Basic information on boats

Discussion in 'Stability' started by Guillermo, Nov 15, 2006.

  1. Guillermo
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    Guillermo Ingeniero Naval

    In post 116 within the thread on STIX vs Old ratios, Crag Cay posted these very interesting thoughts:
    (Bolding is mine)
    Although worried about the people really understanding what numbers are, I feel an strong affection for Crag's thoughts.
    Some questions for everybody: Do you agree with Crag's point of view? If so, What's the minimum information you think should be included in the basic information on a boat? Should that info be mandatory? And down to what degree of detail?
  2. Willallison
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    Willallison Senior Member

    I'd concur, at least to some extent. The problem isn't just confined to the boating arena, of course. The reality is that, for the most part, the general public don't have the expertise to establish seaworthyness (or otherwise) of a boat. And perhaps more importantly, they're not interested in gaining that knowledge.
    STIX, RCD, compliance with ISO and other standards, etc, can at best only give these people a general guide.
    But of course, these things are all so significantly effected by weather, load, crew experience etc etc etc.
    Dunno - it's a tough one....
  3. Frosty

    Frosty Previous Member

    Thats if you choose a boat with your brain. If you choose a boat with your heart --who cares about anything, least of all some numbers or even solid advise from others.

    To gain a competative edge the numbers could be embelished or twtsted, then they would become meaningless, unless coverd by law (now I really dont like where this is going).

    It all very sensible,--If only human beings were as sensible.
  4. Willallison
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    Willallison Senior Member

    The day people realise that there's nothing very sensible about spending a million bucks on a toy that might get used 30 days a year, we'll all be in trouble... the boating industry will end there and then!
  5. Vega
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    Vega Senior Member

    Yes, I agree.

    I have posted this on other thread, but it makes more sense on this one:

    Yes I agree with most of what you say. But far meaningless than STIX (regarding stability assessment) were what Guillermo calls “Old Ratios”. Those were very inaccurate tools that are only applicable (and very roughly) to a certain type of boat. They are meaningless if applied to modern bulbed sailboats.

    The information that you say is available, is not. The sellers will not have a clue about what you are talking about and the boat manufacturers don’t disclose that information to the public. You have to ask for it, and sometimes they give it to you, others they don’t.

    I believe you are overestimating the average knowledge of the typical boat buyer. Fact is that even professional specialized press, completely disregard the information about safety stability in the boats they are testing for their magazines. Even the British press that usually publish the GZ or RM curves of the boats they test, don’t make any comments about them, neither when they are very bad, nor extremely good.

    If these guys don’t really know how to interpret those data, how do you expect the average buyer to do it?

    STIX has the advantage of simplicity in its interpretation, the bigger the better, and even if far from perfection, it can give you an approximate idea of the boat’s stability. Better than nothing, I would say.
  6. Guillermo
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    Guillermo Ingeniero Naval

    Tentative list

    Here my first tentative list for the basic information (brochures, web, etc) to be provided for all over 6 m sailing boats, from manufactures/designers:

    Basic info:
    (metric and imperial units)
    Displacement in MOC
    Maximum load displacement
    Ballast (fixed)
    Lwl at MOC
    Bwl at MOC
    Body draught
    Total draught (with and without lifting keels and the like)
    Engine mark and model
    kW or HP (DIN) and rpm at continuous duty condition
    Propeller type, diameter and pitch
    Fuel tanks capacity
    Range at 1.1 (imperial) SLR
    I,J,P,E (And mizzens' or other if it's the case)
    Heeling arm for IJPE area + lateral hull & deck profile
    Sailing areas upwind and downwind
    GZ curve for MOC, indicating downflooding angle and GMo
    Roll period at MOC
    (indicating if measured or estimated for these two last)

    Parameters and Ratios:
    (imperial and metric units)
    Roll Acceleration
    Dellenbaugh angle
    AVS (Although already constant at the GZ curve, also to be explicited here)
    Negative/Positive GZ curve areas ratio

    RCD info:
    RCD approved Category
    STIX and its Factors.
    Watertighteness degree of hatches, etc.
    Notified Body
    Assessment Module used.

    Structure & Construction
    Rules and regulations used and level attained
    Hull & deck type of construction and materials
    Basic scantlings
    Mast & rigging type, materials and scantlings
    Rudder type, material and attachement to stock
    Stock material and diameter
    Stock bearings
    Steering system
    Propulsion shaft material and diameter
    Propulsion shaft bearings
    Engine bed type. Mountings.

    Basic equipment list and price,
    with marks and models.
    (Specifying water and retention tanks)

    Optional equipment list
    with marks, models and prices (mounted)

    Full profile with precise WL at MOC
    Interior lay-out
    Deck arrangement
    Midships section.


    Type(s) and duration, for construction and equipments

    This should be something like a 'Minimum Code of Practice' among designers/manufactures.
    Now, your proposals.....
  7. marshmat
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    marshmat Senior Member

    Guillermo, if all manufacturers disclosed all of that, the number of boatbuilders would be cut in half. The crappy ones couldn't pass off CSM-covered putty as "advanced composites" if all of that info were available to buyers!
    Granted, though, it's a good list and I for one would want to know all of that, plus a lot more, before dropping several years' salary on a big hole in the water.
    I'm not sure, though, how buyers would react... after all, there are an awful lot of people who can afford a boat, and go out and buy one, and have no real idea how to use it. Let alone understand why it would behave as it would if it ever left its pier.
  8. Guillermo
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    Guillermo Ingeniero Naval

    :D :D :D
    Absolutely. But we have to try, at least, for the ones who really care.
  9. SuperPiper
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    SuperPiper Men With Little Boats . .

