Mini Ocean Racing Scow

Discussion in 'Sailboats' started by Doug Lord, Aug 2, 2011.

  1. peterchech
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    peterchech Senior Member

    You know the entry to this scow seems almost spherical, as though it would not really be "cutting" through chop even if sailed on its ear (unlike a traditional developed surface flat bottomed scow). If so, then no matter if it heels over or not it would present a similar blunt entry at the bow.
     
  2. Doug Lord
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    Doug Lord Flight Ready

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    Peter, the boat maintained it's superiority in very choppy conditions in part of the Transat so ,apparently,sphere or not, it works.... Looking at the hull on its side it appears to me that the boat woud have a significantly narrower entry forward when heeled. Heres a good picture:
    click on image:
     

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    Last edited: Nov 16, 2011
  3. ancient kayaker
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    ancient kayaker aka Terry Haines

    I seems to me that as any boat advances through the water the key issue is how it moves the water around it. A sharp plumb bow is clearly intended to move the water to each side. Conversely a pram or garvey would move proportionately more of the water beneath it.

    The scow appears to be like the pram when upright, the bluff bow is above the water surface riding over the water and only smacks the waves under a press of sail. When the scow heels the hole it makes in the water becomes narrower and - obviously in order to maintain displacement - deeper as well. When this occurs proportionately more water would be moved to the side.

    Whatever the heeling angle there is always a considerable reserve of buoyancy available to keep the bow from being pressed down, and I believe it is designed so when it strikes the sides of an oncoming wave, the slope of the bow is always such as to slide up the wave rather than dig into it.
     
  4. peterchech
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    peterchech Senior Member

    I love the concept. Probably lots of pitchpole resistance too in that bow. Maybe this allows crew to wait longer before deploying a drogue in heavy conditions?

    It would be interesting to see something sized like the i-550 using this concept...
     
  5. Doug Lord
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    Doug Lord Flight Ready

    While I think what David Raison has done with the 747 Scow design is outstanding I can't wait to see what Welbourn's super narrow DSS boat does.
     

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  6. sharpii2
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    sharpii2 Senior Member

    Unless it going to be in a predominately upwind race through choppy water, I would stick with the 'scow'.

    As much as I love narrow boats, high speed really isn't their forte.

    A narrow boat can be heavy for its Beam and light for its Length. All good for a pleasant ride with reasonable speed.

    Greater speed usually comes with greater initial stability. And boats that are light for their Beam have that in spades.

    A multihull is nothing more than a boat that is light for its beam and has super slim hulls.

    In the earlier days of the BOC races (round the world, single handed) narrow boats were made with deep, sometimes bulbed keels.

    They were roundly beat by boats that were much wider, but had the same kind of keels. Many ended up obsolete the day they were launched.

    This is one of the hazards of a 'box rule'. It can be quite ineffective at ruling less safe types out.

    I once suggested a 'sum trade-off' for Beam and Draft, with the stipulation that all would have to prove a minimum of self righting capability.

    The sum I once recommended was half the length, for an 'open 60'.

    If the boat was 20 ft wide, it would only be allowed a 10 ft draft, for instance.

    For a 'mini', I'd be more generous. Perhaps two thirds the Length. A nine foot wide mini would then be allowed a five foot draft.

    Even with a canting keel, you would quickly run into diminishing returns by going either too wide or too deep.

    Now, you simply design to the limits of the 'box'.

    The pram like boat does a better job of that than a the narrower, arguably more sensible design shown here.
     
    Last edited: Nov 17, 2011
  7. Doug Lord
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    Doug Lord Flight Ready

    But the DSS boat is both narrow and wide. It is a different configuration than has ever been seen before.
     
  8. sharpii2
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    sharpii2 Senior Member

    Not seen before?

    I don't think so.

    Asymmetric hulls have been around for decades.
    The basic concept is sound. Have a wide stern, to get the sail carrying ability and have a pinched bow to slice through waves.

    Even some work boats were designed this way.

    But there is a price to be paid.

    Once the boat heels to any degree, the bow submerges, just as it is pushing water aside more than ever. Since it is heeled, it is pushing more water aside to leeward than windward. This gives the boat a tendency to round up wickedly, to the point the boat must reduce sail just to be controllable.

    With some work boats, such as heavy channel cutters, this is not a problem.

    But with boats that are supposed to be pushed to planing speed and beyond, this is likely to create serious control issues.

    The auto helm batteries will be drained flat in no time.

    Only if the skipper manages to keep the boat level with the canting keel, will he be able to get the best out of this boat, which may mean he will need an automated system to change the cant of the keel with every gust.
     
  9. Doug Lord
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    Doug Lord Flight Ready

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    Sharpii, there has never been a Mini that used the DSS foil before-it has never been used in this class of boat thruout the history of the class. It represents an entirely new technology that gives the boat advantages of a narrow hull AND advantages of a wide hull with the tremendous extra righting moment generated by the DSS foil. And the DSS boat is very narrow compared to every other mini-it does not have the wide transom characteristic of most Mini's.

    Pictures: L to R--1) DSS hull with narrow hull and narrow transom, 2)& 3)- typical Mini 6.5 transoms( 3 is a rendering done by Yves Tanton)
     

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  10. Perm Stress
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    Perm Stress Senior Member

    Narrow hull is also much lighter, so less weight has to be pushed on the plane, so it could be supported by smaller area of flat bottom, allowing even more narrow and still lighter hull, and so on for some time (while stablity to carry sail is provided by DSS foil, which is getting longer, as the hull gets narrower, within the "box"); it looks like a design spiral is converging in the "right" direction here.
     
  11. sharpii2
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    sharpii2 Senior Member

    Sorry, Doug.

    I must have missed the part about the foil. (now that I look at the picture, I can see it hiding in plain sight) I get confused by some of this jargon once in a while.

    With the lifting foil, the boat might actually be faster than the scow.

    Will this boat have a canting keel as well?
     
  12. Doug Lord
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    Doug Lord Flight Ready

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    I'm not sure yet-I imagine so. I've written Hugh Welbourn for more details....
     
  13. Perm Stress
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    Perm Stress Senior Member

    My guess she will not have a canting keel.
    To save overall weight, and complexity, if for nothing else.
     
  14. Doug Lord
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    Doug Lord Flight Ready

    Raison Influence?

    Doug Schickler on SA says its a Nacira Open 40-what it really is unknown today. Looks like someone who just couldn't bring themselves to go all out "Raison Scow"!
    click on image-
     

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  15. ancient kayaker
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    ancient kayaker aka Terry Haines

    That would probably be easier to build, and perhaps achieve similar results. Looks like a barge!
     
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