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Hello All,

I’ve been doing some math. Then I decided to do a drawing using the measurements that many of
you have discussed in the “Neck & Fretboard thing again” thread, relating to bridge height,
saddle height, neck angle, and so on.
I have an architectural software program that I use to design homes I build. It also can be
used as a very accurate drafting program. In the drawing, the body and neck are only to approximate size.
The Bridge, Saddle, Nut, Fingerboard, and frets are to actual HEIGHTS not widths.

The interesting thing, is when I used the measurements that have been discussed for Bridge and
Saddle height, plus making sure that the nut would allow a 1/32" space between string and first fret.
I get the 3/32" space between the string and the 12th fret that matches what StewMac considers medium action.
You probably can’t see the gap at the first fret, but, it is there. If you could zoom in, you would see it.

So, here it is. Let me know what you think!

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Everything has beauty, But, not everyone see's it!

There is something you need to be aware of. Scale length is not the string length. If you set up the guitar with the strings the same length as the scale you will be sharp.
   The scale length is static , that is the spacing of the frets on the board. Then we have compensation angle , this allows the working length of the string to vary for the different strings.
   last we have the compensation length. This is what the strings are in the working length.
So on this set up you would want to add .100 for light and .125 to the front of the saddle for mediums. Strings will be longer at work than at rest. If you look at an electric guitar , where each string has its own adjustable bridge you can see where this is in effect. On acoutics you can't have that kind of adjustability so we take as much into the saddle to do compesation on them to get intonation as best as we can.
   Look at any steel string and you can see the angle in effect. Martin uses a 3 degree angle and Gibson uses 4.
   this can get you very close on your intonation. also you want to measure along the strings length not center.
john hall

Robert,

Pretty cool.

Difficult to tell from your drawing but the neck is usually set at a slight angle from the top (pointing down) rather than parallel to the top plane. This brings the string line a little bit closer to the fretboard line. If you factor this in and readjust your first fret height you may get slightly different measurement at the 12th fret.

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Dave White
De Faoite Stringed Instruments
". . . the one thing a machine just can't do is give you character and personalities and sometimes that comes with flaws, but it always comes with humanity" Monty Don talking about hand weaving, "Mastercrafts", Weaving, BBC March 2010

Robert,

Apologies - I see you mention neck angle. What neck angle did you use?

_________________
Dave White
De Faoite Stringed Instruments
". . . the one thing a machine just can't do is give you character and personalities and sometimes that comes with flaws, but it always comes with humanity" Monty Don talking about hand weaving, "Mastercrafts", Weaving, BBC March 2010

Thanks All for looking, I really do appreciate your input.

First, let me remind everyone, that this is a StewMac Dreadnought Kit.

The fingerboard was already to the thickness noted, slotted, and shaped to, what I would think is
a standard radius. The bridge is completed, along with the angled slot for the saddle.
The bridge will need a slight radius at the underside, but, appears to me, will only lose maybe 1/64" in height.

Also, I noticed that the drawing lost some of its accuracy when I saved as a .jpg file.
If you could see it on my computer, in my software, there would be no doubts to its accuracy.

More over, the drawing is, for the most part, a mathematical test. It is as you all have said, “A Perfect World”

So, given the measurement for saddle height, which has widely been agreed on in past threads,
and string spacing, suggested by the StewMac Manual, combined with the existing measurements
of the bridge, fingerboard, and fret crown height. It seems to me, that the math works, and a
medium action has been achieved.

Now, as always, with more posts, arise more questions.

Hesh, I’m assuming when you say “range of possibilities” You are referring to (in general) the adjustability
of saddle height and nut height?

Mr John Hall, I don’t believe I have given you due credit for your input yet. Let me do so now.
It has become very obvious to me that you are well versed in guitar building.
You have very precise explanations, that are very clear to understand. Thank you, so much!
You mentioned “scale length”
As for the saddle angle, I’m pretty sure it has the 3 degree angle you were talking about.
As to where to measure for scale length, you‘ve got me thinking.
I have assumed that it is measured from the fretboard side of the nut to the center of the saddle,
along a center line of the fretboard to the center of the bridge. (Between the 3rd & 4th holes)
Is this correct?
I should also tell you that I bought a “Saddlematic bridge saddle locator” from StewMac, and
plan to install the neck, fingerboard, and then the frets. I will then use the “Saddlematic” for what
seems to me, to be an almost flawless bridge placement.

