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Thread: Rogue waves & yacht design

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    Default Rogue waves & yacht design

    Now that reality is setting in, and the actual cases of rogue waves have been better documented & found to be more common than imagined - how must naval architects respond?

    Here are a few videos: https://youtu.be/zlPpAhDBlfk
    https://www.youtube.com/watch?v=0YVZ...FBE5EA5E56AF7E

    A few highlights from the videos, when they used the satellite system to count the actual number of waves over 75 feet in a 3 week time frame, they got 10 of them.
    (Granted, this was off the south cape of South America, but still)

    We've also had various cases of sunk cargo ships due to rogue waves:
    https://en.wikipedia.org/wiki/List_of_rogue_waves


    Will design change to reflect these common rogue waves? Can a 30-50 foot yacht be designed for safety in rogue waves?
    etc etc

    thanks for your thoughts

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    Default Re: Rogue waves & yacht design

    As I understand it, rogues are more common than previously thought and there may well be multiple combination causes. It appears that areas where an ocean current counter powerful winds encourage rogues. Similarly, severe temperature gradients and strong winds.

    Given how rogues do not appear to travel far, it seems likely that at the minimum a rogue must involved compounding from two or more wave chains. We see compounding often in normal sailing. It's not that every seventh wave is larger, but if you have two strong wave chains coming along at some shallow intersecting angle and/or and one chain overtaking the other, there will be regular moments where the crests coincide to make a larger wave.

    One thought is this basic phenomenon made up of more wave chains. This makes sense for those rogues that are still basically trochoidal but there are limits to the trochoidal shape. Simple trochoidal waves have a wave length to height ratio of about 7:1. Steeper than that and the peak tends to collapse. One can poetically imagine how the peaks of several strong chains could coincide to produce the rogue that's been described by some survivors as looking like a vertical wall of water, not breaking, just hurtling at them. But so far as I know, no generated waves and no good math has shown exactly how this might be.

    Hence, we are better off in knowing that there are more rogues and in knowing when and where they are more likely. We are not yet better off in fully understanding their physics.

    It may be that rather counter-intuitivly the smaller ocean cruising yacht can survive a rogue better. The nature of stress build up versus material strength makes it that the smaller boat can easily be stronger in relation to the stresses it takes than a larger boat. A one or two tonner would be rolled about a bit but would not be as likely to suffer a hull breach and might even emerge on the other side rig in tact.

    If one had adequate warning of an approaching or developing rogue, it might be that a good sea anchor over the stern to keep you square to the face and pull you though might work. However, modern sailing generally favors maintaining sailing control in the direction you desire over passive survival tactics and rogues do develop in conditions that, which extreme, are not beyond the abilities of modern design.

    So, it remains, a judgement call as to balancing going a bit light, to reduce stresses when the water crashes down on you, and having the hull and rig strong enough to survive.

    Nothing but a submarine is really proof against rogues.

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    Default Re: Rogue waves & yacht design

    Quote Originally Posted by Dirc View Post


    Will design change to reflect these common rogue waves? Can a 30-50 foot yacht be designed for safety in rogue waves?
    etc etc

    thanks for your thoughts
    Just a guess and stating the obvious I suppose, but the more you design anything with one very specific and extreme function in mind, the less likely it would be practical for general purposes.
    There is no rational, logical, or physical description of how free will could exist. It therefore makes no sense to praise or condemn anyone on the grounds they are a free willed self that made one choice but could have chosen something else. There is no evidence that such a situation is possible in our Universe. Demonstrate otherwise and I will be thrilled.

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    Default Re: Rogue waves & yacht design

    I suppose a point to bear in mind is that although they have been found to be 'more common than previously thought' they are not actually any more or less common than they have always been. The balance of risks people take when going to sea has not changed.

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    Default Re: Rogue waves & yacht design

    I think this knowledge of increased chance of rogue wave encounter falls in the wheelhouse of seamanship rather than design. Be prepared for what might happen; have a well-thought strategy in place for in the event of, etc.

    Kevin

    Edit: What I don't understand is: Where do rogue waves end up? Do none make it land? None? Hard to believe.

    K
    There are two kinds of boaters: those who have run aground, and those who lie about it.

