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# How much lift is created by a half-sized rotor? Answered

if there is a rotor of 26ft rotating at 600 rpm and lifting 635kg of weight at 1200ft/min 14000ft so if there is rotor of 13ft HalfSized 26/2 =13 and same rpm 600 & same power so will it lift half of the weight like 635/2=318kg at 1200ft/min 14000ft ? if not then how much half sized rotor will lift at same rpm and power if 26ft rotor is lifting 635kg at 600rpm at 1200ft/min upto 14000ft then how much 13ft rotor will lift at same rpm and power at 1200ft/min upto 14000ft ? The helicopter used in this example https://en.wikipedia.org/wiki/Robinson_R22

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## 4 Replies

liquidhandwash (author)2017-05-11

The question is ambiguous, as a half size rotor is not clearly defined. A 26 ft rotor blade would have an area of 530 square feet, when spinning and a 13 ft rotor blade would have and area of 132 Square feet. So is it really a half size rotor?

ThirdEarthDesign (author)2017-05-10

Why do I get the feeling this is another one of those 'homework' questions?

With the lack of formatting in the question I can barely get my head around what I'm reading, never mind the math!

rickharris (author)2017-05-10

+1

iceng (author)2017-05-10

Assuming You have a perfect scale down reproduction which you can't because of shaft diameter stays the same as does motor output power to ask this question.

Also if the RPM stays the same then the power will be less OR if the power stays the same then the RPM will be more (That's Obvious)...

The gas medium itself 28% O2, 70% N2 and 2% trace gases does not reduce in dimension so now Bernoulli's equations will produce a way different drag coefficient and prop tip vertices..

My guess would be to reduce the lift by the cube root of the diameter change..