RCU Forums - View Single Post - found this interesting discussion on Spiral Slipstream

09-08-2012, 01:04 PM

#35

rhall999

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RE: found this interesting discussion on Spiral Slipstream

Quote:

THE JET ROTATION IS NEGLECTED!

So much for the slip stream rotation being important in the design of a propeller! Happy weekend

Yes, You are right.......BUT, reread the text and what you even quoted, especially the part Imade red. Idon't recall anyone ever being concerned with design of the propeller in relation to the spiral slipstream. It is the AIRFRAME the propeller is bolted to that is designed with the spiralling airflow in mind. EG, leading edge of the fin offset a degree or two, bit of right thrust, whatever. It is the ability to calculate the spiral that allows those adjusments to be made to said airframe.

Look in a ducted fan at the design of the stator vanes. You will notice that they are almost alwaysat an angle to the straight through airflowand curved like a old timer free flight airfoil.. Why is that??? Simply because the airflow does NOT flow straight through the duct. It comes off the fan on a spiral. Since it can be calculated how much "angle" there is to that airflow, the can put those stators at the right angle to most effeciently "capture" and straighten that airflow. If the spiral slipstream was a myth, there would be no need for even bothering to put the stators in there, other than to support the motor.

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