Did I invent this or is it old and/or failed?

Discussion in 'Boat Design' started by clmanges, May 1, 2021.

  1. clmanges
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    clmanges Senior Member

    I was thinking about yulohs a few years ago and came up with this idea. Called it the 'Yuloh-Matic', even though it's no more automatic than a traditional yuloh.

    The reason for the topic wording is that in the past I've come up with a few other ideas for things I'd never seen or heard of but thought were pretty cool, and later found they were ancient and/or impractical. So there might be a 150-year-old patent laying around for something very like this.

    I never finished working out the details; I wanted some way to adjust the blade stops for an effect similar to adjusting propeller pitch. Also, I figured it wouldn't be too hard to make it so it clamps on a transom like an outboard and can be swung up out of the water. More complexity would lock the blade at a chosen angle so it would act as a rudder; not sure if it might not do that to a small degree anyway if just held to one side or the other.

    Obviously, part of each side-to-side stroke will be wasted while the blade flops over, and there might be something about it that makes it even worse than that. You can see I've already anticipated some unwanted sideways thrust, though I could be wrong about that.

    The best advantage I can think of for it is that it allows the operator to work it from a sitting position. It could also be rigged up with some cables and operated with a foot lever.

    Pick it apart, have fun with it. yuloh-matic .JPG
     
  2. waikikin
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    waikikin Senior Member

    Kind of.. looks hard... with the "Power Fin"


    There was a bloke demonstrated a "sculling machine" at a classic & wooden boat show a few years ago, cant remember his details.

    Jeff.
     
  3. Dejay
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    Dejay Senior Newbie

  4. jehardiman
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    jehardiman Senior Member

    There have been several HPVs and robotic experiments with arguably similar systems. Google "oscillating fin propulsion" for lots of papers and patents.
     
  5. garydierking
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    garydierking Senior Member

  6. alan craig
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    alan craig Senior Member

    It's old. You'll find quite a few flappy paddle ideas on Youtube. And I started making exactly what you describe last year! O/B tilt/clamp to mount on transom, a piece of string through a restraining location, adjustable length to allow variable "angle of attack', and a foil with camber that changes on each tack. And a flapping rudder to absorb some of the energy wasted in wagging the back of the boat.
    Half way through the build I changed to two mirror image flapping foils, photo attached of finished article. It's a bit like a Mirage Drive but with pivots way above the waterline. The rudder is concentric inside the tube which transfers torque from pedalling to the fins. Not in picture - low mounted pedals with pivots above gunwale height to give a comfy pedalling action, facing forward. Hobie fins shown; cambering fins also tested. Also not seen here, a string system to adjust the angle through which the fins tack.
     
    Last edited: May 2, 2021
    DogCavalry and Dejay like this.
  7. clmanges
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    clmanges Senior Member

    This one appears to emulate the behavior of a traditional yuloh pretty closely, where the mechanism causes the oar blade to flop over when the direction of stroke is reversed. I know that a yuloh blade is asymmetric face-to-face, whereas ordinary oars often aren't. My perception of both of those is that the developed thrust is far more vertical than horizontal, and I was trying to overcome this with my design. IMO, my design offers an advantage in being compact, both inside and outside of the boat. I've read of people who can stand at the transom and scull with an ordinary oar held quite vertically, which is pretty much what my design does except that it can be operated sitting down--plus, such sculling seems to be a skill that is difficult to master. I design for low operating positions because I favor small, light boats that I wouldn't dare stand up in.
     
  8. clmanges
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    clmanges Senior Member

    Intricate and fascinating. I can't figure out how it works from the photo, though. Does it work well?
     
  9. Will Gilmore
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    Will Gilmore Senior Member

    Clmanges, sailors have been flapping their rudders to gain a little movement when the wind died since well before I first set foot in my first Opti in the 1960s. It was never very effective. My uneducated suggestion is to add some flexibility on the rudder to give it more of a caudal fin action. Also, a skeg right in front of the side-to-side movement might help steady the stern from simply sliding laterally in reaction to the lateral force. Last, as a short cap wing to the bottom to focus the flow from down to aft.

    -Will
     
  10. Zilver
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    Zilver Junior Member

    Hi CLmanges,
    It will work, but would benefit from having a twisting blade (like the miragedrive) . You could see it as a propeller blade making a small portion of the full rotation.
    A simpler "sculling method with one leading edge" is the AD scull. You could google it. It's from the same person (Atsushi Doi) that made the "powerfin"in the video above. The AD scull is not foot operatable, but it is kind of automatic rotating, and the driving force is diverted by a "strong rope". You only have to move the blade back and forth. I use one myself and it works good.
     
  11. clmanges
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    clmanges Senior Member

    Looks like that one's already been improved upon ...
    a.b.b. - amateur boat building - howto Japanese sculling oar https://amateurboatbuilding.com/articles/howto/sculling_oar/i-scull.html
     
  12. alan craig
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    alan craig Senior Member

    Does it work well? It was useless! that's why I didn't brag about it on Boatdesign last year! To sum up my thoughts:
    The Mirage Drive is usually for a canoe/kayak - much smaller, lighter and thinner than a rowboat.
    The MD uses the hull as an endplate making the fins more efficient whereas my fins operate right at the surface.
    My fins, including home made ones not shown, were too small.

    How it works: the wooden lever at top is oscillated back and forth by strings from pedals; this motion is transmitted down a tube to another lever, and pushrods from each end of that lever transfers oscillating motion to each paddle.

    I think your idea will work fine if you make the fin big enough and place it deep below the surface. I'll try to post a pic. of my string adjustment of flapping angle, later. You might also need to add a fixed fin to the back of the boat to stop the energy sapping wagging of the back of the boat, which you can see in the Youtube flappy fin videos.

    p.s. One thing I didn't like about my invention was that even if it worked well it filled the boat with pedals, mounting frame, backrest, string for the tilt facility and string in the passenger location from pedals to the device.
     
  13. alan craig
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    alan craig Senior Member

  14. alan craig
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    alan craig Senior Member

    clmanges: quote - I wanted some way to adjust the blade stops for an effect similar to adjusting propeller pitch
    Two months later! here is a picture of the adjustable "tacking" angle string mechanism on my flappy fin thing. The single pulley can be moved up the threaded rod to reduce the tacking angle. Also you can just see original fins from flexible material which change camber on each tack.
     

  15. Squidly-Diddly
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    Squidly-Diddly Senior Member

    I might do a long tail shallow water capable fishtail on a SOT kayak rudder operated by feet/legs.
    Issues are existing steel cables seem to have lots of drag and bit sticky, which is fine for use as rudder but not so good for constant use in propulsion. But maybe just an upgrade to some rollers instead of cable sheathing when the cable needs to go around corners would do the trick, or change to nylon etc cord even if it wears out much faster.
    Then again this would be mostly for still having some maneuvering when "Fish On!" so high drag might not be a deal breaker for first iteration.
     
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