Seaworthiness

Discussion in 'Stability' started by Guillermo, Nov 26, 2006.

  1. Frosty

    Frosty Previous Member

    Ive said it once and Ille say it again--nothing is seaworthy --some are better than others. By the very nature of this discussion it is obvious no one agrees. This discussion and debate has been going on for thousands of years. They launched an unsinkable ship only 100 years ago --she was called the Titanic, complete with the very latest technology.

    Todays ships/boats/yachts will be laughed at in another 100--and the debate will continue.
     
  2. Mikey
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    Mikey Senior Member

    Well, no, but... the crew (family) would take quite a beating from being exposed to the high accelerations. Marchaj writes that drouges are good survival tactics early in storms when waves are still relatively short but that sailing is a better option later when long waves have been built up. Would they be in a state to do that or would they be too tired and beaten up?

    A yacht cruising the oceans will normally be crewed by a couple or a family, not by 25 - 35 year old men who are out running 10 km every morning.

    Mikey
     
  3. RHough
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    RHough Retro Dude

    Very good point! However, look at the number of "well-designed" cruisers in any marina compared to what gets sold to and sailed by the great unwashed. :) The price of a Shannon 43 is about 6 times the price of a Catalina 42.

    The cost of building "well designed" cruising boats puts cruising beyond the means of most sailors. People go to sea in what ever they can afford. If you insist on Bristol Channel Cutters instead of Catalina 27's you will have very few boats in the marina and many unemployed designers and builders. Yet there are probably more Catalinas that have crossed oceans than Shannons. "Seaworthy"? I say it has more to do with the sailor than the boat.
     
  4. Mikey
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    Mikey Senior Member

    I would say that sea worthiness of a cruiser crewed by a couple or family is infinitely linked to sea kindliness

    Mikey
     
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  5. Mikey
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    Mikey Senior Member

    Aren't we overestimating the ability of Joe Blog? Does he really know how quickly his Pogo 40 can turn turtle sailing the English Channel in early May? Does he know that it may take 15 minutes for it to righten itself again?

    We all know what the IOR rule did to reduce sea worthiness of boats designed "using" those rules. I do not think that the average sailing enthusiast working as a middle level manager in the city knows the full extent of it.

    We certainly do have a responsibility, not to control but to educate

    Mikey
     
  6. RHough
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    RHough Retro Dude

    This comes right back around to how often you find yourself in these conditions.

    It is not hard to plan a passage to minimize the chances of sailing in gales, much less storms. I would say that it is possible to plan a route almost anywhere that is within the ability of almost any production 30 footer. If you don't fall into the trap of having to sail to a certain place at a certain time, you can pick your weather. Don't leave Auckland in June and head for the horn. :)

    If the size and range of your boat limit your routing choices (speed is a factor) you must have a boat that can stand more abuse. If your boat can cover 3,000 miles at a whack, there is little chance of ever seeing a storm that you can't sail in.

    The Class 40 "Cruisers" are getting maligned here. Let's make a different comparison. The Cruising Pogo40 Displaces 11,660 pounds, my Catalina 30 displaces 11.500. The Pogo has a 14.5 gal holding tank, my C30 has 17. The Pogo carries about 40 gallons of water, my C30 carries the same. Both boats can spend about the same time on a passage, which boat is more likely to face conditions that would overwhelm it? Which boat has more options when chosing routes? Which boat is more likely to have to heave to or lie ahull or use a drogue?

    I'm not saying that my C30 is an ocean class boat, far from it. Ask any world sailor if they have seen a C30 in port after making an ocean passage. I think the ability to survive major storms is overated when compared to the chances of ever having to do so.
     
  7. M&M Ovenden
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    M&M Ovenden Senior Member

    Reading threw this thread the answer to seaworthiness is staying very broad. Obviously each others views on seaworthiness are flawed by our own sailing habits and preferences. Perception of risk and safety changes depending on many personal characteristics: age, family, experience, sailing to go fast or sailing to travel, on holiday or all year around, in cold or warm water...
    So what is considered seaworthy for the professional racing skipper can't be the same then what is considered seaworthy for the traveling family. As numbers of pro skippers are a lot more limited than “go happy sailing family”, what cruising boat (or characteristics) would each of you find suitable for that family for it's around the world trip assuming they are competent sailors? Obviously basing the answer on what we consider seaworthy not looks or ultimate luxury.
    I'm sorry for such a personal question :) but I believe that this is probably the scenario which rounds up the most realistic perception and need for a vessels seaworthiness.

    Cheers ,
    Murielle
     
  8. fcfc
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    fcfc Senior Member

    I am dumb. I am very dumb.

    Here are the web site of french and UK marine investigation:
    http://www.beamer-france.org/
    http://www.maib.gov.uk/home/index.cfm

    When did a boat killed or injured someone because of not fast enough re righting ?

    Your idea will only make boating more expensive for thousands of boaters and will save NO life. The only effect will be to disminish your fears about racing fastnet 1979 and racing Sydney Hobart 1998.

    Meanwhile, a boat severely injured 2 people in 2 different accidents, simply because the mainsheet block is at the heigh of the crew head.
     
  9. fcfc
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    fcfc Senior Member

    I am sorry for the stupid answer, but the first essential characteric is that you can afford it. The second one is that you can maintain it. The third one is that you can live in it.

    Only after that you can speak of seaworthiness. And you can only choose seaworthiness features that will match the three first criterias.

    I have seen too much initially fine boats starting sailing around the world, and then with boat aging and finance degrading, becoming complete unsafe wrecks mainly due to lack of maintenance.
     
