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Even though this is my 3rd I still have a mental block about using the radius dishes & in particular setting that angle for the neck. everything is square right now. I am wondering should I set it in my 25 ft. dish & scribe the sides to get a line & then take the bulk of it off with the block plane, and then dish the curve, then the flat in the upper bout....? The only video I've seen is the John Hall one about prepping the rims but still don't get it all. Are there any other videos out there?

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Mike McNerney

You could take it down in the dish or take off the bulk first with a plane, spokeshave, etc... taking some off first will reduce time driving the bus.

If you do drive the bus the whole way, make sure to do a few strokes then spin and do equal. Otherwise you might end up with an unintentional wedge body.

As far as flattening the upper bout, I’ve used Hesh’s tutorial from here on the last few and it works well. I haven’t tried that approach on a Uke yet. I will this summer during Uke building season.

Brad


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If by square, you mean unprofiled, then roughing the back of the rim down to profile with saw, knife, and plane will save you a lot of time. For the top of the rim - which we radius to 28' - there is no real advantage to much in the way of profiling, as material removal goes pretty fast.

Cumpiano has a good procedure for laying out the rough cut line:

1. Flush the neck and tail block to the top edge
2. Mark the tail block depth less 1/16" (for 15'/28' radii) and extend that line to the waist (this is the trimming line for the back of the lower bout)
3. Using a straightedge and square, mark the sides 2" below the waist (this will be on the back's lower bout trim line
4. Mark neck block depth less 1/16" and extend that line with a flexible ruler to the 2" below waist mark on the lower bout trim line
5. Trim the back edge of the rim to the constructed line
6. Sand in dish
7. Install linings and touch up radius

The alternative to wedging the upper bout of the top is to radius the rim at 28', brace in that 28' dish with X, tone bars, and fingers radiused to 28', and use a 60' upper transverse brace installed on a flat caul. While 12 fret-to-neck guitars may need to gently flatten the very middle of the extension area, but on 14 fret-to-neck, not so much.

We don't 'drive the bus'...a reciprocating motion with rim in mold and spreaders inserted is faster and results in as even a result...two Bessey clamps provide both additional weight and handles.

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For the times they are a changin'

- Bob Dylan

I dome the upper transverse brace and upper bout, rather than leaving them flat. This complicates neck setting, as you need to either taper the end of the fingerboard from underneath or use a filler wedge there to get everything to work right. I do feel the domed upper bout is more stable over time, though.

I also use a dish.
I’m not nearly as experienced as some here... but this is what I do.

—After the rims are glued to the blocks chalk the rims and sand w the dish. Make sure you remove all the chalk. The chalk in the waist area will be the last to go.

— when you get done flip the fish over to the FLAT side. Press at the top so that there is a gap at the lower bout and go back and forth to remove the radius in the upper area

— glue on the Kerfing and do the same thing again. Making sure to remove all the chalk.

— repeat the process of removing the radius in the upper area thus flattening it

—- personally I have been gluing in braces above the sound hole flat / not radiused.

You’ll still have a slight fall away at the finger board body intersection. Or you can flat sand that area even once you fit the neck and the body


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Thanks all. It's clear in my head, I will now proceed

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Mike McNerney

I don't know if I have read all the guitar making books out there but probably most of them and none of them really seem to address this issue well. It stumped me in the beginning as well.

I finally sat down one day and drafted out a model that works for me. I also arch the UTB as well as cant the top from the back of the sound hole to the neck block. That sets a 'ramp' so that the fretboard line goes right up to the bridge at the proper height. I think that's the idea behind using radius dishes but since I don't use them I could be wrong. But anyway if you leave the top rims flat all the way around then you will not have the right geometry. In that case you would need to make a wedge shim under the fretboard extension.

I did searches on the various guitar builders' forums once to see how big the neck angle issue was. Needless to say, there were 100's of pages of people having problems with neck angle. And you're right, most of the popular texts fudge around the issue or are just plain wrong. There are numerous different ways of getting it right and many more of getting it wrong, and mixing different ways of getting it right will almost certainly ensure that the outcome is wrong.

Probably the biggest single mistake is not thinking about the issue soon enough. If you only start to think about neck angle when you have the box in one hand and the neck in the other, it is way too late. Neck angle is a subject that permeates the whole building process, starting with the build methodology (dishes, go-bar decks, outside moulds, bolt-on necks, in my case), choosing your target string height over the sound board and target action, to making sure you hit those figures in a complementary way due to using a build process that is in control. So there is hope for those who like to learn from books! (Discussed on p 4-89 in Design and permeates from Chapter 1 (Chapter 1 is just the introduction!) throughout the Build book).

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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

"But anyway if you leave the top rims flat all the way around then you will not have the right geometry. "

Many guitars have been built with a flat rim and a flat top. It is the arching of the soundboard that throws off the line of the strings. The advantages of the arched soundboard (lighter weight , added stiffness) out weighed the ease of building with a flat board.

Ha! Funny. I just checked and my bookmark at the moment is at 4-80 as I slowly pick away at it. Skipping ahead I do see a well detailed explanation of neck angle. I think what most of us do at first is start the building process on page one and then when you get to the neck part you are left scratching your head. So yeah you need to be thinking about it early and often.