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Thread: Wedge-shaped hull at stern?

  1. #1
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    Default Wedge-shaped hull at stern?

    I watched the film _Following Seas_ about the cruising family Griffith, which naturally made me curious about their boat. They sailed an Uffa Fox-designed 53 footer, the Ahwahnee. A bit of googling turned up a 43 ft study plan at Karsten Marine Designs based on the Ahwahnee, the Ahwahnee III 43.

    The description of this hull study describes the Ahwahnee as a canoe-shaped hull that is advantageous in heeling as the canoe shape prevents the stern riding up in the water in heel, like wedge-shaped hulls do. This was said to prevent certain steering effects.

    Could anyone point me toward a description or example of what makes a hull wedge-shaped?

    Thanks.

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    Default Re: Wedge-shaped hull at stern?

    Maybe they mean 'double ended'?
    It's all fun and games until Darth Vader comes.

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    Default Re: Wedge-shaped hull at stern?

    I believe they're talking about boats with wide transoms that carry their beam a long ways aft. The ultimate "wedge" is "Comanche", but they were writing rather before her time

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    Default Re: Wedge-shaped hull at stern?

    Transom overhang vs. canoe or doublenders. Transom being the hull overhang beyond the rudder, not the flat part of a boats bum.
    At sea ina gale, boats with long transoms especially, can get into danger when the stern is lifted by a big wave.
    Cuz when de starn go up..de bow go dung.

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    Default Re: Wedge-shaped hull at stern?

    At the risk of offending those of more delicate sensibilities by posting such pictures, some of the more recent plastic boats are rather wedge shaped:

    Jeanneau Sunfast 3200 for example:

    20ff1c1ba81c4492bedd54b2d483c41b.jpg

    Lots of room down below and they are a hoot to sail when going downwind in a blow, but they do tend to take a nose-down attitude when heading upwind:

    005-Jeaneau-Sunfast-3200-Dare-Dare.jpg

    One of the reasons why many of these sort of designs have twin rudders (which then can make them 'interesting' to handle under power in a in a tight marina).

    A canoe stern will heel much less awkwardly, but you lose out on accommodation below and perhaps some downwind surfing potential.

    Everything's a compromise...

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    Default Re: Wedge-shaped hull at stern?

    Thanks, y'all. I was picturing the wedge as pointed downward into the water. Based on your comments (and pics), it seems clear to me that "wedge-shaped" refers to the outline of the hull in plan view from above. On second thought, though, a wedge pointed downward would have the same effect of lifting the stern and pitching the bow.

    Btw, Ahwahnee is a double-ender. There's some footage in the film of following seas that caused me to reconsider their benefit.

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    Default Re: Wedge-shaped hull at stern?

    I've long wondered whether the lee topsides of a heeled "wedge" hull pushes the hull to windward as it progresses on a beat, like asymetric leeboards or bilge boards do?

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    Default Re: Wedge-shaped hull at stern?

    Quote Originally Posted by Nicholas Scheuer View Post
    I've long wondered whether the lee topsides of a heeled "wedge" hull pushes the hull to windward as it progresses on a beat, like asymetric leeboards or bilge boards do?
    I don't believe so. But it does tend to increase weather helm dramatically. All-out racers have swinging ballast keels to keep them on their feet, and more recently horizontal foils as well. Here's a concept for a true wedge boat with all the appurtenances needed to keep it at an effective sailing attitude.

    -Dave

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    Default Re: Wedge-shaped hull at stern?

    "I've long wondered whether the lee topsides of a heeled "wedge" hull pushes the hull to windward as it progresses on a beat"

    "lee wave", "lee surge" ... there are various expressions in the old books to refer to "the lateral force of the hull" or "Hull Yaw Moment" or "Munk Moment"

    https://fr.m.wikipedia.org/wiki/Moment_de_Munk

    https://en.m.wikipedia.org/wiki/Michael_Max_Munk

    In this question we have to remenber Thomas Harrison Butler

    https://en.m.wikipedia.org/wiki/Thomas_Harrison_Butler

    but do not get carried away by appearances, I mean that a modern light or ultralight hull may be equal to or even better balanced than the magnificent Harrison Butler sailboats

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    Default Re: Wedge-shaped hull at stern?

