Water Rocket Computer Model Help      
Rocket Coefficient of Drag

The rocket's coefficient of drag is a measure of how much
resisting force the air around it exerts on the rocket when
it travels through the air at speed. The higher the number,
the more drag and the more it will slow down. Best results
with an elliptical nose cone.

Typical values are:
Straight side=0.68
Tapered skirt=0.52
Tapered rear half=0.56
Full-length taper=0.35