Here provides Excell tables to calculate the curves of internal venturi nozzle. The internal venturi nozzle have the advantage that the turbine blades are placed at a maximum radius in the nozzle, which gives a lot more torque. Also the number of blades is much larger, although their height, in this example, 570 mm, not greater than 12 mm .. But it can be done with plywood modeling ..
http://www.new4stroke.com/Inner570mm.zip
Andrew
