Understanding Neck Angle

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Alexander Higgins
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Understanding Neck Angle

Post by Alexander Higgins »

A noob question for sure, but humor me:

What is the purpose/advantage of designing a neck angle (plane of fingerboard not parallel to plane of body) into a guitar or bass design? A Les Paul seems like the most common example. The big tune-o-matic bridge set way above the body would otherwise make the strings too high at the top frets, so he angled the neck, but why bother with the high bridge at all? Was it the carved top that drove that decision? Leo Fender went the opposite route, no neck angle and a low bridge, which seems simple and works perfectly well. I'm in the end stages of laying out my "Hossenfeffer" bass (a re-creation of a bass for my own use by a famously litigious american instrument maker who shall remain nameless) and have read descriptions of it having a 1.5 degree neck angle to the body. Unfortunately, I don't have access to an original source instrument to verify this, and NO accurate plans are available online due to aggressive copyright enforcement. This is a neck-through bass, so that is sounding like a real PITA to incorporate. Is it really necessary for such a small angle? The fingerboard is already raised above the body by a "shelf" of neck wood around 3/16" high, and the original fingerboards were nearly 3/8" thick, so the fingerboard is pretty high already with respect to the body. My approach so far has been to model the position of a string in CAD as a perfectly straight line from nut to bridge saddle at the mid-range of it's height adjustment to see how it relates to fret height at various points, but maybe I'm missing some subtlety here. Advice?

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Barry Daniels
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Re: Understanding Neck Angle

Post by Barry Daniels »

I don't use CAD but have hand drawn a full scale side view of guitars to determine neck angles based on the desired height of my bridge. Just draw everything carefully and you can get close enough for a bridge that has some adjustable height. It is best to make the drawing at the center of the guitar as if you cut everything in half; basically a center-line cross-section. Include the strings at your desired action height, and draw the bridge at the center of its adjustment, or maybe a bit lower.
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Pete Halliday
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Re: Understanding Neck Angle

Post by Pete Halliday »

Answering your why question with a bit of a guess...I think that the neck angle on an LP is due to the carved top and it would look rather silly (in my opinion) to have a zero angle neck with the carve. Gibson already had a long history of building archtops with neck angle and the requirement of a relatively tall bridge to get the correct downward pressure on the top so the design of the solid body seems more evolutionary in their case.

That said, the early LP specials did have what looks to be a zero angle neck on a slab body and a TOM bridge with the fingerboard on a bit of a shelf--maybe 3/8" or so--much like the litigious American maker. I have made a couple guitars with that set-up and think that it works and looks fine. Barry's response covers the how-to well and while I agree with him about laying out the center-line, make sure that you do pay attention to the various heights of pickups and what not at the outer strings as well. It will be those strings that set the maximum height that the pickup can be raised to and the minimum height that your bridge body can be.

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Barry Daniels
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Re: Understanding Neck Angle

Post by Barry Daniels »

Good point, Pete.
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Gordon Bellerose
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Re: Understanding Neck Angle

Post by Gordon Bellerose »

In addition to what the other guys have stated, there has been some discussion as to how the height of the strings above the body affects tone.
But I agree with Barry. It seems as though the history of Gibson building methods, were the driver in the decision to angle the neck, because of the T.O.M bridge. That is pure speculation on my part. :o

Scale length has everything to do with the angle also, as I'm sure you know.
24.75 scale usually has a 4 - 5 degree angle.
25.5 scale has a neck angle of about 2.5 - 3 degrees.

The longer bass scale you speak of would be in the 1.5 degree range.
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Paul E Buerk
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Re: Understanding Neck Angle

Post by Paul E Buerk »

The nice thing about working this through CAD is that you can group all of the layers/elements of the neck/fingerboard, assign a pivot point where you want it, rotate the group and measure the resulting angle.

Since I've made neck angle miscalculations before, I've made it a habit to draw out a thorough side view, noting several elements:

- nut height
- fret height
- action
- bridge height
- bridge adjustment range
- planes of top and fingerboard
- radii of fingerboard and bridge (but not always, but usually when doing it in 3D)

I suppose you could also throw in fingerboard relief and string gauge, but for the most part the adjustability of the bridge will compensate for these measurements.

Eric Baack
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Re: Understanding Neck Angle

Post by Eric Baack »

Yeah, the 3d cad comes in very useful. I've also used it to get a rough idea of what I want the top carve to look like. Then I will make a topographical map of the top to make templates for rough cutting it with a router. I make slicing planes every 0.10" then I can trace that onto the top for reference. I did the same with the neck.

It does get the action quite close as well. I run a 3d sketch to represent the strings so I can set the general action height.

