Canoe length, efficiency and speed

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

  1. portacruise
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    portacruise Senior Member

    If the rules allow it, maybe try to work on the weight aspect? If the 375# can't be cut back, maybe the canoe part could be made lighter using SOF or inflatable design? Even weight may not make that much difference, it may be difficult to maintain 5 miles per hour average over a day, unless you are able to build up to elite athlete status.

    PC
     
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  2. philSweet
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    Location: Beaufort, SC and H'ville, NC

    philSweet Senior Member

    I used Kaper and came to a similar conclusion to Dolfiman. The Kaper calculation hueristic for surface area computation is rather weak and fussy to use. You can't get an updated area by changing a single parameter - you have to go back and adjust the draft and other features first. Increasing displacement (and making the appropriate change to Cx) doesn't generate an resonable change in area. So I rate Kaper as useless for displacement traces. You need to bring your own surface geometry to the game. I used Kaper's area as a first run and hand adjusted the area for different displacements.

    Having said that, your suspiciously light displacement figure works out to a waterline @4" of about 16.0 feet and a beam of 2.30
    feet. That gives you a D/L of 46. If you add 100 pounds, you'd want about a foot more. You also need to consider volume. You want to be able to sleep and cook in a Y1000 boat. That means real estate is at a premium. You also want to work in plenty of tumblehome where the paddles operate. It's easier to do that on a longer boat.

    You may want to look at the Yukon River Quest rules as well. Their boat specs are a bit different. And they have an additional beam spec for concave gun'ls SCR types.
     
    Last edited: Oct 27, 2018
  3. Dolfiman
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    Dolfiman Senior Member

    Yes, based on the loaded canoe. Here attached in complement, this Beam investigation with the Canoe Loa 17', to show its influence on the GM, all other things equal inc. the payload.
     

    Attached Files:

  4. BlueBell
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    BlueBell Ahhhhh...

    But why 375# when it's two guys, their stuff, paddles and canoe?
    More than 375#...
    Total racing weight is given earlier in the thread isn't it?
     
  5. ben schmidt
    Joined: Oct 2018
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    Location: alaska

    ben schmidt Junior Member

    Our body weight is 325#.
    Plus gear. My sheep hunting camp is 40# for just me, including my rifle, so 45#for two liteweights seems adequate. Last time I had a guy with the kitchen sink and the time before that we were required to bring a lot of food. So I haven’t really ran it ultra lite yet.
    The canoe weight is in addition to the 375#. I am planning on testing Innegra/foam core this winter. I hate to say it’s weight because no one will believe me, but I think a 20# canoe is attainable. If that actually happens our total weight will be <400#.
     
  6. BlueBell
    Joined: May 2017
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    BlueBell Ahhhhh...

    Wow!
    I'm 200#, so I'm impressed.
    So what team were you (or are you) on the website list?
    You're going to need to test the sh*t out of that thing well before the race, but you already know that.
    Does 400# include the rifle? It must. You can't win if you're dead or injured right?
    What thickness foam?
    Your plan or modified bought plan?
    I'll be some impressed if you build a 20# canoe, that lasts the course!
    When is the race?
    It's every two years now, so spring 2019?
    And you've already done it twice!
    Did you finish twice too?
     
  7. ben schmidt
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    Location: alaska

    ben schmidt Junior Member

    First time was in 09. We were the Frozen Hobos. This year I filled in with a polish guy last minute, for Independent Poland. I can get 1/4” foam here. Innegra isn’t very rigid, but it’s very tough. So rigidity is the only problem. After this thread I’m liking the freedom 17’ and the Cirrus 18’ and ya I’d have to modify some. Next run should be 2020. We are considering running the quest but our summers are so short, I don’t think I can race every year.
    The first time we were the third place canoe. This year we were the second canoe.
     
  8. BlueBell
    Joined: May 2017
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    BlueBell Ahhhhh...

    Wow, nice countdown, 3rd - 2nd - win!

    You could do raised ribs out of foam on foam with lots of angles for rigidity.
    I have built, and am building, with epoxy/fiber on foam.
    Mostly solid foam with a very small, enclosed, one-man cockpit.
    Not really what you're doing, but I'm with you.
     
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  9. DCockey
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    DCockey Senior Member

    Any concerns about puncture resistance? Foam with thin skins usually is not very puncture resistant. Or are there no sharp obstacles along the course?
     
  10. ben schmidt
    Joined: Oct 2018
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    Location: alaska

    ben schmidt Junior Member

    This boat definitely will not be built to general purpose durability. There are no submerged rocks. So just the ones at the landings. The river does have a lot of power, but a solid class 2 is about all there is for whitewater. I’m thinking rigidity is my main concern to stand up to the hydraulics of the river. There are lots of powerful boils. Having said that, Innegra is stronger than glass or Kevlar and lighter than carbon. It just isn’t rigid. I’m banking on the width of the foam to do that for me. If not, I’ll need to use a woven carbon/Innegra fabric which is ok too. I don’t know what weight fabric was used, or what gun was used, but there is a video out of Innegra catching a bullet. But I suppose under the right situation, glass would too.
     
  11. Dolfiman
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    Dolfiman Senior Member

    I can propose you this comparison based on info and data available for the Freedom 17' and the Cirrus 18', and a free interpretation with Gene-Hull that I called F17 and C18. For C18, as there was no indication on the Cp, I take the opportunity to investigate on this value, and the lowest drag at around 5 mph is obtained with a Cp of 0,52 (below this value, we are outside the limit of validity of the residuary drag computation from Delft series). A slight reduction of the Lwl (at @ 4'' waterline) also contributes to a drag reduction of the loaded canoe, and I pay attention to put the free boards and the Bwl/Lwl ratio in exact agreement with the Yukon 1000 rules. This version is named C18 V3 in the document here attached. This version shows a slight advantage / F17, 5,11 instead of 4,99 mph at propulsion net power 75 W, so +2,2 %. This advantage becomes quasi null when we add the aero drag due to an head wind of 12 knots.The stability is also a bit better for the C18 V3.

    I takes the opportunity of this thread to also develop a specific Gene-Hull version for Canoe hull, with the VPP application connected, here is the file and the User guide for this spreadsheet (free of charge and open source). The file is an .ods to open and use with either Open office or Libre Office (also with Excel I think but I have not test this). The input data in place on the file are the one for C18 V3, so you can use it to develop your own version. The other versions (F17 and previous versions of C18 that I also tested) are stored in the "Hulls storage" sheet. By hoping that can be helpful.
     

    Attached Files:

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  12. ben schmidt
    Joined: Oct 2018
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    Location: alaska

    ben schmidt Junior Member

    Wow. Thanks. I’ll spend some time here.
     
  13. Dolfiman
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    Dolfiman Senior Member

    2 minor Errata : a copy-paste mistake (for the hydrostatics data of the C18 V3 version in the comparison document), and it is "Bwl/Loa" (as rightly computed) and not "Bwl/Lwl" >>> the corrected documents here attached.
     

    Attached Files:

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  14. eyschulman
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    eyschulman Senior Member

    several years ago I rigged an 18 ft rotomolded Oldtown canoe with an Onboard rowing rig with 9 ft oars. The Onboard rig had a fixed seat and moving foot and oar section keeping porposeing down to a minimum and with the long oars a very stable rig. I believe sustained 6K speeds possible with a conditioned oars-man. I suspect a 24 ft craft if kept light would be even better especially if given the option of one or two oars-men.
     
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