Official Luthiers Forum!

SnowManSnow - yes, if you want the 1.3-1.5 degrees that Ken speaks of, then you will need to machine that into your neck - sanding, routing, paring or otherwise, as the StewMac necks still come at 90 degrees (I believe)

Page two of the KMG neck set instructions give you one straightforward approach to adding the matching angle to your upper bout once you've adjusted the cheeks on your neck.

http://kennethmichaelguitars.com/NECKSET.html

I'm working on refining the upper bout geometry on two guitars right now - aiming for 3/32", but allow for some slight variation. I always adjust the neck/upper bout angles prior to top routing/binding, or glueing on the fretboards. This allows me to make any final adjustments (so far every one has needed a little upper bout adjustment) smooth any transition to the waist, and then cut my top binding channels for cleaner / even binding depth.

I need to go back and make absolutely sure that as I flattened the area of the upper bout I didn't impose a forward leaning angle into the rims


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My confusion is because of the following.
The angle of the neck isn't 90d g to the fretboard, so it is leaning back as it should. I cut relief as prescribed in the instructions and the cheeks sit down just right all around.
But... when I put down a strait edge it contacts the soundboard right around the rosette area. Until then there is adequate clearance. So... I'm not sure where to go with it since I can't move forward in the instructions.. at the index card step.
HOWEVER...
If the neck was leaning forward... then there would be NO gap at the soundboard, as the fingerboard base and the soundboard is level....
scratching my bald head.



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You may directly measure the clearance of the neck plane from top of the guitar at the saddle area, so there is no need to complete and fret the board before establishing the neck angle, although you may wish to have a pretty good idea of the finished thickness of the board and what frets you plan to install. Further, you may fret with fretboard off the neck, on the neck but off the body, or after assembling the guitar as is usually done in this shop for acoustics - there are advantages and disadvantages to each approach, but all work for their practitioners.

The key bit of information needed here to determine if the neck angle is at or close to correct is the clearance between the neck plane and the top at the saddle location. This allows the neck angle to be set, at which point the extension fit to the body may be refined and any gap addressed.

What is the rationale for flattening the tenon/cheek area of the body? If you could point to the source of that guidance, I'd be interested in understanding the pros and cons of the approach.

I will relay, Dr. Kennedy - the degree of regard in which he holds you may be deduced from the labeling on our set of templates and fixtures for profiling tapered heels. The box holding the heel templates is labeled:

Ole Doc Kennedy's Patent Wizard Elixir & Tapered Heel Profiling Templates:
(Treats Gout, the Flux, and Ugly Guitar Necks...apply liberally!)

_________________
We have become a civilization that elevates idiots, prostitutes, and clowns. Am I still to defend it? Yes, for its principles. Yes, for what it was. Yes, for what it still may be.

-Mark Helprin, The Oceans and the Stars: A Sea Story, A War Story, A Love Story (A Novel)

For that, I'd just floss the under side of the fretboard extension so it has a little taper to the sound hole. That way you are not thinning out the top plate, especially as you get closer to the sound hole. I made that mistake once and actually sanded through my rosette!

That is assuming that you have the correct clearance at the saddle. If your geometry is correct, and the neck angle is giving you the correct clearance at the saddle, then don't change it. Just taper the under side of the fretboard extension. There is no problem with that. You are just adapting to the radius of the top in the upper bout.

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Tony Thatcher
Bozeman, Montana

Basic geometry.

If the neck heel has a Martin style V profile, flattening the area where the heel shoulders contact the body makes life simpler.... it means that you are then mating two plane surfaces together.

If the heel has a parallel profile, flattening is not of any benefit.

Wow, I've never achieved that. I always aim for slot depth times 2 Not sure if I ever achieved that either). In the end, its how well it plays and sounds. I normally lay a straight edge along fretted board and hope for around 3/32' to 1/8' above front edge of bridge. I'm working one now that scares me.

This is a fascinating conversation! It appears to me that there are several schools of thought on neck setting, to include:

- Those that control body shape (really, top contour) and neck angle throughout the building process to hit a target string height at the saddle

- Those that adjust body shape and bridge thickness after construction to hit a target string height at the saddle

- Those that are aiming for a different target entirely (e.g., a set saddle height) and accept a range of different string heights at the saddle location, provided a bridge of minimum thickness with adequate saddle depth can be accommodated.

