Hull type performance questions.

Discussion in 'Multihulls' started by SpiritWolf15x, Nov 2, 2012.

  1. SpiritWolf15x
    Joined: Apr 2010
    Posts: 194
    Likes: 1, Points: 18, Legacy Rep: 15
    Location: Vancouver, Canada

    SpiritWolf15x Senior Member

    Hey again everyone, I have a few performance questions for the forum gurus.

    Which hull type is quicker "over-all" flat bottom? Rounded? V-shaped? What about these "semi planing" types I've been hearing about? Are there "hybrid" types? What advantages/disadvantages do each type offer? Is there a magic do "everything" type?

    Thanks,

    Wolf
     
  2. tunnels

    tunnels Previous Member

    you talking
    sail boat??
    power boat ??
    inboard ??
    outboard ??
    How many motors ??
    fishing ??
    pleasure ??
    cruising ??
    fishing ??
    go fast ??
    How fast ??
    lenght ??
    Wood ??
    fibreglass ??
    aluminium ??
    steel ??
    :confused:
     
  3. SpiritWolf15x
    Joined: Apr 2010
    Posts: 194
    Likes: 1, Points: 18, Legacy Rep: 15
    Location: Vancouver, Canada

    SpiritWolf15x Senior Member

    Racing sailing trimarans of the 16' and 33' range. Plywood/fiberglass and foam/fiberglass.
     
  4. PAR
    Joined: Nov 2003
    Posts: 19,133
    Likes: 488, Points: 93, Legacy Rep: 3967
    Location: Eustis, FL

    PAR Yacht Designer/Builder

    Too broad a set of questions to answer quickly, can you refine the questions a bit?
     
  5. SpiritWolf15x
    Joined: Apr 2010
    Posts: 194
    Likes: 1, Points: 18, Legacy Rep: 15
    Location: Vancouver, Canada

    SpiritWolf15x Senior Member

    In 16 to 33' sailing racing trimarans, what are the stability, performance and handling characteristics differences between a flat bottom design, a rounded bottom and V-Shaped at speeds ranging from 5knots to 20knots? What are the MAJOR advantages and disadvantages to each to each hull type? Is one design by far the "better" choice or does it really not matter all that much? :confused:
     
  6. PAR
    Joined: Nov 2003
    Posts: 19,133
    Likes: 488, Points: 93, Legacy Rep: 3967
    Location: Eustis, FL

    PAR Yacht Designer/Builder

    There are no "far better" choices, just some advantages and disadvantages to consider trading off with, in regard to sailing attributes and preformance envelop. In terms of racing, most every aspect is geared to get the best speed, assuming certain safety issues are addressed. Some choices can produce ridiculously fast, craft, that are also fragile and costly, while you can sacrifice some speed potential for a larger safety margin and more durability. It all depends on the way you prioritize your needs and assemble the SOR. If all out speed and preformance are desired, then you'll have a costly likely dainty, but fast vessel, built with exotic materials and clever engineering. If a preformance orientated craft is desired, but with some accommodation to other aspects of the SOR, you'll subtract from the speed and preformance potential for these elements.

    Simply put, you establish an SOR and make design decisions around it, best fitting the goals set within. This simply means there's no "best" of anything, just various choices and compromises you have to sort through.
     
  7. SpiritWolf15x
    Joined: Apr 2010
    Posts: 194
    Likes: 1, Points: 18, Legacy Rep: 15
    Location: Vancouver, Canada

    SpiritWolf15x Senior Member

    This is all very confusing XD
     
  8. Leo Lazauskas
    Joined: Jan 2002
    Posts: 2,696
    Likes: 151, Points: 63, Legacy Rep: 2229
    Location: Adelaide, South Australia

    Leo Lazauskas Senior Member

    Step 1. Write a Statement of Requirement (SOR) for your vessel.
    (You need to provide more than the speed range and possible hull shapes.)

    Everything else will soon fall into place and make sense.
     
  9. SpiritWolf15x
    Joined: Apr 2010
    Posts: 194
    Likes: 1, Points: 18, Legacy Rep: 15
    Location: Vancouver, Canada

    SpiritWolf15x Senior Member

    Well the 16 footer is a day sailor/racer and the the designer of the 33 (Crowther) calls it a "performance coastal cruiser". So i guess the questions would be for those two types.
     
  10. warwick
    Joined: Jan 2012
    Posts: 423
    Likes: 7, Points: 18, Legacy Rep: 63
    Location: papakura south auckland new zealand

    warwick Senior Member

    Spiritwolf,

    is that you want to know more about the performance trade off? compared with the various hull shapes. such as vee bottom, flat bottom and round bottom.
     
  11. cavalier mk2
    Joined: Mar 2010
    Posts: 2,123
    Likes: 55, Points: 48, Legacy Rep: 214
    Location: Pacific NW North America

    cavalier mk2 Senior Member

    V-shape softer riding in rough seas but more wetted surface so light air penalty.
    Flat bottom- some turbulence from chines, can be harder riding.
    round bottom-least wetted surface for displacement, less hard riding than flat bottom.

    And every variable in between to blur the differences. A planing or semiplaning hull would normally use the flat bottom or round bottom shape. For a comparison your Bucc main hull is slender to slice through the waves at speed but with enough round built in to add some carrying capacity . A round hull version might be slightly faster in the light stuff but I doubt you'd notice. My tri has a fuller round main hull for more capacity and to rise up on the water to semiplane. The forward sections rise up on the bow wave keeping the stern in the water. This reduces wetted surface but the boat has more of a speed transition barrier than a thin hull regardless of shape. So every thing is connected, length, width, shape....a wide V will plane if shallow enough as can be seen on chine powerboats etc.....
     

  12. SpiritWolf15x
    Joined: Apr 2010
    Posts: 194
    Likes: 1, Points: 18, Legacy Rep: 15
    Location: Vancouver, Canada

    SpiritWolf15x Senior Member


    Exactly
     
Loading...
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.