You also need an accurate speed measurement and the gearratio to calculate the slip%.
I guess the mistake is in the gearratio ? check it by turning the flywheel and counting the prop-rotation.
the slip% is usually calculated on top speed. It's important to simultaneously measure top speed and rpm's. As I learned from someone who should know, the slip% usually varies from 5 to 15% and depends on different factors.
1. Water resistance of the hull on the water
2. Air resistance (aerodynamics)
3. Propeller height in reference to the hull bottom
4. With or without skier
5. (other factors : circumstances, prop type, fresh/salt water,...)
In order to reach the highest top speed, you must try to minimize the slip%.
Boatdesign is important, but also the pilot.
One pilot can reach higher top speeds because of his skill. He is able to trim the optimal angle. Too little trim is obviously not good, but also too much trim is not good because air resistance is increasing with too much bow lift...
Good luck with the calculation,
T.
Linear Mode
