Here's something to tickle the gray matter. I've got 2 guitars on the go right now and all the body has been kept, braced and glued in RH control of 40 %.
I've been building tops with a 25' radius, and backs with a 15' radius. I can get a perfect neck set in these conditions, but when I bring the body out into the real world of Tropical North Qld. at this time of the year, the top sucks up moisture and the dome in the top increases well past my 15' gauge, so it's probably around 12'. This of course throws off the neck set by a fair bit, making the action far too high. I could set the neck for this, and then have different saddles for wet and dry season, but it seems to be a compromise.
I've been wrestling with how to build with a happy medium between wet and dry season, and even moving the instrument from the coast up to the table lands where the humidity can drop 20-40% within an hours drive.
I was wondering if you were to build with a much tighter radius, will this help hold the the dome, or at least limit the amount up upward-downward movement due to humidity fluctuations.
Dave White might have some insight into this, as he's the only person that I've heard of using much tighter radius's in his instruments. Any one with an idea, please throw your 2 cents into the discussion.
Stability of top and back with tighter radius?
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Bob Connor
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Dunno about the radius Allen but I do know that the reason that Maton increased the thickness of their tops to 3.2mm was because of concerns of their dealers in Queensland.
I think the dealers got pissed off with having to do setups on Matons all the time due to the tops moving because of humidity changes.
Obviously the thicker top won't move as much but there is the distinct possibility that it won't sound as good.
I don't know what effect having thicker tops with lighter bracing would be particularly up where you are.
Bob
I think the dealers got pissed off with having to do setups on Matons all the time due to the tops moving because of humidity changes.
Obviously the thicker top won't move as much but there is the distinct possibility that it won't sound as good.
I don't know what effect having thicker tops with lighter bracing would be particularly up where you are.
Bob
Sounds like you need to investigate an adjustable neck Allen. A fine craftsman by the name of Grant Goltz does a very interesting variety that has the fretboard end floating and the heel pivoting into the neck block. It looks conventional and adjust very quickly. Dennis Leahy done a copy of Grant's neck on his first, maybe he will tune in.
Grant did do a great tutorial that he posted over on luthierforum but all the images seem to have been stripped out of it, what a crying shame. Anyhow, below is a link to as subforum that had all the detail on that neck joint. It may still be worth your while to work your way through each topic as some of the text may be enlightening.
I have also started a topic over there asking what happened to the images and asking if they can be reloaded. Grant done a mock up of his neck joint that is being mailed from builder to builder all over the USA to luthierforum members who have signed up for it, I wish it would make it's way down here but I did not bother to ask as the demand is high, the list is long and I am sure their would be a little trepidation about posting it to AU.
Dopey me forgot the link 
http://luthierforum.com/index.php?showforum=28
Just checked, the images are back
Cheers
Kim
Grant did do a great tutorial that he posted over on luthierforum but all the images seem to have been stripped out of it, what a crying shame. Anyhow, below is a link to as subforum that had all the detail on that neck joint. It may still be worth your while to work your way through each topic as some of the text may be enlightening.
I have also started a topic over there asking what happened to the images and asking if they can be reloaded. Grant done a mock up of his neck joint that is being mailed from builder to builder all over the USA to luthierforum members who have signed up for it, I wish it would make it's way down here but I did not bother to ask as the demand is high, the list is long and I am sure their would be a little trepidation about posting it to AU.
Dopey me forgot the link http://luthierforum.com/index.php?showforum=28
Just checked, the images are back
Cheers
Kim
Last edited by Kim on Sat Feb 09, 2008 9:50 pm, edited 1 time in total.
Hi Allen… good post, a topic anyone building a guitar in the tropics needs to consider.
I’ve been thinking about this issue in preparation for the ones I have on the drawing board and haven’t found a good answer yet. I discovered how hard the rapid changes in humidity can be on a guitar when I took my perfect 40s built classical to Atherton for a few days and discovered two cracks in the back and one in the front a couple of days after getting home.
My thinking is that an arch is a strong shape so increasing the radius will decrease vibration and change the voice of the guitar. Also an arch is only strong against forces applied to its apex of so having a tighter curve probable won’t do much on a guitar top where the ends are fixed, the expansion has to go somewhere and in the case of a guitar this can really only be up.
