## Furl Mass Calculation

Discuss furling in small wind turbines.

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Abdur.Rahman
Posts: 5
Joined: Wed Jan 18, 2012 11:33 pm
Organization: Institute of Space and Technology
Location: Pakistan

### Furl Mass Calculation

I am working on the designing of a furling mechanism for a horizontal axis wind turbine.
Turbine diameter is 5.6 m. I did following calculation:

Turbine thrust is 1.628 kN (using WT_perf) at 20 m/s wind speed (speed at which furling should start)

Offset between generator and tower axes is 0.28 (5% of Turbine diameter)

Turbine Moment is 0.4558 (kN-m) (Turbine Thrust x offset)

Boom length is 2.8 m (Turbine radius)

Fin Area is 1.23 m^2 (Turbine swept area x offset = 2 x Boom Length x Fin Area)

Angle of Fin bracket from vertical is 20 degree
Angle of Fin bracket from the plane of the blades 45

Fin mass is calculated from following relations:
Turbine Moment = Fin Moment
Fin Moment = Furl Resistance x Boom Length
Furl Resistance = Furl Mass (kg) x 9.8 x sin20 x sin45
From above three equations we can write that:

Furl Mass = Turbine Moment / Boom Length / sin20 / sin45 / 9.8

Furl Mass = 0.4558 x 1000 / 2.8 / sin20 / sin45 / 9.8
So, Furl Mass = 68.7 kg
Its look too much.

I go through from data available for different HAWT furling system, and found that they use around 30 kg furl mass for 5 to 6 m diameter HAWT.

Is this Furl mass OK (68.7 kg for 5.6 m diameter HAWT)? Or can you identify the mistake.
Thanks

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