Fin under boat

Discussion in 'Powerboats' started by valkon, May 31, 2011.

  1. valkon
    Joined: May 2011
    Posts: 1
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    Location: holland

    valkon New Member

    Hi guys

    New here!
    i have a question...i was thinking about putting some fins under my 20ft maxum
    like the fins undeer a ski boat,hoping this would help me go in a straight line at slow speeds.

    under the keel in a straght line

    but i am worried than a hi speed turn would flip over the boat....what would you think:confused:

    thanks Valkon
  2. PAR
    Joined: Nov 2003
    Posts: 19,133
    Likes: 474, Points: 93, Legacy Rep: 3967
    Location: Eustis, FL

    PAR Yacht Designer/Builder

    Yes a skeg or fin if you will, is going to help your tracking, particularity at low speeds, though at low speeds it needs to be a fairly large appendage. This is the rub, at high speed you want as small an appendage as you can live with, but at low speed the reverse is true.

    In the end, you have to decide what you really need. If you spend a large percentage of your time at low speed, then a big skeg will help straight things out (literally), though you'll have additional drag and disturbance at high speed. A skeg will not make your boat flip over. A lot depends on you boat (it's shape), but generally boats that flip over in turns, dig in their chine(s) and started skidding sideways first, which you can feel. If you ignore this and slam down the the throttle or have attempted to execute a very sharp turn at way too high a speed, then yep, you sure as hell can "trip" over the chine and roll the boat. In reality, once the chine digs in, the out drive or outboard starts to ventilate as the boat starts hopping over the new wake it's creating with it's chine and slows down, which prevents the roll over. In extreme conditions or if the skipper has no brained himself into a hole, she'll flip, but the vast majority of the time the boat just skids, hops and pounds hard sideways, then falls into the hole it's generated with a dramatic lose of speed.

    In short, no a skeg or fin will not trip your boat in turns and yes, it will help both low and high speed straight line tracking.
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