On Fri, 16 Sep 2011, Onno Meyer wrote:
Travis replied to me:
Sailing only works when you have two different moving fluids.
Hello Travis,
that is certainly the case for sailing anywhere close to the
wind. But some early balloons had sails -- was that just a
misunderstanding of the physics?
http://selfinger.com/fp/art/andree.htm
Consider this ASCII art:
/ Sail
/
Wind -> O Center of mass
/
/
Would this contragrav craft move in the direction of the wind,
or at a slight angle?
Also, would it start to rotate around its axis?
With time, the craft would probably accelerate to the speed
of the wind, and it would be at rest relative to the air
around it, if the speed and direction of the wind is
constant. What happens when there are gusts?
I don't know about baloon sails, but they could also have been to maximise
the amount of wind you catch, when it blows in the right direction, and to
be removed at other times.
Some types of sail, like the ones modern sailing yachts use, are not
intended to be used to catch the wind and get pushed, but they give a
shape similiar to an airplane wing, and that gives you the movement.
There is some movement from getting pushed, but that is small due to the
resistance the water gives, especially given that thoose boats are built
to maximize the resistance for sideways movement.
If your ascii sail were such a sail, there would be some movement
downward, though if you mount it on a baloon, i suppose it would be
minimal compared to your movement due to being blown around.
How much is a contragrav vehicle like a balloon though? I don't remember
if the rules in vehicle are specific on that, so if you don't put your
vehicle in a background that has precedence cases, you might be able to
pick something that suits your vehicle.
And there is an other idea. Could you add additional contragrav units, to
influence the wind around your vehicle?
One mans groundfloor is an other mans earthmissle
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Johannes Trimmel
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