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Re: Understanding Neck Angle

Post by Chad McCormack »

Gordon Bellerose wrote:In addition to what the other guys have stated, there has been some discussion as to how the height of the strings above the body affects tone.
But I agree with Barry. It seems as though the history of Gibson building methods, were the driver in the decision to angle the neck, because of the T.O.M bridge. That is pure speculation on my part. :o

Scale length has everything to do with the angle also, as I'm sure you know.
24.75 scale usually has a 4 - 5 degree angle.
25.5 scale has a neck angle of about 2.5 - 3 degrees.

The longer bass scale you speak of would be in the 1.5 degree range.

Hi Gordon.

I'm actually just starting a 25.5" scale build right now of a guitar that I've only done 25" scales on until now, so your post piqued my interest. Would you care to elaborate on those numbers for us? My calculations have a 24.75" scale length (hypotenuse) at a rise angle of 5 degrees yielding a vertical rise of 2.157" from nut to saddle. A 25.5" length at a rise angle of 3 degrees corresponds to a nut-to-saddle rise of 1.335". I can't see how designing for a scale length difference of only .75" would cause anyone to adjust their neck angle so severely. Keeping with 3 degrees, for example, the difference in nut-to-saddle rise for a 24.75" string length vs. a 25.5" string length is only 0.040", amounting to just a turn on the posts of your typical T-o-M style bridge. Perhaps I'm missing something? Please do chime in!

Chad

Alexander Higgins
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Re: Understanding Neck Angle

Post by Alexander Higgins »

Thanks for the replies all. I've read that the Hossenfeffer source bass has a 1.5 degree neck angle, but where is the pivot point, bridge end of the fingerboard, with the neck falling away towards the nut? The Hossenfeffer bridge doesn't look a whole lot taller than a fender bass bridge, which brings me back to the original question: Why do I need a neck angle at all? I'll try laying out a couple versions of a neck section at centerline , with and without neck angle, and see what it does to the action. If I post a few images maybe you all can set me straight.

Eric Baack
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Re: Understanding Neck Angle

Post by Eric Baack »

There's not a pivot "point" Think more in planes. The neck angle is measured from the flat plane fo the back of the guitar. The height of the neck from the back of the body, combined with the position and height of the bridge will determine the neck angle.

Art Davila
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Re: Understanding Neck Angle

Post by Art Davila »

I have seen guitars with T O M bridges that are recessed into the body and I thought that was a weird design because the access to the intonation screws seemed to be hindered.
What advantage would there be to use a recessed tom bridge with zero neck angle over having a neck angle that did not require recessing the bridge?
Or is there no reason and it was just an aesthetics choice?
I have a lot of experience on how "not" to do things.

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Pete Halliday
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Re: Understanding Neck Angle

Post by Pete Halliday »

My guess is that it started as a way to salvage a guitar that was not well thought out.

Gordon Bellerose
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Re: Understanding Neck Angle

Post by Gordon Bellerose »

Chad McCormack wrote:
Gordon Bellerose wrote:In addition to what the other guys have stated, there has been some discussion as to how the height of the strings above the body affects tone.
But I agree with Barry. It seems as though the history of Gibson building methods, were the driver in the decision to angle the neck, because of the T.O.M bridge. That is pure speculation on my part. :o

Scale length has everything to do with the angle also, as I'm sure you know.
24.75 scale usually has a 4 - 5 degree angle.
25.5 scale has a neck angle of about 2.5 - 3 degrees.

The longer bass scale you speak of would be in the 1.5 degree range.

Hi Gordon.

I'm actually just starting a 25.5" scale build right now of a guitar that I've only done 25" scales on until now, so your post piqued my interest. Would you care to elaborate on those numbers for us? My calculations have a 24.75" scale length (hypotenuse) at a rise angle of 5 degrees yielding a vertical rise of 2.157" from nut to saddle. A 25.5" length at a rise angle of 3 degrees corresponds to a nut-to-saddle rise of 1.335". I can't see how designing for a scale length difference of only .75" would cause anyone to adjust their neck angle so severely. Keeping with 3 degrees, for example, the difference in nut-to-saddle rise for a 24.75" string length vs. a 25.5" string length is only 0.040", amounting to just a turn on the posts of your typical T-o-M style bridge. Perhaps I'm missing something? Please do chime in!

Chad
Chad,

The only thing I can tell you for certain, is that one of the latest flat body electrics I built, has a T.O.M. bridge, a Stop-Tail-Piece, and a Bolt-On neck.
If we assume that the bottom of the neck heel is parallel to the fingerboard, I had to cut the neck pocket at 2.8 degrees.
I reached this angle by first stopping the rout depth at 9/16 deep at an angle of 2 degrees. It was too flat, and the bridge could not be adjusted low enough.
I then routed the pocket to 5/8 deep, at an angle of 2.4 degrees. This was closer, but still a bit low. As the guitar was not getting a pickguard, I wanted to bring the fingerboard extension a bit lower to the body anyway, so I went to 11/16 deep at the heel, and ended up at 2.8 degrees.
Not a real scientific approach, but the result was great.

