Making Propeller from Scrap (II)

Here is an update from PRABHURAJ.C.U on his excellent propeller build:

i made another modification to my propeller.
that is,shape of the propeller is changed,you can refer the attachment.this is done because of the following reason.

if you analyse the commercial propeller,you can see that its strength if uniform through out the propeller blade.but in our early propeller,due to the use of soda bottle plastic its strength is not uniform.this is why,while rotating the propeller end will be deflected if we provide large area.so that, i reduced area by providing elliptical shape(see the pictures).

this propeller will run smoothly than the early one.its rotating speed also improved.

(prabhurajpudussery@gmail.com)

5 thoughts on “Making Propeller from Scrap (II)

  1. That is a much better blade planform.

    If you look at good propellers, you will see that the blade is twisted. At the hub the blade chord is parallel with the shaft and perpendicular to the plane of rotation. As you move out to the tip, the blade chord twists to a lesser angle to the plane of rotation. Model propeller blades are often formed on cans or bottles to produce a twist. They are called “can formed props”. They are set at angles of 15 to 20 degrees to the axis of the can. The twist is the result of the blade centerline rotating around the cylender, as it is helical. You might try making blades with a greater angular offset. They should perform better.

    Rotational speed is not the measure of propeller performance. The job of the propeller is to turn torque into thrust. A propeller that produces sufficient thrust to fly the plane at a lower rotational speed will keep the plane in the air longer than one that turns faster to produce the same thrust. The faster turning propeller uses up the turns in the motor sooner.

    Gary

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