Let´s be practical. Are we in the right way?

Discussion in 'Stability' started by Antonio Alcalá, Nov 6, 2007.

  1. CT 249
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    CT 249 Senior Member

    By the way, Brent, can you provide us with examples of the heavy boats that have demonstrated comparable performance to a lightweight of similar SA/D as you mentioned earlier?

    There seems to be an immense amount of information that confirms that factors other than SA/D have a huge amount of impact on performance so I would be glad of information to confirm otherwise.\

    PS that 32 of yours featured on this site looks like a sweet boat.
     
  2. MikeJohns
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    MikeJohns Senior Member

    How do we get this back in line with the main thread topic (sorry Antonio).

    Yes to all the accounts. This is what seems to make you so uncomfortable.

    Analyze the modes of failure,
    Is this what we would predict,
    Is there any other possible explanation,
    Could the vessel be improved to prevent that failure.
    Is this significant with respect to a yacht being designed today.
    How can we make similar vessels safer in the future
    Can we retrofit anything to existing vessels to make them safer.



    For example

    Would we expect a 3” solid GRP garboard to split on a conservative 42 footer ?
    Would we expect a 35 foot lightweight with low AVS to be inverted ?
    Would we expect decks and upperworks to be damaged in minimal strength lightweights?
    Would we expect highly stressed keels to fall off
    etc

    Some factors are immediately apparent and even exclude other explanations.
    Others are just conjecture but we can reasonably expect certain levels of reliability in certain vessels based on historical observation too.

    You like the Swansons, ironically In the last 4 years I have surveyed a Swanson 36 that nearly sank after developing a major leak alongside the stern tube. Another Swanson broke one of her chainplates and on inspection I thought they were very poorly designed and affixed.


    Proof isn’t really a word we use in engineering. “Indication’ is probably closer to the mark. But lets not get hung up on this. If you want a leak in the hull that is still well within the point I was making before.
    Think; why would a thick solid GRP hull develop a leak ?
    You want to believe the sea just cracked it from slamming in the storm ? Yet this is not an observed phenomena in heavily built solid GRP hulls unless there is a mitigating factor.

    Pulled out and gone home minimizing the exposure storm by motoring back to a sheltered coast. If she had been heading back and been rolled and suffered damage I would argue strongly for her inclusion.

    Then they let the vessel sink; [Once under tow] no buckets, no manual pump, no auxiliary pump from the rescue vessel. They were too tired perhaps? It appears to me that the boat was certainly well insured, but that may be an unfair comment.


    The synopsis sounds like they just let it sink once under tow which is what my comments were about, do you know if this is correct?

    Eh? People drown, get mashed by violent inversions, boats remain upside down too long, decks and deckhoses get smashed. ; Insurance?

    Dovell himself says many are compromised by their design, if they fail in the predicted manner do we really need to look further?
    If I do a stress calculation from a predicted static load with a FOS of 2 applied and the material is well past its ultimate strength then it’s failure is clearly a design issue.

    I don’t see that, I think it is more a case of a racing mindset slowly and painfully acknowledging that problems inherent in lightweight racing trends are becoming more apparent.

    The charts are a simple scatter graph, you do not need to normalize the data, clusters of points indicate trends. There were numbers of larger lightweights too but they generally fared well and are represented in that data as is every vessel in that race. The inference is that smaller boats of lower AVS are at greater risk. I think that is very clear.

    I would also query the wisdom of heavy weather in traditional old planked vessels, and maybe unless you are sure of the history and condition I would check 25 year old hard used solid GRP vessels before willfully venturing into a storm . (see Vega’s How long lasts fiberglass thread).

    I'm not being patronizing but perhaps you need to look at this with the mindset of an Engineer rather than a Lawyer. :)
     
  3. Brent Swain
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    Brent Swain Member

    A friend was racing around Auckland . He said the lightweights smoked past them downwind. When they reached the downwind mark and had to beat against a rough chop, the heavyweights quickly caught up with them and passed them.
    With the amount of debris and ships with no one on watch out there, I wouldn't consider going to sea in anything too light and flimsey to survive a moderate collision with anything.
    Show us a picture of a beneteau that survived T-boning by a freighter, like the steel boat in the picture.
    Brent
     
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  4. MikeJohns
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    MikeJohns Senior Member

    Brent

    Many of the lightweights have huge Sail area to displacement ratois and can stand up to a large press of sail to windward, this usually powers them well up the velocity-resistance curve.

