On area on a model, let me explain again. I am measuring T Q n and shift speed V. So, this will give me K T equal to T by rho n square D 4 which I know K Q is equal to Q by rho n square D 5 which I know Q I have measured. Then I know K T and K Q. I know my propeller diagram, open water diagram. If I assume that the propeller is generating the same thrust and torque as in open water at the same r p m and speed, then I can enter the K T chart and get the J. This J is V A by n D.