Best Hull Shape A or B for a 14-16ft Rowing/Sailing Skiff?

Discussion in 'Boat Design' started by MarkOHara, Feb 8, 2024.

  1. MarkOHara
    Joined: Oct 2021
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    MarkOHara Junior Member

    I would very much appreciate your help in this.
    This discussion started at work many years ago, but unfortunately the person I was having the conversation with, is no longer with us.
    Your professional opinion would be greatly appreciated.

    Factoring in both boats are the same in LOA, LWL & Beam, the body plan is multichined and both boats have the same moderate rocker.
    Which in your opinion would be the faster of the two hulls for Sailing?
    For Rowing?
    For overall best performance of both?
    A or B?
    And Why?

    Thank you for your input!

    Boat Shape.jpg
  2. bajansailor
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    bajansailor Marine Surveyor

    Mark, I presume that you must have lines plans for both A and B, as this discussion started at work years ago - if so, can you post copies of them here please?

    How much transom immersion is there on A and B at their design displacements? I presume it is ideally barely immersed?
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  3. MarkOHara
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    Location: Bataan Philippines

    MarkOHara Junior Member

    No actually, it was a model brought into the yard that started the conversation. The maker and designer of the model was fully convinced that a wedge shape similar to "B" would be faster than shape "A" that tapered from amidships to the transom. Yes the transom would be barely immersed with a moderate rocker. The design the model maker had in mind was good enough for rowing but would plane easily when under sail, hence the generous width at the stern.
  4. BlueBell
    Joined: May 2017
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    BlueBell . . . _ _ _ . . . _ _ _

    There is a huge lack of information here.
    But from what is given:
    They would row at the same speed.
    B would plane sooner in high winds so would be considered "faster".
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  5. messabout
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    messabout Senior Member

    Be concerned about wetted surface if you want the boat to row well. I will go with plan view A if the rocker is located such that the curve of areas is smooth and makes the maximum area somewhere near the middle of the curve. Try to avoid even the slightest reflex in the curve.

    I assure that the A plan view boat will plane readily. It will do so if you keep the run of the aft bottom as near straight as is practical. Not only that but the heeled area curve will look better than the heeled B plan. The near minimum wet surface can be achieved with the trapeze section layout. It is better than a vee section, and way better than a flat bottom and nearly as good as a difficult to build rounded bottom and chine.
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  6. wet feet
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    wet feet Senior Member

    Impossible to provide decent estimates or opinions without knowing what underwater shapes are involved.It might also help to understand what factors might be considered important for "best overall performance";are we limited to top speed under oars or is planing with an outboard the main area of interest? Area of use also has an effect as a lake boat won't see the conditions that a boat intended for launching through surf will routinely meet.
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  7. sharpii2
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    sharpii2 Senior Member

    Plan "B" would likely be the faster sailboat, because the added initial stability caused by the wider aft sections. If you can use as much Sail Area as the Hull can stand up to it will definitely be faster.

    Plan "A" would likely be a better rowboat because it would likely have less whetted area. It would also likely be faster, as sailboat, if the Sail Area is limited by a racing class rule, for the same reason
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