Seaworthiness

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

  1. RHough
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    RHough Retro Dude

    One of the intrinsic characters of boats is to capsize if the waves are large enough. All changing the design can do is increase the size of the wave required to capsize it and reduce the time spent inverted when it does.

    The boat itself as the last line of defense? The boat can capsize, they all can according to that 1984 report. Why would I consider something I know can be overturned as a last defense? The intrinsic nature of a series drogue is to protect the boat from itself.

    I think it is a mistake to rely on the design of the boat. The boat hasn't been built that cannot be capsized unless active measures are taken.

    That is why I think that too much time trying to improve stability and reduce inversion time past what most production boats have is a poor use of time and resources (in other words, I think it's silly). :) The Class 40 types are clearly above average in terms of +/- area in the stability curve when compared to most production boats.

    Make the boat easy and enjoyable to sail. Make the interior safe and usable at sea. Make the hull easily driven and use 15 degrees of heel as one design point and 10 knots of wind as another. When you are done and into the second or third trip around the design spiral, then see if you can increase stability without giving up other design goals.

    It is just a matter of priorities. Loads go up exponentially with size, for a given length, a lower displacement boat does not generate the loads that a heavier boat does. The challenge is to design a boat that has an easy motion at sea without adding lead to it. A boat that has good manners at anchor and is quiet (no "slap stopper" needed) should also be a higher priority than increasing the AVS from 130 to 150 or increasing the +/- ratio from 5:1 to 6:1 or 7:1

    No one has shown that the Class 40 cruisers are not seaworthy. No one has shown that the beam distribution has any effect on the inversion time. The perception that the Class 40 boats have extremely wide beams has proved false. When compared to other production 40 foot boats the Class 40's are only marginally wider. When compared to other boats with 40 LWL they are notwhere near extreme in beam.

    It is my opinion that the negative reaction to modern, fast, lightweight cruisers is not founded on science, but on personal bias and outdated studies and reports.

    I don't see a problem with production boats being unsafe at sea from the standpoint of stability. I think that some people are looking for solutions to a problem that does not exist. :)
     
  2. KevlarPirate
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    KevlarPirate Junior Member

    danishBagger

    “acting all backwards and unaware of the metric system”

    “but an enormous share of them/you haven't got a clue. Notice I never said "Americans don't know **** about the metric system" If so, you would have a point, as there is quite a difference between the two statements.

    Dear danishBagger:

    Please explain that difference , my simple mind is having difficulty parsing those statements.

    I have read your posts and I cannot find where you have offered any technical knowledge or experience or references to literature. With your great wisdom, I seems like you are a little behind.

    Perhaps some reading will bring you up to speed with the technical merit of this thread. After you come up to speed , perhaps you can share some of that with us. Notice I didn’t insult your country, only you.
     
    1 person likes this.
  3. Guillermo
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    Guillermo Ingeniero Naval

    "There's no worst blind than the one who doesn't want to see." (Proverb) ;)

    :D
     
  4. hiracer
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    hiracer Senior Member

    Bingo, we have a winner here.

    RHough, I'm a major fan of JSD myself and in the middle sewing one for my boat, but I recognize that if I'm disabled for whatever reason, there is little chance that my 5'1" non-metric wife can deploy the thing. A JSD is no lightweight especially with the chain at the end, and it's ungainly. On an actively moving boat in storm waters, it could be washed overboard before deployment as much as anything can be--especially if my wife is in charge.

    You are free to give up boat stability as a last line of defense, as is your right, but many of us don't feel as immortal as you even with a JSD on board. Even though boat stability can be defeated by a major storm, I still want it in my corner because it certainly can't hurt and, who knows, it might make the difference. Seaworthiness making the difference between life and death has happened before and it probably will again.
     
  5. RHough
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    RHough Retro Dude

    Once again, when confronted with fact, the response is a snide remark.

    Please re-read this thread and show where any objective data has been put forth that would make an un-biased person conclude the a Class 40 boat is un-seaworthy. Please note that an unbiased person would not modify the STIX number of a boat to try to make a point.

    Do your homework and prove that my statement that the beam of a Class 40 boat is not extreme when compared to other boats of the same waterline length. I could have been wrong when I did my research. No one questioned the results of my little sample when I posted it in this thread.

