Official Luthiers Forum!

I have been fiddling with the action of my Korean made Avalon DS200 guitar over time...I have had it for two years, and the action is getting higher, and higher, with the saddle getting lower and lower.. ....it could only mean one thing..

Neck reset...on a dovetail joint.. (to me, the concept is horrendous, bolt-ons are MUCH easier!!)

So I am resolved to concentrate on building as stable a neck as possible on the myrtle/spruce OM I have started building. I found installing CF rods easy and am going to use the same process this time.

After doing some OLF and Google research, I have found various tutorials on adjustable necks, I know that Dave White has built a few into his builds.

Now I need some "heads up" from the luthiers on this forum, please, have many of you built adjustable necks at all, and has time proven that the design has worked?

I am obviously a little anxious about the potential difficulties that may arise from building one at the ametuer stage I am at, and need some advice, please.

I haven't built any adjustable necks, but I would mention that your Avalon
is not likely to be a dovetail joint. Chances are it's a flat butt joint with 3
or 5 dowels.

And resetting dovetailed necks is much more intimidating to many than
it is difficult. After your first few hundred neck sets it's something you can
do in your sleep. Since I'm not really tooled up for building right now,
I still find it less hassle to cut a dovetail by hand on the occasional neck
than to make a bolt on. It's really not nearly as difficult as most people
fear.

Still, I'm all in favor of more easily adjustable necks as soon as the
market is willing to accept them. Opinions have started to shift a little
more widely as of late. There are still big pockets of resistance even to
standard bolt-on necks in more traditional circles, but many folks are
coming around.

With a cantilevered extension there are a lot of ways you could go about
making a neck angle more easily adjustable, but I think dodging the
plethora of recent patents would be one of the biggest obstacles.

_________________
Eschew obfuscation, espouse elucidation.

[QUOTE=Sam Price]

Neck reset...on a dovetail joint.. (to me, the concept is horrendous, bolt-ons are MUCH easier!!)

So I am resolved to concentrate on building as stable a neck as possible on the myrtle/spruce OM I have started building. I found installing CF rods easy and am going to use the same process this time.

[/QUOTE]
Sam-
I'm not a 'luthier' (official or otherwise), but even more of an amateur than you, so you should keep that in mind...

I don't think that neck reset problems are necessarily due to neck stability issues in most cases, but to a change in the geometry of the guitar body- ie the neck block and sides have changed angle/position relative to the bridge. This can be due to bellying of the top, combined with the back flattening and allowing the neck block to 'tilt'.

So stabilizing the neck block and looking at changes in the top shape are issues as well.

Do you use a '100% bolt-on' neck or do you glue down the fingerboard? If the former, you could use shims to change the neck angle at some point in the future. I think Taylor does this, and no doubt their legal mavens have the idea locked up somehow.

Adjustable necks with elevated fingerboards are really slick. I watched one being built in Sergei deJonge's shop and it's not a trivial exercise, especially if you don't want the 'gap' to show at the heel.

It's on my 'To-do' list, so please keep us posted here with your progress.

Cheers

John

I normally glue down the fingerboard, but this time I am primed to build a fretboard extension support for a "floating" fingerboard.

I think this looks incredibly slick, with access to the neck via an allen key inserted into the back of the guitar.

Babicz's adjustable neck joint...

Sam-
I agree- the Babicz system (patented, natch) is pretty slick.
It does mean that you have to have a 'full-width' heel and a good fit on that sliding mortise and tenon joint. Mechanically, it would be fairly simple to do, since it looks like the head of the height-adjusting bolt rests on the metal plate.

It's not clear to me how much of the 'neck needing reset' problem is due to angle changes (ie neck block moving) and how much just to height issues (bridge bellying up with top movement). The Babicz system only addresses the latter. Rick Turner and others have stabilized the neck block with braces, but it's not clear if this is to avoid neck resets as well as to free up the soundboard upper bout.

