Nylon string archtop jazz guitar

[Brian Evans]

In the context of a carved top guitar designed for classical technique and nylon strings, I am wondering about the bridge/tailpiece. I am wondering if putting a traditional bridge on an archtop (glued to top, strings tied to bridge, string height off the top closer to what a traditional classical guitar would have, so less neck angle) would drive the top better than a floating bridge with tailpiece, which is what Benedetto did on his nylon string archtop. I am planning a fairly thin top carved to around .150", with recurve carved thinner, and about a .75" arch, and fan bracing to try to engage as much of the top as possible. Any ideas?

[Randolph Rhett]

There was a post, I think by Alan Carruth, on the vastly different physics of the pinned bridge vs the floating bridge. Someone wanted to do the opposite of you by building a flat top with a tail piece and floating bridge. Suffice it to say that my takeaway was that they are so different that "converting" one form to the other requires such radically different bracing/carving so as to be a complete journey into the unknown.

I think that unless you are prepared to build several experimental guitars to see if you can find a bracing pattern and arch carve that works for what you had in mind, you probably should stick to a tailpiece/floating bridge. I built over a half dozen bodies I couldn't use when I was experimenting with building my arch tops with carbon fiber soundboards. Chances of stumbling on a design on the first try for something radical is slim.

OTOH it was a freeing and fun process (even if it hurt in the wallet). Maybe you will come up with something you really love.

[Brian Evans]

I think I will pretty much follow the Benedetto pattern, his bracing and bridge/tailpiece is well documented. I am thinking Alaska Cedar for the top, some random hardwood for the back/sides. Probably mahogany that I can buy locally.

Brian

[Beate Ritzert]

There is (among a few others) a German luthier who realized such a guitar (Stefan Hahl). From what i saw on his website he uses a lightweight Maccaferi like bridge, and the top seems to be a bit thinner than usual.

Rob Benedetto / Damon Mailand also did a Nylon string archtop, and they mention fan bracing of the top.

The rest is the usual thrill in going new ways?

[Brian Evans]

I have some block against either repeating a thing I've done before, or building a mainstream anything. It goes back decades, to when I was building vintage race cars. I had to have a car no one else had. A cross-over classical archtop seems appropriate, and I am researching as much as possible so the links you've given me are appreciated. Here is an overview I posted on Acoustic guitar forum...

I am honing in on the design for my next project. For those who like and play cross-over guitars, I am planning this:

Archtop, fan-braced light build per Benedetto nylon string design.
Nylon string, floating bridge, wood tailpiece.
Top - fully carved Alaskan cedar.
Mahogany or other interesting hardwood back and sides, carved arch.
Neck - possibly cypress,, or mahogany.
1.9" or thereabouts nut width - advice appreciated.
Fretboard - 25.4" classical scale, around a 20" radius or flat - advice appreciated.
Some kind of high end piezio pickup in the saddle, Benedetto uses what I think I will probably use, but advice appreciated.

The guitar is intended to be highly jazz fingerstyle oriented, for performance and recording. The player uses both a Guild traditional steel string archtop and a high end classical guitar. This should merge and meld those ideals.

Ideas appreciated!

Brian

[Alan Carruth]

'Stop' bridges, such as the ones used on Classical or flat top guitars, and 'tailpiece' bridges, do work differently, but it doesn't make as vast a difference, as some folks think. Basically, in both cases, the main string force driving the top is the 'vertical' component of the transverse force of the string: the string moves 'up and down', and pulls the top up and down. The strings do change in tension twice per cycle, which pulls the top of the bridge toward the nut on a 'stop' bridge, but not on a 'tailpiece' one. This is a smaller force in general than the 'transverse' force, and is much less effective at driving the top or producing sound for a given amplitude, so it ends up being more a contributor of tone color than actual power. If the main driving force on arch tops really was the tension change signal, they would sound an octave higher then flat tops, and they don't.

Orville Gibson used a glued on pin bridge on his early arch top guitars. It strikes me as an odd choice when you're trying to ape the 'perfection' of the violin.

The tailpiece can be useful in tweaking the sound.I heard Jim D'Aqiusto say in a talk at a GAL convention that he could change the sound quite a lot with different tailpieces. For one thing, the tailpiece has it's own resonances, which can couple with the top and thereby with the air inside. The most important one has the tailpiece swinging up and down, and tuning it to work with the 'main air' resonance can make quite a change in the low-end function of the instrument. You can often hear this pitch simply by tapping on the tailpiece. Making it heavier, or moving the center of mass of the tailpiece so that it's more centered between the bridge and the pivot will drop the pitch. The shorter the back string length between the bridge saddle and the tailpiece the more tightly the tailpiece will be coupled with the top. There are probably other modes that come into play as well.

I found it a bit tricky to make a good archtop nylon string guitar, but I did get a couple of them to work well. The main issue was to get the top right, as usual. You can go pretty big with these: I had more luck with a 16" Smal JUmbo platform than with the 15" 12-fret 000 size, and I can't see any reason a 17" nylon archtop would not work well if you got a light enough piece of wood for the top. I used round holes on mine, as I was looking for a Classical sound. I also used X-bracing, but would probably go with 'parallel' next time.