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Forum Index : Windmills : Prop walking and furling

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old mate's mate

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Joined: 11/08/2010
Location: Australia
Posts: 15

Posted: 10:45pm 19 Aug 2010

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Forum members, felicitations .........

Re. Automatic mechanical furling:

Does anybody know if the rotational direction of the blades should be considered when deciding on which sides of the yaw bearing to offset turbine and furling tail ?

In a shaft driven boat the phenomena of 'prop walking' can be used to advantage to move the stern of the vessel sideways when docking. I know it to be a considerable force in that context but suspect that the proximity and shape of the hull are the major drivers.

Is there any discussion on the subject relative to wind turbines ?

I remain

always curious

OMM

VK4AYQ
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Joined: 02/12/2009
Location: Australia
Posts: 2539

Posted: 12:04am 20 Aug 2010

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Hi Old Mate

On the turbines I have the the offset is on the side of the down going blade, looking from the front of the turbine.

I believe that in a boat it is the lower section of the blade that controls the action of prop walking as it is exposed to open water whereas the top of the blade is closer to the hull and the rotational energy is partly dissipated against the fixed object. Our old bay cruiser could be moved around by the effect, but that was forty years ago maybe now its different since we went metric.

All the best

Bob

Foolin Around

niall1

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Joined: 20/11/2008
Location: Ireland
Posts: 331

Posted: 12:18am 20 Aug 2010

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hi Mates mate

i think this effect in mills has been documented and tested before ....my disjointed (very) grasp on this effect is kind off like this ...

say if a prop rotates clockwise and is suddenly flicked to the right during furling the prop tips will tend to want to go in one off two directions ..either closer to the tower or away from it ....reverse the furl direction and the the effect ..(i think..

.) ..will be opposite ....that seems to be the logic ...i wish i could understand it better

i think Hugh has changed his latest plans to incorporate this effect to aid in helping avoid tower strikes ....(kind of belt and braces) Edited by niall1 2010-08-21

niall

fillm

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Joined: 10/02/2007
Location: Australia
Posts: 730

Posted: 01:13am 20 Aug 2010

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I have mine furling to the side of the blade on the up for CW rotation , the effect that is being discussed here, I would think does not come into play in either direction as it will always be balanced by the top or bottom,up or down blade in either direction into and out of furl, unless there is a difference in wind speed over 1/2 the rotating face .

Either way I think it is the 6 or 1/2 a dozen rule .

PhillM ...Oz Wind Engineering..Wind Turbine Kits 500W - 5000W ~ F&P Dual Kits ~ GOE222Blades- Voltage Control Parts ------- Tower kits

niall1

Senior Member

Joined: 20/11/2008
Location: Ireland
Posts: 331

Posted: 01:49am 20 Aug 2010

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its interesting thinking about this....my mill is foreward and offset to the right and has anti clockwise blades ...it wasnt meant to rotate that way ...it just wound up like that...i suppose i cant help wondering about these things.....

Edited by niall1 2010-08-22

niall

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