Official Luthiers Forum!

The neck block is 90 degrees to the soundboard. When the soundboard is tipped back by the UFB arch, the neck block tips with the soundboard. The neck block is glued to the soundboard first, along with the heel block, before the sides are glued to the soundboard, unlike most mold-building techniques, where the neck block and heel block are glued to the ribs, before the soundboard and back are glued on.

_________________
Old growth, shmold growth!

If I read you correctly, that sounds about right, since your soundboard will also tip to conform to the rims. Do you use a mold? If so you may run into problems.

_________________
Old growth, shmold growth!

What I really like about this build method is the simplicity of it. If my cuts are accurate, there is no cheek paring, no flossing, very little finiting. And there is no falloff where the neck joins the body, the fret plane is straight to the end of the fretboard.

With the tapered heel and angled cheeks, there is usually some falloff of the fretboard where the neck joins the body, when the fretboard is deflected downward when glued to the soundboard. At least, that's the case with every Martin and most Martin-style builds I've seen. A tapered shim under the fretboard tongue solves that problem, which is what I do when I reset the necks on them.

_________________
Old growth, shmold growth!

What specifically are you disagreeing with? My statement that there is usually some falloff? I'm going by the Martins I've worked on, and most of the dreadnaughts from manufacturers that I've seen.

_________________
Old growth, shmold growth!

The pictures just appeared.

So your UFB is flat, but your top is domed?

_________________
Old growth, shmold growth!

He also said he elevates his lower bout by an eighth of an inch prior to sanding the upper bout flat. This would result in a tipped soundboard, similar to those old Mandolins with bent soundboards but not as dramatic, and in the upper bout instead of the lower bout.He also didn't provide info as to whether or not he was using a mold. I think you misunderstood his question.

With a mold-built guitar and a domed top, your illustrations are what would be expected.

If he's building without a mold, and changing the contours of his rim, most likely he is in fact tipping the soundboard as well, similar to what I learned to do, although my rim plane is straight. In fact, 1/8th of an inch is the arch I use for my x-braces. If he builds on a workboard, and glues his neck and heel block on before his sides, moslt likely the 90 degree neck joint will work very well, with minimal finiting, assuming his neck block was in fact square prior to gluing to the soundboard.


I like what you are doing. I don't have space for a neck jig right now, or storage space for molds and dome surfaces. I guess that's what appealed to me about Cumpiano's method. It was great fun to go up North and spend time with him in his shop, as I knew intuitively that what he was doing would work well for my space.

_________________
Old growth, shmold growth!

Having a hard time getting this visually in my head.

I guess I will have to read this a few more times and sleep on it.

_________________
Wisdom is justified by her children

Something I wanted to throw out there for discussion - I recently started cutting fretboards designed in CAD and it became obvious that it's pretty easy to design and manufacture a fretboard with a very accurate taper from nut to bridge built in to it.

Would it be of any value to use such a fretboard? i.e. if such a fretboard were available, would it help out the process at all? I'm thinking that it would allow 90 degree cheeks on a neck but fine tuning would be difficult.

I can see a problem that in a form built guitar, you'd have to carve a taper on the bottom of the fretboard to get it to match but, that could be roughed on the CNC machine.

Would the taper ruin the way the truss rod adjusts?

_________________
http://www.birkonium.com CNC Products for Luthiers
http://banduramaker.blogspot.com

What it all boils down to is that you have to pick a neck alignment system that has a track record in experienced hands and then build a lot of guitars and observe what they do for a few years.
Everyone's instruments move a little differently and settle in a little differently. I'm in the angled upper bout/flat UTB/neck jig camp but as I observe the behavior of my instruments over the years I'm still making little tweaks. At one time I thought I had a "set it and forget it" system but surprises lurk when your babies get out in the real world.

_________________
It's not what you don't know that hurts you, it's what you do know that's wrong.

Yes, they do the same thing but in a different way, and will be affected by the use of a mold or not.

Molds tend to keep the block 90 degrees to the top of the rim created by the sides, prior to any contouring, such as back arching. If the top is arched, the resulting dome raises the angle of the top in relation to the rims, as is seen in your pictures (as you obviously already know.) When the sides and back are glued, the neck block/top angle relationships is maintained. A radiused dish is usually used to contour the rims, kerfing (!) and neck block to the correct angle to accept the soundboard, so the top of the neck block angle is adjusted at that time. You can rough cut the angle into the block ahead of time and finesse it with the domed sanding board. The cheeks can be pared and the neck heel is tapered to compensate, and if done correctly the line from the nut to the end of the fretboard is straight. In a Martin it seems that there's usually some fall-off, at least in all the Martins I've seen.

