, no one that I recall mentioned anything about neck modification except for nut width. I clamped the neck into a slight backbow and tightened the rod as snug as I dared, and it is now dead flat with no string tension on it. I should mention that the FB was glued on using epoxy.

So here are my questions for those with 12 string experience and/or humidity warranty issues:

1. Could the high temps and humidity in Hawaii be responsible for the neck developing excess relief?

2. What is my best course of action at this point? I have researched some techniques for straitening necks including heating, compression fretting, and gluing in frets while the neck is back-bowed. I could also refret the neck with tall fret wire and level out the relief. All these assume the neck has reached equilibrium and will hold its current state, not becoming worse in the future.

3. Do I owe this guy a new neck as a last resort? If so, what should I do differently?

Thanks for any help.

Hey Greg!

Sorry that you have to deal with this my friend. Here are my thoughts regarding your questions:

1) Yes - exposure to very high humidity AND high temps can harm the best built instruments. I had my first ever Heshtone failure last month. The client left it in 100 degree heat in a car for a week.....

Result: Warranty is voided for anything that is humidity or heat related going forward. I reglued the bridge for him for free anyway because I can and he is a friend but I did not have to do this and the client is very grateful. The client also understood that it was on him and wanted to pay me anyway but I refused.

2) It sounds to me as if the exposure to high RH over time permanently altered the neck shape and that again is a result of "abuse" and not something that I would ever jump through my sphincter to accommodate as a warranty failure. When I think of some of the most successful 12's out here such as the older Guilds other than the increased width of the nut and neck they used the same rods, wood, etc. and no reinforcements such as CF that they did not even have back then. I'm also reminded of Occam's Razor in so much as the most likely cause of something is often in fact the real cause of the problem. As such blame the client.....

3) I don't think that you owe the client anything but this also does not mean that you can't be compassionate and maybe cut them some slack while still being true to yourself by charging what it costs you in opportunity costs to repair this one.

A lot depends on your relationship with the client. Many of my clients come to my home and jam with me and we get together for other reasons too so I likely would take hit to some degree out of friendship.

What ever you do it needs to be appropriate for the strings that the client has access to and will likely use. Silk and Steel are not always easy to find so folks often go with steel only and this can be problematic on certain instruments such as Gild classicals converted to steel and not braced for it.

At the very least try to get an all expenses paid trip to Hawaii out of it too!

FYI - Bob Gleason of Pegasus Guitars in Hawaii told me that he has to run the dehumidifier 24 hours a day in order to keep the sop humidity low enough to build.

Silver lining: be glad it wasn't the other end of the spectrum with a customer out in 10% humidity

Based on what is stated on your web site and other details mentioned here -- I see nothing but a cost of "repair scenario." Through neglect, the owner breached the integrity of the instrument, he/she surely understands that the maker has no liability.

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Ken Cierp

http://www.kennethmichaelguitars.com/

I've had my issues with humidity over time until I learned the facts about it all...that being said a '78 Martin D-28 reacted to Santa Cruz's humidity by back bowing on the neck, and that makes sense...wood gets humid, it expands...there's more wood on the top of the neck/fretboard and in some way it logically leads to the conclusion that back bowing results...if this a rule (don't ask me...) then the fact that too much relief in your case points to some other failure and should be warrantied...

I will say again, don't ask me on the reality of the subject, just offering a thought on direct experience with a guitar without an adjustable truss rod.

.012" relief is not a whole lot. I like to have about .007" when strings are tensioned. So if you leveled the frets, taking about .005" off the upper and lower frets (and not much off the middle frets) then you should be in pretty good shape. If there is not enough fret height to do this, then the next option would be to pull the frets, level the fretboard and refret. Neck straightening with heat would be a last resort, and really does not sound necessary in your situation. Also, the first thing you should do is let the guitar dry out a bit and see if things go back to where they started.

Double action truss rod?

Relief spec is very much a playing style thing, and I don't consider 0.012" that far out of line. 0.004" for many players would be insufficient -- my standard target is 0.008-0.010". Having said that, seasonal changes in relief due to humidity are to be expected.

