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

    I am interested in a simple front-rowing system for my small sailing dinghy as I have to contend with narrow bridges and floating stuff like trees at this time of year, and the odd rock. Performance is less important than simplicity and compactness.

    I like Squidly’s idea but I was concerned about making the curved channel and perhaps the forces on the carriage bearings. From that idea I dreamed up this simple linkage system, which might be easier to make and can use store-bought parts or even plywood. It only has 3 moving parts and 4 simple bearings - Lazy Susan bearings would be ideal and are very cheap.

    The link lengths need to be changed for rowing but my drawing software is not well adapted to optimizing linkages.

    The bearings marked “F” are mounted on the gunnel.
     

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  2. Squidly-Diddly
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    Squidly-Diddly Senior Member

    ancient kayaker, that drawing is a Eureka! moment.

    I knew something like that would show up.

    I'll do it in Solidworks when I get a chance. SW is good at changing up dimensions and does all sorts of moving parts and motion simulation.

    Not sure about the Lazy Susan Bearings. They are cheap, but set up to take a load flatways and their thin metal housing wont take abuse in the wrong loading direction. LSBs are also prone to getting debris into the tracks if used in anything but a kitchen cabinet. Most have greased open bearings. I've used them on inventions before.

    I would spindals for the 'F' bearing, maybe wheel-barrow bearings separated on vertical shaft 6" or more.

    Or use plain 'pins' similar to standard oar locks, and have a collar with bearings around the oar with the collar supported by a cord to so you would get a little unneeded parabolic movement.

    Or have the oar raised a bit at the "T" and connect the two oar handle ends to keep them from flopping down.

    Or another set of trapezoidal braces which would set against the hull, but lower than the gunnel and support rig at the outer bearings. It would be another sets of pinned joints to move, but each such joint would have very little additional friction. I think that would be the way to go, and have the oars able to pivot up and down on straight pins at the "Tee" and have the pinned joint still holding the "T" at 90' as shown in the SW drawing I posted in this thread. The "T" joint would only need to move 20' or less up and down. That would also allow the use of any oar with any mods or damage.

    I never liked the typical rear Derailleur on 10 speed bikes because it added a couple extra tight reversals to the chain, but they seem to work OK, and no one is winning races with any other system.


    As far as my track system, I'm pondering using In-Line skateing bearings, and probably the wheels as well. Used bearing and wheels are free all over town and the bearings can come in several quality grades and are sealed. I might use skateboard wheels and bearings(some are open and greaseless) but most likely the In-Lines. Older sliding seat boats had skateboard wheels just riding on a pair of flat areas in the cockpit.

    When you think of the weight and impacts they take, I have no fear using them, and they should ride nicely in a curved track. They seem more than 50X the robustness of single seat rollers.
     
  3. Jeremy Harris
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    Jeremy Harris Senior Member

    The plain bearings I've used on the handle and loom pivot pins are oilite "top hat" bushes, 10mm ID, 13mm OD, 16mm flange diameter. They are cheap and easy to fit into drilled holes. The reversing link bearings use some cheap surplus 10mm stainless steel rod ends, with Teflon bearings (I got them from ebay for a few $ each).

    I've tried to use bearings that require minimal maintenance and will cope with getting wet. The bearing pins are cut down 10mm stainless steel bolts, or 10mm cotter pins running through the rod ends.

    Jeremy
     
  4. upchurchmr
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    upchurchmr Senior Member

    Squidly,

    Watch out for Inline skate wheels, they are so soft as to not control anything for position. If you are just using the bearings that would be much better. I had to go to Nylon wheels using similar sized bearings so that the wheel had enough stiffness to be useful in a sliding rigger running on 1" Aluminum tubes.

    Marc
     
  5. ancient kayaker
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    ancient kayaker aka Terry Haines

    I have used the LSBs for this kind of thing before but I had another bearing in the center to keep the LSB under pressure and take the lateral load - forgot to mention it - then the LSBs relieves the center bearing of the cantilever load. I have used them up to the 6" size for bar stools, very solid - but you’re right about susceptibility to debris, perhaps large diameter nylon washers would be simpler and better.

    As drawn it is intended for a narrow boat, but for my fat little sailboat I can turn the trapezium inside out so it’s inboard.

    For the track system, there’s no need to pair the bearings so they run along both sides of the “U” of the channel at the same time: with a slight clearance one wheel will do the job. It’s not a precision machine. You can get cam followers that will fit right inside the channel that come with prelubed sealed bearings, they’d pretty well be forever. I’ve seen them as cheap as $10 and you only need 2 per side. Nylon would be quieter though. You need some arrangement to control vertical motion and pitching of the carriage too, but the forces are much less.

    Linear bearings are the class act and take care of everything at once including pivoting the oars up and down but they are fussy about the pipe they ride along.

    How do you plan to bend the channel? It may collapse in a pipe bender. An old trick was to fill it with lead but a close fitting copper pipe might do if you can get the right size.

    I don't think it's been mentioned yet, but Squidly's idea has another advantage as it increases the effective length of the oar by moving the virtual pivot point beyond the ends of the handles. My rather inadequate 6.5' oars - chosen to fit neatly in my small sailboat without making nuisances of themselves - become the equivalent of 10.5' oars if this system can be made to work, without snagging on the narrow bridge I have to row through (it's also too low to raise the mast)
     
  6. ancient kayaker
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    ancient kayaker aka Terry Haines

    I have redrawn the linkage as an inboard system to suit my sailboat, and adjusted the geometry to provide approximately the same leverage (1:2.25) that I have at present using the oars conventionally. It may be better to have a higher ratio but as previously noted performance is not important. With this geometry my 6.5' oars become effectively 9.4' long which should allow a longer stroke.

