Incredible Scow (from SA)

Discussion in 'Sailboats' started by Doug Lord, Jun 3, 2010.

  1. Doug Lord
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    Doug Lord Flight Ready

    From the SA front page here is part of the article:

    The SCOW 1420 pictured above is a monohull of 14.20m (rule maximum) having a flat bottomed hull inspired by the A scows. The aim is to maximize power for a given efficiency. Scow hull shapes generate up to 30% more power than a standard hull shape for a given beam and displacement. The long overhang forward reduces bow down trim and increases waterline length when beating upwind or reaching.

    There is thus no need for aft water ballasts or to increase bow volume. The canting keel can be used to heel the boat to leeward when the boat is under powered in order to reduce wetted surface area. This project was introduced during the 2008 Bol d'Or and both sailors and organizers showed a strong interest. Since then, the boat has been fully developed, a boat builder has been selected and the cost has been reduced. The sailing conditions on lake Geneva tend to create highly powered sailing yachts. The recent LX-TCFX ranking allows all extreme monohulls to race against each other in real time. It is therefore a great place for naval architects to experiment. Recently, there has been a few lightweight multihulls and foilers on lake Geneva. Foilers have still not proven to be the best solution for the conditions of Lake Geneva due to the lack of wind. The LX-TCFX ranking is generally won by one of the Psaros 40 (2nd in 2009, 1st in 2008). VPP studies show that the Scow 1420 is 10 to 15% faster than the Psaros 40.. The next Bol d'Or will start on the 10th of June. -
    Thomas Tison.

    Conceived of and Designed by Thomas Tison

    Click on image to enlarge:
     

    Attached Files:

  2. daiquiri
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    daiquiri Engineering and Design

    Hello Doug,
    Nice planing machine. The missing link between a sailboat and a windsurf. :)
    I enclose a video here, which shows what it will look like, once they put it in water: http://www.youtube.com/watch?v=uwSyOmYyMsY&feature=related

    One note about mr. Tison's comment: "Scow hull shapes generate up to 30% more power". He probably meant to say "requires 30% less power for the same speed" or "attains 30% more speed for a given power", who knows? A hull surely doesn't generate power, all it can do is to transmit the power from wind to water. ;)
     
  3. Doug Lord
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    Doug Lord Flight Ready

    ====================
    Thanks Slavi-I've raced as crew on a 28' E scow-great experience and fast!
    When I was a kid there was a regatta in Pensacola where one of the highlights was a race between a Shark catamaran(20') and an E-scow-very evenly matched and exciting to watch!
    I've written to Thomas Tison-maybe he will post here.....
    --------------------------
    I'm thinking this boat could be a candidate for a Trapwing on-deck sliding ballast system?!
     
  4. tspeer
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    tspeer Senior Member

    Actually, scows are the missing link between monohulls and catamarans. If you grab a rubber dinghy by the gunwales and start pulling it apart, just before it snaps into two hulls you get a scow.

    When heeled, I used to be able to look over the bilge and see the centerline on my scow. The M20/A20 scow bottom actually humps up in the middle to reduce wetted area.

    But they do plane nicely. Unlike a dinghy, there's no sudden leap onto the plane. The transition is smooth and gradual - fingertip control throughout. Due to the wide flat run aft, the stern wave produces a forward thrust in the semi-planing regime just below hull speed.

    I believe he really meant, "30% more heeling moment". "Power" being often used by sailors to mean sail area or sail trim, rather than thrust times velocity.
     
  5. Munter
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    Munter Amateur

    Do you mean "30% more righting moment" or do I misunderstand?
     
  6. yipster
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    yipster designer

  7. messabout
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    messabout Senior Member

    I can't even remember how many boat types that have owned me. My all time favorites were, not one but two, M20 scows. They were not the fastest boats I have ever sailed but they were faster than most monos in that size range. (FD sailors will argue that point) and in light to moderate air they would go quickly and quietly. The M20 is a partially tunnel hulled boat, the tunnel diminishes near the transom. When heeled it is esentially a catamaran. but when flat it is a mono. I was once part owner of a decrepit old E-scow and it was a pure joy to sail, just a little too big for my tastes. Talk about big and powerful and you are talking A-scow. I once crewed on one of those and it would go like nothing I have ever experienced. The A would go very fast while making very little fuss. That speed was decieving and it could get an inattentive skipper into big trouble.
     
  8. Doug Lord
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    Doug Lord Flight Ready

  9. tspeer
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    tspeer Senior Member

    We're talking about the same thing. Righting moment from the hull; allowable heeling moment from the rig. I probably should have said righting moment.
     
  10. sharpii2
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    sharpii2 Senior Member

    My first sailboat was a 10 ft scow built from some plans i bought from Science & Mechanics magazine. It was probably the worst built boat that ever successfully sailed. It was four feet wide and about seven and a half inches thick. It carried 85 sf of visquene sails. It had straight, vertical sides, and the only curves on it were the fore and aft curve of the bottom and the fore and aft curve of the deck.

    It first successfully sailed against an onshore breeze of about 15 kts and four foot swells and amongst large boulders. Across the wind and down wind it went incredibly fast. Maybe 10 to 12 kts. Upwind, it tended to stuff waves. It tracked very well yet was more than sufficiently maneuverable. It sailed maybe a total of 12 times before it succumed to dry rot. During those 12 voyages, it taught three people how to sail, none of whom had any personal instruction.

    The pdracer is a class of small scows that routinely sail past 5 kts and are probably the best boats to learn how to sail on. They are not tippy like your average 8 ft dink and have plenty of room to sprawl about in. they are best suited in protected waters which are the best places to learn how to sail anyway.

    My personal opinion is the scow type, with proper proportions can be quite seaworthy. A small fleet of pdracers sail the Texas 200 coastal voyage and always finish. The race is primarily down wind which probably explains their success rate.

    I'm thinking a narrower scow with high sides and a deeply cambered deck could be successful on all points of sail, even high swells. I already have such a design drawn up and hope to build it soon. It won't be anywhere near asw fast as a more traditionally proportioned scow but will be every bit as simple to build.
     
  11. DrCraze
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    DrCraze Junior Member

    A hull creates lift does it not? So A hull can create power just as a sail does. Never the less he probably misspoke.
     
  12. daiquiri
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    daiquiri Engineering and Design

    If hulls could create power, we wouldn't need sails and engines.
    We could actually plug a number of sufficiently big hulls to a public electrical grid, to generate electricity for our homes. ;)
     
  13. DrCraze
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    DrCraze Junior Member

    If sails could create power we wouldn't need wind. Not all hulls create power but with a proper design it will create lift to windward. Why are you having difficulty seeing that?
     
  14. daiquiri
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    daiquiri Engineering and Design

    I am not having a difficulty, I just thing that it is improper to say that hull creates power. The power you are talking about comes from the wind. If you had a hull without a sail or an engine, it would not be able to create a force component to winward. The energy comes from the wind, which draws it from the earth rotation and from the Sun.

    Of course, if you start considering just parts of the system, than it all becomes very relative.
    From the underwater point of view, you would see a hull which moves driven by some misterious force and imparts motion to the water. Thus, water does see a hull as a power-generating device.
    From the point of view of an observer which moves with the mass of air (and thus sees a still air), you would see a sail as a device which agitates air, and thus generates power.

    But we can do better than that, and see the whole picture - hull, sail, water and air. ;)
     

  15. DrCraze
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    DrCraze Junior Member

    There is at least one hull that creates power. I believe a Japanese engineer created a system that creates power from wave induced pitching. You are right about nothing creating power. Power is very subjective, the proper term we are looking for is force/lift
     
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