Your regular 6-string truss rod should be just fine for a 12 string and should permit more than enough adjustment if current relief is 0.012".

Action of 4/32 is starting to be on the high side, and that has very little to do with the relief or truss rod -- that is a structural change in the body, neck joint or top rise. So I'm a little confused by why you're focused on the neck relief and very little concerned with the neck/body geometry?



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Thanks everybody for the comments and suggestions. Much appreciated.

Tim, as you noted setup specs can vary a lot. From my perspective, .012 is a lot of relief for an acoustic and 4/32 action is really high. Also, this guitar has .012 relief with the rod adjusted as tight as it can go, no more adjustment available. I've made a lot of measurement of the body and while it does show some signs of over-humidification there doesn't appear to be much if any neck block or bridge rotation, and the top rise is minimal and within tolerance. I set up dozens of guitars a month and in my experience, adjusting relief can make a significant difference in action. A lot of this is an individual guitar thing, and how each neck and rod acts. In this case from what I can see, most of the high action is due to this excess relief.

I am letting the guitar dry out to see what happens. Right now I am leaning toward leveling the frets to remove most of the relief and resetting the bolt-on neck to get the action back where I want it.

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It will probably be alright.

Heat and humidity is how you bend wood.

The guys in far north Queensland have been fighting this problem for years. Necks tend to "fold" just where the heel transition starts - 10th fret for a 12 fretter, 12th fret for a 14 fretter. The way the locals have gotten around it is to build tilt-neck guitars, i.e. user-adjustable neck angle and truss rods with plenty of power to keep the whole neck shaft straight. There are lots of variations on adjustable necks but most are permutations on the Stauffer mechanism.

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Trevor Gore, Luthier. Australian hand made acoustic guitars, classical guitars; custom guitar design and build; guitar design instruction.

http://www.goreguitars.com.au

I am guessing really, if its not mostly in the body, but mostly in the neck, then the wood will have deformed slightly under the pressure/temperature conditions and that this neck will mostly stay its current shape now. That is, I don't think humidification alone will re-straighten the neck. If you think about it from the guitars' perspective, I kinda like that the box did so well under the adverse conditions. So you can always relevel the fretboard and get back home. I guess it would just nag me about that particular neck moving. I would always be coming back and checking it again to see if it moves in the future, without the adverse conditions. Some mahogany is pretty light in weight, under 2.8 pounds/foot, say. I know lots of builders like a light weight piece for the neck- I am just fairly sure strength and density are coupled. I like the epoxy for the fretboard, so you could not have introduced moisture there.
Am just wondering what you recall about the neck mahogany you used

Mike, I was pleased (if one can be pleased under the circumstances) that the body seems to have held well under rather extreme conditions and also that the bridge held tight with 12 strings pulling. The neck blank I used was African Mahogany with two Maple stringers laminated in. I didn't weigh the neck but I had it in my shop for about 4-5 years and have made several 6 strings from the same neck wood. None of them have had any issues. Just from feel I would say they are a bit heavier than necks made from Honduran blanks.

One of the reasons I began using epoxy to glue on fretboards was to get rid of introducing moisture.

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It will probably be alright.

Also, while the neck relief is clearly part of the problem, it isn't responsible for all of it. In addition to getting the frets level I am going to have to reset the neck. I am probably going to lower the saddle somewhat and include a set of shims so that the owner can make his own adjustments in the future. "The future" is something I am just as concerned about as getting the action corrected for the present. Neither I nor the owner wants to keep shipping the guitar back and forth.

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It will probably be alright.

I guess I am always trying to outthink the wood. African is slightly less stable according to book, but with the maple strips it would seem really stiff in my mind. African is generally denser, so I would think it stiffer. I guess Hawaii with no climate control would be just like Missouri or here in Kentucky. Could not be much more severe a test. Well I suppose we can lock a guitar in a minivan.