    I agree with some of the generalisations about extreme boats and I agree that boats with higher ratios of positive to negative area on their stability curves are more seaworthy than boats with lower ratios. The fact is that the Pogo 40 has a better ratio than most boats. I think those that paint the Class 40 boats as extreme and un-safe did so based on personal bias and prejudice. Now that the stability curve is a matter of record and the beam has been compared to other production boats of about the same size and was shown not to be extreme, no one wants to say that perhaps they were a bit hasty and jumped to a false conclusion.

    It goes back to the designers and their concern for safety at sea. Finot would not enjoy a good reputation if they designed unsafe boats.

    As far as the JSD being hard to use:

    "Launching the Drogue
    One of the design objectives of the drogue is that it may be launched with one hand under storm conditions without leaving the cockpit and that it will not foul even if the boat is rolling or yawing. This capability has convincingly been confirmed as described in Performance at Sea."

    I'm almost certain that a standard issue 1550mm wife/mate could toss the chain overboard. The drogue will follow. :D

    I have never advocated going to sea in an un-safe boat. I seem to be alone in thinking that no boat is completely safe. All boats can be capsized or overwhelmed by the sea. It is the sole responsibility of the skipper and crew to take care of the boat. That means taking action to avoid sailing in extreme conditions and being prepared to take action if extreme conditions cannot be avoided. It is obvious that the ability of a boat to cover a greater area in 24 hours reduces the possibility of having to use active survival techniques. It is also obvious to me that choosing a less able boat increases risk.

    It is not the responsibility of the boat and it's designer to take care of the skipper. I think people that place their faith in the boat rather than the people have it backwards. That's okay with me, I'm quite comfortable being a pair of brown shoes at a black tie affair. Go ahead, put your faith in the boat and sleep well ... that's what Ken Barnes did. :p
     
  6. hiracer
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    hiracer Senior Member

    You mischaracterize my position.

    I agree that safety lies primarily in the competency of captain and crew, but recognize they are not aways able to function on account of illness or injury, at which point the boat is on her own. For me, it's not a matter of faith in the boat as much as it's a lack of faith in the infallability of captain and crew.

    Bad things happen to good people, even the best of captain and crew. And the older we get, the more it happens. A boat design that recognizes these facts is a good design, IMO.
     
  7. hiracer
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    hiracer Senior Member

    You have conveniently left out the hard part: getting the darn thing out of the cockpit lazarette. Way far in the back, strapped next to the steering quadrants. Have you actually ever manhandled a JSD on a pitching, heaving, yawing boat? Mine has 123 cones on 300 feet of 3/4" line. Plus chain. In one bag. Total weight is a substantial portion of my wife's entire body weight.

    And she gets seasick very easily.

    I'm sorry, but I am not describing a failsafe system. The boat may be on her own without JSD, despite my best of intentions. In my experience, that's how things work out sometimes.
     
  8. hiracer
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    hiracer Senior Member

    I stand corrected. My wife is metric, given the fact that she was born and raised in Korea.

    * * *

    My wife and I are both on the wrong side of 50. A couple of slips away is a Valiant 40 who is captained and crewed by a couple in their 80s. They still take her out.

    I want to grow up and be like them. Maybe that gives some context to my perspective. I suspect a few decades ago I may have sounded much like Rhough.
     
  9. KevlarPirate
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    KevlarPirate Junior Member

    Randy

    Your work on the weather routing hardware and software is very impressive; I read it on the weather routing thread. I can’t trust it however, and that is based on some first hand knowledge gained in Feb 2007, where the input data gave false wind speed predictions on a race I ran, because of too much dependence on interpolations an extrapolations.

    It will take much more development for me to
    trust that over a robust boat of known behavior. You can be the
    data point on that one, not me.

    Certainly all of us intending to cruise would be foolish not to use
    all the tools available to us which we can trust, afford an have room for onboard for. For instance, I will certainly consider a drogue of my choosing even though my boat would handle larger beam on waves than most.

    Some of these tools however cannot be relied upon for valid, experience gained reasons discussed here by myself and others.
    You claim we have forwarded non-convincing arguments which amount to sea stories.

    Personally, I gained a Masters Ocean Operators License in 1989,
    with sailing endorsement and had logged 840 days at sea as one of the qualifications. That was 18 years ago. I also have a technical background to couple that experience to. From the posts on this thread, I think others have quite a bit of experience also.

