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single sculling oar

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  • 25 Jan 2023 17:57
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    Reply # 13072545 on 3243507
    Anonymous member

    now everything should be clear.
    thanks!

    ueli
  • 24 Jan 2023 23:07
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    Reply # 13071378 on 3243507
    Anonymous member

    From Alan:

    It still won't let me answer 

    "I wasn't very clear. 

    Basically the force on the oar is transmitted to the boat. Like grabbing the oar and pushing the boat forwards by hand.

    So if the oar is forced forwards, this force drives the boat forwards. 

    So the low pressure needs to be to the fore of the blade, and the high pressure to the aft of the blade. 

    The forward side of the blade is therefore best curved. The forward side is the underside. 

    Also, forcing the oar forwards also forces it deeper into the sea, this is counteracted by the lanyard. "
  • 24 Jan 2023 21:32
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    Reply # 13071260 on 3243507
    Anonymous member

    All I can say, Arne, is that I copied and pasted what Alan sent me.  And I'm sure he thought carefully before doing so.  However, I'll send this thread to him for comment!
  • 12 Jan 2023 18:03
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    Reply # 13054665 on 13053602
    Anonymous member (Administrator)
    Anonymous wrote:

    I asked Alan if he'd reply, but for some reason he couldn't get on to the site.  Anyway, he sent me this:

    .the flat side of the blade is upper most. 


    Think of the blade as being at an acute angle into the water...the required force is to push the blade backwards ....like an aircraft wing the curved side is the desired direction...in a wing upwards...in a yuloh backwards.

    Annie, a little typo here?
    I would swap your very last word,  backwards with forwards... ☺
  • 12 Jan 2023 17:51
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    Reply # 13054624 on 3243507
    Anonymous member

    hi arne

    Arne Kverneland wrote:

    Ueli

    As I understand it, a yoluh, just as an aeroplane’s wing, work with one high-pressure and one low-pressure side. The low-pressure side is the one with convex curve on it.
    In the wing’s case, that is the upper side.
    In the yuloh’s case, this is the side facing partly downwards and partly forwards.

    Arne

    that's exactly what i wrote – nothing like 'pushing the blade backwards' as the 'desired direction'…

    ueli
  • 12 Jan 2023 17:04
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    Reply # 13054519 on 3243507
    Anonymous member (Administrator)

    Jan,

    it appears that you are describing two different principles of sculling oars here.

    One sculling oar is used in the so-called fish-tail style sculling (often used in the West). The  same edge of the oar blade is the leading edge all the time. The oar blade’s section is symmetric, just as a rudder blade. This sculling type is fine for free-hand sculling of light and easily driven vessels, and can result in quite some speed in the hands of an expert. Most of the prams in Norway were made with a notch in the transom to let one use one of the rowing oars for sculling.

    The yulohs, on the other hand, as used in the Far East, all seem to be of the falling-leaf type. Since the edges of a yuloh’s blade shift between being the leading and trailing edge, one side of the blade will always be the low-pressure side, and should be rounded. These yulohs are quite powerful and need a line from the handle down into the boat to take the vertical forces.

    I had a go, making a yuloh for my Johanna in 2008. The story speaks for itself...
    A test yuloh for Johanna.pdf

    Arne
  • 12 Jan 2023 14:19
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    Reply # 13054180 on 3243507
    Anonymous member

    It doesn't matter if a sculling oar has a curved side up or down or is symmetrical or if it is in the horizontal plane or the vertical plane. What matters is the angle of attack that the operator gives the blade on each stroke. For a yuloh it makes sense that it is pulling downwards at the blade so that the handle end is levered upwards and tensions the line holding it down to the boat so that the operator can push or pull the line to help with the angle of attack. For a non-yuloh, freely held sculling oar it's important that the oar is made with the correct balance and weight so that it doesn't jump around in the oarlock or exhaust the operator. I've never used a yuloh but I can scull my punt with my symmetrical bladed rowing oar held vertically or horizontally (not very efficiently I must admit). 
  • 12 Jan 2023 13:08
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    Reply # 13054089 on 3243507
    Anonymous member (Administrator)

    Ueli

    As I understand it, a yoluh, just as an aeroplane’s wing, work with one high-pressure and one low-pressure side. The low-pressure side is the one with convex curve on it.
    In the wing’s case, that is the upper side.
    In the yuloh’s case, this is the side facing partly downwards and partly forwards.

    Arne
  • 12 Jan 2023 11:44
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    Reply # 13054020 on 13053602
    Anonymous member
    Annie Hill wrote:

    I asked Alan if he'd reply, but for some reason he couldn't get on to the site.  Anyway, he sent me this:

    .the flat side of the blade is upper most. 


    Think of the blade as being at an acute angle into the water...the required force is to push the blade backwards ....like an aircraft wing the curved side is the desired direction...in a wing upwards...in a yuloh backwards.

    this sounds strange to me. the intention is to push the boat (and therefore the blade of the yuloh) forward, not backwards.

    in my understanding of physics alain is right when he says that the flat side is the upper side of the blade. but when he explains why, i'm almost sure he is wrong…

    ueli
  • 11 Jan 2023 23:37
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    Reply # 13053602 on 3243507
    Anonymous member

    I asked Alan if he'd reply, but for some reason he couldn't get on to the site.  Anyway, he sent me this:

    .the flat side of the blade is upper most. 


    Think of the blade as being at an acute angle into the water...the required force is to push the blade backwards ....like an aircraft wing the curved side is the desired direction...in a wing upwards...in a yuloh backwards.
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