However, maybe its really the fretboard causing the pressure. I seem to recall ebony being the species the moves the most in length along the grain of most any species. If that is true, and with the fretboard naked so to speak, its increased length might be the root cause.
If that is true, then drying might really help. Maybe you better wait a bit longer. Worth a try,perhaps.

Pretty sure the finicky reputation of 12 string guitars is well earned. Especially all manner of neck distortion. The old Guilds had/have a reputation of staying playable even for road musicians but I'll tell ya' those things are over built, weigh a ton and even have "two" truss rods.

Back when I was a kid it was said "with a 12 string guitar you spend half your time tuning and the other half playing out of tune."

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Ken Cierp

http://www.kennethmichaelguitars.com/

above I noted my experience with my '78 D28...the warranty guys said humidity had caused the back bow...

yeah, fretboard soaking up the moisture...this for all intensive purposes causes the fret tangs to be too large for the slot, which causes back bow...compression fretting is used to cure too much relief in necks without an adjustable truss rod...

What kind of truss-rod? The dual-acting, different thread pitch models have a very limited adjustment. They max out pretty quickly. The old-school, single threaded rod models, and the dual action reverse-thread models allow a lot more adjustment.

Bottom line is the guy abused the guitar. Intermittent? 90degrees and 100% humidity for a week? Warrantee void and charge plenty to repair it. No deals because you feel any guilt.
I've built quite a few 12 strings, never had a problem with necks...and I use cables instead of strings. I've used the Blanchard T/R and it works extremely well.

What I'd be curious to know is, what would happen to that neck if you dried it out to 10-20%, and then humidified it back to 80-90%, without any strings or truss rod pulling on it? Would it remain in its current shape the whole time, or bend one way when dry and the other when wet? My guess is that if would stay the same, since it isn't returning to straight just by drying it out.

Most likely, the permanent bending only happens when the humidity is changing. So instead of trying to dry it out, how about trying to keep it wet? Then you can get it all adjusted properly, and it will be happy in its humid home. 100% RH is certainly more than one should expect a Kansas City built guitar to withstand, so warranty is void, but if all the glue joints in the box remained intact, then it actually is capable of it.

FYI , from a strictly biz pt make the customer happy!. and you will get more referrals from a happy client . Piss off the client , even if it was their fault, they will tell at least 10 people, been there done that

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Ken Cierp

http://www.kennethmichaelguitars.com/

DennisK,

It's a common misconception that guitar string tension is a big deal when, in reality, the wood is only slightly stressed. Consider how small the actual change in action is in a neck with a slack truss rod compared to one that is properly adjusted... In almost all cases, everything happens within 1/8", and for an acoustic that's pretty much all in the body.

So to answer your question, without any tension the instrument geometry will change if exposed to changes in humidity. As proof of this: when I worked in the adhesives industry I often received samples of various products the client company swore were produced in climate controlled conditions at all times (especially from places in Central and South America). The problem is that I had access to CTH chambers (Constant Temperature and Humidity), which I would also monitor with data loggers for further evidence. Hardwood flooring, for example, is flat when it's made, so I would start by taking the sample to almost 0% moisture content (by placing it in a lab oven running at 190°F for a few days), measure and record the exact geometry, and then move it to a humidity chamber and monitor moisture content (by weight) until it was dead flat. Then I knew what the actual initial conditions were during production. The final report would explain the need to maintain wood moisture content between 6 and 9% for optimal results (if we're talking about plain old PVA).

Been there. Don't do that anymore.
I had a customer that dried out a mandolin so bad the back split and bowed up badly at the tailpiece. I spent quite a few hours repairing it and refinishing the area (let's say over a thousand easy). He sent it back a year later with "high" action. He had put a sponge in a soapdish drilled full of holes. When I opened the case, the felt was wet, the wire strings RUSTED, and I bet I squeezed a cup of water out of the sponge. Hold your breath and puff out your cheeks as far as you can. That's what the mandolin looked like.
No matter what you tell some of these people ( I enclosed a detailed care sheet with every instrument), they are dumb as a box. Like running your car oil dry and wondering why the engine blew.