If a workboard is used with a dome top, the neck block can tip back toward the soundhole, as the block is orthoganal to the soundboard dome (90 degrees to a tagential plane to the soundboard dome) and when the sides and back are glued on, the angle is maintained, in effect tipping the shoulders back, maintaining the square relationship of the neck to the body whilst maintaining the correct bridge height.

If a facet is sanded into the rim instead of doming the top, the same relationships apply. Faceting the rim tips the soundboard back, as the soundboard follows the rim contour, but the use of the mold or not will determine the angle of the neck block in relation to the soundboard, and whether or not the neck block needs to be angled on top to accept the soundboard.

This assumes the mold doesn't have a shim that tips the shoulders back, but why would it?



The idea is that you want the fret plane to be straight from the nut to the end of the fretboard. A tapered bottom would be of no value, it would simply influence the final angle of the fret plane slightly, which would have to be accounted for in the overall design of the instrument, whether or not the rim is straight or contoured, and whether or not you used a mold.

If the top was not domed or arched and if the neck block was square to the soundboard, and if the neck angle was set back at a 1.5 degree angle, then the fretboard over the body would have to be shimmed with a tapered shim. In that case, a fretboard with a built-in shim machined into the bottom of the fretboard where the fretboard touches the soundboard would be useful. That would most likely require finiting of the neck joint anyway, and would not necessarily make it that much easier to get a good neck angle relationship, IMO.

The truss rod function would not be impaired in any way, I don't think.

_________________
Old growth, shmold growth!

Either system can age well or badly, depending on the quality of the materials and the skill of the builder, yes?

I simply don't have the space for the equipment necessary for mold building, especially with my sizeable wood stash, and the fact that I also build electric guitars and basses with their space concessions.

_________________
Old growth, shmold growth!

I use a mold and build in the style of Frank Finochio. As part of the neck fitting, (if necessary) I position the neck onto the body (mortise and tenon) and then place the fingerboard on top of the neck with some double stick tape underneath the top portion. I sand the top a little to make sure that the "fretboard falloff" doesn't happen. This seems to have worked for me in the past. Is this the wrong thing to do?

_________________
Steve Sollod (pronounced sorta like "Solid")
www.swiftcreekguitars.com

I'm not familiar with Finochio's method, but I'm guessing that you glue the neck block to the ribs in the mold, then facet the upper bout after gluing the kerfings (kerfed linings, whatever) on, correct?
If so you are angling the neck block where it glues to the soundboard, regardless of whether or not the neck block was square to begin with, unless your mold is shimmed to tip the block back (they almost never are). This means the neck angle where the neck attaches to the body will not be 90 degrees square.

So as to the original question in your very first post, this means that you will likely need to taper the heel and trim the cheeks back, and perform the neck finiting procedure. I would use a sharp chisel, but if you want to floss the entire fit, you can, it will just take longer. If part of finiting the neck to the body includes sanding the portion of the soundboard slightly to obtain the flattest surface to glue the fretboard down onto, that is acceptable, and usually necessary as well.

_________________
Old growth, shmold growth!

I don't want to beat this thread to death... but, Robbie O'Brien's video I think has a nice visualization on this discussion...
http://www.youtube.com/watch?v=yzlZvDyKnPI

_________________
Steve Sollod (pronounced sorta like "Solid")
www.swiftcreekguitars.com

Nice video! It demonstrates very well the neck fitting and finessing procedure necessary with a mold-built guitar.
At 1:57 you can see the angled gap that will exist under the fretboard, that's where falloff occurs but a tapered shim will account for that, unless it is accounted for elsewhere in the design.
In this case, as the heel is tapered back to the correct angle, the neck pivots at the point where the neck joins the body, tipping the headstock back and the end of the fretboard up off the soundboard face.

This is the same procedure I use when resetting old Martin necks, except it's a little more complicated with the dovetail, and I use a chisel to create the new angle.

_________________
Old growth, shmold growth!

Why not just cut the neck at 1.5 degrees and be done with it.It works for me every time.It will get me between 1/16 and 3/32 gap at bridge position on any body style Before fretboard or bridge applied.This gives plenty of room to accomodate different actions for different playing styles.
James

_________________
James W Bolan
Nashville Tennessee

The OP had a very good question. If I cut my necks at 1.5 degrees over 90, it would not work, for instance.

I think, through all the discussion, it seems to me that it has been established that with his construction method, Robbie O'Brien's video demonstrates the best way to determine the correct angle that needs to be cut into the neck.

_________________
Old growth, shmold growth!

I build my boxes exactly like Robbie does and guess what ? 1.5 degrees every time gets me close enough.Just make sure your neck block is at 90 when the rims are glued to it,and your on a flat surface with the soundboard side down.Soundboard side of the rims should be un -profiled and glued flush with your neck block.The only thing that can screw you up is if you don`t flatten where the neck attaches.
James

_________________
James W Bolan
Nashville Tennessee