Surface Drive Prop Bollard Thrust?

Has anyone got any knowledge regarding the bollard thrust performance of surface drive props? How do they compare with conventional props? We are talking 250 – 400 BHP and 2000 rpm. Max speed 7 knots. It will have depth control.

Thanks

Michael C

Floatainer Systems

 

Thank goodness you will have depth control,without it you would be in trouble somewhere sometime. Why are you concerned about bollard thrust do you intend trawling?. Surface propulsion is usualy suitable for faster lighter craft to improve speed with less drag features.

 

A barge tug in very shallow water. It could be down to 1 m in places. I think we will go with conventional with depth control. Just not sure how much thrust we will get when the prop is up behind the transom. But we have another idea. Checking it out now.

M

 

Surface Drive Bollard Thrust.

I am used to thinking 10 inches of water as shallow and I have done a lot of boating in those depths. With the drive lifted up so that half of the prop was in the water below the hull. The boat had a 4 inch draught and 6 inch deadrise. To get good thrust in such depths you would need a large diameter prop or high speed shaft (4000 RPM). A propeller opperating close to the surface is not working in dense water as it would be say two feet down in a deep V hull. My drive could be used as a Surface Drive or as a conventional Sub-Surface Drive.

 

The advantage of surface propellers is that the blades can be loaded higher than on the conventional type without concerns about cavitation.

 

Won't work

If you are wanting to use a surface drive with slow speed applications, the prop efficiency at 7 knots is negligible. They simply do not work well with those applications.The bollard pull on surface piercing propellers is not good (This is not what they are designed for)

Understand wanting to use our drive or an Arneson drive for the low draft. Unfortunately, using a conventional propeller with a trimmable drive is not a good solution and will make things worse. You will have cavitation issues and be replacing propellers constantly.

Send me a note with your details and I can ask our office to propose a solution for this application using a conventional propeller.

 

Surface Drive Prop Bollard Thrust

www.youtube.com/watch?v=3x_mBpkW2io

 

Any propeller can be used in Surface Piercing Mode. The concept was recognised long ago in racing using the then popular propellers. They may have now been refined and may be more efficient for just Surface Propulsion.