We're not really sure where the initial idea came from. But we noticed that even typical "performance" boat propellers didn't seem to be that well designed. The design process used by the leading manufacturers seemed to be mostly trial-and-error, as well as a traditional "black-art" type design.
We started wondering how much of a performance increase there would be to have, by moving away from the experience / "black-art" based design process, to a more scientific method. Surely there must be many % of improvement available?
We decided to find out!
Having some knowledge of hydrofoil operation from our X-1 ground effect vehicle testing and rotational profile physics from doing some Sikorsky Challenge calculations, we had a good starting point to do some initial physics guesses. The biggest unknown was how much drag our test boat had, and hence how much reaction force would need to be produced by the propeller. The higher the reaction force for the blade area, the higher the slip. Slip means efficiency losses.
On the other side of the optimization curve we have blade drag. Larger then optimum blades produce more drag losses than what they reduce slip by.
So we needed to get values for the slip amount we where going to be running with our test boat flat out. We had no way of getting these values, so we where simply going to have to measure it, by testing different propellers.
We started designing our propeller dimensioning tool (basically just a fancy calc sheet), and from that designed the actual model with our SolidWorks CAD software. Once we had the model dimensions done we ordered in some billet aluminum raw material. While waiting for the raw material, we imported the CAD model into our PowerMILL CAM program to design the milling process, to actually manufacture the propeller.
Test results in future articles!