boats?

[UncleWillie]

Re: boats?

BTW, the benefit of turbines isn't mainly in weight savings, it's in the high-altitude performance that they are chosen in high-altitude aircraft. Once you get in the 10,000+ (and really 20,000+) that turbines see huge efficiency gains over the piston-engine counterparts. The ability to compress the thin air at altitude is an advantage that nothing but turbo-charged piston aircraft can do. The efficiency of a propeller is also greatly affected by altitude, which further exacerbates the piston-engine problem...

The reason Turbine aircraft fly high is to get the colder air to get reasonable efficiency out of the Turbine engine.
The turbine engine is a heat pump, the colder the input air the higher the efficiency.
The piston engine is an air pump, the denser the input air, the higher the efficiency.

The old DC3 had higher efficiencies than todays Turbine aircraft.
Of course a 15-18 hour NY to LA flight at 200 mph at 8000ft. with 3 stops, does not sound too tempting to todays passengers.
We accept the inefficiency as compensation for the speed advantage.

 

[Home Cookin']

Re: boats?

just as friction causes a loss of direct energy and makes the perpetual motion machine fail, a boat prop as a screw in water is terribly inefficient, too, in terms of slippage. A car tire on ice, spinning at 60 mph while the car goes 10 mph.