Acoustic Guitar Construction

So as a thought experiment, I will assume CF rods keep the bock from rotating holding the neck.

Let remove all of the braces and think about what will happen under load. I contend that the front of the bridge will dive and the back of the bridge will rise. It will roll in effect. So we need to brace the top so that the bridge will rotate no more than 2 degrees or so, at least starting out.

Now your two almost vertical upper braces come to a point in the center of the bridge. With regards to preventing the bridge from rolling we can think about those two braces as 1 brace down the center line. At that angle each brace provides maybe .7 of the vertical strength of the braces so those 2 braces for the purposes of supporting the bridge are equivalent of a single brace down the center maybe about 20% taller.

Assuming that you have you can fully couple the load to the bridge plate, combining with the lower vertical brace which is coupled to the bridge and bridge plate you can have braces strong enough to prevent the roll if the load was even side to side. But given bass strings are on one side and treble strings on the other your bridge is going to want to roll on a diagonal because the upper braces support only goes to the center of the bridge.

If you follow a Kasha design, besides creating a space for each of the frequency ranges it makes sure the braces are structurally balanced vs the string loads. The idea was using engineering to just balance the forces.

When doing an X-Brace guitar one makes sure that the X braces cross the outside ends of the bridge to provide both vertical and lateral support. Moving a x-brace design from 12 fret to 14 fret care is taken to maintain the bridge to X-brace relationship. I just modified a 12 fret ukulele design to a 14 fret ukulele moving the bridge up. It is a fan based design so besides moving the sound hole up a bit, I moved the outside fan braces out to keep them on the edges of the bridge.

This one stumps me. I have not seen a design where the bridge is placed at what appears to be a single point convergence of the main braces (there are some secondary braces that focus on the ends of the bridge).

Tentatively, I'd say the bridge is very free to move. But that is not necessarily desirable. The point of bracing, conventionally speaking, is to control how the top responds. This appears to relinquish a lot of control, leaving the bridge to do what it may.

Sometimes I think we are seeking a Holy Grail of brace design that is currently unknown and that will take the acoustic guitar to some "next level" or "beyond" what we have now, yet keeping it squarely as an acoustic guitar. I am not sure this exists. The X, fan, and ladder brace schemes (with their variants) may be all that is necessary to produce what the acoustic can produce and still be heard as an acoustic guitar.

Even Fred Carlson, the creator of new, unique instruments, does not stray far from conventional bracing. His success in seeking something "beyond" what we have now is legendary. But basically, he simply adapts a combination of traditional approaches to his free formed, extremely complicated sound boards. (He often cuts tops from redwood stumps on his property.) What he gets no longer sounds like a guitar, nor is there much music written for it, nor are there many who can play it even minimally well. "Far out" is not always what it is cracked up to be - though he is obviously having a great time with what he does. Music is played around 6:30.

"he is obviously having a great time with what he does"


Lucky is the man of which that can be said...

Sounds more like a cacophony starts at 6:30. For instrument from someone who probably has too much time on his hands. He does seem to enjoy it!

He also builds some kick-ass harp guitars and simpitars played by some good musicians, including a 39 string model played by someone named Alex DeGrassi.
And a sweet double-neck Classical guitar recorded by Todd Green.
http://www.toddgreen.com/audio-todd-green-music.asp

The instrument in the previous Calson video is a simpitar version of a harp guitar plus a lot of embellishments. But John P has a point. When one ventures that far outside of tradition, getting to really great music is not guaranteed. This is GREENSLEEVES played by Alex De Grassi on a less divergent instrument that lacks some of the features found in the Carlson video version (Carlson appears committed, these days, to making every build into a unique instrument). The sound is hardly "bad", and represents pretty much the best there is for these singular instruments, but does not get as far for my ear as the greats who play "normal" guitar. It does excel in the "interesting" department. And I give a lot of credit for the fact writing for and playing such an instrument is akin to re-inventing the wheel if you are designing cars.

My bias is that the creativity that stands on the shoulders of giants is the creativity that moves the ball the furthest down the road. The lone wolf does not get as far.

Hide(glue)-bound traditionalists!!:-)

It takes all kinds, I suppose. I like the fresh breeze from the land of innovation just as well as I do the beauty of a good traditional instrument.
And I do appreciate great failures - someone who has a reasoned and reasonable idea, who wants to make some sort of contribution beyond the carpentry - who goes for it and falls on his face. I admire that person.
And I do appreciate copy cats as well - who faithfully attempt to hone their skills on tried and true models, and are successful.

Live and let live, I say.

(Reminds me a bit of the joke about the philosophy instructor who got fired for falsifying the results of a thought experiment.)