Wing (foil) Length v Width

Discussion in 'Hydrodynamics and Aerodynamics' started by BobBill, May 13, 2012.

  1. BobBill
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    BobBill Senior Member

    I believe I know the answer but,


    Long narrow hull...say 20 loa, .4 meter beam center bottom...with long narrow wings, or simply wider bottom...say about .4 meters, to lift hull?

    Or, slightly beamier hull with added foam hull/glass bottom, to form softer chines and V bottom? I use the idea that if it does not contribute to lift, it drags.

    As most know, I have no clue...but these ideas keep coming up whilst I fiddle with altering Malibu Outrigger hull...

    I wish to add slightly more beam and maybe get more of hull out of water...more free board, but not detract from VMG, generally.

    Whacked project, but keeps me thinking.
     
  2. philSweet
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    philSweet Senior Member

    True enough, but if it lifts, it necessarily drags even more.
     
  3. BobBill
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    BobBill Senior Member

    Really? Oh my...I was hoping less hull in water translated into at least a tradeoff of sorts. Looking for means to build this hull with wider bottom and lift it enough to lower plane speed??? Remember, I am clueless with this stuff. Thought the longer "foil" might offer some lift, maybe even reduce drag...etc.
     
  4. Doug Lord
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    Doug Lord Flight Ready

    Lift

    Come on, BB- vertical lift thru planing and/or lifting hydrofoils is used on many, many sailboats from the Laser to Banque Populaire V. It is a major element in the design of performance sailboats whether small or large, multi or mono.
    You need a more specific question to get the answer you want.
     
  5. BobBill
    Joined: Oct 2009
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    BobBill Senior Member

    Well, I had in mind, as long as the bottom is tacked on last, to make it wider than the hull beam from near bow to stern, but then I thought, why not just make the hull beamier?

    I am looking to make cockpit area larger, but still beachable and trailable...and swift outrigger type.

    Of course, I could snap up old say Windmill hull and fool with with, but too short and not deep enough...just checking. Like I wrote, Doug, I am oblivious.
     
  6. Doug Lord
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    Doug Lord Flight Ready

    BB, if you want a planing boat, there is a lot of research you can do:
    1) Sail area & weight & bottom area
    a. look at other proven planing boats like the Windmill, Laser, 49er(capable of upwind planing)-get actual measurements.
    b. rule of thumb: 500sq.ft. sail area per long ton required to plane.
    --
    2) Foil assist-
    a. gave you Tom Speers rule of thumb in previous thread which shows how big the foil has to be to have a positive L/D ratio for any particular application: rule of thumb-foils must reduce boat wetted surface by 4 times their planform area. See other thread for how to calculate this using Lb's per inch immersion.
    b. Sail area-same as for planing boat.
    -----------
    This stuff gets you in the ball park but is no substitute for careful design....

    my Windmill, singlehanded-
     

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  7. BobBill
    Joined: Oct 2009
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    BobBill Senior Member

    Was looking at Windmill, and Speer's material...even thought of using Windmill hull and adding outrigger (I know, sounds crazed, but was a thought) so maybe simple MO with a bit wider beam will do it...with 300 sq ft sail area.
     
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