  10. Guillermo
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    Guillermo Ingeniero Naval

    But, although reluctantly, you are going the other way round, as far as I know. You even have the RCD in full force!

    I find that comparing a Pogo 40 footer against a Catalina 30 is not fair. You may also have asked about prices comparison and then some other questions too.

    Probably (And unluckily) ;)


    And I wouldn't buy a Pogo 40 neither a Beneteau for serious cruising. Nor my beloved Banjer, wich although with an STIX probably well over 50 it's not an ocean going boat in my opinion (Although some of my fellow members have crossed oceans and go globetrotting around). I'd rather go for something like the EFES 56 I posted at the STIX thread (http://www.efesyat.com.tr/project.html). Probably with some modifications. But that's my choice, of course.

    Cheers.
     
  11. Stephen Ditmore
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    Stephen Ditmore Senior Member

    I assume you're referring to a boat with a large roll gyradius being resistant to capsize by a sudden, brief gust and/or wave action. Does Marchaj address this? I've seen it discussed in an article by Art Paine (Art, for those who don't know, is Chuck's identical twin brother). One of the things Art claims is that Hinkley Bermuda 40s, which have a rather low LPS, nevertheless have logged an extraordinary number of sea miles with an excellent safety record.

    This means reducing weight aloft is a mixed bag. It lowers VCG and thus increases LPS, but it also decreases roll gyradius. Do I have that right, Mike? I think this explains why the STIX committee did not rely on a single measure like LPS. Would the men who died in the Sydney-Hobart race (and other incidents cited by Mike) have lived if the boats in question had re-righted faster? Maybe, maybe not. Perhaps the better way to protect people is to design boats unlikely to capsize (or unlikely to invert) in the first place. If you're involved in regulating passenger vessels, Mike, you know that's the approach generally taken in commercial marine regulation. You don't think powerboats need an LPS>135 to be safe, do you? What if we looked at ratios of (sail area*heeling arm) / (displ*area under the righting arm curve from 45-90 deg)?

    Responding to M&M, I think the International Standards Organization (ISO), in formulating STIX and other standards, is actually doing quite a good job of synthesizing a lot of information to come up with something usable. It may be subject to improvement and further study.... but what they've done is a beginning. Unfortunately, it takes having a spreadsheet or computer program and time to run numbers on a sampling of boats to fully understand the implications of STIX. It's possible a formula will be found which is both simpler and more predictive (wouldn't it be cool if it were the one I just proposed? :cool: ) but until it is, perhaps a decent STIX spreadsheet is what we should be working with.

    Mike, how do you feel about boats having masthead floats like the one on this catamaran to keep them from inverting?
     

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  12. Stephen Ditmore
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    Stephen Ditmore Senior Member

    Perhaps I should be less amotional. ;)
     
  13. rayk
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    rayk Senior Member

    A competition for seaworthy and seakindly design;

    Part I

    Design your boat.

    Wait for the worst storm in five years.

    Position boat in path of storm.

    Close hatches.

    Hand cuff yourself to the compression post or mast.

    Press play on iPod.

    Part II(If still alive post storm)

    Return to port without assistance and sell design.

    If you need to summon assistance, go back to the beginning and start again.


    "This is extreme design, a new sport that takes men to the edge of endurance and beyond fear!
    These heroes put their lives on the line for a higher purpose, you."
     
  14. fcfc
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    fcfc Senior Member


    In red lies the big problem.
    I think there are in the world a number of lifeboat builders. Yet they have tremendous difficulties to sell extreme seaworthy boats that comply with all the above to other people than lifesaving organizations. I do not think that Textron marine has sold a SINGLE 47 MLB to an individual.
     

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  15. MikeJohns
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    MikeJohns Senior Member

    Stephen
    Yes he does, In detail. he also draws on 2 good papers on sailing yacht capsize and dynamic stability:
    Kirkman Nagle Salsish SNAME 1983
    Stephens, Kirkman, Peterson SNAME 1981
    I am also aware of two other detailed studies One Japanese one Australian that all corroborate.

    Yes

    Surprisingly to most people the rig is the main contributor to the roll moment of inertia (Ir). For the benefit of clarity to others Ir=m.k^2 that is the inertia is equal to the mass centre of gravity times the distance from the rotational centre to the COG squared. K is called the radius of gyration.

    There are three ways of increasing this;

    A long strut and a big ballast bulb .
    Weight in the rig.
    Forcing entrained water to rotate along with the hull (to some extent).

    In a dynamic environment Ir is a very important element in resisting capsize due to breaking waves.
    In layman’s terms “the mass does not have time to react to the force of the wave”. Also our concepts of static stability are no more than a rough guide in the “open system” that a boat is, when in a seaway where dynamic forces tend to predominate considerations of stability.

    As an analogy of dynamic boat stability Crag talked before of motorbikes being inherently unstable and like a bicycle that knife edge stability requires a support (a foot) when stopped but when moving it is all dynamics.

    Cats are a different paradigm altogether, the work required to invert one (area under the RM curve) is huge compared with a mono-hull and given their absolute form stability you want as light a rig as possible or we have the immovable object (Inertia) fighting the irresistible force (RM) and the consequent forces are not conducive to structural reliability. A float on the mast is a good idea in a smaller cat since it significantly aids recovery. Large cats are so stable as to be virtually un-capsizable and are a arguably a safer hullform than many of the monohulls that some of us have been lambasting.


    Power boats are different again (but that will really confuse the issue) suffice it for the moment to leave the powerboat to the lottery of being engineless in heavy weather ………………:)

    Cheers
     
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