    With narrow plumb bows they cut through smaller seas decreasing pitching induced resistance, but the payoff is that they can be very wet and uncomfortable with no shelter. A dodger adds aerodynamic resistance. All comfort goes for racing performance.

    To windward they are not in danger of broaching and give the helm more balance. Every vessel has certain combinations of wave height and period that will stop it in its tracks to windward.

    The heavier cruisers are carrying long term durability, collision safety, extra internal volume and all the hydrodynamic performance compromises of a more comfortable home at sea and in port. With all this they can still be designed with 'good' just not 'sparkling' performance. Light air tends to be the bugbear for the cruising boat particularly the sloop rig.
     
    Last edited: Jan 27, 2008
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  5. Ramona
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    Ramona Senior Member

     
  6. CT 249
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    CT 249 Senior Member

    Mike, if you have scrutinised all the accounts of the boats in trouble in the S-H so closely, how did you not pick up that Solandra either rolled or came close to it? How did you not notice that Loki, which is estimated to have rolled to 120-150 degrees, is included in the "rolled" list but not the heavyweight, high LPS Solandra which had a "major major knock down and roll" and was close to 180? Convenient that the high LPS boat that went further is missed from the data, isn't it! You didn't know of the Adams designed cruiser that was knocked down, either. If you didn't pick that sort of stuff up, then how good is your analysis?

    "The synopsis sounds like they just let it sink once under tow which is what my comments were about, do you know if this is correct?"

    If your research, your analysis of failure, is so detailed how come you didn't know that Mintanta's crew bailed her for many hours? It is not hard information to find the testimony her skipper and two crew gave to the coroner. They then got out because they felt that the boat was in a dangerous condition and would probably go down. Yes they had equipment failure (buckets and pumps) but equipment failure is also the reason for the loss of the sailors from WC and perhaps from SoO, therefore consistency demands that we not just ignore Mintanta for that reason. Oh, and lightweights suffered similar pumping equipment failure but stayed afloat.

    "If she had been heading back and been rolled and suffered damage I would argue strongly for her inclusion."

    I still find it strange that because she sank despite being in a safer position, she isn't counted. Some years ago, two boats failed (dismasted) inside the first 10 miles. No one said that they were excluded from criticism because they were in a safer area.....they were seen as unseaworthy. Why do different rules apply to Mintanta?

    You say I should look at things like an engineer - is that like the sort of engineer who was there (Dovell, Emerson from Mintanta who said the boat failed around the keel but whose testimony, credibility and honesty you attack)??

    Or is it the sort of engineer who wasn't there, ignores heavyweights that rolled or came close to it, and ignores the fact that 89% of the fleet (his claim) were short keelers and therfore it is logical that 64% of the boats knocked down or rolled (his charts) were light?? Do we think like the engineer who you quote as writing "Those interested in the Long/Short keel debate may note that none of the 11 per cent of the fleet with long keels was rolled” when it is (as far as I can see) impossble to define "long keel" in a way that makes up 11% of the fleet even if we ignore that either one or two of the longer-keel boats rolled 150 degrees or more?

    I haven't tried to look at anything as a lawyer - I've actually been discussing the approach with a science PhD student, tutor in stats and research methods at one of our top universities. As any basic text on stats and research will tell us, we have to look at the population we are studying. This is a fleet that is overwhelmingly light and therefore of course there's a cluster of points in the lightweight area. It's just like the fact that more white cars are involved in accidents than vermillion cars.

    "Eh? People drown, get mashed by violent inversions, boats remain upside down too long, decks and deckhoses get smashed. ; Insurance?"

    No, I never said they were insurance jobs - most of those boats got home, even the very heavy Kingurra which had some of the deckhouse smashed and had a crewman mashed by violent inversion before he went over and was saved from being a statistic by the fluke of a chopper being nearby.

