Sailing a pontoon boat

Discussion in 'Sailboats' started by pontoonsail, Nov 10, 2015.

  1. upchurchmr
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    upchurchmr Senior Member

    Probably, maybe.

    There is no value to this comment unless you have an example with facts and figures.
    There is a huge wake pulled up by a "pontoon". This means drag.
    The only time you get a reduction in drag is when the speed is high enough to get a clean exit of the water from the edge. Similar to a power boat that is planing. At any speed lower there is a huge drag which requires lots of power just to get going. Unfortunately, you have to get started and sail thru this high drag speed range to get to the "planing" speed.
    There was even an Americas cup sailboat that tried this "theory" which failed miserably because at normal sailing speeds (slower) the drag was so high.
     
  2. OzFred
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    OzFred Senior Member

    Perhaps you should hold yourself to the same standard you ask of others: provide some evidence that quantifies the effect of a square stern on a long, narrow hull of the type used for a pontoon boat.
     
  3. upchurchmr
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    upchurchmr Senior Member

    Oz,

    I did not suggest a square stern.
    I saw the effect of immersing a semi-circular stern in the water on a Tornado Catamaran.
    At low speed it had a noticable, significant effect on speed.
    It was quantified by the boat sailing along with me on the same point of sail, pulling away until I shifted Crew and Myself fwd to raise the stern out of the water.

    The race course is generally a good place to do comparisons because it it a place where changes matter.

    So what do you have for your point of view?

    You might look up the Americas Cup boat designed by Brit Chance - If I remember correctly.
     
  4. OzFred
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    OzFred Senior Member

    The effect you're describing is common in small sailing boats, especially dinghies. In light conditions, getting the transom out of the water helps because the forward sections are rounder and therefore reduce wetted surface for the same amount of buoyancy. Stern sections tend to be wider and flatter, and therefore have much more surface area (hence drag) for the same buoyancy. So it's about reducing surface drag, not stern turbulence.

    A pontoon boat with a long, narrow hull primarily has surface drag. Tapering the stern to reduce turbulence may also have a tiny effect on wave drag, but it will increase surface drag (by a similarly tiny amount) so the net effect will be very small. The OP shouldn't expect a noticeable increase in performance just by putting a cones on the hull transoms.

    The reduced turbulence might make the boat a bit quieter for those near the stern, but some may like the quite burble of the stern wake. ;-)

    So the bottom line (for me) is it should be done only if there's nothing better to spend the time and effort on.
     
  5. upchurchmr
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    upchurchmr Senior Member

    Oz,

    I thought you were going to give some "data" on your theory instead of commenting on mine?
    In point of fact, the Tornado has very slender sections up front and a semi-circular section in back.
    Shifting the CG forward means you have to sink the narrow sections up front much more than you raise the aft wide sections.
    In any real evaluation, the surface area increases quickly which in your theory should increase the surface friction slowing the boat.
    That does not happen.

    Have you ever actually been on a sailboat like a Tornado that more closely represents the pontoon boat?

    And it is your concept that the end would be a simple cone, not mine. To get a real value a more complex shape would be needed. One that didn't have a sharp break at the intersection of a "cone" and the cylindrical hull. But again we would need to talk about the speed at which you would want to be traveling. Not making a general one size fits all statement.
     
  6. Westel
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    Westel Senior Member

    Perhaps that people who would buy/sail this kind of vessel aren't too much interested in drag/wave resistance/ math etc...etc...and probably wouldn't even notice a 15% increase in "performance" when sipping the Martini at ....3 knots....with or without modified "tube ends".
    "Sailing pontoon" people will be interested in how easy it is to get that thing to sail and how stable it is and how comfortable it is.
    If they were interested in "numbers" they probably would consider anything but a sailing pontoon.....

    I think there is a market for this
     
  7. upchurchmr
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    upchurchmr Senior Member

    And more power to them.

    But, statements that are just wrong shouldn't be allowed to stand, others will be misled and we will have even more people operating from false data.

    Then many sailors will act just like politicians.
    Just because it has been said it's suppose to be true.
     
  8. PAR
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    PAR Yacht Designer/Builder

    The small sailboat market is less than 10% of the pleasure boat market in the USA. The market for an odd, slow, lacking good maneuverability sailboat, will be considerably smaller than you might think. I agree in that most interested in this will be novices and/or those not all that interested in sailing, possibly just the novelty of it. The idea of stern cones improving efficiency, with the Fr numbers you could expect from this seems, just as convoluted as the rest of the concept. I guess it depends on how she trims, but if she's typical of a power pontoon, there's a pretty good hole being dragged along, but the small fraction of a knot you might realize, will make you question the effort to install cones.
     
  9. myark
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    myark Senior Member

    I agree as if I was to own a sailing boat it would be a pontoon Posted by pontoonsail as said may lose performance but what's damn hurry when holidaying.
    The saving in gas consumption and quiet while blending in with nature on ones favorite remote lake with the bonus of landing on a paradise beach
     
  10. Mr Efficiency
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    Mr Efficiency Senior Member

    Just pinch the ends of the tubes together to end in a vertical join, can't think what else would work better.
     
  11. Westel
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    Westel Senior Member

    Is the time, effort and money invested to change the stern of such magnitude that this Pontoonboat will be a better boat with the new stern ?
    The market may be small but I'm sure Pontoonsail is intelligent enough to realize that he's not going to be a millionaire in recordtime with selling this kind of product,
    Maybe he looks to be a happy man, making an honest living with something he likes to do and if that means that he only can sell a few pontoonsailers a year, so it be.

    I think Myark has put this kind of boat in the right place, get away from all the "modern" madness and enjoy what surrounds you in the most comfortable, affordable and safe manner.
     
  12. Mr Efficiency
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    Mr Efficiency Senior Member

    Seems pretty simple to alter it to something more favourable than an abrupt cut-off, the thing will be slow enough without further handicapping it.
     
  13. OzFred
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    OzFred Senior Member

    Please provide your detailed evidence of the performance gains of some alternative design so the OP can determine whether they are worth the effort.

    Indeed.
     

  14. upchurchmr
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    upchurchmr Senior Member

    Fred,

    I offered my experience in a situation where the comparison was direct and immediate.
    I offered a physical explanation which I know to be true from the geometry of the boat I used.

    You are the person who offered nothing but an opinion. Not even a justification from experience.

    I'm finished with you. Everyone can judge for themselves which is more reasonable. My reason for continuing this was to keep others from believing silliness, not to convince you.
     
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