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Hey all

I am starting #9 and I have the basic mechanics down for each of the many weird steps we do with instruments, but I still have questions about getting the neck angle right. I use M+T joints with inserts. I would like to go over how I do it and have you let me kow if I am missing anything, if I am doing too much, or have it all wrong.

When I started this curious journey 7 years ago, none of my woodworking experience prepared me for the neck angle geometry. I struggled but got lucky for the first 2, then decided to dig into it. KGM (?) had a neat approach, Hesh had a fabulous toot, and many others had great ideas, but I am one who has to understand what I am doing - it bothers me to go on blind faith, even if it might work. I do most of this by hand and don't have any router jigs for this, but if I did I would still want to understand everything. So I have come up with a system.

First I radius the rim of my straight-edged sides to my chosen 28' radius using a sanding beam. Then:

picture #1) I set my gauge for 1/8" (a little less for a 13" guitar, but 14-16" this seems to work) and mark at the neck block, then continue the line tapering to zero at the bottom of the upper bout (upper part of the waist).

2) I remove most of the excess with a block plane, chalk the surfaces, then use my flat sanding beam to even things out. I treat my rims twice - once before the lining and once after the lining is installed

3) When the box is closed, I set my fretboard over the neck block, put on 2 shims the height of my frets, fasten down the bridge, then use a 14" bevel gauge to get the angle. At this stage I can thin the top a little over the neck block to change the angle a bit, but If I went too far before the top went on it means a shim under the fretboard - only had to do that once out of 5 and that was on a biscuit bridge resonator because I didn't understand things as well as I thought

4) I check it just to see, and this time it is an even 2°

5) I draw the angles on my neck blank and cut the tenon and the cheeks with a backsaw

6) Right off the saw the angle looks very very close - I only had to floss this one a little side-to-side and it was good

So this helps me keep control of what I am doing and gives me confidence that the end result will be what I want. Is there something magic about having a 1-1/2° neck angle that I should go for that by maybe reducing the 1/8" cut at the neck block? Are there steps here I don't need or steps I am missing? Is there a better system (I know Hesh will get all over me for not just following the toot)? Does anyone have insight to better understand this?

Thanks so much

Ed Minch

With the stripped neck in place, the angle needed to get about 1/10" of clearance between the plane of the bare neck surface and the saddle location on the top should be pretty close for initial neck set. The radiused top can be an issue for fitting if the UTB has not been flattened, but some equal-thickness shims at the neck and the saddle location may allow direct measurements. That looks like an amazing guitar...any other shots of it?

_________________
For the times they are a changin'

- Bob Dylan

I do my neck angle a bit differently now.
First, radius rims 28' after fitting liners.
I use an ~60' radius UTB.
I made an ~60' radiused convex "stick" with small blocks at each end and drop it into the rims at the UTB position then block plane the neck block/FB support extension to meet that 60' radius "stick".
Then sand a 60' radius with a sanding beam into the top of the kerfs only (mark with chalk) on the previously 28' radiused rim above the UTB position, and flatten the liners parallel to the FB extension for about 1" each side with a block plane.
I fit the top, ready to glue but with no actual glue, onto the rims, weighted down in position at the X brace and UTB ends, and use a straight edge pressed on the upper bout over the neck block and check the clearance between the straight edge and the top at the saddle position, aiming for around 2.5mm. (6mm FB, and 1mm fret height)
Adjust slope top of neck block if required with block plane.
Then after closing the box, etc. using a sliding bevel take the angle between FB extension and the top of the sides and cut that angle into the cheeks at heel end of the neck.

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The name catgut is confusing. There are two explanations for the mix up.

Catgut is an abbreviation of the word cattle gut. Gut strings are made from sheep or goat intestines, in the past even from horse, mule or donkey intestines.

Otherwise it could be from the word kitgut or kitstring. Kit meant fiddle, not kitten.

I don't think there is anything magical about 1.5 degrees other than it is "about right." fretbaord thickness, bridge thickness, fret height among other things will have an effect on what the actual "ideal" angle is for any given guitar. You don't even really need to measure it. As long as the upper bout geometry works with the fretboard/bridge. . . to give you acceptable string height at the saddle, you can just use your bevel gauge to transfer your angle to the neck blank. I've never measured my angle and don't even have a means to do it reliably if I wanted to.

Unless I am mistaken, taking 1/8" off the heel block and planing to the waist is essentially the same thing as Hesh's tutorial. With that method, you are raiding the tail block 1/8" and sanding the heel block down to the waist area.