    But it is interesting how, even when the engineer who owned Mintanta and was there said in testimony that he believes that Mintanta cracked her hull, you suddenly start throwing insinuations of criminal conduct around when another heavyweight gets in trouble (your sources having already ignored the damaged heavy Solandra and her injured crew for example). Interesting that you cite Taylor, whose charts indicate that Mintanta rolled twice, yet earlier said that she wasn


    You keep on excusing the failures because they threaten your theory - keep on saying that people didn't bail (they did so for hours and gave consistent evidence to that effect), say that there must have been a leak in the stern gland (which the engineer who was there and looking for leaks did not see), noted that the boat was "well insured" (your evidence????), and insult the builder (as Ramona pointed out, many of the "Swansons" were home built under the mould hire system).....it smacks a lot of someone looking for a reason to exclude evidence that would threaten your theory.

    I would also, frankly, be concerned if I was a leader of your professional association and found one of my members making public insinuations of criminal conduct about a fellow engineer. I shall no longer bother to discuss things with you as I find it difficult to deal with people who insinuate that others are frauds and criminals without strong evidence.


    Brent, a tale from a mate in an unnamed race is not exactly persuasive when it comes up against the huge mass of other evidence, like thousands of similar apocryphal tales and a mass of race times etc.

    I don't want a Beneteau and I don't plan my sailing around getting T boned by freighters any more than I plan my bike riding about getting T boned by semi-trailers.
     
  7. SeaSpark
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    SeaSpark -

    The difference between planning boat trips and road trips is clearly illustrated by the different types of GPS devices.

    "At the next roundabout....."
     
  8. MikeJohns
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    MikeJohns Senior Member



    I think we should analyze each vessel as I clearly said before. I also said I lack both the time and the resources at present to do this justice. Events need to be sorted into significant and insignificant.
    For example;……. Is it significant that an Adams performance cruiser was knocked down? I would say we could rightly expect it, but it is what happens after it was knocked down that interests us. I have sailed extensively and been knocked down several times in several different boats but I wouldn’t condemn a vessel for that.

    It is not that detailed as you well know, it is the hull-form and construction that interests me. It would have been constructive to go through each case with you if you could become a little more detached emotionally.

    I said I am happy to accept that the vessel may have split its garboard, but can you accept that this would be more likely to be age and construction related ( 25 yr old GRP non water resistant polyester resin) ? I feel that it is not a good representation. Apparently you do. My conjectures as to the source of the leak are just that; conjectures.

    No, you talk of proof , insinuation, frauds, criminal conduct. Whereas I want to know what failed and how we can stop it happening again and whether it was predictable.

    If they didn’t know than it was conjecture, if he thought it likely that is notable but it is not a fact. To say this does not threaten anyones honesty or credibility. Perhaps you’d like to quote what he said in his own words ?

    This was a good point and I noted it.
    What about length ?

    One half decent pump transferred from the towing vessel would have saved the boat, and these are not my words “…..they then let it sink…….. ”, You seem to concur. If you have more information it would be relevant. Remember this is a discussion not just statement of facts.

    Little dot to put her on the chart, not a big dot to show she was rolled twice. My fault posting low res images sorry.


    No I was saying there could have been; their reasoning appears to be no water flowing over an aft bulkhead and no one is questioning that. The rest is conjecture. I said let’s not get hung up on this, I said …lets accept for argument that it had a crack.


    The Swanson (a similar aged vessel) that I inspected that had clearly failed in the stern tube to hull bond was built by Swanson’s and surveyed by the same at a later date. This in itself is not that significant, but it should give you an idea of age related problems.

    Really you are drawing inferences and conclusions from extremely skewed observations.

    That is uncharacteristically unreasonable Chris.

    I acknowledge that you have some deeply held convictions but I have seen your own views change over time. I like your knowledge of the racing fleets and you are able to contribute a great deal, it is also good to get the opinions of a devout lightweight racing man, it would be even better if you could do so without getting so stressed.

    It is by education, observation, discussion and analysis that we come to conclusions. A forum is a place to air and discuss views and introduce thoughts observations and seek advice. Isn’t it ?
     
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  9. Guillermo
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    Guillermo Ingeniero Naval

    Chris,
    I think you're 'losing the papers', as we say around here. Your accusation on the implications on Mike's words is not fair at all. It may indicate you're beginning to have no arguments to sustain your position, so you have to fall into personal attacks. No good.

    Cheers.
     
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