On Mon, 17 Jan 2011 11:59:05 -0800, CLewis95 wrote:

No numbers, but:
- multiple impeller blades destroy efficiency due to interference
between the blades. Its similar to the inter-plane drag than makes
biplane less efficient than monoplanes. As a result, the fewer blades
the better, hence the superiority of the two blade propeller provided
speeds are low enough to avoid tip compressibility problems.
- a bigger diameter impeller is better because moving a given mass of
air slowly is more efficient for generating thrust than moving it much
faster as is required by the smaller impeller.

Against that, about a ducted fan can offer is reduced tip losses.

That has to make an Antares-style pop-up system that turns a large, two
blade prop a better bet than a ducted fan system.


--
martin@ | Martin Gregorie
gregorie. | Essex, UK
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