On Fri, 2 Oct 2009 17:42:17 -0700 (PDT), Frogwatch
wrote:

On Oct 2, 8:02*pm, brian whatcott wrote:
Goofball_star_dot_etal wrote:

...

Hmmmm. a mostly reasonable review - but the idea that force times
distance *is not equal to work is somewhat radical, don't you think?

I said no work was done *on the (air)plane*. Since we only have the
airplane and the air, the work done by the thrust of the engine moving
the airplane through a distance all goes into the air as (kinetic)
energy or heat in its wake.

If I push a sled over snow with force F for distance D
it's usually accounted that the work I did ON the sled is F X D

...but I won't beat the topic down....
:-)

Brian W

In regard to sudden gusts, why not use a breakaway strap like some
rock climbers use whose stitches break at some load allowing the sail
to be let out all the way.
How many boats get knocked down anyway? I mean cruising boats, racers
intend to be on the edge. My own boat, a 28' S2, if a sudden gust
came up, I'd never be able to hold the tiller and she'd round up into
the wind before getting knocked down.


Not really a problem to design a boat that won't be knocked down. Good
form or ballast stability and a small rig.

Of course, as soon as the bloke buys this no-knock-down marvel he will
get a cruising gennaker, a storm spinnaker and fit a topmast so he can
fly a topsail. Probably it is impossible to build a vessel that is
impossible to knock down if the owner is in any way adventurous.

After all they once built an airplane that wouldn't spin and wouldn't
stall. It wasn't immensely popular.

Even full rigged ships quite frequently could send down their topmasts
in bad weather.

Cheers,

Bruce
(bruceinbangkokatgmaildotcom)