Using Deep-V Hull As Displacement Boat

Discussion in 'Boat Design' started by MyMarineSurvey, Jun 30, 2008.

  1. MyMarineSurvey
    Joined: Jun 2008
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    Location: Utah

    MyMarineSurvey New Member

    I have a Bayliner 2859 with bad engine. My friends cruise in displacement trawlers traveling 8 - 10 knots. I am considering installing a deisel and optimizing my planng hull to the 10-knot speed range and giving up the ability to plane. Help me understand the issues I may face so far as handeling in heavy water, etc. Any comments or opinions would be appreciated.

    Thanks in advance for your opinions.
     
  2. messabout
    Joined: Jan 2006
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    Location: Lakeland Fl USA

    messabout Senior Member

    Heavy water in Utah? My first impression of this conversion is that it will be ill advised. If a deep vee hull is left as it is, the transom will drag a lot. That will waste more than a little power. If you are willing to add some length to the boat you might pull this off. Added length at the transom would be pinched in to a point wherein you'd have a double ender. Seems to me that you'd be better advised to forget the Bayliner and just build a trawler that better suits the intended use.
     
  3. Grant Nelson
    Joined: Feb 2005
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    Location: Netherlands

    Grant Nelson Senior Member

    The big challenge will be optimizing your hull - the sharp cut off of the shap at the stern, with a deep V form, will not allow the water to slip off and away from the hull with ease, and you will, in essence, be adding a ton or two of weight to what your engine has to move (a cubic yard or so of water that stays with the boat behind it) and some resistance from eddies, etc.
    When you reduce your HP, etc. you will need a new prop to get your best economics. The rudder was probably a bit small to optimize it for planing speeds, and now that you will be going slower, you might have less manouverablity - but that will be about the same as you experienced at low speeds already, so you know what that means. Ditto, the small rudder will be a problem in following seas.
    10 knots is a bit above hull speed if your water line is 28feet (it would be more like 7). To reach 10 knots you will need a fair amount more hp which might not be what you want.
    Go buy Gerrs 'The Nature of Boats' - its easy reading, but very informative, including lots of simple equations and tables to help you optimize your boat in another configuration.
     

  4. MyMarineSurvey
    Joined: Jun 2008
    Posts: 2
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    Location: Utah

    MyMarineSurvey New Member

    Stern Drag & Rudder

    Thank you both for your thoughts. Sounds like drag at the stern and lack of rudder area in a following sea will be big issues. I appreciate the reading reference and will be ordering. As for heavy water in Utah? I failed to mention that we use the boat on Puget Sound in addition to Utah. However, we do get some nasty storms on Lake Powell, our primary cruising grounds. It is absolutely beautiful! I hope you have a chance to visit some day. You will see an assortment of boats ranging from ski boats to coastal trawlers and house boats. It is quite a place.

    Best,
     
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