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Right now I'm getting ready to start making jigs to work on my first neck. I am going to start with a holding jig to cut the neck tenon. I have the SM template, and I am going to do a dovetail joint. My top has a full 30' radius, and I am going to sand a flat in the area where the fingerboard will be glued to the top. The SM jig calls for a 1.5 to 2.0 degree neck set angle. My question is, is this angle proper for doing a radiused top, or should I change the angle?

Vince

Hi Vince.

Yes it is 'proper' for a domed top. It even could be proper for a true flat top, it really all depends on the height of your bridge.

I'll try to explain...

Since your top is domed, the place where the bridge will sit is higher than the joint between the side and the top where the neck meats the body. Therefore, if you do not induce an angle in the neck, your bridge will need to be really thin (too thin, as a matter of fact) in order for the strings to have proper action.

I suggest you draw everything on a paper to clearly understand. And ontop of it, it will allow you to define the exact neck angle you will need, taking into consideration your 30' dome and your bridge height.

Hope this helps!

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Alain Moisan
Former full time builder of Acoustics, Classicals and Flamencos.
(Now building just for fun!)

My neck angle is almost 2 degrees and my top is a 25 foot radius in the lower bout...but there is no radius placed on the bracing above the sound hole...on my guitar.

Someone that can answer this question a little more thorough will come along any moment now.

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There is no difference between the man that thinks he can....and the man that thinks he cannot.

Hi again Vince.

I took the time to draw a little example where you can see the impact of having no angle (or too low of an angle).

And by the way, no comments on my Mspaint skills!

Again, I hope it helps!

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Alain Moisan
Former full time builder of Acoustics, Classicals and Flamencos.
(Now building just for fun!)

Okeh Alain,
I won't say what a lovely job you did on drawing those two guitars with Mspaint. Great job!

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"After forty-nine years of violin building, I have decided that the search for a varnish is similar to the fox hunt. The fun is in the hunt."
Jack Batts Maker and Repairer of Fine Violins

Ok then, 'positive' comments are allowed on my Mspaint skills....


Thanks!

_________________
Alain Moisan
Former full time builder of Acoustics, Classicals and Flamencos.
(Now building just for fun!)

Another positive comment Alain - nice illustration!

Vince do you know about the Woolson neck tenon jig? I gave my last set of plans away recently or I would send them to ya. The OLF used to sell the plans and perhaps they still have some of these left - don't know. Anyway this jig will permit you to determine the proper angle for your set-up.

Some influencer's are degree of dome on the top, height/thickness of fret board and frets, bridge height, and if you have the desire to have the low E string have 1/2" of height above the top at the leading edge of the bridge (this is what Martin does).

With a 25' dome that I use on everything a 1.5 degree neck angle gets me close and flossing of my cheeks (no pic requests please.... ) takes it the rest of the way.

I (and my students) approach neck angle somewhat diffferently .. I (we) actually dont care what the angle is, but its usually in the 1.5 area. So, why ????

Well, a 28 foot radius domed top with the area under the FB smoothed flat (UTB is still 28 ft radius) will set the plane of the FB to shoot about 1/16 of an inch or so above the top where the bridge will lay. This is what I am after. I would imagine a 25-30 ft radius will pretty much be the same, only a slight difference).

Now add up the numbers for where the strings will sit relative to the top - 1/16 (65-75 thou) inch gap, 1/4 inch FB, 35-40 thou frets, 95 thou action - thats about .450 total - right near the 1/2 inch string height everyone talks about. If you want the strings to be slightly higher, you can always angle the plane of the FB while radiusing and levelling to aim a bit high.

So, to cut the neck heel angle, I take a sliding bevel, and set the angle to be cut with that, measuring directly off the guitar - not knowing at all what the number of the angle is - because it doesnt matter. I simply want the FB to sit flat on my top - because if it does, then the geometry works.

If your top is designed differently, such that the plane of the top area under the FB gives you a different gap at the bridge, then IMO you will have to do one of two things .... taper the FB end, or shim it. Otherwise, the strings wont be anywhere close to the 1/2 inch mark above the top at a reasonable action setting.

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