Electric Surface Drive

[justinDesign]

Has anyone ever seen or heard of an electric surface drive? Would one be able to achieve slow speeds with an electric surface drive say with the equivalent power of a trolling motor, would it be real noisy.

I am contemplating such an idea for my thesis project and would appreciate some opinions or any possible information. The vessel I am creating is about 14 feet, and for inland fishing of low water areas.

It has also been suggested to me to us paddle wheels for slow speed electric propulsion. How noisy is this? How efficient would it be? Is there a certain shape to the paddles that would serve me better than other?(I desire both forward and reverse) Any examples of small craft like this would be appreciated.

Please post any links or pics if you have them.

Thanks
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[Guest625101138]

Surface drives enjoy an advantage in high speed applications where appendage drag for a conventional prop is substantial. Typically speeds over 40kts.

The surface prop works as a pump impeller rather than a foil. There is no Coanda effect so only the back face has pressure. The fact that the blades are passing in and out of the surface means there is a good degree of splashing and some noise compared with a fully submerged prop. I have made a surface prop but it was based on a foil and not very efficient. I have not studied the physics of these props as there is not much published and they are not as efficient as a submerged prop.

If draft is a real issue then you could make an enclosed jet that would be slightly more efficient and quieter than the surface prop. Google Hamilton jet.

An optimised submerged prop for a trolling motor can achieve efficiencies around 85%. The surface drive and jet are probably more like 50 to 60%. Modern paddlewheels with articulated blades sized correctly should also get around 85%.

The paddlewheel will have a little more noise associated with the splashing.

I have attached a screen dump from JavaProp to give you an idea of what is possible with a high aspect submerged prop. You can see this would need a lot of water to operate in. I have only guessed at what the design speed might be. Google JavaProp to find the Applet. I can help in setting values if you want.

For the paddlewheel you need thin blades that enter and leave the water cleanly. This means the blades need to be articulated on the main spider and this is usually achieved using an ecentric spider connected to articulating levers on the blades. There are samples around like this one:
http://www.youtube.com/watch?v=lcHISHYeEjc

The first step in any of the propulsion designs is to determine the drag versus speed for the hull and decide on what power you intend to use. I am thinking blades about 12" wide and 4" deep would be in the right order. I have attached a picture of a pedal paddlewheel to give an idea of size.

Rick W.

[Frosty]

A surface prop can work at slow speeds, as slow as you want . Up till now people think that they are for going fast. Thats because thats simply all they have been used for.