Hopefully, some more experienced hands will pitch in here.

John

Thanks John-I forgot to add in the first post that I will install flying buttresses too. Possibly using CF rods.

My adjustable neck joint is based on the Howe Orme design from the mid 1890s and is similar to the August Larson patent of the early 1930s.   Anyone is free to duplicate it with no patent issues what so ever. You can see a picture of it on the cover of American Lutherie from about seven years ago, and there will be a photo essay on how we build them in an upcoming issue of Fretboard Journal with very detailed photos of how it all goes together.

It's easy, especially if you don't mind doing a bit of metal working and getting a welder involved on the truss rod fabrication. One of the tricks for me is terminating the truss rod at a 3/8" steel dowel that goes down into the heel and has a couple of the bolts that adjust action and lock the angle going through it. The use of the dowel takes any stress off the short grain of the wooden neck heel.

You get total action/neck angle adjustability; you get overall intonation adjustability; and you get a minimally braced upper bout with no fingerboard glued to it. I cannot see one single thing wrong with the system other than it not looking "normal". In fact, it's traditional if you dig deeper than the Martin tradition.   C.F.Martin himself learned to build guitars in a shop noted for adjustable neck guitars...in the 1820s.

Having been accused off-line here of holding secrets, I have to say that anyone can do what I'm doing and I don't care. But...I do not have written instructions; I do not have plans; I do not sell the hardware. You're all free to come look and see this stuff up at Healdsburg, but then go do your own work to duplicate it if you want to.

Also, unlike John would have you think, I've been absolutely clear here that what I do accomplishes at least five important (to me) things, and I've been quite forward on this forum about it...if you read all my posts. The issues are:
1) Stabilizing the structure of the guitar and preventing rotation of the neck block.
2) Freeing up the upper bout to produce tone rather than having to be structural and supporting the neck and fingerboard.
3) Making action adjustments simple and easy for the guitar owner.
4) Enabling us as luthiers to dial in an optimal height of the strings above the top for the tone we seek and not having to compromise that distance for action.
5) Making it possible to move the entire neck in and out to do overall adjustments of intonation

If you want to see pictures of one of the guitars and read a review, the latest Guitar Player Magazine with Joe Satriani on the cover has a nice three and a half page spread on a Koa/Russian jumbo Compass Rose (the brand name) with all the tricks.

No patents, no problems, just go ahead and do it if you want to.

uhmmmmm .. if its indeed a dowelled neck the only I know of to get it off is with a saw .... there is pretty much no way to steam those suckers out - one of my students and I tried on a new POS Epi .. only to find out the neck simply broke off after steaming and thinking it was a dovetail - its pretty much a non repairable guitar (at least not worth it to most repair shops) - which is total bunk for what it likely cost you. On the frets website Frank shows a quick and dirty reset on a spanish heel students guitar - cut a wedge out of the heel with a razor saw and then simply bolt the heel back down to change the neck angle.

_________________
Tony Karol
www.karol-guitars.com
"let my passion .. fulfill yours"

Tony-an Avalon employee will confirm tommorow whether the Silver range is dovetailed or not.

Rick, thanks for the richly supplied information. I'll try and get hold of a GP Mag.

Good call Sam . I had a client who wanted me to reset his Lowden, and I wasnt sure what the neck joint type was and they were very helpful and responsive in replying back to me.

_________________
Tony Karol
www.karol-guitars.com
"let my passion .. fulfill yours"

Rick - how much vertical travel does your system allow?  I've been working on a design of my own and have assumed that around 1/4" total should be sufficient, but having never actually seen a joint with vertical adjustment I'm guessing a bit. 

Since I'm asking questions... what about the neck angle adjustment, how much travel is needed? Assuming that the top of the joint stays static and you measure the travel at bottom of the heal.

I'm not sure where I read it, but I believe that you have stated that the vertical adjustment allows for experimentation to determine optimal bridge and saddle height.  If that is the case, have you come to any new conclusions?

