slightly Arched V hull

Discussion in 'Boat Design' started by Titu, Jul 22, 2023.

  1. Titu
    Joined: Sep 2022
    Posts: 7
    Likes: 1, Points: 3
    Location: Halifax, Nova Scotia

    Titu Junior Member

    Hello again after a long time.
    I'm looking into V hull designs and wondering about the difference between the traditional V hull (Hull-A)and the slightly arched V hull (Hull-2). Can anyone explain their distinctions and how they impact boat performance?


    Attached Files:

  2. comfisherman
    Joined: Apr 2009
    Posts: 539
    Likes: 266, Points: 63, Legacy Rep: 10
    Location: Alaska

    comfisherman Senior Member

    Only anecdotal. But my last bay boat had near as no difference same beam and draft as my new one. Old one had a traditional v and slapped a little in 2-3 foot chop. Nothing bad but noticeable. New one doesn't, it seems to cut and cushion on the smalle chop.

    My old boat had hull slap atb6-7 foot chop about the same as 2-3. This new one with the arch slams exceptionally harsher in the 6-7 foot slop. Dunno if it's just a resonance or what but it handles small better but is rather jarring in bigger slop.
    jehardiman likes this.
  3. jehardiman
    Joined: Aug 2004
    Posts: 3,690
    Likes: 1,077, Points: 113, Legacy Rep: 2040
    Location: Port Orchard, Washington, USA

    jehardiman Senior Member

    Pretty much a Comfisherman says. In small chop, the concave "V" is significantly narrower (i.e. the bottom is more vertical) to reduce ride harshness. However, in a full slam, the hull is significantly flatter (i.e. the bottom is more horizontal) so the heave force is greater. FWIW, concave V-hulls also track a little better, but there are many other factors so YMMV with that aspect.

  4. messabout
    Joined: Jan 2006
    Posts: 3,346
    Likes: 481, Points: 83, Legacy Rep: 1279
    Location: Lakeland Fl USA

    messabout Senior Member

    Random thoughts ...........
    Here is one way to get a handle on the physics of the two bottom shapes. Make a large drawing, or reasonably accurate sketch, of one of the forward sections of the boat. Place your finger at the keel line and move it upward along the section line. stop at the first location, maybe a few inches up. Observe the slope of the bottom at that location. The slope is fairly steep. Now move upward to the second location, observe the slope of the bottom at that point. Slope is not quite as steep. Do that progressively and when getting closer and closer to the chine, the slope will be much smaller, almost flat. In the Cartesian graph system, the slope will approach zero. That means that at that particular location the bottom is essentially flat.

    The shape of the curve, or the relative curvature will provide some clues about how badly the boat may slam....or not . Although this may smack of a differential calculus drill, one needs no mathematical skills to look at a section drawing and to imagine what will happen when the section slams downward into solid water.

    "Gentleman's runabouts" (Chris Craft, Century, Riva, etc) of the past had curvature in the forward sections. The rationale was that spray would be deflected outward away from the passengers. Not only that but the appearance was kind of sexy.

    From a construction point of view, the inward curve, everything else being equal, cannot be as strong as an outward curve would be.
    bajansailor likes this.
Forum posts represent the experience, opinion, and view of individual users. Boat Design Net does not necessarily endorse nor share the view of each individual post.
When making potentially dangerous or financial decisions, always employ and consult appropriate professionals. Your circumstances or experience may be different.