wrote in
news:Rd8Cg.17729$Qu4.9630@trnddc04:


On 8-Aug-2006, wrote:

Yeah, I really meant the parrot which is about 115 knots with 120 hp.


--If you believe in miracles. By the laws of aerodynamics, for a
given airframe (i.e. same drag characteristics) the airspeed in level
flight will increase as the cube root of the increase in power.
According to the cited webpage, the Parrot cruises at 75% with a 100
hp engine at 115 mph (100 kts). They PROJECT that 75% cruise speed
will be 130 mph(113 kts) with a 120 hp engine. But according to the
cube root law, you would need to increase engine size to 144 hp in
order to get 75% cruise to increase from 115 to 130 mph. In order to
do it with only 120 hp you would have to have a miraculous increase in
propeller efficiency (not likely, and anyway you can't do better than
100%) and/or a huge reduction in cooling drag (also unlikely). More
likely, 75% cruise with the 120 hp engine will be around 122 mph (106
kts).


-Elliott Drucker

It could also be the efficiency of the "100 hp" Rotax comparted to the
120hp Jabiru. Cooling drag WILL come into effect as the Rotax is water
cooled and generally not well baffled in the engine compartment except
for the radiator.

Also for some reason they want to put a 3 blade propeller on these Rotax
LSAs, and I mostly see 2 bladed props on Jabirus.

Maybe wont make up the whole difference, but time will tell I suppose.

--
-- ET :-)

"A common mistake people make when trying to design something
completely foolproof is to underestimate the ingenuity of complete
fools."---- Douglas Adams