front rowing system for canoe

Discussion in 'Boat Design' started by jyoder111, May 3, 2011.

  1. ancient kayaker
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    ancient kayaker aka Terry Haines

    Need so me more detail to see how it can be made: the principle is clear enough. Many of our ideas have foundered on the rock of "how do we build it" ...

    I like the idea of a simple method of levering or gearing the foot motion.

    A plan view would identify the pivot point and give insight into stresses and gear ratios.
     
  2. Squidly-Diddly
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    Squidly-Diddly Senior Member

    yjoder, could you show a top view?

    I'm not quite grasping how leg power is getting to the oar blades.

    Seems like the legs are just repositioning the pivot point, but I must be wrong and it is late for me.

    I'm not afraid of including springs, even if against the direction of "work" if it makes it more ergo-metric, and keeping the rowers weight in one place is really helpful. That is half the reason why shells are so long.


    On another note: I'm going to play with a standard "double jointed" system, but make it so as it can use almost any existing oar with a clamping collar.

    The idea will be to offset the handle shaft and oar about 4" vertically, and hopefully the handle of the oar won't interfere with the rowers belly or knees, and there will be enough clearance for the rowers knuckles (maybe a knuckle-guard on the handles).

    That way, you'd only have the Double-Joints and half-handles in addition to standard oars, and the oars could always be used conventionally.
     
  3. jyoder111
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    jyoder111 Junior Member

    That's correct. The arms and legs are working against each other, both functioning as lever fulcrums. That way, you have the least amount of body movement and don't have to bend your back.

    [​IMG]

    I'm thinking adjusting the lengths between the pivot points and fulcrums would allow you to gear it so your arms and legs exert an appropriate amount of force.

    One problem I see already is that your legs would move very little because their extension is limited by the length of your arms. Maybe reversing the lever would work better- instead of pivoting on the bottom of the boat the pivot could be up above your hands and oars. That way your legs could move farther than your arms because they are naturally longer. However, this would mean your legs would be geared lighter than your arms, which is usually opposite of what you want.
    [​IMG]

    Here's how the lever works. See how you get lots of blade movement without much long-distance internal travel? You don't have to overextend your limbs and bend your back/waist like with traditional oars to get the same travel.
    [URL="[​IMG]

    I'm not well versed in this stuff, so please let me know if you see an obvious flaw in my reasoning.
     
  4. ancient kayaker
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    ancient kayaker aka Terry Haines

    Your reasoning is correct, as is your analysis of the system's flaws. Both the legs and arms need to move over a longer distance to do effective work. That means the handle-to-pivot length must increase in proportion, to keep the sweep angle within reasonable bounds. It is also important to have the lengths on each side of the pivot in the right ratio; too high and the force on the handles becomes excessive.

    The forward rowing systems we looked at earlier usually had a point about which the oar rotated that was - in many cases - close to the opposite gunnel. If a physical pivot had been used the oars would have crossed and interfered with each other. However these systems could work because they used virtual pivots not physical ones. You will likely have to replace your simple pivot with a linkage or other device for the same reason.

    I was asked earlier why I did not add a sliding seat to one of my concepts. I think my reply mentioned that the entire oar and linkage system would have to get larger to accomodate the much longer stroke that a sliding seat system would require.

    You have the start of a nice idea; now you have to develop it . . . your biggest problem will probably be keeping the stuff in front of the rower small enough so it does not interfere with arm and body movement.
     
  5. upchurchmr
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    upchurchmr Senior Member

    Looks like you are going to have pretty high forces on your arms, just looking at the oar total length to the "handle" end to your hands.

    Actually my instinctive reaction is that I like to bend my body to row. Sitting there like a statue does not appeal to me. Reminds me too much of being at work in front of the computer.

    Marc
     
  6. Squidly-Diddly
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    Squidly-Diddly Senior Member

    Here is re-dimensioned Reelfoot with sliding seat and 10' sculls

    The dual pivots ended up about 4' from amidships.

    Note the pivoting handles, so you don't need to bend your wrists. I noticed most double jointed rigs had extreme angles at start and end of stroke, and many users were older folks with arthritis.

    The holes in the oar were just for fiddling with Solidworks. I'd want a clamping collar to enable the rig to use any oar without damaging it for normal use.



    Also is a pic of a "Cross Rower"(conventional backwards facing) where the rower would use opposite hands to grip the oars, thus allowing gunnel mounted full length sculls on a canoe (3' beam). This would require the inner shafts of the oars to bend around each other, so they should be metal pipe. I'll figure out the bends later. Maybe this would work well with common shorter wood oars; the shorter wood oars would fit inside the pipe ends at the oar locks, thus making a full length(and normally expensive!) 10ft scull out of much cheaper and common wood oars.


    The rectangle in the boat is 4' x 2' outside-outside and is for reference.


    The oar blade on the Reelfoot is backwards and wrong in these drawing, my mistake.


    Does anyone have good pics of video of how the oars are dipped and un-dipped with one of these double jointed Reelfoot rigs? Do they rely on the force transmitted through pivot pins so the inner and outer shafts are locked into the same plane?

