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Old 11-23-2010 | 12:40 PM
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eddieC
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Default RE: Three bladed props vs. two bladed props.
Talking about prop blades, any reason there is no "turbofan blades" like props ?

EDIT: I mean like this : http://history.nasa.gov/SP-4219/4219-322.jpg
That is the UDF (UnDucted Fan) NASA worked with back in the late '70's IIRC. They created a hybrid between a propeller and ducted fan on a jet. It was meant to go on a STOL inter-city commuter. They were looking at better fuel economy (where a prop is best), low noise (that whole tip speed thingy), high thrust from a jet engine. This was back when ducted-fan jets were just coming out. Probably no application in RC. Lots of engineering.

The ultralight guys play with props much like we do. They find that a 2-blade is more efficient, i.e.: same cruise speed but better fuel economy with the 2-blade over the 3.

I'm talking most efficient, not most thrust from a given engine. Our RC stuff is quite overpowered, I'd say our primary limit is ground clearance. Also, all but the recent turboprops are fixed pitch.
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