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    Default Re: Rogue waves & yacht design

    It may be that rather counter-intuitivly the smaller ocean cruising yacht can survive a rogue better.
    I suspect this is true. A beach ball can survive all wave conditions. The further you get from such a solid, compact design, the harder it becomes to engineer a boat that can handle the stresses. Small cruisers get dismasted often enough, but once the extremities have been removed the remaining capsule is pretty secure as long as it hasn't been holed.
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    Default Re: Rogue waves & yacht design

    Quote Originally Posted by Breakaway View Post
    I think this knowledge of increased chance of rogue wave encounter falls in the wheelhouse of seamanship rather than design. Be prepared for what might happen; have a well-thought strategy in place for in the event of, etc.

    Kevin

    Edit: What I don't understand is: Where do rogue waves end up? Do none make it land? None? Hard to believe.

    K
    Oh, they definitely do make it to land. The west coast of Vancouver Island is liberally coated with "Watch for Rogue Wave" signs, and the internet is liberally coated with stories of people who didn't. And small vessels near shore get caught too.

    I'm guessing there might be different strategies for dealing with rogue waves farther out. I think when they get inshore they're steeper, as they run up against a shallow bottom? Tricky...

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    Default Re: Rogue waves & yacht design

    Oh, they definitely do make it to land. The west coast of Vancouver Island is liberally coated with "Watch for Rogue Wave" signs, and the internet is liberally coated with stories of people who didn't. And small vessels near shore get caught too.
    People get washed off jetties, breakwaters and piers during storms ( or when storms pass offshore causing big seas in calm weather) all the time. Those waves aren't typically rogues waves--their just big storm waves. The kinds of sizes these rogues are supposed to be, there would be instances of landscapes dramatically changing, not just sweeping a human to sea.



    Kevin
    There are two kinds of boaters: those who have run aground, and those who lie about it.

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    Default Re: Rogue waves & yacht design

    Quote Originally Posted by Breakaway View Post
    I think this knowledge of increased chance of rogue wave encounter falls in the wheelhouse of seamanship rather than design. Be prepared for what might happen; have a well-thought strategy in place for in the event of, etc.

    Kevin

    Edit: What I don't understand is: Where do rogue waves end up? Do none make it land? None? Hard to believe.

    K
    Ian answered the question. The rogue is not one wave, it is several waves adding up when they all pass the same place at the same time. All of the smaller waves continue on. Sometimes several waves reach shore at the same time.

    I was trolling for pompano in a guideboat just outside of a roughly one foot surf near Melbourne Florida around 1977. Two huge breakers came out of nowhere. I had just enough time to crank the boat into them and get one stroke in before the first one stood me on end, maybe two more strokes before the second one hit. They broke over the bow, hit my head and the end of the deck at the stern. Then there was nothing but the small swells and ~1' breakers and I hardly shipped any water. Maybe not huge, but in a small rowboat, a 6' breaker seems huge.
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    Default Re: Rogue waves & yacht design

    Ian answered the question. The rogue is not one wave, it is several waves adding up when they all pass the same place at the same time. All of the smaller waves continue on. Sometimes several waves reach shore at the same time.
    I can't doubt, Ian. In fact, I have experienced the so-called "Three Sisters," whereby a wave larger than the prevailing waves, and larger than even the biggest waves in the sets, has come along, " out of nowhere." These are said by lore to be the result of three waves almost combining into one. Perhaps a single 8- or 10-foot wave on a 4 foot day.But nothing on the scale of what is being discussed here.

    The source material in the OP references single waves reaching as much as 80 feet in height.

    Kevin
    There are two kinds of boaters: those who have run aground, and those who lie about it.

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    Default Re: Rogue waves & yacht design

    By coincidence (perhaps) this was featured recently on the BeeB http://www.bbc.com/earth/story/20170...-actually-real
    It really is quite difficult to build an ugly wooden boat.

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    Default Re: Rogue waves & yacht design

    It is not known how long along the crest the true rogue or ultimate (as it was called in the '60s when most oceanographers dismissed it as myth) wave can be or how long they last. Some of the newer satilite evidence indicates that at least some of these ultimate waves might roll along for hundreds of miles. This is thought to be a very different formation than the cumulative one spot synchronization of several wave trains.

    One of the wonderful things about advances in science is when we find that we don't know what we knew yesterday.

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    Default Re: Rogue waves & yacht design

    When the 10,000 ton Town-class cruiser HMS Sheffield met a rogue wave on her way to escort a Russian convoy in WW2, the force of the water squeezed the side of the turret in so far that the top of the turret popped off and went overboard. The Sheffield's turrets were made of 1" thick steel armour. If you can't resist the force of a rogue wave with an inch of top-quality steel then it seems better to try to dodge them or roll over the top.