The timber used in the top could make a lot of difference, I have a friend here in Townsville with a guitar that has a yellow cedar top and it is remarkably stable with changes in humidity. It goes from his dry air-conditioned office to a boat on dive trips and the action doesn’t change at all. I’ve only built one steel string and it had a pepperwood top (rainforest tree from NQ not the one that you get pepper from). The action on it got couple of mm higher when I took it from a very dry Canberra to super humid PNG. I did the same trip a few years later with an off the rack guitar that had a solid sitka top (laminate back and sides) and the action got so high it was unplayable. I’ve also heard a couple of local player say that they went for WRC tops because it seems more stable with humidity changes. I suspect the reason for this could be that WRC and Pepperwood are very soft so the timber is able to compress to some extent rather than deform when it expands.
I’ve noticed that you use a variety of top timbers, have you noticed much difference between species? It would be interesting to do the experiment and compare a guitar with spruce against one with WRC.
At the end of the day I suspect the only real answer for keeping a perfect action is Kim’s is suggestion of an adjustable neck.
I’ve been thinking about this issue in preparation for the ones I have on the drawing board and haven’t found a good answer yet. I discovered how hard the rapid changes in humidity can be on a guitar when I took my perfect 40s built classical to Atherton for a few days and discovered two cracks in the back and one in the front a couple of days after getting home.
My thinking is that an arch is a strong shape so increasing the radius will decrease vibration and change the voice of the guitar. Also an arch is only strong against forces applied to its apex of so having a tighter curve probable won’t do much on a guitar top where the ends are fixed, the expansion has to go somewhere and in the case of a guitar this can really only be up.
The timber used in the top could make a lot of difference, I have a friend here in Townsville with a guitar that has a yellow cedar top and it is remarkably stable with changes in humidity. It goes from his dry air-conditioned office to a boat on dive trips and the action doesn’t change at all. I’ve only built one steel string and it had a pepperwood top (rainforest tree from NQ not the one that you get pepper from). The action on it got couple of mm higher when I took it from a very dry Canberra to super humid PNG. I did the same trip a few years later with an off the rack guitar that had a solid sitka top (laminate back and sides) and the action got so high it was unplayable. I’ve also heard a couple of local player say that they went for WRC tops because it seems more stable with humidity changes. I suspect the reason for this could be that WRC and Pepperwood are very soft so the timber is able to compress to some extent rather than deform when it expands.
I’ve noticed that you use a variety of top timbers, have you noticed much difference between species? It would be interesting to do the experiment and compare a guitar with spruce against one with WRC.
At the end of the day I suspect the only real answer for keeping a perfect action is Kim’s is suggestion of an adjustable neck.
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Dave White
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Allen,
As you know I use the radiuses I do for tonal reasons. A bigger radius will mean the movement is less but if the instrument keeps going between really high and really low humidities you will still get some movement. An adjustable neck joint is the way to go there as you set the saddle height for the sound yiou want and ajust the neck for the playability - better imho than having different saddle heights. Grant has his system, Rick Turner has his and so does Mike Doolin amongst others. I adapted mine from Mike Doolin's.
As you know I use the radiuses I do for tonal reasons. A bigger radius will mean the movement is less but if the instrument keeps going between really high and really low humidities you will still get some movement. An adjustable neck joint is the way to go there as you set the saddle height for the sound yiou want and ajust the neck for the playability - better imho than having different saddle heights. Grant has his system, Rick Turner has his and so does Mike Doolin amongst others. I adapted mine from Mike Doolin's.
Dave White
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Dennis Leahy
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Reading Allen's initial post, I immediately thought of using an adjustable neck joint to solve the issue.
Kim is right, I used a slight variant of Grant Goltz's neck joint (I omitted the spring washers.) I liked it better than Harry Fleishman's neck joint, mostly because the mortise and tenon joint looked "right" to the woodworker in me and the butt joint looked "less right."
I drew my neck in a CAD program, and rotated the neck through the range of motion (and a bit beyond.) It was easy to see that creating an arbitrary pivot point nearly a foot away from the saddle was slightly changing the effective scale length of the strings as the neck is adjusted. I was creating some experimental bracing, and did not know if my braces would hold the soundboard arch (25') or not, so for me, the adjustable neck joint was done primarily to give me the flexibility to get a proper neck set angle, after the top settled in to its quasi-permanent shape. I also noted (in CAD) something like .004" difference in the length of the strings would occur by adjusting the neck angle, not in the extremes, but over what I would consider a normal amount of adjustment leeway in action. I was satisfied that the intonation change over .004" would not be very perceptable to the ear (even though a strobe tuner would certainly "hear" it.) But, my main concern was to get the neck angle properly set (after the soundboard relaxed), and not really to make further adjustments. I assumed that further adjustments might require refining or creating a new saddle, to get the intonation right again. {which is hell of a lot simpler than a typical neck reset}
When I first tried to install my neck, I could see that the mortise pocket was off by a tiny bit (maybe one-forth to one half of a degree), but that was enough to make it impossible to place the bridge dead center in the guitar. THAT made me rethink about the yaw adjustment screws that Fleishman used. (At that time, I don't think I realized that Doolin used them too. I don't think Doolin's system was published 2 years ago.) [Using upper adjustment setscrews] would have been a simple solution. (A little chiseling on my mortise pocket on one wall got me back to a straight neck-to-body, but then, I lost that *perfect* mortise and tenon fit.) It made me think even more about those yaw adjustment screws...