Guitar looks nice what is the back and side wood?

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Bryan Bear PMoMC

Take care of your feet, and your feet will take care of you.

Woody
I treat my UTB and the area around it as flat and have not had a problem. I have been thinking about a way that does not require putting the fretboard and fret-height shims on the top - but that is a pretty direct way to see what is happening. I just sent a PM.

Colin
Setting the top on with weights is a good idea - will try that before I glue on the top. I tried something like that when I did #2 (IIRC) but could not seem to make sense of it - I will try it again. Is the 2.5 mm the gap between the top at the bridge location and the straight edge coming off the bare neck? The top at the upper bout should be in line with the bare neck at that point. Where does the 6mm and 1mm measurement come into play?

Bryan
If you don't measure the angle, how do you get it right?

Thanks for seeing the guitars. The top two shots are of a 3/4 size Gibson L-2 interpretation in Osage Orange with a 12-3/4" lower bout and a 22-3/16" scale, and the bottom 4 are of an all-Alaskan Yellow Cedar early Gibson L-0 with a 13-3/4" lower bout and a 25-4" scale - all the same wood even the braces, 1/2 the lining, and the neck. The little one is tremendous fun to play, and the AYC one sounds really clear and sharp.

Osage Orange - click left and right, text below
https://www.flickr.com/photos/ruby1638/14705530506/in/album-72157641029319394/

Yellow Cedar - my daughter plays it at the end
https://www.flickr.com/photos/ruby1638/30816154577/in/album-72157688488198220/

I didn't say that very clearly. I don't measure the angle in degrees. I just measure the projected string height at the bridge to make sure I am in good shape. I use the shim at the tail and sand the upper bout flat method and it pretty much comes out right. I do put a very slight radius on the UTB. If the projected string height is where I want it, I don't really care if the angle is 1 degree, 1.5 degrees, 2 degrees. . . I copy the angel with my sliding bevel and transfer it to the neck blank. Think about it like this, when you taper a fretboard you want the nut width to be x and the 12th fret width to be y so you cut it to those dimensions, you don't really care what angle that makes.

The obvious question is what do I do if the projected string path isn't where I want it. That happend on my last two (made at the same time). I was making 12 fretters with shorter bodies and wasn't thinking about that when I sanded the upper bout. It wasn't off by much but I wan't happy with it. I drew it out and decided what thickness shim I needed at the bridge location to make a line to the heel end of the rim at the correct angle. I think it worked out to be about 2.5 mm. I taped a strip of wood of that thickness across the lower bout at the bridge location and used my (straight) level as a sanding beam. I had sand paper only on the heel side of the beam and nothing n the side that rode on the shim. I sanded the fretboard extension area until it was flat. It didn't really take off much material at all. The tops are a little bit thinner at the upper end of the sound hole but not enough to be a concern.

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Bryan Bear PMoMC

Take care of your feet, and your feet will take care of you.

More or less, just semantics - I'm checking the angle of the top of the upper bout, and the 2.5 mm the gap is between the top at the saddle location and the straight edge are coming off the top at the upper bout
Just take care not of compress the top with the weights, I use block planes right over the rims at the end of the braces
And of course when you fit the neck it will be in line with the top of the upper bout.
Please ignore the 6 and 1mm mentioned, it's just what I use for calculation of desired height of the saddle above the soundboard, which is what I work to, rather than bridge height.

_________________
The name catgut is confusing. There are two explanations for the mix up.

Catgut is an abbreviation of the word cattle gut. Gut strings are made from sheep or goat intestines, in the past even from horse, mule or donkey intestines.

Otherwise it could be from the word kitgut or kitstring. Kit meant fiddle, not kitten.

I rough the angle but set it up as I do in this video
https://www.youtube.com/watch?v=nF57G5Ih-qY&t=86s

_________________
John Hall
blues creek guitars
Authorized CF Martin Repair
Co President of ASIA
You Don't know what you don't know until you know it

It's best not to think in terms of angles at all, as others have mentioned (or implied in their techniques). My "going in" position is that I want the neck surface (no fretboard) and the upper bout to be co-planar. That means I don't have to kink the fretboard (wedge it up or down) when I glue it on. This means that it is the longitudinal curvature on the upper bout which sets the neck angle and that curvature is right when a straight edge placed on the upper bout and extended over the saddle position gives a clearance to the top of 2.5mm. This gets the string height above the soundboard and the action at fret 12 all in the right ballpark. For typical top dome dimensions (28' -33') and frets clear (12 or 14) the right longitudinal curvature is obtained when the transverse curvature in the UTB position is ~ 60' or its equivalent lift. (I use a curve with a flat on it where the fretboard goes, so not a true radius). The ~60' number changes slightly with top dome, frets clear, etc.

