ORIGINAL: Lowlevlflyer
Being a full scale pilot as well as a beginner in R/C, I can tell you this... ALL of the fastest and most maneuverable full scale single engine aircraft run three bladed props: V-35 and A-36 Bonanza, Cessna Centurion, Piper Malibu Mirage, Piper Lance, not to mention all the higher end Aerobatic craft like the Sukhoi, Edge, Extra, most of the Pitts, CAP, the list goes on. i've flown a tad over 3,000 hours, and around 1,000 hours of that in 450 and 600hp B model Ag Cats, and the ones I've flown with three blade prop conversions ALWAYS performed better... higher cruise speed, lower fuel burn, less noise, and a shorter take off roll with a heavy load.
Generally, props with fewer blades tend to be more efficient.
Like all rules, though, this one needs to be applied with an
understanding of the underlying assumptions. A big assumption,
which is really significant when comparing models to full scale
aircraft, is that the tips of the blades are not operating too close
to supersonic. This essentially limits the prop diameter, which
means that you need to get the necessary thrust out of a fixed
size propellor 'disc'. One good way to do that is to add more
blades. A three blade prop with subsonic tips is probably much
more efficient than a two blade prop with supersonic tips.
On most models, the two blade and three blade props you would
use would both operate with subsonic tips, and the two blade prop
would probably be more efficient, partly because it would have
larger diameter, which in itself is more efficient, all other things
being equal. On a full scale plane, with higher airspeed and much
larger absolute diameter, the prop tips are much more likely to
approach supersonic or transonic speeds, so the best prop choice
needs to take that into account.
There may be other significant differences between model props
and full scale props, but I'm guessing this is the big one.
banktoturn