    From my aeronautical point of view, sailboat design until yesterday afternoon has been something a bit primitive, so to speak

    naval engineers believe that a sailboat is a ship with sails, because indeed they were like that in the past, anyway this is a long and tangled historical issue

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    Default Re: Wedge-shaped hull at stern?

    It comes down to a matter of choice.
    If you enjoy speed, and can handle sailing the boat 24-7 without respite, go for a beamy flat overblown dingy form.
    if you want a boat that can be left to her own devices whilst you cook a meal, clean into dry cloths or sleep, go for a less beamy hull with a moderate or no counter.
    Be aware that sensible cruising designs fell out of favour when ad men started pushing less safe racing boat clones to aspirational yotties in their yellow wellies.
    It really is quite difficult to build an ugly wooden boat.

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    Default Re: Wedge-shaped hull at stern?

    Or it could be that sensible wide stern light short cruising/cruiser-racer designs fall out of favour when ad men start pushing "character cruisers" to aspirational yotties in yellow wellies who normally sail around SF Bay, Sydney Harbour or the Solent but feel that they need an "ocean cruiser" to do it. :-)

    I tend to favour more moderate stern widths than that of the Sunfast and Opens, but such boats can certainly sail on their own devices and an autohelm while you sleep, eat or change.

    It is of course a matter of personal taste, but try as I might I cannot find actual objective evidence that the modern boats are overall "less safe" than "sensible" cruisers. In the database of about 500 boats that were studied in the reports into the bad Hobarts and the 1979 Fastnet, for example, the "sensible" boats prove no better in terms of boats and lives lost as a proportion of entries.

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    Default Re: Wedge-shaped hull at stern?

    Quote Originally Posted by Chris249 View Post
    Or it could be that sensible wide stern light short cruising/cruiser-racer designs fall out of favour when ad men start pushing "character cruisers" to aspirational yotties in yellow wellies who normally sail around SF Bay, Sydney Harbour or the Solent but feel that they need an "ocean cruiser" to do it. :-)

    I tend to favour more moderate stern widths than that of the Sunfast and Opens, but such boats can certainly sail on their own devices and an autohelm while you sleep, eat or change.

    It is of course a matter of personal taste, but try as I might I cannot find actual objective evidence that the modern boats are overall "less safe" than "sensible" cruisers. In the database of about 500 boats that were studied in the reports into the bad Hobarts and the 1979 Fastnet, for example, the "sensible" boats prove no better in terms of boats and lives lost as a proportion of entries.
    The bad Hobarts and the 1979 Fastnet were extreme events. It is a bit like comparing survival after being hit by an avalanche in modern kit as you are in tweeds and a knitted sweater.
    If you enjoy spending the day flogging round the buoys, have at it.
    If you are going blue water passage making, remember that self steering gear can fail for several reasons, as can bits of the rig.
    I would not fancy running down wind in front of storm seas in one of those bloated dingies.
    Last edited by Peerie Maa; 11-23-2020 at 06:51 PM.
    It really is quite difficult to build an ugly wooden boat.

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    Default Re: Wedge-shaped hull at stern?

    Quote Originally Posted by Juan View Post
    From my aeronautical point of view, sailboat design until yesterday afternoon has been something a bit primitive, so to speak

    naval engineers believe that a sailboat is a ship with sails, because indeed they were like that in the past, anyway this is a long and tangled historical issue
    Dunno; there are many factors in boat design that a strictly aeronautical point of view may not pick up. And aircraft designers and creators like Burgess, Sopwith, Ted Wells, Fairey and many others were involved in sailing and boat design so it's not as if aeronautical concepts were unknown in sailing.

    The more I look into older designs, the more I can understand why they did things that we now think were bad ideas. One of the few things that I still find puzzling was why they could not get detached rudders to work well, but if I recall even Froude had the same issue with understanding the flow over detached rudders on steam-powered sailing warships. One also suspects that the very low aspect ratio of old rigs is also understandable, even if sailors of the 1930s could not work out why their predecessors had not developed higher aspect rigs sooner.