I adjusted my adjustable neck last night. The action had gotten higher (it has been very dry, around 25% to 30% RH in my house), and I wanted to drop it down. I also noticed that the intonation was further off with the high action (I could easily hear it), and the intonation was much better when I dropped the action down (noting that the intonation on the saddle was originally done when the action was low, so dropping the action was bringing the intonation back to the original setup.)
I'm offering these details for a reason. Harry Fleishman, Mike Doolin, and now Dave White got that detail right. (I have not seen Rick Turner's neck joint.) Those upper adjustment screws, which I had locked into my brain as being purely for yaw adjustment, can also be used (in tandem) for adjusting the intonation. Unless you want to make different saddles, you need those adjustment screws to fine tune the intonation.
After building my first (and so far, only) guitar about two years ago, I have thought a great deal about adjustable neck joints. I have come up with three other joints that are different than anything I have seen - two of those designs would not need adjustment screws (yaw or pitch.) The one new design that would still need the adjustment screws is a variant of the Jeff Babicz (patented) adjustable neck, but is different enough not to infringe on the patent. In fact, I drew Babicz's design in CAD, and I see that (in spite of his claims) his design suffers from the same problem, and the intonation will change a little bit when his neck is lifted or dropped for action adjustments.
Dave White also got the proportions of the fingerboard extension right: you need some significant wood beneath the truss rod, so that when the rod is tightened, it won't crack through. The mass of that chunk of wood should also ensure that notes played on the upper frets (above 14) should have as strong a resonance as notes played elsewhere on the neck.
So, yes Allen, I highly recommend an adjustable neck joint. Look them all over and see which method you like best. (If you use Grant Goltz's, I recommend that you also add 2 upper yaw adjustment screws.) In fact, I can't see any reason not to copy Dave White's variant. (Thanks, Dave!) The two new engineering designs I have come up with (that would not require adjustment screws) are both better suited for someone with CNC capability.
Dennis
{edited for clarity}
Kim is right, I used a slight variant of Grant Goltz's neck joint (I omitted the spring washers.) I liked it better than Harry Fleishman's neck joint, mostly because the mortise and tenon joint looked "right" to the woodworker in me and the butt joint looked "less right."
I drew my neck in a CAD program, and rotated the neck through the range of motion (and a bit beyond.) It was easy to see that creating an arbitrary pivot point nearly a foot away from the saddle was slightly changing the effective scale length of the strings as the neck is adjusted. I was creating some experimental bracing, and did not know if my braces would hold the soundboard arch (25') or not, so for me, the adjustable neck joint was done primarily to give me the flexibility to get a proper neck set angle, after the top settled in to its quasi-permanent shape. I also noted (in CAD) something like .004" difference in the length of the strings would occur by adjusting the neck angle, not in the extremes, but over what I would consider a normal amount of adjustment leeway in action. I was satisfied that the intonation change over .004" would not be very perceptable to the ear (even though a strobe tuner would certainly "hear" it.) But, my main concern was to get the neck angle properly set (after the soundboard relaxed), and not really to make further adjustments. I assumed that further adjustments might require refining or creating a new saddle, to get the intonation right again. {which is hell of a lot simpler than a typical neck reset}
When I first tried to install my neck, I could see that the mortise pocket was off by a tiny bit (maybe one-forth to one half of a degree), but that was enough to make it impossible to place the bridge dead center in the guitar. THAT made me rethink about the yaw adjustment screws that Fleishman used. (At that time, I don't think I realized that Doolin used them too. I don't think Doolin's system was published 2 years ago.) [Using upper adjustment setscrews] would have been a simple solution. (A little chiseling on my mortise pocket on one wall got me back to a straight neck-to-body, but then, I lost that *perfect* mortise and tenon fit.) It made me think even more about those yaw adjustment screws...
