Swain BS_36 Stability curve

Discussion in 'Stability' started by junk2lee, Mar 9, 2011.

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  1. Wynand N
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    Wynand N Retired Steelboatbuilder

    Brent, if the weight of the ballast is the same in both a single and double keeler and place as such that the VCG is at the same spot, there would be no difference in stability when heeled or turned over.

    Let me explain very simply; CG is a product of mass and a geographic point in the hull. When the boat heels, the mass does not change hence the VCG stays at the same place unless something heavy moves around that may affect it like the engine.
    However, what does alter when heeled, is the hole in the water and that effect the COB that moves outwards from VCG creating a righting lever.
     
  2. HReeve
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    HReeve Junior Member

    Are you actually suggesting that some people's personal waste is less polluting than others, based on their finances?

    The rotting hulks NEVER move, and that's the problem. They dump all their waste directly into the Bay.

    And they have clogged up the anchorage to the point that people visiting the Islands go elsewhere, because there is no room in the Bay.

    And they aren't quiet! On welfare cheque day, it's quite the party out there!

    Then there are the ones that are sunk (or nearly so), that are unlit. Creating a hazard to navigation.
     
  3. Jack Hickson
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    Jack Hickson New Member

    Right Wynand. The single keeler in Jim's stability curve has nearly 6 ft draft compared to around 4 ft for the twin keeler.
     
  4. Jack Hickson
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    Jack Hickson New Member

    The mast displaces 12.56 lbs of water per linear foot.
    , but weighs 7.54 lbs per foot, leaving a buoyancy of 5.02 lbs per ft. Multiply that by the length of the mast, 48 feet, and you have 240.96 lbs of total buoyancy ,centered at 24 feet above the deck. Multiply the buoyancy by the distance and you have the righting moment in ft lbs, 5783 ft lbs of righting moment. The weight of rigging and Tangs will reduce this a bit, but nowhere near below 4,000 ft lbs.
    If it did, at 45 degrees below horizontal, with the center 12 feet out, it would still have 2,000 ft lbs of righting moment at 135 degrees.
    True , at 180 degrees, it would have no righting moment , but that rises quickly as she starts to right herself .
    This number would be even greater, if you add the distance from the VCB to the mast.
    You are right when you say the Witch is so badly designed, in terms of initial stability, that there is no way she could carry a proper modern rig. The one I referred to, which sailed home with her deck under water most of the way, had Colvin's standard ketch rig on her, as designed by Colvin..
    So what are the advantages of such a hull shape? Performance? No way!
    Roominess below?No way!
    Aesthetics? Subjective ,but not in the eyes of most cruisers today!
    There are absolutely no advantages in such a hull shape, and many disadvantages..
    Your point about the fallibility of calculations is right on. One number wrong, and everything from there on is wrong. Reality and experience is far more reliable.
    Reminds me of the friend who had his Colvin Gazzelle hauled out . Designed displacement 22,000 lbs
    Actual weight 32,000 lbs
    One someone moves aboard, all the designers numbers go out the window, in an extremely unpredictable way, depending on the habits of the owner.
    Some would try to convince us otherwise, in an obviously , transparently false way.
    So what does that leave us with to gauge a boat? Only past performance.
    A new, never sailed design is a crap shoot , to a large extent.
     
  5. Jack Hickson
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    Jack Hickson New Member

    Whats the difference between what rich people's **** in North and West Vancouver, Vancouver, Nanaimo, and Victoria does compared tot hat of boaters? It simply travels through a longer pipe, and is totally concentrated at single points.
    When they initially plumbed Vancouver ,they connected the sewers to the storm drains, and it all flowed together. During winter rains, there is no way any sewage treatment plant can handle it all, and it all flows untreated into Georgia Strait, right across from you.
    That shouldn't bother you, as it comes from wealthier asses, and thus is environmentally benign, and doesn't stink.
    And you are worried about a few blind mullets in the bay?
    It's also quite a party out there when cruising clubs have their rendezvouses there, has been for years.
    But being first class citizens instead of second class citizens ,they can make all the noise they want? When they pump their heads in the bay, their **** doesn't stink as much as poor people's ****.?
    I don't believe boats should clog our anchorages while their owners have no intention of ever using them again. However a boat, when it is the only home someone can afford, and the only thing between them and homelessness, it is a totally different story. It has been ruled by the Supreme Court of BC that shelter is covered by the charter right to Life Liberty and Security of the Person.
    Making the desperate even more desperate ,doesn't improve the security or quality of life for the rest of us in any way. It does the opposite.
     
