New Propeller Design

Discussion in 'Propulsion' started by Barry, Apr 2, 2020.

  1. Barry
    Joined: Mar 2002
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    Barry Senior Member

  2. gonzo
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    gonzo Senior Member

    Interesting. I would like to see independent testing though. It does not explain how there is less wear and tear on engine systems.
     
  3. Mr Efficiency
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    Mr Efficiency Senior Member

    Hard to get a grasp of the geometry of it, but direct comparison testing with existing designs is the acid test. Other than that, I got a migraine looking at it.
     
  4. bajansailor
    Joined: Oct 2007
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    bajansailor Marine Surveyor

    The Boattest.com lads tested three Sharrow propellers and wrote a long report about them here -
    Sharrow Engineering Propeller https://www.boattest.com/Sharrow-Engineering-Propeller

    Here is a copy of their summary :

    After our testing and driving the boat with all three props, our conclusion is the following. The Sharrow Propeller™—

    1. Performs significantly better at idle.

    2. Plans at a lower RPM

    3. Is faster at all RPM settings

    4. Gets significantly more mpg at 3000 and 3500 RPM

    5. Is more fuel efficiency at every speed-through-water setting

    6. Is as much as 18% more fuel-efficient at 26-28 MPH

    7. Produces the highest top speed

    8. Creates noticeably less vibration

    9. Is generally quieter

    10. Has superior handling in tight turns at high-speed

    11. Improves handling in reverse

    12. Provides the greatest range at all speeds
     
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  5. jehardiman
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    jehardiman Senior Member

    What they have done is split the blade area between two foils, slightly staggered. My money says that the trailing one is slightly up pitched. However, linking the two blades at the tip, cannot improve efficiency...UNLESS...you compare it to something that is not the same. Because propeller efficiency is measured by thrust to torque, they could be playing with BAR to reduce Tq, especially if the trailing blade is pitched up to account for swirl. Anyway, it is not hard to make a prop with a blade shape that will be 10-15% better that a B series considering the latest design work on them was just post-war for full bodied ships.
     
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  6. Mr Efficiency
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    Mr Efficiency Senior Member

    Thanks to bajansailor for those tests, which do look very promising, especially mpg figures, the rest isn't as important as that. Could prove to be a real innovation, for some reason I had a vision of a foreign object getting jammed in the apertures, which might be a problem if access is difficult.
     

  7. Barry
    Joined: Mar 2002
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    Barry Senior Member

    A significant problem. When we purchased our first Volvo Stern drive boat with counter rotating duo props, a friend who had pretty much the same drives and chartered a bit so he was on the water several hundred hours a year stated that
    he kept an extra set around because if you hit even a small log, the counter rotating props would not shed the small diameter log and often caused horrific damage to the props. An element of a small log not being able to be pushed clear of the
    prop.
     
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