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    Default Re: Rogue waves & yacht design

    Having made the acquaintance of a 'rogue', I would say that designing for the rollover and self righting/self rescue is the point. Odds of meeting one are tiny, but its there. As for surf, don't turn your back on it.

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    Default Re: Rogue waves & yacht design

    Yeah, the really big ships which were lost due to rogue waves:

    https://en.wikipedia.org/wiki/MV_Derbyshire

    https://en.wikipedia.org/wiki/MS_M%C3%BCnchen MS München

    and especially this one: https://en.wikipedia.org/wiki/USS_Tennessee_(ACR-10) since there seems to be more info & being naval, probably better accounts & corroboration

    unreal

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    Default Re: Rogue waves & yacht design



    Design does come into the issue. Some boats stay upside down more readily than others, for example.

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    Default Re: Rogue waves & yacht design

    I think a rogue wave is a freak where the normally circular orbital water particle motion is kicked up to a mostly vertical orbit, sort of like a boat wake just before planing. Depicted below is the equilibrium circular motion out to sea and the horizontal motion near coast.



    So by mathematical combination or whatever a steep much higher wave can arise. I doubt if they roll onwards in lengthy solitude, but like a tsunami would even out into multiple equilibrium waves. I have seen videos of rogue waves from ships with a unique shape that I am familiar with. A steep wall of water that doesn't curve concave into a crest but forms sort of a convex lump at top.

    I have seen and felt that at a smaller scale at out-of-control surf sites. I used to go to those outside of lifeguard hours when they are kicking out non-pros, and experience the waves just before they broke. Wave height and steepness means little; it's all about the internal circulation. Some would eject me out the backside in freefall - superfun! Others could be these monster, steep, "fluffernuters" with no horizontal circulation where you bob harmlessly. They had that same shape of a vertical wall not threatening to crest over and topped with a lump.

    OK, coastal is idiosyncratic so let's consider boat wakes. They can be far less disruptive to cross than an equal size ocean wave at equilibrium, I think because they start with a mostly up and down internal orbit and little horizontal push. I have several boats with a Euro rating for particular wave height, and they have a sidenote that double that size of boat wake can be tolerated. Of course a wake should evolve towards the circular, but should be dissipating by that time.

    Phil Bolger once designed a boat solely for minimal boat wake at displacement speed (in order to slice thru FL residential canals harmlessly). He optimized it for minimal side waves, just up and down energy. It worked great, and I think because he was shaping the initial orbital motion mostly vertically rather than horizontally.

    Bottom line is I think a rogue wave is more of a rapscallion wave, slightly less sinister than it looks and unlikely to maintain it's character for long. Maybe a sailing keelboat with low freeboard handles it best.
    Last edited by rudderless; 05-18-2017 at 08:36 PM.

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    Default Re: Rogue waves & yacht design

    Paul Johnson Venus ketches going to come back into popularity again?

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    Default Re: Rogue waves & yacht design

    Here's a good read on the subject. A blend of science, research and surfers searching for 100+ rouges.
    Steve B
    TraditionalSmallCraftAssociation
    DowneastTSCA.org

    TraditionalSmallCraft.com
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    Default Re: Rogue waves & yacht design

    Wave that contain such massive energy that they rise over fifty feet, even to almost one hundred feet, when they "feel" a bottom of such a shape and slope that they can mount that high without breaking are the dreams of surfers, especially now that they can be towed into a start, but they are probably not the same physics as the off-shore "ultimate wave" that forms in deep water.

    It could be that the wave or wave combinations that form an ultimate wave are reacting to a temperature of deep current gradient that acts rather like a shoal, but that's far from demonstrated and the shape of the off-shore ultimate wave, so far as it's documented, appears different from the more common combination rogue that can produce a six to ten footer in an ambient two foot swell. Or a thirty to forty footer in sustained fifteen foot storm seas.

    We have models that provide a sense of understanding the combination waves. These are the standard rogues and they can be deadly enough. Many of us have experienced something of these. But the "ultimate wave" appears to be different and therein lie the controversy and mystery. Unlike the basic rogue, there are very few survivors to report the events, and among those, fewer who have coherent descriptions. At least with deep drilling rigs, ocean buoys, modern instrumentation on oceanographic vessels, and satellite data we have gotten as far as the admission that Ultimate Waves exist.

