A fix prop torque???

Discussion in 'Powerboats' started by SKOPE, Dec 6, 2009.

  1. SKOPE
    Joined: Dec 2009
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    Location: New Zealand

    SKOPE New Member

    Hi I have built a inboard V-drive and are experiencing prop torque problems, As it is a ski/wakeboard boat one side of the wake is different to the other, not by much but enough to be noticeable. The boat seems to ride slightly higher on one side due to the torque of the prop.

    Any help appreciated.

    Cheers
     
  2. marshmat
    Joined: Apr 2005
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    Location: Ontario

    marshmat Senior Member

    Hi Skope,

    This 'problem' is inherent to all planing hulls with single inboards. It's just part of their nature- put a lot of power through a single high speed prop, and it will try to twist the boat around.

    The best solution I know of is the one used by Gar Wood and other runabout builders back in the days of classic wooden powerboats. The hull bottom would be a very slightly different shape on one side than the other- just enough asymmetry, figured out through much trial and error, to counteract the prop torque.

    On an existing boat, trim tabs would probably be the easiest solution.
     
  3. StianM
    Joined: May 2006
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    Location: Norway

    StianM Senior Member

    You mean because of the rotation of the prop?

    Trim flaps would solve it or use contra rotating props.
     
  4. apex1

    apex1 Guest

    How would he do that on a single V drive?
     
  5. SKOPE
    Joined: Dec 2009
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    Location: New Zealand

    SKOPE New Member

    What about a wedge on the trailing edge of the rudder on side that is "riding high?" None of the other inboard ski boats have two trim tabs.........
     
  6. Frosty

    Frosty Previous Member

    I am dying to know what that will do apart from send the boat in circles.

    I assume this is not a shallow V /nearly flat hull. The rear of purpose built ski boats are generally flat.
     
  7. SKOPE
    Joined: Dec 2009
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    Location: New Zealand

    SKOPE New Member



    Yes the deadrise is relatively flat, at 12 degrees

    Tried the wedge this morning and it works, its 6mm thick tapering 40mm and 100mm long, placed on the trailing edge of the rudder on the side that was riding high.

    Thankyou to those who offered helpful advice
     

  8. ls1boat
    Joined: Jan 2010
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    Location: melb

    ls1boat New Member

    hi mate this may help had same sort of proplem ive got a inboard sysndicate boat about 450hp at speed boat wanted to roll to one side and the front would try to dig in after talking to a lot of people found this does happen the proplem was and you could never see it but the skeg would twist and move a couple of mm we made a big steel plate bolted the skeg to it and it was bolted to the bearers with this modification boat picked up 10mph 1000rpm and now sits beutifly at 65mph with 2 skiers
     
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