Dave, to tell the truth, I made no allowance for neck angle in the drawing. The top of the body,
and the top of the neck (Without fretboard) are parallel. But, now that you’ve mentioned it.
Would not even the slightest angle of the neck you are referring to make enormous changes to
bridge height?

Robert

_________________
Everything has beauty, But, not everyone see's it!

Thanks Robert, very useful and informative!

Robert,

Scale length is along the 1st string, high "e" in most cases. There is comepnsation even at this sting as, as John states, the sting length changes all of the time. As you press the string to fret it, you have stretched the string longer. The compensation issue is used to address this change and is different for each string. Once you do your set up you will see as you intonate each string with your saddle matic. BUT you want to be "close" before you you start as you are limited in adjustment by the angle of your saddle and the width of you saddle.

John will probably explain better!

Shane

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Canada

Nice looking model, great in theory - your guitar neck will however require some relief, ie curvature, likely 4-10 thou at the 6-7 th fret, with the string being held down at the 1st and 14th frets - thus the FB is not flat - it could be setup this way, but more likely than not the low F# and G will buzz when played. Just experience of a few hundred setups, and close to a hundred builds talking ... with lower action, more relief required.

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

Also your first fret height of 1/32, thats 31.25 thou, is pretty high - you wouldnt like playing this guitar setup that way for long, especially with medium strings. Shoot for more like 15-20 thou high to low to start, then as the guitar settles in, maybe take it down more. I measured Bob Bennetts older Ryan GC a few years back, it was 11-16 thou, pretty much the limit.

What you will obviously find that is when the first fret number drops, so will the 12th fret number - so to get back to 3/32 action you will need more saddle height.

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

Hello Tony, Thanks for chiming in!

I guess there’s still a lot more to this neck setup thing I need to learn.

After reading your post, I thought I should go back and check the StewMac manual again.

Well, I think I owe an apology to StewMac. Turns out I should have read the next page.
Don’t I feel a little dumb right now!

The manual states that the final clearance at the first fret should be:
“E (1st), 0.012"; B (2nd), 0.012"; G (3rd), 0.014"; D (4th), 0.014"; A (5th), 0.016"; E (6th), 0.016".

Thank you Tony for pointing this out.

Oh well! Back to the drawing board

Robert

_________________
Everything has beauty, But, not everyone see's it!

    I hope I can help here in that it matters not where the kit is from or what the scale length is. For this I am discussing steel string not gut or nylon as they are a different animal all together.
   Scale length: This is a static ( non changing ) dimension. IE 24.9   25.4 ETC
   Compesation angle:
     This is the angle of the saddle on the bridge. Most are using a 3 degree angle of compensation. This equates to about 1/8" fall back from the 1st ( hi E ) to the 6th ( lo E )
    Working length of the string : Dynamic length
This means the length is in constant flux. It is allways changing.
     Compensation length:
    To be honest this is not an exact science as different strings have different lengths . Even the same string as it ages tends to change length.

   With all this info and you want as perfect an intonation as possible you must keep this all in mind as to gain the best intonation and all these have to be taken into mind.
    To determin scale is 12th fret time 2. I will add a compensation length to this for the working length of the string. I use as a rule of thumb .100" for light gage to .125 for mediums. This is to the point if from of the bridge along the line of the 1st string.
   Theorically this is a hypotinuse of the right triangle formed from the perpedicular line from the nut at the 1st string to the saddle and 90 degrees to the point of the 1st strings saddle location .
   So if you measure the distance from nut to the 12th and multiply by 2 and the apropriate compesation to the scale length . this will give you the postion of the saddle in lew of the scale length.
   I normally use a 1/8" saddle width as this affords me some room for additional compesation on the saddle for each string.
    Another influence you will find is action height. The higher the action the more it will pull you sharp. The human ear will tend to pick up a sharp easier than it will a flat. I like to see a good intonation for the open and 12th fret harmonic. You may have to adjust the saddle to compensate for this. You should be a touch flat to true on an uncompensated saddle.
     I hope this helps . I can usually get a guitar to hold within 1 cent to true with this method.
john hall
blues creek guitars