I adjusted my adjustable neck last night. The action had gotten higher (it has been very dry, around 25% to 30% RH in my house), and I wanted to drop it down. I also noticed that the intonation was further off with the high action (I could easily hear it), and the intonation was much better when I dropped the action down (noting that the intonation on the saddle was originally done when the action was low, so dropping the action was bringing the intonation back to the original setup.)
I'm offering these details for a reason. Harry Fleishman, Mike Doolin, and now Dave White got that detail right. (I have not seen Rick Turner's neck joint.) Those upper adjustment screws, which I had locked into my brain as being purely for yaw adjustment, can also be used (in tandem) for adjusting the intonation. Unless you want to make different saddles, you need those adjustment screws to fine tune the intonation.
After building my first (and so far, only) guitar about two years ago, I have thought a great deal about adjustable neck joints. I have come up with three other joints that are different than anything I have seen - two of those designs would not need adjustment screws (yaw or pitch.) The one new design that would still need the adjustment screws is a variant of the Jeff Babicz (patented) adjustable neck, but is different enough not to infringe on the patent. In fact, I drew Babicz's design in CAD, and I see that (in spite of his claims) his design suffers from the same problem, and the intonation will change a little bit when his neck is lifted or dropped for action adjustments.
Dave White also got the proportions of the fingerboard extension right: you need some significant wood beneath the truss rod, so that when the rod is tightened, it won't crack through. The mass of that chunk of wood should also ensure that notes played on the upper frets (above 14) should have as strong a resonance as notes played elsewhere on the neck.
So, yes Allen, I highly recommend an adjustable neck joint. Look them all over and see which method you like best. (If you use Grant Goltz's, I recommend that you also add 2 upper yaw adjustment screws.) In fact, I can't see any reason not to copy Dave White's variant. (Thanks, Dave!) The two new engineering designs I have come up with (that would not require adjustment screws) are both better suited for someone with CNC capability.
Dennis
{edited for clarity}
Last edited by Dennis Leahy on Sun Feb 10, 2008 2:20 pm, edited 1 time in total.
Another damn Yank!
Dave,
I really like your neck arrangement . I have two questions : What happens when it's a cutaway . Do you leave a little of the cutaway sides protrude beyond the neck's side profile ? I can't think of any other way ,but maybe I'm missing something.
Also , do you still use an upper transverse brace with your C.F. rod neck block supports, and if so , why ?
Cheers, Craig
I really like your neck arrangement . I have two questions : What happens when it's a cutaway . Do you leave a little of the cutaway sides protrude beyond the neck's side profile ? I can't think of any other way ,but maybe I'm missing something.
Also , do you still use an upper transverse brace with your C.F. rod neck block supports, and if so , why ?
Cheers, Craig
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Dennis Leahy
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I'll echo Craig, and say I too would appreciate more photos and detail of your adjustable neck joint, Dave.
Grant Goltz demonstrated making a compound cutaway adjustable neck, so that was the example I followed. The binding sits proud of the neck, or you can say the neck slides behind the binding. Even though it is not *perfectly* flush, it still looks slick, and feels smooth.
Dennis
Grant Goltz demonstrated making a compound cutaway adjustable neck, so that was the example I followed. The binding sits proud of the neck, or you can say the neck slides behind the binding. Even though it is not *perfectly* flush, it still looks slick, and feels smooth.
Dennis
Another damn Yank!
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Dave White
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Craig,
You are right about the cutaway - I pondered mightily about it for a long time and asked Grant over at the OLF. If you wan't the neck inlet there has to be a gap somewhere on that outside edge so you have a slight lip. Player wise I don't think it's a big deal. If you are proud to display the adjustable hardware (like Rick T) then you can have the neck with a slight gap from the body and no pocket. This will let you do cutaways "as we know them Jim" but you have another NTVI - "non traditional visual issue"
As for the upper transverse brace - I use one but it is there for pure tonal reasons. I have explained this on the OLF a few times but didn't get much response. I put the top braces on in a set sequence, carve each one and listen to/voice the top as I do it. I start with the X braces, then the lower bout "in between the X's" braces, then the upper transverse brace and then the "finger braces". The time when the top really, really comes alive (all over) in a big, big way is when the upper transverse brace goes on. I dome all of my top braces to 13' except the utb which I radius to 10' like the back braces.
My utb is not built purely for structure - it is the same width and height as my X braces and I taper it from side to side. I also have my design where it locks with the top of the X braces. So the utb shapes the sound and by not having the fingerboard and neck pressing remorselessly on the upper bout area, this part of the top is freer to respond. It's a subltle difference - no utb would not sound as good but the utb is shaped and dimensioned for the sound and not the structure. Hope this makes sense:
Dennis - what other pictures are you looking for that aren't on my website tutorial? Let me know and I'll see if I can find some.
