57es revision #4, helicopter rotor .

Wing one of five, with detail views of tip .

External surface .

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This design modifies the 57es revision #2, (posted 29 July 2010), to address (what i think of as) an error of approach over-emphasizing lift .

In this respect, revision #2 was too close to its wind turbine ancestry

~ and application for which wings, ('blades'), collectively face the air ~

and so was designed in a way that would give it peak efficiency while climbing and hovering .

More adaptation needed to be made to the purpose of accelerating across the wind, and its lack will hamstring it as a helicopter's main rotor :

It would not be able to move forward efficiently .

I think that revision #2 would still make a good, (if long), airplane propeller, (an application facing the air) ; and possibly also a good tail rotor .

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Revision #4 is intended as a main rotor reaching peak efficiency in forward flight :

At that airspeed where (averaged) flow across the advancing wing,

when it is at a right-angle to the direction of travel,

is,

at the design radius of 1, (the hub-ends in these figures),

seven eighths the flow velocity at the tip .

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To pursue this goal, the variables applied in the construction formulas, (based on those from revision #2), change less and more slowly .

Exponents would now, (if expressed all the way to the hub), be 7/8 of their wing-tip values .

Pitch, inversely, becomes 8/7 of its tip value at the hub .

Width also targets an 8/7 value ; though the result may be more complicated .

The effect of these changes is, (or is intended), to produce a rotor which gains efficiency as the helicopter accelerates into its power band .

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Other changes from revision #2 include a much shortened opening flare, and a narrower hub radius .