    It's interesting that designers like Shank, Murray and others were well aware as early as the 1700s and early to mid 1800s that centreboarders could operate in a different way to narrow and deeper boats. Observers also noted that the 1890s Raters were quite different to older yachts and ships. They clearly understood that a sailboat does not have to be like a ship with sails.

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    Default Re: Wedge-shaped hull at stern?

    Quote Originally Posted by Peerie Maa View Post
    The bad Hobarts and the 1979 Fastnet were extreme events. it is a bit like saying that you are no better surviving being hit by an avalanche in modern kit as you are in tweeds and a knitted sweater.
    If you enjoy spending the day flogging round the buoys, have at it.
    If you are going blue water passage making, remember that self steering gear can fail for several reasons.
    Sure they were extreme events, but the point is that even in extreme events one can find no statistically valid evidence that "sensible" boats are safer.

    I've done the odd few thousand miles of deepwater passagemaking, and my own boat sailed half way around the world on one autopilot and one wind vane without problems. It's not as if all "sensible" boats go without such things; I was reading yesterday about an experienced sailor who carries four autopilots on his 19 foot traditional junk rigged cruiser.

    Many people I have known preferred Finisterre types, Tahiti ketches, Malabars etc, and good on them. It's a personal choice and as I noted I tend to prefer narrower sterns for particular reasons, but the point is that these wedgy boats do not preclude anyone from sleeping, eating or changing offshore and there seems to be no true evidence that they are less safe.

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    Default Re: Wedge-shaped hull at stern?

    One of the current competitors in the Vendee noted that she could not hold a pencil and take notes -- the motion of the boat was just too quick and jarring. That's enough right there to put me off the type. I'd much rather move at half the speed and be comfortable.
    -Dave

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    Default Re: Wedge-shaped hull at stern?

    Sure, but that's an extreme boat in extreme conditions, and the traditional cruisers that met the same conditions in the Golden Globe challenge didn't do very well either. It's the same as comparing a hard-driven ORMA 60 tri to cruising on your F27.

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    Default Re: Wedge-shaped hull at stern?

    I believe it was the coxsain of the Peel lifeboat (RNLI Isle of Man), that stated that the broad sterned Arun class was liable to broach in heavy following seas, conditions that the previous double ended boat did not suffer from.

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    Default Re: Wedge-shaped hull at stern?

    Chris, I see you like to compare modern boats favorably with heavy trad cruisers based on how pretty much everybody who got trashed in a race .
    But how many of those boats continued to race /push their boats when they should have chosen to layahull or deploy a broken motorcycle overboard ?

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    Default Re: Wedge-shaped hull at stern?

    Quote Originally Posted by Peerie Maa View Post
    The bad Hobarts and the 1979 Fastnet were extreme events. It is a bit like comparing survival after being hit by an avalanche in modern kit as you are in tweeds and a knitted sweater.
    If you enjoy spending the day flogging round the buoys, have at it.
    If you are going blue water passage making, remember that self steering gear can fail for several reasons, as can bits of the rig.
    I would not fancy running down wind in front of storm seas in one of those bloated dingies.
    Even the most ROBUST Self steering gear...my monitor got busted at sea when a big USCG Zode bashed it during a deep water "safety" inspection.
    We were going upwind and not using it at the time. When I changed course to a reach and noticed it a few days later it was a WTF moment fer sher.

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    Default Re: Wedge-shaped hull at stern?

    Quote Originally Posted by wizbang 13 View Post
    Chris, I see you like to compare modern boats favorably with heavy trad cruisers based on how pretty much everybody who got trashed in a race .
    But how many of those boats continued to race /push their boats when they should have chosen to layahull or deploy a broken motorcycle overboard ?
    But there's no evidence that's a factor in determining the relative safety of each type, in terms of objective data. Some of the classic boats that got trashed were not being pushed, and many of the modern boats that did not get trashed were being pushed.