    I started to read the list syllable for syllable at the start. After a while, I was scanning and near the end, I was skipping.

    Apply this rationale to automobiles. Half the time I can't remember what tire size I need.

    Maybe the "condense it all to a single number" idea is not so bad for 99% of the planet.
  10. Guillermo
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    Guillermo Ingeniero Naval

    Then, what should a basic spec list include?
    Several people at these forums have complained here and there about the lack of info from designers/manufactures and the inadequacy of STIX to tell enough about a boat's seaworthiness (I'm one of those, as evident).
    So, let's concentrate only in stability, seaworthiness and performance matters, to not do the list too long, as SuperPiper complains.

    Alternative lists....? More opinions....?
  11. Stephen Ditmore
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    Stephen Ditmore Senior Member

    I'm afraid you're using abbreviations I'm unfamilliar with, Guillermo. What are Lh and MOC?

    It's interesting that angle of vanishing stability, area under the righting arm curve, and area under the inverted righting arm curve are not on your list. Why not? Roll accelleration is there, but not roll period or roll period constant...?
  12. Mikey
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    Mikey Senior Member

    MOC = minimum operating condition
    Lh = the distance measured from the forward end of the foremost outside surface of the hull shell to the aft end of the aftermost outside surface of the hull shell

  13. Guillermo
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    Guillermo Ingeniero Naval

    Mikey correctly explained the first part of your question.
    AVS is there. Twice. One with the GZ curve and a second and explicit time in 'parameters and ratios'
    Roll period is at the end of 'basic info' as 'Roll period at MOC'
    I did include the GZ curve, but not the areas (Which anyhow may be explicited at the graphic) because I'm trying to get here a basic specification only as this is info for customers, not NAs. If an NA or other interested people wants to know the areas, well, he/she should work out that from the GZ curve. And I have included the negative/positive area ratio, which is the most relevant info to be known for a customer, not the areas themselves.
  14. RHough
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    RHough Retro Dude

    I agree with Crag for the most part. The information should be available to anyone that cares, so they can make a decision based on their priorities.

    Designers and builders of "safe" boats should be free to use the information to promote the "safety" of their boats. Volvo sold cars that don't interest me in the slightest based on "safety". (funny that that they also sponsor the VO70's)

    I do not agree that the designers or manufacturers of boats should decide what is best for others. I think fools should be allowed to be fools, and everyone should have choices.

    I think that most owners of series production boats are basically clueless. That more of them don't die every year is testimony to the integrity of the designers and builders.

    If we want to save lives, we should make boating less attractive to the masses. If we could remind people that their are dragons at the end of the earth they would be less tempted to leave the dock. We can sell them pontoon boats dressed up to look like ocean racers (but with 6 heads and three wet bars) and they can still enjoy their boats as they do now.

    I think that many things that have been done to make boating attractive to the masses have done more to make boating unsafe than any hull form. My background is sail boats, but I'm sure the power guys have some of the same thoughts.

    The great hue and cry for safe cars over better drivers came from the insurance industry. That's what has given us cars that have thousands in extra cost, in order to limit the insurance company liability. If/when insurance companies decide that they are paying out too much money for dead or injured sailors we will see "safety" sailboats.

    Do we really want regulations that demand passive safety on our boats?

    The requirements might look like this:

    "The boat must survive a 4 knot impact with a submerged container. The boat must be unsinkable after the impact. If children are carried, they must be restrained in positive flotation devices and tethered so they cannot go overboard. Any vessel that carries restrained children must be capsize proof or self right from any angle within 90 seconds. In the event of impact of capsize all crew shall be restrained form hitting anything that can hurt them, or all surfaces and structures that could kill or injure a person shall either absorb or deflect energy. No person in any unrestrained position shall be subject to a force exceeding 50g's for 1 second during impact from a speed equal to S/L = 1.1 or a capsize event."

    It has been my observation that the level of driving skills has gone down as cars become "safer" and less dependant on driver skill (ABS brakes, traction control, etc). I have no doubt that the skill of sailors has gone down since the introduction of mass produced plastic boats. As more systems and "features" are added, the number of clueless sailors increases.

    All systems that allow a novice sailor to think they can control a sail of over 150 sq ft should be banned on boats sold to novices. This includes winches and all forms of roller reefing/furling. All systems that allow jobs best done on the foredeck or at the mast should not be allowed to be lead back to the cockpit. Once a sailor has been certified in a basic type, they can add such systems or purchase a boat with larger sails and more complex systems. This seems to work for private aviation, why not boats?

    Cars are sold to people that can't drive and we force them to be more crash-proof. We do little or nothing to certify the driver's ability. Large powerful boats are sold to people that have no seamanship skills. We do little or nothing to certify a sailors ability.

    If you want to make boating safer, refuse to design boats that lull their owners into a false sense of security. If people are too frightened to leave the "safety of the cockpit" they are less likely to leave the dock at all, it no longer matters if the boat will capsize or not. :D

    End of Rant

  15. Kaa
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    Kaa Wanderer

    You understand that the first part of your post -- about people having the freedom to do stupid things -- directly contradicts your rant, which basically states that people who haven't demonstrated competence should not be allowed near anything bigger than a small, basic boat, right?

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