How Does Propeller Size and Placement Affect Water Surface Speed?

[ahawes]

Water Propeller -- General physics questions

Howdy,

I have been following the boat bike concept for a few days and am interested in finding out more on how to get better water surface speed. The props on these bikes look small and the specs are touting no more than 10 km/h.

Can anyone point me in the right direction on where to get general information on boat props, screws, etc. How is the best performance obtained re: placement of the prop or screw in the water? Half in/ half out? Size of the prop in camber and diameter, pitch, etc? I am a pilot and understand a little on how to get more bite out of the air, and am wondering how this translates to the water world.


Thanks for any tips, web sites or information --

-- Andy

 

[russ_watters]

The key difference between a propeller on a boat and one on a plane is the density of the working fluid. Since water is so dense, you don't need to push as much volume to move a boat as you need to push air to move a plane.

The propeller must be completely submerged, otherwise forces will be unbalanced.

 

[ravenprp]

Hi Andy,

That's a great question! The performance of a water propeller is influenced by a number of factors such as its size, shape, and placement in the water. Generally, the larger the propeller, the more thrust it can generate, but it also creates more drag. The shape of the propeller also plays a role - a propeller with a higher camber (curvature) can generate more lift and thus more thrust.

The placement of the propeller in the water is also important. Ideally, the propeller should be completely submerged in the water for maximum efficiency. Half in/half out placement can cause turbulence and reduce performance.

In terms of size, the diameter and pitch of the propeller are important considerations. The diameter refers to the distance across the propeller blades, while the pitch refers to the distance the propeller would move forward in one revolution. Generally, a larger diameter and a lower pitch can provide more thrust, but this can vary depending on the specific design and application.

To get more specific information on boat props and screws, I would recommend researching marine engineering or hydrodynamics. There are also many online resources and forums dedicated to boat and propeller design that could provide more in-depth information.

I hope this helps and good luck with your project!