Acoustic Guitar Construction

Hi all,

I'm not even done with my current build and I'm already drooling over the possibility of a "fifth guitar" (a classical tuned a fifth lower than standard tuning) for playing the Bach cello suites.

Otto Vowinkel builds and sells one on his page. His specs list a scale of 720 mm - at 70 mm longer than a standard 650mm scale, the additional fifth cannot be accounted for simply by the longer scale (that is, adding 7 frets "past the headstock" to tune down a fifth would require more than 7 centimeters). So I'm guessing he has to use a heavier gauge of string to get the lower frequencies as well.

So what might I want to pay attention to, beyond just enlarging the plans for a classical body (length, width, depth). Does the larger surface area suggest a thicker than typical top plate to retain similar stiffness overall?

Thanks in advance,

Larry

Yeah Larry, you're right about the thicker strings. I for me like a bit thinner strings with a bit lesser tension more comfortable (and better sounding) than real thick ones. But you could try that for yourself later on.

And yes , in theory a larger plate needs a bit more beef to stay stiff. But depending on the bracing as well. But in real life I think we are talking about a few tenths of a millimeter.

A 'normal' classical guitar size won't do, 'cause the bridge would be on an undesired place. 35 millimeter down from the sweet spot.
If you don't have a plan, I would start drawing the neck/bodyedge, the bridgeposition and the nut. I take one yard of wallpaper for that.
From there you can draw the rest of the guitar. Enlarging a "normal" shape is an option. But most of the steelstring makers just take a Jumbo or Dread-size. A real huge guitar is not directly comfortable and can get boomy when sound is involved.

Here you can find the baritone I made and its specs:
Baritone

I'd take a look at one of the on line string tension calculators -- figure the average tension for a standard classical then do the math for what you are proposing -- Then make the bracing heavier by the same ratio of tension increase. Actually this is something i discussed with Tom Rebbeke years ago when I was designing a nylon 12 string crossover.