    In the end however, the boat is the final safety net whether you like it or not. You have sold yourself on your own model, good.

    However, you are quite wrong when you say or imply no valid arguments have been offered and that we are biased. You have ignored much of which has been offered free to you.

    Here’s one, Like HOW the static curves are derived now by manufacturers. You claim “as a matter of record” is of your own interpretation. I think the curves are stretched, easily done to data, I work in R&D.

    I think you are believing these curves with no scrutiny, I think YOU are the one biased, you want to believe in it so bad. I inquired and got a LAME answer from a manufacturer, I mentioned this before, you had no comment. For one who is so thorough, I was surprised.

    There is a lot of buzz about LPS and STIX and CSF. Don’t you think the profit (not safety) driven rocket boat manufacturers are very up and sensitive to this. Don’t you see their incentive may be suspect?

    The open 40 has wide beam to the stern with a shortened keel. doesn’t look good to me, sorry. I will need proof.

    I would be much more impressed if you would forward more VALID data in this area, like do some research, especially if the curve just doesn’t look right to the boat you see. Don’t parse the nuances.

    If it is a fat tub it will have a bad curve. If the keel is shortened, the curve will get worse. If it is light weight it will be kicked like a foot ball. If it has a noodle mast it will get rolled quickly ,remember moment of inertia (physics)??

    In other words if it has webbed feet and quacks, it’s a duck.

    I would also like some data which would validate the routing stuff too, from people using it, I will do my own homework there, as for the hull shapes, personally I don’t care, just a matter of interest.

    Over and out!!!
     
  10. Guillermo
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    Guillermo Ingeniero Naval

    Totally agree.
    Cheers.
     
    Last edited: Apr 8, 2007
  11. Guillermo
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    Guillermo Ingeniero Naval

    I think you are the one who have to re-read this thread and all posted attachements, examples, books and other references with care. Excuse me, but from my point of view you're at least as biased as you think other posters here are. Here another proverb from my country: "Thinks the thief everybody's of his own condition" (Just a joke. No offense intended :) )

    Class 40, with a length beam ratio of 2.74, definitely has a wide beam by all means when compared to other boats than modern beamy ones. That's why the STIX (And there you have a carefully scrutinized 130+ boats base data, i.e.) penalizes it through the Beam Displacement Factor, being 0.72 in my estimative and 0.86 as from one manufacturer (???).

    Maybe you'd like to compare it also with something more classic, like the well known John Holtrop's base list of "Best offshore cruising boats" (http://www.johnsboatstuff.com/Articles/best.htm) and "Choosing an affordable offshore cruising boat" (http://www.johnsboatstuff.com/Articles/lowcost.htm). "Best boats" there average a L/B ratio of 3.43

    Let me quote John:
    "Cruising boat designs show a definite trend away from the average boat, with less sail area, more weight, higher comfort factor, lower capsize risk, and half as much acceleration. My interpretation of this data is that it shows that most of today’s boats are designed for high performance and coastal cruising. These are not "bad" designs, they simple reflect what the majority of today’s buyers consider important. It does point out, however, the need for cruising boat purchasers to understand these fundamental differences so that they can make informed decisions based on how they intend to use the boat."

    I subscribe John's point of view.
    Cheers.
     
    Last edited: Apr 8, 2007
  12. rayk
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    rayk Senior Member

  13. Guillermo
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    Guillermo Ingeniero Naval

    From there:
    "The six member crew were sailing from Cape Town to Knysna when the yacht's battery failed and it was not able to pump out water."

    It seems they were not frightened enougth and/or they didn't have bucketts for all of them...! :D


    NOTE: If I click on your first link, I arrive to a Boatdesign.net page where it says:
    "Sorry: The page you requested has been updated to a new location."

    Cheers
     
  14. rayk
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    rayk Senior Member

    Thanks Guillermo, I fixed the link :)
     

  15. marshmat
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    marshmat Senior Member

    (re, second article in post 807) Let me get this straight... the Doughty was completely dependent on one battery bank, without which it was incapable of pumping out the incoming water. No manual pump? No buckets? No way to stem the water flow without outside help? What went wrong, that the boat could be taking on enough water to put it in danger? There's more to this story than is being told.
     
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