    Also, I didn't actually state that modern boats are safer. The point is that no one has shown me objective data that demonstrates that they are, as a whole, significantly less safe than traditional types, and that the available objective evidence of large fleets in storms shows no such trend.

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    Default Re: Wedge-shaped hull at stern?

    Quote Originally Posted by Chris249 View Post
    But there's no evidence that's a factor in determining the relative safety of each type, in terms of objective data. Some of the classic boats that got trashed were not being pushed, and many of the modern boats that did not get trashed were being pushed.

    Also, I didn't actually state that modern boats are safer. The point is that no one has shown me objective data that demonstrates that they are, as a whole, significantly less safe than traditional types, and that the available objective evidence of large fleets in storms shows no such trend.
    There are not enough large fleets in severe storms to provide enough data points to demonstrate any trends, You have to look elsewhere for enough evidence to consider relative safety comparing young athletically fit and resilient crew in race mode with Jo the plumber and his family going for a cruise along the English Channel.
    It really is quite difficult to build an ugly wooden boat.

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    Default Re: Wedge-shaped hull at stern?

    But the odd thing is that many people DO claim that there are enough data points to "prove" issues about seaworthiness. Marchaj and others, for example, claimed that the 300 datapoints of boats in the 1979 Fastnet showed that many IOR boats were unseaworthy. Surely if that is true and we add in the 200 extra data points represented by the bad Hobarts that have been the subject of enquiries, plus other races, we should have enough information to demonstrate trends.

    It's hard to see how 300 data points is enough to work out the impact of design on seaworthiness, but that 500+ data points is not enough to work out the impact of design on seaworthiness.

    It would be interesting to see if one can work out what sort of trend is important and significant, but not significant enough to be demonstrated with about 500 data points. If a trend is so small, perhaps it's insignificant or non-existent?

    If we are looking at Joe the Plumber in the English Channel, then how relevant is "blue water passage making" and "running down wind in front of storm seas"???

    Where is the evidence that Joe the Plumber is actually demonstrably significantly at more risk in the Channel on (say) a Beneteau Oceanis 32 than on a Rival 34? Is any such risk greater than the reduced time at sea (and therefore exposed to the elements, collision etc) than the wedge-shaped boat may give? Is this any evidence that any such risk is less important, in the grand scheme of things, than the fact that the Oceanis may have more space and therefore Joe and family may find it much more enjoyable? Is there any evidence that Joe is "an aspirational yachty in yellow wellies" who is more suspectible to marketing men than the guy who buys a "traditional" boat?

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    Default Re: Wedge-shaped hull at stern?

    Quote Originally Posted by wizbang 13 View Post
    .
    But how many of those boats continued to race /push their boats when they should have chosen to layahull or deploy a broken motorcycle overboard ?
    You forgot to mention: Before deploying motorcycle over the side, slacken engine sump plug till oil leaks, and fill fuel tank with fish oil, the resultant oil slick should calm the waves so one can attend tea and scones at 17:00.hrs.

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    Default Re: Wedge-shaped hull at stern?

    yea, I assume it's a Harley and the oil will come automatically as a feature.

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    Default Re: Wedge-shaped hull at stern?



    in this beautiful video we can appreciate the good hydrodynamic behavior of old solutions with narrow stern

    the question (from my aeronautical point of view) is the stability of the equilibrium of the sum of lateral and vertical forces

    But not all old sailboats deserve the name of "classics" and, on the other hand, there are good modern solutions born in what we can call the forge (1979/1989) of the MiniTransat: "American Express" is at the height level of Harrisons Butler Z4

    http://www.histoiredeshalfs.com/Hist...20Minis/49.htm

    https://www.yachtsnet.co.uk/archives...z-4-tonner.htm

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    Default Re: Wedge-shaped hull at stern?

    This ...

    D / L = 64 (!!!)
    LOA / BWL = 6 (!!!) "The Old Six Beam"

    http://setsail.com/beowulf-the-ultim...ed-march-2014/

    ... is a good solution ... but ...

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