To make this happen, I dome the whole of the rims to radius with a sanding dish, then just flatten the headblock/extension piece (I'm using a "double tenon" joint) until it matches the ~60' caul I used to glue on the UTB. Other re-shaping of the rims is not necessary. The back goes on first and then the top can be dry mounted to make sure all the projections are right, much as Colin described. Then the top goes on. The dish used to sand the top linings can be used as a caul over the whole of the lower bout with a couple of weights. No need for hundred of clamps. The upper bout and over the neck block are clamped in traditional ways.
When the gluing is done, all the projections can be checked again and should be very close to spot on. Any minor adjustments can be made by sanding the upper bout close to the sound hole to reduce the angle or close to the sides at the top of the guitar to increase the angle. The angle between the neck plane and the sides is whatever it turns out to be, but it is typically about 88.5 degrees, i.e. the 1.5 degrees you mention. However this method aims for the 2.5mm clearance of the projection over the saddle position, not any particular angle.

All the details and maths formulae to figure out different scenarios are in the book, of course.

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Trevor Gore, Luthier. Australian hand made acoustic guitars, classical guitars; custom guitar design and build; guitar design instruction.

http://www.goreguitars.com.au

Thanks Trevor

Don't know what it was, but your explanation kicked it over the edge for me. I think I have it. I am doing it MOSTLY right and will switch to a dry fit and altering things from there. I will be sure that your 2.5mm matches my fretboard/bridge/UTB combination to end up with a little more than 1/2" (12.5mm?) between the top and top of the saddle.

I will still use the bevel gauge to record the neck angle and proceed from there. When the box is assembled, I will use John Hall's method of sanding the top of the neck to be flat with the upper bout area of the body.

Am I correct in aiming for just little over the top of the saddle to allow for a slight distortion of the body to bring it down?

Interesting that this is a very critical area of building a guitar but you don't see much discussion of it here on the innerwebs.

Thanks all

Ed

Oh there’s plenty of discussion all right...

Sure is, I've seen lots over the years.

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The name catgut is confusing. There are two explanations for the mix up.

Catgut is an abbreviation of the word cattle gut. Gut strings are made from sheep or goat intestines, in the past even from horse, mule or donkey intestines.

Otherwise it could be from the word kitgut or kitstring. Kit meant fiddle, not kitten.

I'm not saying this is the case for you, but it was for me. I tried to read everything I could about making guitars on the two forums I visit. Really, I just couldn't keep up and some of what I read I didn't understand fully because I wasn't there yet. I found that I gravitated to threads that dealt with things I was ready to absorb. For me, this was more about how to assemble a guitar, how to prepare parts, tools to use and or make. It wasn't until I got a bit of a handle on this that I was able to absorb the other conversations about things like geometry. They were there, I just wasn't seeing them, or maybe not digging into them.

I'm kind of there with the various methods of "tuning the top and back." I know it is being discussed, I just don't fully understand the methods and how they are applied. Eventually it will start to gel for me as I get to a point where I am able to take that step. I'm getting better tone now than before but don't yet have the control I'd like. . .

It was the same with geometry. My very first instrument needed a fair bit of effort to be made playable because I didn't understand what I needed to when I was making it. But that served as a good example to help me understand what I need to know.

_________________
Bryan Bear PMoMC

Take care of your feet, and your feet will take care of you.

Depending on the mobility of the top it can pull up between ~0.5mm to ~1.0mm. And yes, it is something to allow for if you want precision and there are a number of ways of doing this.


On one forum, after a search, I found ~ 90 pages on neck angle stuff. You'll likely find a similar number on this forum. It is one of the areas of building that is least understood and causes the most confusion. The main reason for this is that the majority of texts are just plain wrong, where the authors themselves don't have a clear handle on how it all works. The web is similarly confusing, with good and bad stuff, but a novice would have a great deal of difficulty picking between the two. There is, of course, more than one way to get the right outcome. However, the almost certain outcome of mixing methods is that the outcome will be wrong.

Classical guitars are another problem, because to get the right string height above the soundboard and the right action at the 12th fret the neck has to be tilted forward, not back. There are numerous ways to get this right, but many more ways of getting it wrong.

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Trevor Gore, Luthier. Australian hand made acoustic guitars, classical guitars; custom guitar design and build; guitar design instruction.

http://www.goreguitars.com.au