  6. welder/fitter
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    welder/fitter Senior Member

    No, without the fundamentals, wherein, one learns to perform the calculations and the value of those calculations & the relationship of the various calculations, 40 years experience of not knowing holds little value. Offshore experience only enhances a designer's knowledge, it does not replace it. If that were the case, there'd be many x-navy, x-coast guard, x-merchant-men hanging out their design shingles.

    When in Tad's office, I remember seeing a chart - can't remember which publication - that showed about 700 hours estimate of design time for a 36 or 37 footer. That is aside from designing to a classification. The drawings I've seen for the BS36 look like someone spent a weekend drawing them up.

    But, bottom line; your oft-stated AVS number was a guess & has been shown to be incorrect, to the degree that was possible with the available info. . A responsible designer would now arrange an inclining test - not to prove a point, rather, to determine fact - instead of suggesting that another "go find one"(BS36).
     
  7. welder/fitter
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    welder/fitter Senior Member

    Here's a few attachments that show the boats moored in Silva Bay for March 20-27, 2011. During that week, on only one occasion - at night, of course - I heard what sounded like someone pumping their head, although it could have been a bilge pump. Every morning a fleet of dinghies would make their way to the docks, as people headed off to their jobs, shopping, etc. . The impression I had from meeting a few of the liveaboards was that they were far more environmentally aware than myself or the average city-dweller.

    However, none of this has diddly to do with the stability of a BS36.

    (Btw, Tad, sailing performance aside, I agree with James, that that brigantine rig is sexy!:D)
     

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  8. Wynand N
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    Wynand N Retired Steelboatbuilder

    Brent, this really put a smile on my face :D:D:D

    But it may raise some **** and a stink from some...
     
  9. HReeve
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    HReeve Junior Member

    I wasn't the one to say there was a difference.

    Not starting next January, they can't pump out into the bay.

    When there is a disturbance on the bay, who ever the source, the RCMP and / or CG are called.


    How about the businesses that have been operating on the bay for well over 50 years that are adversely affected by the drop in visitors caused by the over crowding of the bay by the squatters?

    What about the rights of those people to Liberty and Security?

    And I do have to question the environmental credentials of people who use wood as the sole source of heat on their boats. Not exactly a clean fuel. (Not to mention the fact that much of the wood is gathered illegally from private property above the high tide line.)
     
  10. Jack Hickson
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    Jack Hickson New Member

    For a white man living in North America ,calling anyone a squatter is like the pot calling the kettle black.
    If the RCMP knock on my hull while at anchor, I'm under no legal obligation to open the hatch. The Canadian Coast Guard tell me they refuse to do law enforcement. If there is any of that to do they bring a mountie aboard. They have told me that if they were ordered to they would walk out and hit the picket line immediately.
    Starting in January, all pumping will be done at night, just like they do in the US.
    You are downstream from the Fraser River, carrying all the pulp mill discharges from the interior, all the farm pesiticdes and fertilizer runoff from the Fraser Valley , all the auto exhaust and oil leaks from Prince George to Vancouver, and you are worried about a few blind mullets dumped into a bay, which is one of the best tidally flushed in the Gulf Islands, by people who's environmental foot print is microscopic compared to your own?
    Get a life!
    Don't envy, emulate!
    People living in the bay year round ,are consumers ,who buy more from businesses in the whole year, than the brief flurry of summer tourists do in a two day stopover. Cater to them.
     
  11. Jack Hickson
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    Jack Hickson New Member

    Those who deny the importance of offshore cruising experience ,often do so because they have little or none of their own to offer.
    Anyone considering a designer or builder, should first determine how much experience the builder, and, or, designer has in offshore cruising in the type of boat they are considering
    So why don't you, Tad, Wynand, etc, tell ,us of how many miles and years of offshore cruising experience you have ?
    When something has been proven over 30 years, creative accounting won't change that fact.
     
  12. Nurb
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    Nurb Junior Member

    I've read this topic which has gone on and on.

    What would it take to get a BS-36 volunteered for a proper inclining calc on the as-built boat?
     
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  13. TeddyDiver
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    TeddyDiver Gollywobbler

    Those who deny the importance of education ,often do so because they have little or none of their own to offer. ;)

    As said earlier by others.. better to have experience and education..
     
  14. rwatson
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    rwatson Senior Member

    I would have thought that using all possible means of making a boat safe - experience and calculations, would be the best solution - but wouldnt that would be catering to the "rich people" that "Jack" hates so much??

    Dont you know that poor boat designers only need to have been to sea for 40 years, and that is plenty good enough.

    "Numbers and figures are just mumbo jumbo that doesnt mean anything" - talk about inverse snobbery, but maybe poor boat designers **** doesnt stink either ?
     
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  15. TeddyDiver
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    TeddyDiver Gollywobbler

    And as seatime lying at anchor in a free harbour and processing beans to floaters is counted as well... :p
     
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