Thanks

Just looking at a ratio of the lengths involved, you'd be getting almost a 1:4 ratio on the heel movement versus the nut movement (12 fret join, 25.34" scale). So, rotate your heel in 1/4" and your nut moves down ~1". That sounds pretty huge (and doable) to me, and you could probably do with a lot less than that (like 1/8") and have loads of adjustability in there.

_________________
Bob Garrish
Former Canonized Purveyor of Fine CNC Luthier Services

I would not call it vertical movement. That's what Babicz gets with being able to move the neck up and down essentially on tracks.

There are two machine screws threaded into brass inserts in the face of the heel just under the fingerboard, and the heads bear against the guitar body. They are the pivot points for rotation of the neck. About 2 3/4" down there is a 10-32 stainless steel cap head machine screw that turns freely in a hole drilled into the steel dowel in the heel. That is the tilt/action adjustment, and it threads into another brass insert that is mounted in the neck block. Just below that is a 10-32 Allen head set screw threaded through the steel dowel; it bears against the end of the guitar and serves as a locking screw; it is basically the third leg of a tripod with the pivot screws being the other two legs.

One think I forgot to mention is that with this you can also adjust the "yaw" of the neck and tweak the outer strings' alignment with the edge of the neck. Many players prefer just a bit more space between the high E and the edge of the fingerboard so they don't pull the string off the fingerboard.

If you get a copy of Robert Hartman's "Guitars in America" the story of the Larson brothers you'll find an August Larson patent on something incredibly similar to what I do. I based my design on the Howe Orme system and tweaked it only to find the Larson patent a couple of years after I reinvented it.

It does not take very much adjustment of the screws at th heel to make a large difference in action. It couldn't be easier to do, and at shows like MerleFest I demonstrate it as the 15 second neck reset...with half of the time spent looking for the Allen wrench. When I tell people that they just witnessed what would cost about $375.00 or more on a Martin they love it. Very few in that crowd seem to be offended by visible hardware...they see enough banjos not to mind!

Maybe I'm over thinking this.  I have been working on a design that would look and act essentially like Rick described, with the difference being that the neck could also adjust vertically.  The angle adjustment screw would pass through a tennon in the heal of the neck, the tennon would in turn register to a sliding assembly in the neck block ( or heel block as some call it).  This sliding assembly is adjusted by a lead screw that could be accessible from a choice of locations either at the back, top or face of fingerboard.

Apparently in your design Rick you get along just fine without vertical adjustment.  I know that Doolin's system doesn't have this either.  Would vertical adjustment be a benifit?

On a different but related subject... has anyone ever used an internal truss (2 actually) that extends all the way to the tail block to brace the neck block rather than the flying butress to the waist?  I'm thinking of a laminated wood/carbon fiber truss assembly that would replace the conventional back bracing and connect to both the neck and tail blocks.  It seems that this could provide a dramtic increase in back rigidity while solving the issue of disconnecting the guitar top/upper bout from being a support for the neck. 

I don't see any real need for further adjustments other than to complicate an already complicated life!

The neck block to tail block thing is as old as the hills. Look at Tilton's Patent Improvements of the late 1800s; look at the Larson Brothers work; look at what Fender did in the 1960s, look at a recent Paul McGill guitar, look at National Tricone and Style O guitars.   I like the triangulation of running the pairs of flying buttresses down to the sides as it can help prevent any twisting stresses, and the graphite rods are shorter and therefor stiffer. Try to think in terms of all the real stresses working on the guitar and knock them off one at a time with as few parts as possible.

So many good ideas have been done before and were abandoned not necessarily because they were bad ideas but because of other forces in the music industry. Also we have new materials to work with now that can make some of these inventions of the past work better in the present.

There is tremendous benefit to studying the history of our craft back as far as you can, and without trying to beat the dead horse here, being able to get your hands on hundreds or thousands of older guitars will make you a better contemporary guitar maker. That is another reason why doing repair work is so valuable as a learning experience.