    The 3 links just happen to be the same length so - assuming it works - I may be able to to fold it up and tuck it away neatly under the foredeck.
     

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    Last edited: May 18, 2011
  7. NoEyeDeer
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    NoEyeDeer Senior Member

    I don't get how this is supposed to work. If the oars aren't hinged at the pivot point then what are you gaining? Your oars are one piece standard oars, right? And you're pivoting them on the gunwale? So you effectively have a standard oar in a standard oarlock. What's the point of the extra gizmos?

    If you are thinking that you'll push on the power stroke and pull towards yourself on the recovery, you can do that with ordinary oars. It's called "push rowing" and has been around for thousands of years. It's not as powerful when seated. Works best when standing.
     
  8. NoEyeDeer
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    NoEyeDeer Senior Member

    Not quite right. It's not that cleavers do "a better job than is needed". By that reasoning, using a blade that provided no grip on the water would be best, since it would mean you could pull really long oars at maximum rate. :D

    Moving a large mass of water at a slow speed is more efficient, in terms of energy expended, than moving a smaller mass at a higher speed. Reason is that propulsive force is linear in this respect (F=ma) but the kinetic energy expended is not linear (it's proportional to mass x velocity_squared).

    Since the cleaver blade is more effective, you can then reduce the gearing without having to increase your stroke rate. This has the added advantage of reducing the gyradius of the oar, meaning it takes less effort to swing it through an arc.
     
  9. ancient kayaker
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    ancient kayaker aka Terry Haines


    It's important to realize that the oars are not pivoted on the gunnel: they are mounted on a linkage system that is attached to the gunnel.

    In my earlier diagrams the oar pivots about a point to the left of the handle, further inboard although it can actually be beyond the opposite gunnel if the links are so arranged. There is no actual pivot there - it is a virtual pivot or fulcrum. This is therefore a Class 3 lever system where the force is applied between the fulcrum and the load.

    A conventional oar is a class 1 lever where the fulcrum (oarlock) is located between the applied force (handle) and the load (blade).

    The revised diagram splits up the different linkage positions into several stop-motion images: hopefully it is clearer.
     

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  10. NoEyeDeer
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    NoEyeDeer Senior Member

    Aha. I see what you mean now. That could work, but shipping the oars in a hurry (handy in tight spots) could be a problem.
     
  11. Squidly-Diddly
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    Squidly-Diddly Senior Member

    how about foot operated oars w/forward facing rower?

    The oars would look like conventional "pivot on gunnel(or outrigger" oars used by backwards facing rowers, but would be operated with feet, and probably a nice back-brace for the rower similar to recumbent bike.

    One problem I see is the need to lift feet a little to dip the end of the oar in the water, but I think the fact that motion is also on the Power Stroke would help. Maybe have a little elevated tract on which you would rest you heel, and then a lower tract for the recovery stroke.

    Another problem would be the foot motion path would be lower than the gunnel(unless this is on a Sit-On-Top kayak, which might be the preferred application for "fishing kayak"). For a canoe the oar would need to be bent and a bearing on the gunnel/outrigger would need to resist defection in that direction while still allowing dipping in the vertical.

    Like I said, I've working on Solidworks drawings of Ancient Kayaker's system using Off the Shelf and Cheap components. I guess I'll try to make a Front Foot Rower for Canoe or SOT, too.
     
  12. ancient kayaker
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    ancient kayaker aka Terry Haines

    I did an animation: the handle is on the moving link at the far left and the blade is, of course, at the tip on the right. I am not skilled at animations and this is my first attempt so I kept the images very simple. For someone with joint problems (like myself) it has the option of a vertical handle instead of using the end of the oar. I loe the way it magnifies my (cheap - Walmart) oars.

    I would try to design it so the oars could be brought as close to inboard as possible, then in a tight spot they could be brought within reach, unclamped from the linkage and stowed. The 3 links could be either left in place or removed as a unit and folded.

    I have an unfinished canoe n the workshop: I am wondering what kind of rowboat it might make, the discussion thread is http://www.boatdesign.net/forums/wooden-boat-building-restoration/hybrid-construction-36215.html and there is a blog at http://theancientkayaker.weebly.com/canoes-rose-lee.html

    This is as far as it has got so I have some scope to modify it -

    [​IMG]
     

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  13. NoEyeDeer
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    NoEyeDeer Senior Member

    Yes I understand how the rowing motion works. I'm thinking about "then in a tight spot they could be brought within reach, unclamped from the linkage and stowed".

    ETA: oh and for this setup I really think you'll be wanting a boat that is wide enough so that the oars don't cross in the middle.
     
  14. ancient kayaker
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    ancient kayaker aka Terry Haines

    As drawn the oar cannot be brought closer than about 45 deg using the handle which is located at point “X” in this sketch, because the linkage will lock. However the rower can now reach the oar shaft to pull it in further, or alternatively unclamp it from the linkage if it is designed to permit that.


    The earlier linkage in post #46 is entirely outboard so the system can be implemented on the narrowest boat that the rower can enter. I haven’t tried an animation of that but it works on exactly the same principle.
     

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  15. NoEyeDeer
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    NoEyeDeer Senior Member

    Fair nuff. Having it outboard would mean it would tend to drop into the water, rather than sitting inside the boat, when you removed the oar. Would also be more lkely to get tangled up with the things you were removing the oar to avoid. It'd probably be nice to have it all inboard and make the boat wide enough to suit that.

    ETA: But your Rosa Lee would work ok for pottering around if you want to use that hull. I might be inclined to raise the topsides a bit and add a skeg though.
     
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