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Thread: propellers with leading edge roll/cup ?

  1. #11
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    For what its worth.... I had a 32 foot cruiser w/ twin inboards (Mopar 360s). Port prop was a 16 x 16 with minimal cup. Starboard prop (a replacement after an ooops!) was a 16 x 15. so I took it to a prop shop to get an inch of pitch added. "No can do," the man told me, but he hammered a heavy cup on the three blades.

    Both engines ran identically, with rpm and hole shot similar--I did extensive testing. So 16 x 16 mild cup equals 16 x 15 heavy cup.

    Jeff
    "We live at the bottom of an ocean of air." - General Marvage Slatington

  2. #12
    Team Member zul8tr's Avatar
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    Quote Originally Posted by Fastjeff57 View Post
    For what its worth.... I had a 32 foot cruiser w/ twin inboards (Mopar 360s). Port prop was a 16 x 16 with minimal cup. Starboard prop (a replacement after an ooops!) was a 16 x 15. so I took it to a prop shop to get an inch of pitch added. "No can do," the man told me, but he hammered a heavy cup on the three blades.

    Both engines ran identically, with rpm and hole shot similar--I did extensive testing. So 16 x 16 mild cup equals 16 x 15 heavy cup.

    Jeff
    He cupped the trailing edge I assume. The discussion is on lead edge cup.
    " Three may keep a secret if two of them are dead" Ben Franklin
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  3. #13
    Team Member zul8tr's Avatar
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    Quote Originally Posted by rumleyfips View Post
    Google " Face Cup Boat Racing Facts" .
    Tried it as you show it - nada!

    How about you find it and post it?
    " Three may keep a secret if two of them are dead" Ben Franklin
    " ------- well Doctor what have we got a Republic or Monarchy? A Republic he replies if you can keep it"
    Benjamin Franklin, 1787 Constitutional Convention, as recorded by signer James McHenry's in his diary at the Library of Congress

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  4. #14
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    Correct. Should have noted that.

    Jeff
    "We live at the bottom of an ocean of air." - General Marvage Slatington

  5. #15
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    Just tried it and it works for me. You have to use Google, the BRF search is poor. I can email it to you if I get your address.

  6. #16
    Team Member zul8tr's Avatar
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    Quote Originally Posted by rumleyfips View Post
    Just tried it and it works for me. You have to use Google, the BRF search is poor. I can email it to you if I get your address.
    Found it with Google Chrome straight Google was a nada

    http://www.boatracingfacts.com/forum...15002-Face-cup

    He discusses exactly what I posted from his web page leading cup or face cup are not correct. He speaks to adjusting leading blade angle for correct entry angle of attack into the water for low drag and great acceleration and top end.
    " Three may keep a secret if two of them are dead" Ben Franklin
    " ------- well Doctor what have we got a Republic or Monarchy? A Republic he replies if you can keep it"
    Benjamin Franklin, 1787 Constitutional Convention, as recorded by signer James McHenry's in his diary at the Library of Congress

    Location: SW Orlando, Fl

  7. #17
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    Sorry. I was using Chrome . I didn't know it would make a difference.

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    I got a 11.25x18 thru-hub semi-cleaver from Ron that has cupping inwards on the leading edge, only for the last 1/3 of the leading edge before the tip. My initial thoughts were that it didn't look right and that a cavity would be created as it cut through the water. I did hear from a prop lab, when I described it to them, that it does maybe create more "grip". I don't have enough experience to know what that would feel like compared to the same prop without the leading edge cupped inward. Unfortunately haven't had much seat time to do real conclusive testing; only guessing and theorizing at this point...

  9. #19
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    iam thinking of going ahead and doing this to a prop.
    I have to test the prop first as it has already had a good few mods that I want to see the results of.
    one I do the test of mods I will then go ahead and put a leading edge cup/roll on the blades.

    what I am thinking off is something like what I have in this pic, the red line would roughly be the cupped area.

    the prop I will use for experiment is not this one, I will try that on a 13x17 sst.
    Attached Images Attached Images  

  10. #20
    Team Member fs5's Avatar
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    So is this face cup the opposite of doing a Texas cut?
    I have a slt boat a good Texas cut prop runs real good . Rons face cup props drag there arse a bit out of the hole and top end. Trimmed the face cup off one and picked up 3 kph and better hole shot ??
    If you got the dollars just buy a genuine merc clever can't beat them .

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