Quote:
Originally Posted by CabinetMan
Redir, So I'm gonna go with a flat sound board. Since I have a good fit between the neck block and the neck tenon, I "ASSUME" that my neck angle will be correct? Correct?
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Great job on bending the sides, reason I asked is because they fit so perfectly in your mold.
No I would definitely not assume the neck angle will be correct. The goal is to have the string height 1/2in over the sound board at the bridge. So if you have a bridge that is 3/8th inch thick and a saddle that protrudes 1/8th inch then you have a perfect neck angle.
I'll show a picture rather than try and explain how I do 'flat' tops. If it's dead flat then you would have to have a thick fretboard to make that target goal string height at the bridge so there are a few ways you can accomplish that, one is below which uses an arched UTB and a canted (bent) top from the top of the soundhole forward (basically the end of the fretboard). The other way is to set the neck angle so that you get the right string height and then fill in any airspace under the fretboard extension with a wedge shaped shim.
This is my workboard, there is a shim made from balsa that is wedge shaped. I can't remember the exact thickness (I did the math a long time ago) but I think it goes from 1/8in at the head block to zero. That sets the proper angle.
And then also I arch the UTB. So between the arch and the canted top it essentially creates a ramp so that the line drawn from the nut to the end of the fretboard will continue till it just hits the top of the bridge. THen when you add frets and about a 1/8th inch saddle you get the proper string height.
Neck body geometry is something that gets very confusing. It took me a long time to figure out something that works for my method of building, which is the old schools style of using open workboards. You could also look into using radius dishes and how that geometry works as well. But it looks like you are building in a similar style and since you are building true flat you will have to work out something.
The shim method is perfectly acceptable and probably even easier really. Again all you need to do is get that angle right then just fill in the air space. The goal is to have a nice straight line from nut to bridge. IF you jsut tack down the fretboard extension then you will get too much fall away (another geometry concept) and a neck body joint hump.