Acoustic Guitar Construction

I like the Rodrigues bracing. All of the Bracing patterns shown can make good classical guitars. My crossover necks are at least 48 mm. The 1 7/8" is maybe OK. I put a 20" radius on the nylon string neck instead of a 16". I play both finger style steel string with a 1 3/4" neck and I play classical with a 52 mm nut. I am not sure why but I find 48 mm tight on the nylon string.

Herman, you are right about the neck angle being different than a SS. 1/2" string height is a bit higher than the 10-11 mm that I would use. On a cross over not trying to sound like a classical it would be OK but the higher string height tends to create a louder initial sound that drains off quicker. Your 12.7 mm with 3 mm action is easy as you can use no neck angle. The string height ((3.175 *2) + 6 mm (fretboard) plus 1 mm fret = 13.35 mm. Once strung up this will be close to 1/2". I use a reverse neck angle to get the 10-11 mm string height at 4 mm action.

Thanks John, That was my thought too.
If you aim for a negative neck angle, how do you manage the upper area of the top?
All in the aim to have a flat transition on the neck/body area.
Take some wood from the underside of the fingerboard?
Herman

If you have a negative angle and a bolt on, I suggest the upper bout is not angled. Taking a bit off off the extension as you suggested is a fine way to do it. Alternatively you could go with no neck angle and taper the fretboard 1-2 mm nut to sound hole.

With a Spanish heel as the block is connected to the neck the top is naturally pulled in with the neck. Also the neck angle is set when the back is glued on after the top is glued to the rims. I have seen methods where you can bolt the neck on (or even set a dovetail) before the back is glued on. Glue on the back with the neck bolted on and forced to the correct angle. If you do this radius the back with it in the same position.

Wel John, that lokks like a hussle to me.
I think I go with a zero neck angle and adjust the fingerboard thickness, to get the proper
action. along with the 11-12 mm string height at the saddle.
Herman

Herman wrote: ↑Tue Mar 16, 2021 3:33 pm Wel John, that lokks like a hussle to me.
I think I go with a zero neck angle and adjust the fingerboard thickness, to get the proper
action. along with the 11-12 mm string height at the saddle.
Herman

Agreed, that is also a good way. When classical builders talk about the neck pitched 2 mm forward they are assuming a 4 mm action. Going to a 3 mm action almost gets you there with a normal fretboard thickness. I think you would end up with 11-12 mm instead of 10-11 mm. So a 5 mm or 5.5 mm thick fretboard could nail it.