Bold claim for new propellors

Discussion in 'Outboards' started by Mr Efficiency, Nov 7, 2013.

  1. Mr Efficiency
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    Mr Efficiency Senior Member

  2. michael pierzga
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    michael pierzga Senior Member

    I guess the propellor is designed to be efficient at a certain speed...power output of the engine.

    One problem with all props is that they must be one size fits all ..good at low and high speed.

    I dont know much about props but I thought that a lightweight alloy prop was always more energy efficient than a heavyweight stainless prop.
     
  3. DCockey
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    DCockey Senior Member

    Prop efficiency depends on shape, not mass. Prop material only makes a difference if the material drives the shape, or if the material is sufficiently elastic so that the prop distorts a significant amount when under load.

    The other difference prop material would make is how fast the engine accelerates due to differences in inertia of the prop.
     
  4. DCockey
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    DCockey Senior Member

    From the link in the first post:
    The Mercury Enertia ECO was specifically designed for high-horsepower outboard-powered boats, offering boaters a 10 percent increase in fuel economy at cruising speeds while also living up to the performance and reliability standards inherent with all Mercury propellers.

    Relevant questions are "a 10 percent increase in fuel economy at cruising speeds" compared to what other props, and what is the relevant performance at other than "cruising speeds".
     
  5. DCockey
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    DCockey Senior Member

    From the same new release:
    To maximize the fuel economy improvement provided by the Enertia ECO, Mercury Marine engineers designed a new propeller with a broad 16-inch diameter, large blade area and a high progressive rake, a combination made possible only through using Mercury‚Äôs proprietary X7 stainless steel alloy. While the Enertia ECO design results in reduced hull drag through increased bow lift at cruising speeds, it still matches the performance of other Mercury propellers such as the Enertia and Revolution 4. (emphasis added)​

    How does propeller shape affect bow lift? What would be the effect on fuel economy with a different prop of increasing the "bow lift" with motor trim?
     
  6. michael pierzga
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    michael pierzga Senior Member

    Sounds like mumbo jumbo marketing to me.

    The prop pulls the stern down and pushes the bow up ?

    How ?
     
  7. PAR
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    PAR Yacht Designer/Builder

    New advances in prop design are coming along, much because of optimized pressure distribution, but also the exacting tolerances of CNC machining. Most props previously have been essentially hand made, then tuned. Now, a prop can be tailored to specific applications. I recently had a custom prop done by Acme and after an exhaustive set a variables with their tech support, the new prop far exceeds the old Michigan wheel, formerly used on this race boat. Michael, this particulate prop was designed to keep the bow down, not up and could have been tailored to be neural or add some bow up, if desired. It gets real technical real quick, when describing the subtle features of these props, which in my case was fairly simple (max speed and acceleration for the given ratioed RPM and HP). You'll see more of this in coming years. As to the 10% gains, well maybe some marketing hype, but compared to a general purpose prop, I can easily see this level of improvement.
     
  8. powerabout
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    powerabout Senior Member

    there are bow lift props and transom lift ones
    Cleavers are generally transom lift and choppers are bow lift as are most props for recreational boats as they are all built safe so they need bow lift props
     
  9. michael pierzga
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    michael pierzga Senior Member

    For outboard motors ?
     
  10. powerabout
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    powerabout Senior Member

    yes outboard and sterndrives
     
  11. michael pierzga
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    michael pierzga Senior Member

    Hmm. Learn something new every day
     
  12. dinoa
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    dinoa Senior Member

    All else equal isn't a thinner foil section on a prop more efficient than a thick section?

    Dino
     
  13. TANSL
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    TANSL Senior Member

    I do not know much about propeller design. So abusing your kindness, please allow me to ask the following silly questions:
    - Does not have anything to do the direction of thrust of the propeller in relation to the position of the center of gravity of the float? (see attached picture)
    - Serves the power trim, in OB and Z-drive engines, to control the tilt of the ship, before the plan?
    - Could someone explain in simple terms the effect that makes that the propeller, by design, not by the position of its axis, raise or lower the bow.
    Thanks.
     

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  14. PAR
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    PAR Yacht Designer/Builder

    Simply put and typically using blade rake, with positive rake, the prop climbs the water column (clever/surface piercing style) which can pull the stern up or as more typically seen, with aft raked props, the blades tend to want to stay deeper (climb down) lifting the bow.
     

  15. TANSL
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    TANSL Senior Member

    I do not understand (do not worry) but, apparently, the vertical thrust exerted by the propeller is huge. Would not it be better to use the propeller to maximize the horizontal component of the thrust and lift / lower the bow with other procedures?
     
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