On Jul 11, 11:13*am, betwys1 wrote:
On 7/10/2010 8:57 PM, vaughn wrote: *wrote in message
....
They did not tell us what the minimal sink rate of this beast was, but
it had to be pretty low. If it's as much as 300 feet a minute (I think
the weight was 3,500 pounds) that means one would need to deliver
about 30 horsepower to the air). That is not going to happen with only
40 shaft horsepower available.

I don't know where you came up with 30 horsepower for level flight, but if it
has reasonable takeoff performance on 40 horsepower, it can probably sustain
level flight with considerably less.

Vaughn

Turning that earlier estimate on its head: if it can take off and climb
at 300 fpm, then it would need about 10 HP for level flight.

Brian W

Nice point.

It would be interesting to take an hour or two and do a broad brush
design study wouldn't it? If the 'payload' is 225 pounds of pilot and
life support, and you know how many watt seconds per pound the high
tech batteries are good for, and pounds per horsepower of the motors,
efficiency of the solar cells and some related items, and a guess at
the weight per square foot of wing you can pretty well estimate how
big a shadow the airplane must cast to power itself to altitude and
charge the batteries for overnight operation.

Some people have all the fun!