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    Default Re: Rogue waves & yacht design

    The comments about the waves that break and spit you out the backside on breaking vs waves that have some noteworthy internal hydraulics that hold on to you are relevant. The rogue I was involved with was not part of a wave train and despite having a fully done up and fastened floater suit, I was held down (deep) for a long time (more than a minute, less than 3) it felt like being trapped in the hydraulics in rapids and falls that won't let you go. Those of us who had left some fastening of their suits undone, had their floater suits stripped off. The hydraulics were quite different from what one would expect with a 'large' breaking wave. Trying to understand it in terms of wave trains is, I think 'difficult'.

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    Default Re: Rogue waves & yacht design

    Quote Originally Posted by Dirc View Post
    Now that reality is setting in, and the actual cases of rogue waves have been better documented & found to be more common than imagined - how must naval architects respond?

    Here are a few videos: https://youtu.be/zlPpAhDBlfk
    https://www.youtube.com/watch?v=0YVZ...FBE5EA5E56AF7E

    A few highlights from the videos, when they used the satellite system to count the actual number of waves over 75 feet in a 3 week time frame, they got 10 of them.
    (Granted, this was off the south cape of South America, but still)

    We've also had various cases of sunk cargo ships due to rogue waves:
    https://en.wikipedia.org/wiki/List_of_rogue_waves


    Will design change to reflect these common rogue waves? Can a 30-50 foot yacht be designed for safety in rogue waves?
    etc etc

    thanks for your thoughts

    that's scary 10 waves over 75' in 3 weeks in one section of ocean...

    apparently there were more than one wave in excess of 100' recorded by mid Atlantic weather bouy during the "Perfect Storm" Oct 29, 1991 in the central Atlantic mid way between england and Novascotia, east of the Flemish cap.

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    Default Re: Rogue waves & yacht design

    Quote Originally Posted by peter osberg View Post
    The comments about the waves that break and spit you out the backside on breaking vs waves that have some noteworthy internal hydraulics that hold on to you are relevant. The rogue I was involved with was not part of a wave train and despite having a fully done up and fastened floater suit, I was held down (deep) for a long time (more than a minute, less than 3) it felt like being trapped in the hydraulics in rapids and falls that won't let you go. Those of us who had left some fastening of their suits undone, had their floater suits stripped off. The hydraulics were quite different from what one would expect with a 'large' breaking wave. Trying to understand it in terms of wave trains is, I think 'difficult'.
    care to tell the story of your encounter Peter?

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    Default Re: Rogue waves & yacht design

    So I'm thinkin' gee that sounds like a soliton. But other than smoke rings, I can't put my finger on how it would work, so I googled it. Still don't know.


    https://arstechnica.com/science/2010...s-rogue-waves/
    http://www.science20.com/alpha_meme/..._physics-86053
    https://en.wikipedia.org/wiki/Soliton
    https://en.wikipedia.org/wiki/Peregrine_soliton
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    Default Re: Rogue waves & yacht design

    Quote Originally Posted by Daniel Noyes View Post
    care to tell the story of your encounter Peter?
    I read an account of a nightime rogue wave on a Bermuda sailboat race, the individual said 'they suddenly felt like they were in a high speed elevator' (before the rollover); that is a good description of your first clue. From that point, it is reflex survival. I think you can understand a lot about waves, wave and current theory, eckman spirals, etc., but it is like understanding avalanches, your knowledge is not very predictive except in hindsight.

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    Default Re: Rogue waves & yacht design

    Recently i met a tanker captain what has made at least one trip to South Africa and back. Really cool guy, he trolled all the way there and back and caught a lot of fish, but that's not this subject.

    Rare as it is that I'm FTF with a genuine sea-going Captain, I asked him about rogue waves and got two stories immediately. He also spoke of "hot spots" for them, like where there are major current intersections and standing waves from such. Then you mix in the wind.

    My reasoning why rogue waves don't all come crashing onto the shore is that they are simply dissipated as the wind/current/depth conditions change, and that near shore isn't usually their genesis. I've never thought of rogues as a coastal threat, but an AT SEA condition.

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    Default Re: Rogue waves & yacht design

    Quote Originally Posted by Wade Patton View Post
    My reasoning why rogue waves don't all come crashing onto the shore is that they are simply dissipated as the wind/current/depth conditions change, and that near shore isn't usually their genesis. I've never thought of rogues as a coastal threat, but an AT SEA condition.
    Yes, the bigger the wave, the further off shore it breaks in deeper water.
    When the water depth is less than one-twentieth the wavelength, the wave becomes a shallow-water wave (D < 1/20 L). At this point, the top of the wave travels so much faster than the bottom of the wave that top of the wave begins to spill over and fall down the front surface. This is called a breaking wave. A breaking wave occurs when one of three things happen:

    1. The crest of the wave forms an angle less than 120˚,
    2. The wave height is greater than one-seventh of the wavelength (H > 1/7 L), or
    3. The wave height is greater than three-fourths of the water depth (H > 3/4 D).


