Making Nozzles From PVC and Cement

This is how I make my nozzles.

First, you have to design your nozzles with the ideal KN for your motor. You can do this using Richard Nakka's SRM excel program or Burnsim, I use SRM more often now more than I do Burnsim.

My max KN for my G-185 motor is 209. The nozzle throat is 0.375 inches and the expansion ration is 5.76, which means the exit diameter is 0.9 inches.

Here is an illustration on how I do mine. I should mention that I use 1 washer for the throat as a study was done that shows that the shorter the throat Length/Diameter (L/D) ratio is, the more efficient the nozzle. 

The 12 degree is measured from the centerline of the nozzle towards the walls. So a total of 24 degrees if viewed as a cone.

When the nozzle is dry, simply make the throat as wide as the washer with a drill bit or whatever you choose. 

I never had a blowout with a properly made 1 inch nozzle. One thing that contributed to that is I allow the cement to dry for 1 week before use.