Canoe length, efficiency and speed

Discussion in 'Boat Design' started by ben schmidt, Oct 19, 2018.

  1. ben schmidt
    Joined: Oct 2018
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    Location: alaska

    ben schmidt Junior Member

    I am attempting to design a tandem canoe. I am not trying to make it as fast as possible. I am trying to make it as efficient as possible at an average speed of about 6 mph. It must have a length to width ratio of no less than .14375 at the 4” waterline. I have read John Winters “ The Shape of a Canoe” about 10 times. It seems to me that for the given speed, it would be more efficient to build a 17’ canoe with a 29.3” beam at the 4” waterline. Typically a canoe of 18’6” x 32” is used in this particular application. I hate to reinvent the wheel here, but I just don’t see the benefit of the larger boat, since the higher speeds are not sustainable in this environment. Is it easier to paddle a 17’ x 29.3” canoe 6mph than it is to paddle 18’6” x 32” at 6 mph? Thanks.
     
  2. Mr Efficiency
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    Mr Efficiency Senior Member

    Are you choosing between two existing designs ? One assumes if it is performance marginal, carrying the smaller one will be easier, so have that advantage.
     
  3. ben schmidt
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    ben schmidt Junior Member

    Everyone else tends to run the Clipper WW2. I don’t have a specific plan. Just a starting point for now.
     
  4. rwatson
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    rwatson Senior Member

    I can tell you from experience that the extra length makes a whole lot of difference.
    I once built a SOF 21ft long, and its straight line performance was amazing.

    It had a big turning circle, but in the ocean, that really isn't an issue.

    If I had to do it again, I would make it in 3 parts. The centre cockpit, with two removable end pieces. Ths would have the extra benefit of three compartments.
     
  5. gonzo
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    gonzo Senior Member

    6 MPH is a pretty high speed to maintain as an average. That is what competitive long distance racers attain. The average for recreational canoers is about 2.5 to 3.5 MPH>
     
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  6. Mr Efficiency
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    Mr Efficiency Senior Member

    Gonna say, 6 mph did seem lively.
     
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  7. rwatson
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    rwatson Senior Member

    Last edited: Oct 20, 2018
  8. Dolfiman
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    Dolfiman Senior Member

    What are the arguments which underpin such statement ?
    I think that for such light boat, stability consideration is also important, in itself of course but also for the propulsion issue : too low margin of stability ( i.e. too low GM in loaded conditions with two adults) and you are no longer confortable to develop full force with your upper bodies, being also worried by the stability to maintain. And Bwl plays a major role on that : yes a bit less Bwl can lead to a design with a bit less drag (at equivalent displacement), but with a noticeable decrease of the GM margin. There is a trade-off there in my opinion.
     
  9. Dolfiman
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    Dolfiman Senior Member

  10. BlueBell
    Joined: May 2017
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    BlueBell Ahhhhh...

    If efficiency is what you're looking for then buy a good, used tandem canoe.
     
  11. fallguy
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    fallguy Senior Member

    The SOR needs to lead it all. We don't know if this canoe is gonna make the 6mph with a motor or your intended use here.

    If you want a training machine or you want a fishing machine or a camping rig; all different designs. To just say fast is not sufficient. If it were; you would not be building a canoe.

    Canoes are not inherently efficient.
     
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  12. philSweet
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    philSweet Senior Member

    "Normal" paddles and paddling techniques don't even work at this speed. How long do you plan to maintain 6 mph? That's really chopping water with race paddles. The main determiner here is total vehicle weight. Everything else appears to be highly constrained. Open or protected waters has an effect as well. There aren't a lot of recreational paddlers who could maintain 6 mph for even a few miles. If you train for run-and-paddle team biathlons, that's a different story. A quick survey of "canoefest" events reveals a 6 mph pace would put you on the podium in many races over ten miles.

    A 17 foot canoe is designed for about 3 mph normally. This would be one with a low prismatic coefficient. You can tune the displacement curve for a higher speed, but a longer boat is a more efficient one. The 4" waterline business is a bit weird since you don't need to draft 4 inches. And you only need to hit max beam at one point. (There's usually some sort of smooth and convex rqmt that goes along with these beam rqmts).

    If you have Excel, you can play around with Jon Winter's and Matt Broze's KAPER spreadsheet.

    Mariner Kayak's Free Downloads Page http://www.marinerkayaks.com/downloads.htm

    Actually, you might not even need Excel, you might be able to run it right in the linked window.
     
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  13. JosephT
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    JosephT Senior Member

    What is your primary intention/goal for wanting to design the boat?

    -Recreation?
    -Expedition/touring?
    -Race?
     
  14. Manfred.pech
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    Manfred.pech Senior Member

    Last edited: Oct 23, 2018
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  15. comfisherman
    Joined: Apr 2009
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    comfisherman Junior Member

    Betting dollars to donuts, his goal is yukon 1000 style racing. Long range endurance racing in choppy northern watter. Beam ratio dictated via rules comittee. Needs to pack two guys and associated food and tents for 5 to 10 days. Experienced guys in the boat, this is not a family canoe.
     
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