    Note my design using unmodified 10ft scull has members stacked over each other, so I'd need stronger pins and get a little more friction, all things being equal.
     

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  7. jyoder111
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    jyoder111 Junior Member

  8. Squidly-Diddly
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    Squidly-Diddly Senior Member

    I like it, simple and meets the ambitious specs I gave myself

    as far as:

    using existing boat and oars without making them otherwise useless for traditional use or drilling any holes in expensive boats

    and

    parts for under $100 and found at any hardware store

    and

    able to be assembled in a couple hours without fancy shop tools or even welding



    How did you rate the ergometrics of how you got it set up and in your next video could you include laying a tape measure around a few spots and a couple of shots from 'dead midships' and "straight down"(maybe with boat on its side).??

    Have you tired it without the springs?


    Another thing I like about this setup is it would allow for feathering the oars(and skimming the surface) like sliding seat shell on the recovery.

    Another another is it would allow for easy shipping of the oars (maybe flip the ends forward and grab paddle(or fishing pole or shotgun) in certain situations
     
  9. upchurchmr
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    upchurchmr Senior Member

    Jyoder111
    Excellent work. Actually making something that works is fairly unusual. Congratulations.

    Are you going to develop it? Any changes you would want to make?

    Perhaps the next step would be getting the feet into the stroke?

    Marc
     
  10. jyoder111
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    jyoder111 Junior Member

    Thanks. As you can see from the video, I had to bend forward quite a bit and spread my arms awkwardly wide to reach the front of the stroke. Later, I moved the device closer to my seat and that helped some. I still have more testing to do to figure out the optimal position that will still give me enough leg room. I think the oar length is just about right.

    Already there are a few durability issues. There's a lot of force being put on the wood joints. However, I just screwed things together lightly without epoxy so I could easily make adjustments. Once I have the positioning optimized I'll build a more robust version.

    I'll also try lowering and raising the height of the pivot point and spring attachment and see how that affects things. It'd be nice to not have the spring attachment right in front of my face.

    Speaking of springs, I didn't try it without them as I figured it would be too much work to try to lift the oars out of the water. The springs carry the oar weight very well and make it very easy to lift and lower the oars. The spring also helps start the power stroke as well as bring the oars back afterward, which is nice.

    Once I have this all optimized (when I actually get enough time to work on it) I'll consider adding leg power. :)
     
  11. ancient kayaker
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    ancient kayaker aka Terry Haines

    I don't have much rowing experience but I suspect that when you add the leg power it will not increase the force - since that must still pass through the arms - but the length of the stroke will increase to provide the extra stroke power. That will require a longer lever length, and probably longer oars, to keep the angle of the arc within reasonable bounds. I think that will require a significant design revision, due to the limits imposed by arm length.
     
  12. Easy Rider
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    Easy Rider Senior Member

    The advantage to jyoder's system is that the rower's butt stays put ...that is beyond the front facing feature. It looks like it was designed to do just that. It is a system that will work (I think) but has only one advantage over other systems and that is it's simplicity and economy. Oh ...one other advantage over sliding seats is that CG won't be moving back and forth causing the bow to plunge at just the wrong moment. For economical low power rowing this system may/probably be very good but I don't see it as better than Rontilia's Front Rower. An observation of mine is that I think the foot travel is too small until one gets the foot pegs too high. I could measure the foot travel and arm travel on my Front Rower if you like. I think the foot travel and arm travel is the same on the Front Rower.
     
  13. upchurchmr
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    upchurchmr Senior Member

    Terry,

    The feet should add a good bit of extra power, on my sliding feet system the arms and legs act together to apply force thru butt contact. Everything else is moving. It it very obvious when you just row with the arms what the difference. Total distance of sweep is important for how fast you can go, but the power is much less with just arms.

    The interesting thing is that (for me) it is best to start with the feet while basically holding the hands/arm extended, then when the stroke is half finished the arms do most of their work.

    Actually I have not understood the motion/ pivots when a foot motion would be used. Can anyone make it simple for an old guy?

    Easy Rider I would like to know the foot and arm travel on the front rower.

    Marc
     
  14. upchurchmr
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    upchurchmr Senior Member

    Jyoder111

    You might try lowering the oar and spring attach point until the oars are just above the gunnel when the oars are in the water. On a skull the hands are just a little above the waist during the power stroke and in your lap when you recover. Your system doesn't require the handles to drop into your lap on recovery, so you can drop the oars as much as possible.

    Marc
     

  15. Squidly-Diddly
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    Squidly-Diddly Senior Member

    Reason sliding seat has more power than just arms is your grip

    is much stronger than your arms, and you start a sliding seat stroke with straight arms as your legs get things rolling.

    Lots of people can hang from a bar with both arms for some time, but can't do a single pull-up.


    But for rowing it would be mostly the extra distance of the stroke, since each single stoke is normally less than the rower's max arm strength, and the fact the leg muscles are contributing as far as endurance.
     
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