Who's right Who's wrong? Is A Canoe Stern Better Performing Than A Double Ender?

Discussion in 'Boat Design' started by kudu, Sep 29, 2005.

  1. Bergalia
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    Bergalia Senior Member

    who's right who's wrong ?

    Ah Kudu - it matters not - until you come to a sudden stop - and then your 'transom' stern is 'flooded' whereas the canoe stern cleaves it to either side.. :D

    BUT - a big but, it's an argument that is sure to rouse the hackles in either camp - double enders and transomers. Like throwing a stink bomb among the congregation...

    Over here in Australia you get the 'petrol heads' arguing the merits of Ford versus Holden (General Motors). To the dispassionate they are much of a muchness... but both camps claim superiority (I drive a RangeRover Discovery) which is obviously far superior... :D

    So when it comes down to it - each to his own. For me, double enders every time - for safety sake. (That's my contribution with a big spoon) :D
     
  2. dougfrolich
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    dougfrolich Senior Member

    I'll second that, Bergalia---Though I do like those big butts. But then again I thought it was a good idea to sail this across the Pacific.
     

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  3. Skippy
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    Skippy Senior Member

    kudu: Does it really matter that the water from both sides of the hull crashes into each other? It seems, at that point of interference the transom would be one step ahead of it, no?

    You always want the water flow to be as straight as possible. Curved flow/crashing is what creates wave drag. There's no transom on a canoe stern, the curved hull creates a low-pressure area that pulls the water toward the centerline. I'm not sure what you mean by one step ahead.
     
  4. Bergalia
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    Bergalia Senior Member

    who's right who's wrong ?

    Beautiful shot, Doug...but how do I know it's you hidden behind the sail...or if was you, did you hide because you were embarrassed at being caught wearing one of those multicoloured 'weekend yottie' bobble caps... :D :D
    But bravely done Doug. ;)
     
  5. safewalrus
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    safewalrus Ancient Marriner

    Skippy

    That's what I said, two fronts/two a***s! Only without the gobblegook!
     
  6. Skippy
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    Skippy Senior Member

    Gobbledygook is my specee-ality. :p

    kudu: Does it really matter that the water from both sides of the hull crashes into each other? It seems, at that point of interference the transom would be one step ahead of it, no?

    Skippy: I'm not sure what you mean by one step ahead.


    Oh I know, you mean if the water is already past the hull, how can it have any effect? I guess the idea is that energy has already been imparted to the water, and that energy must have been drawn out of the boat. That occurs just before the crash, where the hull is curving inward so the low pressure exerts a drag on the boat. There's also an increase in displacement from the sloped underside of the hull, which I suspect adds to wave drag even more than the sides.
     
  7. kudu
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    kudu Senior Member

    What I mean Skippy is...Isn't the stern moving away from the turbulance? Doesn't the action take place after the transom has moved forward? :confused:
     
  8. dougfrolich
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    dougfrolich Senior Member

    Its like the pic.
     

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  9. kudu
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    kudu Senior Member

    I'm trying to picture this event...As momentum pushes the double ender forward the water sliding past each side of the hull folds upon itself (turbulence) at the trailing edge of the hull/rudder. At this point isn't it similar to the trailing edge of a sail or wing from a plane? Somewhat of a pinch point where the energy pushes one forward? In other words...a good thing, and after this event it becomes a moot point.
     
  10. kudu
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    kudu Senior Member

    Hey Dougfrolich...In a cruising double ended hull, how fast could you be talking about? I'm assuming I'd be real lucky to do 8 knots. What do you think?
     
  11. kudu
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    kudu Senior Member

    Could you elaborate on the Cruiser stern vs a canoe? Thanks
     
  12. kudu
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    kudu Senior Member

    I'm with you Bergalia...There is nothing finer, sweeter, sexier and oh yes, more pleasing to the eye than a double ender!!! I will happily deal with the loss of a + or - 1/2 knot of speed from a double ender, as FastFred describes! :)
     
  13. Sean Herron
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    Sean Herron Senior Member

    I am right - absolutely....

    Hello...

    This is a funny thread for me - just recently I have been thinking about and doodling boats of 22 feet in length and shooting the poop at work with the 'guys' about double enders or transom sterns...

    I have also decided that divorces are expensive because they are worth it - but my wife is still very attractive and she puts up with me so I don't go there... :)

    She is a pain in the *** though - but thats better than fat, boring, and stupid looking I suppose... :)

    So what have you...

    I am suprised old Dave Gerr did not plant himself on this one as he seems to be the only contemporary designer doing proper canoe sterned yachts - which I think are ugly and stupid looking - and I am right - all the time - and in any place - because I am usually by myself there... :)

    Happy wife - happy life - you can be right or you can be happy - you choose...

    So canoe sterns are funny, ugly and weird - at least to me and MY wife - plus they are tricky to loft, fair and build - and hard to explain to people who ask 'why'... :)

    You can draw and hide some flat aft sections into them per the discussion above - but something not mentioned thus far is the lack of bouyancy aft in both double enders and canoe sterned ulgies...

    This is something to consider when taking into thought the use of the boat - how many people and things - gas tanks - water tanks - engines - outboards - rail mounted BBQ's are going to 'hanging' about the back end of the boat while sailing...

    A transomed boat can load up asymetrically quite well for the daysail - and a double ender can load up very well for a long cruise - meaning you can sink the 'transom' of a double ender with little appreciable difference in performance or load waterline plans - sink a 'normal' transom below the DWL on a fatass boat and you get all those ugly eddies and little negative suction thingies... :)

    Aside from all these thoughts - canoe sterns are just ugly and stupid - and I am always right when standing alone in an empty room... :)

    Oh man - life is hard....

    See http://www.donkrafft.com/gerr_boats.htm ...

    SH
     

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  14. Skippy
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    Skippy Senior Member

    kudu: As momentum pushes the double ender forward the water sliding past each side of the hull folds upon itself (turbulence) at the trailing edge of the hull/rudder.

    No, back up one step (actually, move forward :) ). As you can see in Doug's sketch, the hump of water is building up before it clears the stern. That's where the suction slows (and weighs) the boat down, where it's still in contact with the hull.
     

  15. Sean Herron
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    Sean Herron Senior Member

    Tea Pots...

    Hello...

    Don't know if th is makes sense - but think of the tea dribbling down the side of a smooth lipped pot - it has been found that a pot with a sharp edged mouth (unfinished cheap metal) drips less - 'good release'...

    Cheers - sun is out...

    SH>
     
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