Myth -- Magic -- Mathematics -- The Straight Line Principle

[ken cierp]

I believe we can discuss and construct the neck joint much easier when the basic straight line concept is understood:

http://www.kennethmichaelguitars.com/neckangle.html

[Dave Bagwill]

I still say that is one of the best written, most important articles on construction that I have ever read. Everyone should understand these principles. I've probably read it 10 times.
That is not sucking up to the admin; I mean it.


(Though if the admin ever has an extra box of Cuban cigars, I would accept them gratefully :-))

[Preston]

Just follow the instructions carefully and after using the process two or three times it will become even more logical as to why the top slope from the soundhole to the neck block is so important. No more forcing the fretboard extension to the wrong angle and messing up your neck set. Remember as stated in the article it really doesn't take much sanding to get the slope you need. Be sure to watch your fingers - it can bite if you get s stray finger between the rims and the sanding bar. It works great!

[Tim Benware]

A couple things come to mind -

1. The complimentary angles, the radius and, I believe, the bridge thickness all need to match as well. I know there is a little room for play by compensating with saddle height but even there you would want to keep it to a minimum. So, what steps should be taken to ensure you have the correct radius on your braces, correct bridge height and complimentary angles.

It seems like you would have to start with the neck you have to determine angle, then know your bridge thickness and match those to to the proper radius to get your braces to lift the top/bridge to the proper fretboard extension height.

With all that are there formulas to calculate what radius to use for the varying degrees of neck angle i.e. 1 deg., 1.3 deg., 1.5 deg.?

Or am I over thinking this.

[ken cierp]

No you are not over thinking -- yes you are over thinking the need to do a bunch calculations of some sort. The straight line is the neck (finger -board glue surface) and the sound-board (finger-board extension area)--- forget the bridge at this point.

Yes bridge thickness (Martin has at least three sizes) and saddle height determine the comfortable string height. Back to the point, the fingerboard plane is a perfectly straight line -- this is not about whether or not this works -- its about the basic requirement. Failure to understand and follow this rule has caused misery for guitar makers since the dawn of the instrument.

[Tim Benware]

I get the straight line. That makes total sense to me BUT - If you start off with a neck that has a 88.5 degree angle and then sand 1.5 degrees from the neck block to sound hole the radius of the braces needed to get the right height at the bridge (and brace) is different than if you started with a 88 or 89 degree angle isn't it? So I guess what I'm Asking is does a 88.5 degree neck angle go with 25' radiused braces and 89 go with 40' etc. Because otherwise there wouldn't be different radius dishes would there?

[ken cierp]

Respectfully you are not quite getting it -- you are mixing apples and oranges. The distance that the dome (28' 25' 40' etc.) raises the bridge and saddle has nothing to do with the perfectly straight line formed by the neck fingerboard plane and the sound board FB extension area. Be the neck tipped 1.3 1.5 or 2 degrees. The combination of the bridge thickness, saddle height and dome/contour rise determine how high the strings will hover over the finger-board and that of course is key. So as long as you have that initial straight line (or build to attain it at the very offset like KMG kits) You can adjust the hover distance with one or all three of the aforementioned variables. This basic building rule takes the worry of the 14th/12th hump completely out of the picture.