Here's an online Java calculator.
http://www.mh-aerotools.de/airfoils/javapipe_en.htm

This might also be of interest. Download helmholtz.exe
http://home.wanadoo.nl/pereivers/Goodies.html

Personally, I am not inclined to spend the time and money to try and research the right resins, methods, shapes etc. I get little flying time as it is.

I will be using the carbon pipe from [link=http://www.escomposites.com/]ES Composites[/link] for a ZDZ 40 and will be getting one for 50cc also.

For larger engines I am using the KS full length tuned pipes. Excellent performance and the 1080 pipe is almost the same weight as the shorter cannister setups, but more power.