Mailbox Blower

Discussion in 'Props' started by Waterwings, Jan 26, 2018.

  1. Waterwings
    Joined: Apr 2015
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    Location: South Africa

    Waterwings Junior Member

    Good Day All
    I would like to use the boat's propeller to deflect thrust downward to remove sandy overburden. Any advice regarding propeller pitch in relation to diameter and horsepower would be much appreciated
     
  2. jorgepease
    Joined: Feb 2012
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    Location: Florida

    jorgepease Senior Member

    might be better off using it to create a vacuum so you can deposit the sand elsewhere instead of just making a big sand cloud
     
  3. Waterwings
    Joined: Apr 2015
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    Location: South Africa

    Waterwings Junior Member

    Thank you for your response. We move large volumes of sand very effectively, but have severe cavitation issues. This leads me to think our prop choice is not entirely correct. Details are 450 hp swinging a 46 x 46" prop at 1500 rpm with a 1:1 gearbox ratio. Check out this video:
     
  4. johneck
    Joined: Nov 2011
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    Location: New England

    johneck Senior Member

    Those numbers don't seem reasonable. Are you sure about the RPM?
     
  5. Waterwings
    Joined: Apr 2015
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    Waterwings Junior Member

    Very. We do this every day
     
  6. johneck
    Joined: Nov 2011
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    Location: New England

    johneck Senior Member

    So it appears that the prop is inside a pipe with the edges just sticking out. An issue may be the way the flow enters the pipe. A bell mouth and putting the prop fully into the pipe could help.

    However, even if that change makes this better, the tip speed for this prop is over 300 ft/s. 150 ft/sec would be high.
     
  7. Waterwings
    Joined: Apr 2015
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    Waterwings Junior Member

    Another video blowing at 1500 rpm
     

  8. jorgepease
    Joined: Feb 2012
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    Location: Florida

    jorgepease Senior Member

    take a pick, it's either too much speed or too much pitch
     
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