You are right about the cutaway - I pondered mightily about it for a long time and asked Grant over at the OLF. If you wan't the neck inlet there has to be a gap somewhere on that outside edge so you have a slight lip. Player wise I don't think it's a big deal. If you are proud to display the adjustable hardware (like Rick T) then you can have the neck with a slight gap from the body and no pocket. This will let you do cutaways "as we know them Jim" but you have another NTVI - "non traditional visual issue"
As for the upper transverse brace - I use one but it is there for pure tonal reasons. I have explained this on the OLF a few times but didn't get much response. I put the top braces on in a set sequence, carve each one and listen to/voice the top as I do it. I start with the X braces, then the lower bout "in between the X's" braces, then the upper transverse brace and then the "finger braces". The time when the top really, really comes alive (all over) in a big, big way is when the upper transverse brace goes on. I dome all of my top braces to 13' except the utb which I radius to 10' like the back braces.
My utb is not built purely for structure - it is the same width and height as my X braces and I taper it from side to side. I also have my design where it locks with the top of the X braces. So the utb shapes the sound and by not having the fingerboard and neck pressing remorselessly on the upper bout area, this part of the top is freer to respond. It's a subltle difference - no utb would not sound as good but the utb is shaped and dimensioned for the sound and not the structure. Hope this makes sense:
Dennis - what other pictures are you looking for that aren't on my website tutorial? Let me know and I'll see if I can find some.
Dave White
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Dennis Leahy
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It might all be there, but the pictures (even the slightly larger ones) are too small for my poor 'ol eyes to see. I'd love to see the finished pocket from a couple of angles. Are you purposely creating a neck heel with a constant width, or was that a compromise to the method of the adjustable engineering. (Hope that came out right!) Like, I think Babicz's method requires a constant width of the pocket and the same for the width of the neck heel. You're tilting, not lifting, your neck, so you could cut out a curved/tapered (woman's high heel-shaped) neck heel pocket, right? (That is, if that agrees with your aesthetic.)Dave White wrote:Dennis - what other pictures are you looking for that aren't on my website tutorial? Let me know and I'll see if I can find some.
"My eyes are dim. I cannot see."
"I'm just a poor old man. ... My legs are grey. My ears are gnarled. My eyes are old and bent."
Thanks!
Dennis
Another damn Yank!
Thanks a heap for your reply Dave ( aka Spock ) but not as we know him , not as we know him 
Your picture of your top raises another question . It shows a Lowden type A frame. Do you use this in conjunction with the C.F. rods, or is this top prior to you using the C.F. support rods ?
It's interesting that you find the UTB improves your sound while Rick prefers to go without. I'm guessing because you both have differing bracing /radius' etc . and Rick's version has no pocket for the fretboard extension ,that they can't be compared ,and what suits one may not suit the other. My thinking is that a UTB would be a big help in maintaining the dome in that area .
Many thanks for your help Dave .
Cheers Craig
Your picture of your top raises another question . It shows a Lowden type A frame. Do you use this in conjunction with the C.F. rods, or is this top prior to you using the C.F. support rods ?
It's interesting that you find the UTB improves your sound while Rick prefers to go without. I'm guessing because you both have differing bracing /radius' etc . and Rick's version has no pocket for the fretboard extension ,that they can't be compared ,and what suits one may not suit the other. My thinking is that a UTB would be a big help in maintaining the dome in that area .
Many thanks for your help Dave .
Cheers Craig
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Dave White
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Dennis.
OK - next time I have a neck off I'll take some photos. The straight wide heel is just laziness - this is the easiest shape to make the pocket for a good fit. One day I'll have a go at a "curvy" one.
Craig,
The A frame braces go with the cf flying butresses. I think that the area around the sound hole is a good one to concentrate on structurally and the combination of the soundhole re-enforcement piece flanked by the A frame braces that lock into the neckblock gives a lot of strength here. As you can see from my ladder braced guitar thread I adapted this aspect for my ladder braced instruments.
OK - next time I have a neck off I'll take some photos. The straight wide heel is just laziness - this is the easiest shape to make the pocket for a good fit. One day I'll have a go at a "curvy" one.
Craig,
The A frame braces go with the cf flying butresses. I think that the area around the sound hole is a good one to concentrate on structurally and the combination of the soundhole re-enforcement piece flanked by the A frame braces that lock into the neckblock gives a lot of strength here. As you can see from my ladder braced guitar thread I adapted this aspect for my ladder braced instruments.
Dave White
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