As you are working through the process of designing and building a guitar, don't just copy what Martin did or Ramirez or whoever. Stop and think about each and every piece in the instrument and ask yourself why it's there, what it actually does, and why it's designed as it is. Try to get into the head of the person who did something you're about to do and work through the design process. You may wind up agreeing with the process or disagreeing with it. I've seen a lot of guitars where I just scratch my head and wonder "what were they thinking." Then again, many designs are just wonderful in how they work and sound. But the usual suspects...Martin, Gibson, de Torres, Loar...are not the only games in town.

[QUOTE=Rick Turner]
As you are working through the process of designing and building a guitar, don't just copy what Martin did or Ramirez or whoever. Stop and think about each and every piece in the instrument and ask yourself why it's there, what it actually does, and why it's designed as it is. Try to get into the head of the person who did something you're about to do and work through the design process. You may wind up agreeing with the process or disagreeing with it. I've seen a lot of guitars where I just scratch my head and wonder "what were they thinking." Then again, many designs are just wonderful in how they work and sound. But the usual suspects...Martin, Gibson, de Torres, Loar...are not the only games in town.[/QUOTE]

Rick, it is quite a pleasure to read your posts when you arent being confrontational. (even when you are dead right!)

I posted some questions about tone bar bracing a week or so ago and this is exactly the thought process I had in mind when I posted it. As far as I can see, there are thousands of luthiers/guitar builders that can build some mighty fine sounding guitars, but for a lack of a better phrase, martin or Gibson copies.

I dont want to be this type of builder. Dont get me wrong, I dont think there is anything wrong with building copies of great sounding guitars. It just isnt what I want to do. What I do want to know about is the resonance of tonewoods, their strengths and weaknesses, and bracing patterns that have been tried and worked, and even the ones that failed miserably. In this case, it is solving the problem of neck resets and string height adjustments. A common problem in the trade, but I am sure there has to be a good solution (s).

I suppose I am looking at resonance of the guitar from an acoustical and mechanical engineer's prospective and I see things that are sometimes hard to put into a coherant thought or sentence as to what I would like to accomplish. I have several of these wild ideas that I am in the process of experimenting with right now.

Sharing what you have found in your research saves me the trouble of wasting time looking through thousands of books also. It also leads me to the place that I can find documentation on what it is that I want to try, and I am thankful for you sharing this information with us. As stated in a previous thread, sometimes answering the stupid/redundant/obvious questions over and over again sometimes leads to information that is truely remarkable. This thread is a fine example of how this works!

_________________
Reguards,

Ken H

Ken - my sentiments exactly.  I know that there are those out there (and they may be right) that will say that the relative newbie shouldn't have these thoughts, but what fun is that?

I'm beginning to think that there may not be any new ideas, just a bunch of reinventing of old ideas, which makes Rick's admonition to do more research spot on.  I have all kinds of crazy ideas like a top with no bracing at all (which is currently being done), or a top with after-the-fact tunable braces, or a top that is coupled to the back via the stings or adjustable sound post, or stings that anchor at the tail block and route inside the guitar before they go up and over the saddle.  I have no doubt someone, or several someones have tried all these things before.  Seems like I need to do more research to find out why they didn't work.

[QUOTE=Rick Turner]

4) Enabling us as luthiers to dial in an optimal height of the strings above the top for the tone we seek and not having to compromise that distance for action.

[/QUOTE]

I've always been curious about that.  I hear people talk about string height occasionally but I'm not sure exactly what they are referring to and why.  Are you simply talking about the combined bridge/saddle height?  On conventional guitars with conventional necks, you can't really adjust the string height over the top without shimming the fingerboard extension or changing the bridge/saddle height.  Changing the bridge or saddle height obviously has any number of effects on tone but are you talking about a seperate effect of the strings being at different heights off the top?