    It really is quite difficult to build an ugly wooden boat.

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    Default Re: Rogue waves & yacht design

    Quote Originally Posted by Peerie Maa View Post
    Yes, the bigger the wave, the further off shore it breaks in deeper water.
    tales are told of the mountainous seas that find bottom 200 miles from shore on the Grand Banks and stand up 5 stories tall to thunder and crash just yards form the schooner fleets, anchored like little ducks on their mothers back in the lee of the banks.

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    Default Re: Rogue waves & yacht design

    here's a photo of a small sail and oar boat that met with a Rouge 40 miles off the Welsh Coast and her skipper lived to tell the tale...just.

    His 20 foot, Gloucester built Banks Dory was tossed and capsized like a bit of straw on the water, Johnson lost his stove and square sail in the encounter, and rated it, later in his life, as the most menacing sea he encountered in 40+ years captaining a schooner out of the port of Gloucester and sailing the oceans deeps.


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    Default Re: Rogue waves & yacht design

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    Default Re: Rogue waves & yacht design

    Did nobody mention wiki's list of dozens specific supposedly rogue waves https://en.wikipedia.org/wiki/List_of_rogue_waves ? Not garden variety 100+ft hurricane waves, but isolated events like the rather small one below. Sure, half of them have sketchy evidence, but the other half include clickable references.



    I still think wave theory as confirmed by wave tanks are flawed. High tops may fall down in the (windless?) wave tank by the 1/7 ratio rule, but really high tops may hang around for a destructive while just by chance, in spite of being "unstable". I have experienced looking up at freaky "walls of water" like from the trough of the upper examples shown below (and like the wiki first-hand accounts mention) which are different from the more typical examples shown lower below in their near tumbledown state. They weren't noticeably concave but have steep planar faces with a large mass of water behind them. EDIT=> And not looking inclined to break!

    Last edited by rudderless; 05-21-2017 at 09:10 PM.

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    Default Re: Rogue waves & yacht design

    ^ What mechanism keeps liquid water piled up for any length of time? No such thing as anti-gravity, so what stops the tall peak collapsing to its natural level?
    Waves happen because the water flows in a circular motion, flow being the optimum word, it is not a static system but constantly changing.
    That you were in a trough looking up at a wall of water is not because the wave waited for to you to turn up, but because you were in the right (wrong) place at just that moment.
    It really is quite difficult to build an ugly wooden boat.

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    Default Re: Rogue waves & yacht design

    One of the first (if not the fist) freak waves to be studied and understood was generated off South Africa in the Agulhas current after the Bencruachan survived.
    This illustrates what she experienced

    A combination of a fast current, sea bed topography and big storm waves rolling in from a couple of storms in the preceding week adding to each other.

    This is what it did to her
    It really is quite difficult to build an ugly wooden boat.

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    Default Re: Rogue waves & yacht design

    Quote Originally Posted by Peerie Maa View Post
    One of the first (if not the fist) freak waves to be studied and understood was generated off South Africa in the Agulhas current after the Bencruachan survived.
    This illustrates what she experienced

    A combination of a fast current, sea bed topography and big storm waves rolling in from a couple of storms in the preceding week adding to each other.

    This is what it did to her

    Rogue waves in this part of the Southern Ocean are expected as a result of the current opposing the SW wave train, compounded by other wave trains, as you say Nick.
    Speed has to be a factor in this incident,t though, a the ship wa reportedly traveling at 20 knts into the waves and with a following current of at least 5knts would have slammed into that wall of water at these combined speeds; not considering the speed of the traveling wave.

    Seamanship and the boat/ship suitability needs also to be factored in.
    This is roughly the same area where Bernard Moitessier was rolled in his wooden boat Marie Therese, and when he thought internal ballast (concrete) was excesive.

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    Default Re: Rogue waves & yacht design

    ^ She also briefly accelerated down the slope of the trough, so she buried her bow and all of the fo'c'sle into the solid wall of water. It was this weight of water pinning the bow down against the hulls buoyancy trying to lift it that caused the buckle.
    It really is quite difficult to build an ugly wooden boat.

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