Is there validity to the notion that a pointy stern, a canoe stern, is safer at sea

Discussion in 'Sailboats' started by saltydog123, Jun 5, 2008.

  1. saltydog123
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    saltydog123 Junior Member

    I wonder if this is an accurate notion, or, a "fashion" of the day from 1970's designed pleasure sailing boats...
     
  2. Tad
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    Tad Boat Designer

  3. bntii
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    bntii Senior Member

    I once attended a talk given by Bill Crealock. He had quite a sense of humor on this point. He started his talk by saying that he would love to tell us that if 100 yachts set off across the Atlantic and only one had a canoe stern that 99 of them would sink :)
    Went on to provide the tech basis but I just remember the joke....
     
  4. TeddyDiver
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    TeddyDiver Gollywobbler

    It's more relevant issue on shoals and coastal waters with "sharper" wave patterns, and then a double ender is (in my opinion) more comfortable. In small open boats without reserve boyancy also safer..
     
  5. rwatson
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    rwatson Senior Member

    Hmmm, prehaps a big curling 50 ft wave coming up astern would look less scary in a big wharram cat which is pointy both ends, than an open ended, inward sloping transom yacht, as Mr Wharram states on his web site.

    All the cray fishing boats around Tasmania have canoe sterns because they have to "pull up" to recover cray pots. Often they have to reverse quickly if they overshoot a bouy . The fast tides and wind arent always in sync.

    I think there are a lot of scenarious where canoe sterns are usefull - but a lot if situations where they are just not needed.
     
  6. Tad
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    Tad Boat Designer

    A parting of the waters....commonly known as the "Noah effect".

    Like any subjective argument concerning a complex system, this one is endlessly circular. Trying to label one small feature as better or worse doesn't work. It must be addressed within the context of the whole boat. Taking a bad design and making it double-ended won't help, there are hundreds of other factors that add up to seaworthiness.

    Making any boat double-ended won't improve buoyancy aft, it severely reduces pitch-damping, and reduces stability thus power to carry sail. Making the form double-ended makes the waterline fine aft, reducing the prismatic and potential speed is lower. The double-ended form is good at reducing wetted surface and is useful at low speed where it produces little or no waves.
     
  7. rwatson
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    rwatson Senior Member

    That would be the MOSES effect! Noah didnt part waves, just floated on them as I remember (yes, i am that old :)

    Actually, the question of whether a pointy end increases bouyancy depends on whether you replace the wide transom with a pointy one, or extend the wide transom out to a point.

    Obviously the last approach will definitely increase the bouyancy dramatically, as well as presenting a lot less resistance to following tide, wind or waves.

    But, I agree with the point made - the stern design has to be considered in conjunction with the whole design purpose, and some boats just dont need them.
     
  8. Tad
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    Tad Boat Designer

    Right you are....I'm not that strong on Biblical matters apparently. But Noah's boat might have been double-ended?

    If one takes a 30' transom stern boat and adds 3' to the stern making her double-ended, she will be a somewhat better 33' boat. On the other hand a 33' transom sterned boat will be lots better than the 30' version. Faster, roomier, less pitchy, and with greater stability.

    Comparing a 30' transom stern boat to a 30' double-ender the DE hull will be smaller inside and on deck, have a smaller cockpit, be more sensitive to weight aft, be slower, less stable, pitch more.

    Thus the argument remains circular. The legitimate reason for having a double-ender is that you want a double-ended boat. Below is a recent 34' double-ended boat of my design.
    3401green04.jpg
     
  9. DanishBagger
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    DanishBagger Never Again

    Couldn't a legitimate reason for wanting a double-ended boat (besides the want-part, of course), that the extra carrying capacity is unneeded to some, and that at low speeds, it conceivably could be more efficient?

    Of course, I'm thinking of some of those "trollers" (I believe that's the term) I've seen with pointy sterns.

    Anyway, I like pointy sterns - especially on a long and slim hull (and with that we're back to the "I don't care, I like it"-part.

    edit: Oh, I forgot to mention, let's assume you make a racer with a very little reserve buoyancy at the stem (not stern), but at the same time give it a wide arse with huge reserve buoyancy, wouldn't that actually be less safe than to put a pointy stern on that boat, reducing the risk of lifting the stern too high in huge waves, thus reducing the risk of broaching?

    Am I grasping at straws here in an effort to find something good about pointy sterns?
     
  10. Tad
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    Tad Boat Designer

    I think that's a want-don't want argument......:D And all reasons are legitimate when talking about your own boat!

    I know I can design a transom sterned hull that is double-ended at the waterline and of equal efficiency to a "real" double-ended hull.

    As to matching bow with stern, that gets into the overall design. Poor double-enders can be designed just as poor transom sterned boats can be.

    Behavior of a particular boat running in a big sea or wind has much more to do with what's under water than what's above. But I doubt my argument will change the minds of DE evangelicals.
     
    Last edited: Jun 8, 2008
  11. DanishBagger
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    DanishBagger Never Again

    He he, thanks, Tad. It figures I was grasping at straws :D
     
  12. Mynhardt Coertz
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    Mynhardt Coertz Junior Member

    I agree ,all depends on the whole ( bow to stern ) underwater , for me there must be a flowing rythim to it all on the eye.
     
  13. mydauphin
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    mydauphin Senior Member

    Actually, the problem is that a lot of boats, and some ship's transoms are too low. Ask this question... What happens if you boat loses power and gets a 10 foot wave break on it from the rear or side. Remember boats are about safety first, navigation second, comfort third, looks last.
     
  14. Fanie
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    Fanie Fanie

    I was always under the impression that these double ended canoes were made that way so you can quickly reverse (paddle backwards) when the tanker suddenly appears from out of the mist...

    Moses may not have had a double ended boat, but his staff (fishing rod ?) was for sure.
     

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  15. robherc
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    robherc Designer/Hobbyist

    I like double-ender designs because I think it's cool to leave so little wake behind me when I'm sailing my cat in light conditions. :p
    Realistically, I'm pretty sure a canoe stern would get pitched about a bit less by a large following sea than a transom on an otherwise identical ship...but you'll have trade-offs for that at higher speeds I guess...
     
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