And if you change the string height and keep the same bridge/saddle height (and same action), then you are changing the angle of the string pull and torque on the bridge, right?  I used to add a wedge under the the f/b extension to make a more positive neck angle with the idea of imposing less torque on the bridge.  Not to the extreme of the millennium guitar, just adding less than 2 degrees.  I never tried to really a/b test the results though and eventually went back to convention, partly because I was tired of people thinking I screwed up the neck angle and needed to fix it with a wedge.

Anyway, I'm just curious exactly what aspect of string height you're talking about and what you think the effect on tone are and why.

_________________
http://www.chassonguitars.com

Draw a line about 30 inches long on a piece of paper. Add a saddle witness point near one end of the line. Add a nut witness point at the other end. Add in a gently curved line from a bit below the nut witness point that represents the line of the fret tops with action you like. Those are your constants in the design process.   Now put in the back of the neck as you like that thickness...that's a variable. Now draw anything you want to and figure out how to make it work and imagine the forces working on what you've drawn. Imagine the vibrations from the strings starting to shake and twist the top.   Now rotate your view point 90 degrees and work on the guitar shape profile. You've started your design process at the very core of what's happening...the string vibration. Think about separating stress and strain from vibration as much as possible.   See if this doesn't make you rethink how to design a guitar.

And Kent, yes, I'm talking about all those factors, and I don't necessarily have answers to the question of what's best.

I can tell you that the tension modulation of the string vibration working through the torque mode on the bridge doubles the fundamental frequency and all the harmonics of the string. Torque mode vibrations are a 2 x all string freqencies, so anything that enhances the torque coupling into the top will enhance mids and highs.

I made a pickup once when I was doing R&D for Gibson which perfectly tracked the 2X tension modulation of the strings. The idea was to have a pickup that would halve the time it takes for a synth converter to react and lock onto a note.   After the proof of concept, I was told by the CEO to stop working on it even though we were busy spending about half a million developing a guitar synth converter which was never released. We maybe could have had a converter that was twice as fast as the nearest competition, but no...

[QUOTE=Rick Turner]
I can tell you that the tension modulation of the string vibration working through the torque mode on the bridge doubles the fundamental frequency and all the harmonics of the string. Torque mode vibrations are a 2 x all string freqencies, so anything that enhances the torque coupling into the top will enhance mids and highs.
.[/QUOTE]
Rick:
Interesting stuff- thanks.
Does this mean that a string vibrating at 100Hz causes the bridge to vibrate (torque mode vibration) at 200Hz and up?
I don't understand how this works- how does the fundamental note get translated into sound coming from the (acoustic) guitar?
Sorry to be a bit thick here, but I couldn't find any info on torque mode vibration in a quick web search.
Thanks
John

John, there are only a handful of us who have looked into this, and as far as I know, none of us have published.

The quick answer to your question "Does this mean that a string vibrating at 100Hz causes the bridge to vibrate (torque mode vibration) at 200Hz and up?" is yes, but the doubled vibration is only in the torque mode of the bridge rotating along it's long axis.

Look at a stationary string as being at the zero point of tension...that's it's static position. When the string is pushed aside by a pick or finger, it is stretched to a slightly higher degree of tension with the maximum being at the greatest excursion point.   The string is released and goes back through zero on its way to another maximum tension excursion. What you now have is + 0 + and you have that condition for every full sine wave. To the lever of the bridge saddle a plus is a plus and it doesn't matter whether the string went left or right, up or down, north or south to create those tension modulations.

These torque modes are going into the top and are part of the modal vibrations that are then causing in and out of phase vibrations with the top, so you are getting some of this stuff being created by the torque and then canceled by the modes of top vibration.   

This is just one more reason why modeling guitar vibration is so, so difficult. Just when you think you know how a guitar works, along comes another set of issues.

Al Carruth and I have kicked this one around a bit, and neither of us is quite sure what it all means in the real world, but it is there.   