Image

Image
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Paul E Buerk
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Re: Understanding Neck Angle

Post by Paul E Buerk »

There's not a pivot "point"
Sure there is, but I didn't explain it well. If you take a side view of the body, neck, and fingerboard/frets, etc., then group everything on the neck/fingerboard/headstock/etc (everything except the body and bridge), then you can set a pivot point at the precise point where you want the neck/body join to be. For example, if you want the fingerboard/neck joint plane to be located exactly at the top edge of the body, you put the pivot there and adjust the angle so that the strings hit the bridge where you want them to. If you want the end of the fingerboard to sit directly on top of the body, put it there.

Aryeh Barson
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Re: Understanding Neck Angle

Post by Aryeh Barson »

With regards to your build, Melvin Hiscock's book gives a very good explanation and example of why body to neck angle is required, and it's like what Eric Baack says above. I understand why you used TOM bridges as an example, but it really applies to any bridge: the TOM is simply more pronounced.

My first bass was also a neck through and I omitted this step. I ended up having to route out material under the bridge in order to get the correct string height, which I would not have had to do if I had built in the body to neck angle. If you've found the angle of the original, I would recommend reusing it.

Alexander Higgins
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Re: Understanding Neck Angle

Post by Alexander Higgins »

Is it fair to say that the height of the bridge determines the necessity of a neck angle? Most bolt-on necks appear to have a fingerboard parallel to the body, and it works fine because a fender style bridge is so low-profile? They also typically have little to no headstock angle, so they need string trees. The part I'm still struggling with is why I need a neck angle at all, if I can simply raise the fingerboard with respect to the body plane. Raising the bridge saddles increases how out of parallel the string is to the fingerboard, thus raising string height at the upper frets. I read the Hiscock book a while back, I'll have re-read it, still not grasping the concept. Thanks for the responses all.

Aryeh Barson
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Re: Understanding Neck Angle

Post by Aryeh Barson »

Using Fender as an example, the neck is parallel to the body and bridge. That said, the neck sits proud of the body, so it is on a different plane.

When I made my neck-through bass, the neck blank and body were all on the same plane. When I glued on the fingerboard, it now had an "elevated plane" above both neck and body. Strings are suspended above that plane in parallel. Unfortunately for me, the plane of the strings didn't coincide with the bridge correctly. If I had introduced some neck to body angle, I wouldn't have had to rout under the bridge to get the string height right.

I don't know if it's allowed to include a link to an external source, but maybe the illustration at the Tundraman site would be helpful: http://www.tundraman.com/Guitars/NeckAngle/

Eric Baack
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Re: Understanding Neck Angle

Post by Eric Baack »

I like the feel of a guitar with some neck angle to it. It's just more comfortable for me to play.

Alexander Higgins
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Re: Understanding Neck Angle

Post by Alexander Higgins »

Aryeh,
I just stumbled on the Tundraman neck angle calculator last night, that really clears it up for me. the diagrams are much clearer than the Hiscock book version. I entered my current bass design info and it spat out a neck angle of 0.585 degrees, which seems like a whole lot of trouble in the build for such a tiny angle. Is it really worth doing at such a small angle? I found this interesting link to a guy who did a recent Rick bass restoration:

http://www.carltonguitars.com.au/resour ... c_4001.htm

He ended up bagging the neck angle and raising the fingerboard up by veneering a strip of maple to the face of the neck to avoid having to use a 3/8" thick fingerboard blank. He estimated top of fingerboard above body as 10 mm, which is what I used for the neck angle calculator.

Here are two potential neck sections, taken at centerline, both with bridge saddles bottomed out, and .022" clearance below string at the first fret, one with no neck angle, one with .585. I used the center of the 20th fret, which is where the fingerboard crosses body, as the center of rotation for the angled neck version. The fingerboard is assumed to be perfectly flat for this excercise.

The no angle neck yields .079" (1/16") clearance below the A or D string to top of 20th fret.

Advice? What would you do in my shoes?

The 0.585 angle effectively lays the A or D string in contact with the 20th fret at .007" clearance.

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Chad McCormack
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Re: Understanding Neck Angle

Post by Chad McCormack »

Hi Alex. Keep in mind that the clearance of approximately 1/16" that you mentioned for the no-angle neck is likely calculated based on a laserbeam straight neck. You're going to get a little relief in the neck when strung up and under tension, and the result will be a lift in the the playing action. Of course, a truss rod will be able to counter that relief, but I know a little relief is desirable by most players in a guitar setup. I've never built a bass, so perhaps somebody else can chime in here for you.

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