Two of the three approaches focus on a set geometry at the saddle, while the third is a different goal entirely. For those following the third school, such as Mr. O'Melia, what is the range of acceptable string heights, bridge thicknesses, and saddle projections for your guitars? Martin seems to adhere to the third school, with at least four different bridge thicknesses I've seen, saddle heights from just 0.090" to 0.180", and final string heights at the saddle of about 0.42" to about 0.58" (thanks, Mr. Parker!)...that seems like a huge range of possible results in exchange for simplifying the construction process, but their customers seem satisfied with the results.

Mr. McLeod - exactly! For a butt-jointed neck without fretboard installed, adjustments to back and side angle could be done on an abrasive-covered surface plate, versus the tedium of neck joint flossing. But how would one avoid thinning the binding under the heel cap, or disguise the loss of 0.015"-0.020" of binding thickness so as not to be noticeable?

_________________
We have become a civilization that elevates idiots, prostitutes, and clowns. Am I still to defend it? Yes, for its principles. Yes, for what it was. Yes, for what it still may be.

-Mark Helprin, The Oceans and the Stars: A Sea Story, A War Story, A Love Story (A Novel)

" and final string heights at the saddle of about 4.2" to about 5.8""

I think your decimal point should go a digit to the left, Woody. Not trying to be persnickety, but some folks could get confused by the numbers and wind up with a harp instead of a guitar.

There's many thoughtful responses.

This reminds me of the cold and flu isle at the pharmacy. There's as many remedies as possible to fill it top to bottom. And some might even have more than a placebo effect, but I doubt it.
It is all in fun so don't het me wrong.
When I made my first acoustic guitar years ago I followed a mixture of ideas which led me far astray when it came to meeting the neck to the body and having the proper projection. Problem was a good thing because it forced me to plan better from the beginning.
I now use the classical guitar method of building on a plantilla. Even with steel string guitar's. This way I can have different shapes for the body and still have the correct string height in the end.

Obviously from viewing many fine guitars built using radius dish method for the body, it can be worked out. But I think it takes more than one guitar to get right. There are too many variables with the bracing in the upper bound in conjunction with any angle that put on the rim.

So anyway that's just something to think about if anyone reads this, doing the research before building it's a good idea to build with the top down on a workboard or plantilla.


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Ken

This is a valid concern and one reason that we stress the importance of following the assembly sequence when using the KMG assembly manual construction process. However, when using the parts supplied with our KMG kits the flatting of the area in question is merely a clean up to remove glue squeeze out.

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Ken Cierp

http://www.kennethmichaelguitars.com/

Woodie, I was thinking more of a very localized flattening, with a tapered custom made sanding block, which would flatten an area of maximum 2.5 " at the soundboard, tapering to like 1.25" at the back. This would be advantageous no matter what the type of neck joint employed ...butt, dovetail, bolt on, whatever (always assuming that the neck heel is a V-profile, of course}

This flattening to be done before the binding channels were routed. Any subsequent adjustment to be done on the shoulders of the neck heel ...just as if you were doing a neck reset.

I envisage that if you were building a parlor guitar with a very tight and pronounced radius to the upper bout, you would be more or less forced to do this (assuming you were using a V profiled heel, of course).

Ken, are we talking about the same thing ?

I was referring to the area where the neck heel mates up to the body. I am not familiar with your KMG kits, but I cannot visualize why there should be any glue squeeze-out in this area, irrespective of what method of neck attachment is employed?

Yes we are --- side/rim butt joint on the neck block

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Ken Cierp

http://www.kennethmichaelguitars.com/

When you glue the sides to the neck block you can have some glue squeeze out, pre-dovetail/tenon route

You can beat this to death, its time to make some shavings

well yes ... I thought the thread was about neck angles ...with basic glue ups already taken care of ..

It's important to get it right but it's also real easy to way over think it.

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Steve Smith
"Music is what feelings sound like"

Overthinking is very popular on this board.
I just eliminated the problems completely by making the top cylindrical. The top is basically flat from dovetail to end block. I look for a 1/16" gap in the straightedge above the top at the bridge. Done...

I also think not reading " all " the posts in a thread before comments are made or questions asked can lead to misunderstanding intent of some of the posted comments. But no harm no foul its a forum.

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Ken Cierp

http://www.kennethmichaelguitars.com/