The pickup I made that works in this "Z" mode tracked the frequency doubling extremely well though there were issues of the tension modulation operating over the entire string length and thus there were some strange artifacts that crept in as you fingered up and down the neck. Cliff Elion (my chief engineer at Gibson Labs in 1989) and I were not permitted to delve further into this whole thing though we both felt that the approach offered a lot of potential as a synth pickup.

Maybe I'll get back into it when I retire...

That certainly sounds like a tough puzzle to crack Rick, especially with
any attempt to quantify. I've wondered how much influence the overall
tension change you're speaking of would have on torque at the bridge
relative to longitudinal waves. Both will effect torque, but the change in
tension (being a scalar quantity) makes sense as being double the
fundamental frequency. Longitudinal waves are a vector quantity
however, and so the frequency would not be doubled at the bridge. The
two must obviously interact to form a sum magnatude of force at the
bridge, although I would have to wonder how their influences are related,
or even their phase relationships.

With the rather unpredictable variables involved once you place this
string coupled with five others on a guitar, then throw a player in to the
mix it seems like you could end up with a pretty intimidating formula. I
have a few of Rossing's books and I know I've read some formulas on
relating lateral waves to longitudinal waves after figuring in the string's
modulus of elasticity and a few other variables, but I don't immediately
recall any calculation of the forces you're referring to. I do recall reading
something in line with this theory at some point before, but I can't recall
where. In any case, it's interesting. I would have to think that this would
be rather specific to steel string instruments and much less influential
with nylon or gut strings.

_________________
Eschew obfuscation, espouse elucidation.

I can tell you this: trying to do FFTs that translate into digital modeling algorithms by tapping on guitar tops proved to give way too much low end to the resultant models that were developed from that data. I believe it was because tapping results in too much piston motion of the top compared to what real strings do. In the development of Mama Bear we found that the best results came from actually plucking the strings which (duh!) sets the top into motion the way plucking strings does while playing. My guess is that the frequency doubling effects do not happen with thumping or tapping and so the models did not represent how all the vectors add up in the real world of playing a guitar.

I'm not sure why this wouldn't affect nylon strings just as much as steel. You have the same zero crossing at 2X. Now with an instrument that has a tailpiece the story would be quite a bit different as the Z axis modulation will pass over the bridge and show up at the termination of the string at the tailpiece.

My pickup design was a replacement "stop tailpiece" as is used on Les Pauls, 335's, etc. The string ball slipped over a lever that went down to two piezo blocks, one acting as a pivot point in front of the lever and the other below it on the back side of the lever. It worked in a push/pull mode and gave remarkable string to string isolation as well as being very specific to the tension modulation of the strings.

I got a chance to show it to Les Paul at one point...

I know a mathmatics professor who studies the chaos theory. This sounds like a good example. There are so many variables involved that is nearly impossible to predict the outcome. One model they use is a particle bouncing off the sides of a box, although the angles and velocity are known, after a period of time the path can't be predicted. At least that's the way I understood it.

Or if you've seen the movie "The Butterfly Effect", it only takes one change in chain of events to totally change the outcome.

Tough nut to crack.

_________________
Horton, MI

The only basis I have for speculating the lesser effect on nylon strings is
the difference in the modulus of elasticity. At a point when I was
considering the effect of lateral waves vs longitudinal waves in
considering saddles being perpendicular to the top vs tilted back by a few
degrees I did a little number crunching. I recall the resulting longitudinal
waves in nylon strings being a small percentage of what they were in steel
strings, since they increased much less in tension with the same amount
of deflection from it's static position.

Of course in practice a nylon string is deflected much farther than a steel
string when playing, so I'm not sure how my speculation there adds up.
It's been long enough since I gave it much thought that I don't recall what
factors were considered. In any case, though I doubt I'll be delving in to
advanced research on this topic, it's an interesting seed of thought to
tuck away somewhere for future reasoning and problem solving.

_________________
Eschew obfuscation, espouse elucidation.