I had been wandering around the internet and found a number of interesting sites on the Golden mean ratio, a non repeating possibly infinite decimal like Pi, that is found both used in art as a design parameter and in nature as the relationship in natural fractals. 

I thought that possibly using this ratio could help produce a superior instrument. 

I used the largest diameter I could turn on my lathe, 11 inches, as a base measure. I made the bowl depth also 11 inches in the hope that might help produce standing waves, which might increase the acoustic signal. I divided the head diameter by the 1.618 as a manageable part of the ratio to obtain the port diameter, and multiplied by that to obtain the port length. I tapered the port so that it would end at the 11 inch diameter of the head, with a small horn flare to increase signal dispersion. 

It seems to work well. 

Each iteration brings fine tuning to the design, I regularly search out materials and hardware that could be useful. 

These so far have been made in fiberglass. I am planning to try one soon in carbon fiber.