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'[TECH]: DDWFTTW: directly down wind faster than th'
2010\11\05@212133 by YES NOPE9

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>
> On Nov 5, 2010, at 10:05 AM, Alex Harford wrote:
>
> http://www.wired.com/autopia/2010/08/ddwfttw
>
> I am still trying to wrap my head around how it works, especially how
> it can actually start moving.
> My thought is that there may be a misunderstanding about what 'traveling downwind' means.
I do not think a vehicle can travel on a vector in alignment with an unvarying wind unless it stores energy before it reaches the speed of the wind and then uses that energy to exceed the speed of the wind.  I would consider that cheating.
If you were traveling around a cylinder ( in zero gravity ) and the wind was always tangent to the surface of the cylinder ( at all distances from the center of the cylinder ) you could 'travel faster than the wind'.  At least it might appear that way to a casual observer.  In reality I would argue that you were cheating by not really traveling in the same direction as the wind.  I would bet that nothing new is being demonstrated and this is a hoax or a misunderstanding.  I saw nothing in the video that suggested that anything amazing had happened.  www.wired.com/autopia/2010/08/ddwfttw/4/
Gus in Denve

2010\11\06@000829 by Alex Harford

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On Fri, Nov 5, 2010 at 6:21 PM, YES NOPE9 <spam_OUTyesTakeThisOuTspamnope9.com> wrote:
>>
>> On Nov 5, 2010, at 10:05 AM, Alex Harford wrote:
>>
>> http://www.wired.com/autopia/2010/08/ddwfttw
>>
>> I am still trying to wrap my head around how it works, especially how
>> it can actually start moving.
>>
> My thought is that there may be a misunderstanding about what 'traveling downwind' means.
> I do not think a vehicle can travel on a vector in alignment with an unvarying wind unless it stores energy before it reaches the speed of the wind and then uses that energy to exceed the speed of the wind.  I would consider that cheating.

Fair enough, but the vehicle shown can sustain the FTTW speed indefinitely.

> If you were traveling around a cylinder ( in zero gravity ) and the wind was always tangent to the surface of the cylinder ( at all distances from the center of the cylinder ) you could 'travel faster than the wind'.  At least it might appear that way to a casual observer.  In reality I would argue that you were cheating by not really traveling in the same direction as the wind.  I would bet that nothing new is being demonstrated and this is a hoax or a misunderstanding.  I saw nothing in the video that suggested that anything amazing had happened.  www.wired.com/autopia/2010/08/ddwfttw/4/
> Gus in Denver

Perhaps these two videos will clarify:
http://www.youtube.com/watch?v=g8bxXRQtcMY
http://www.youtube.com/watch?v=Ufk6HVWdSzE&NR=1

2010\11\06@002531 by John Gardner

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Enjoy...

http://www.rose-hulman.edu/~moloney/AppComp/1999Entries/entry09.ht

2010\11\06@015959 by Oli Glaser

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On 06/11/2010 04:25, John Gardner wrote:
> Enjoy...
>
> http://www.rose-hulman.edu/~moloney/AppComp/1999Entries/entry09.htm

Maybe I'm missing something with this, but it seems the points made are pretty obvious. Also, the proposed setup works differently from what (I think) the student describes. The setup seems to just use the sail to deflect the air in the appropriate direction needed for propulsion, rather like a hovercraft or similar vehicle would. Also, the point "Actually, the greatest effect is obtained by removing the sail entirely!" seems the most obvious of all to me - this removes any obstruction to the propulsion so of course it would..
The students proposition seems akin to standing on a cart and "shunting" yourself along using changes of momentum, like the wind hitting the sail in short blasts.
Rather tired (05:58 here) and brain is overworked today so it's very likely I have completely overlooked something here, sure someone will put me straight if this is the case.. :-)

2010\11\06@125302 by YES NOPE9

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{Quote hidden}

After watching this video ....
www.youtube.com/watch?v=k-trDF8Yldc&NR=1
I feel my grip on reality is more tenuous than before ( especially during the latter parts of the video )
gus in Denve

2010\11\06@194006 by Chris McSweeny

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On Sat, Nov 6, 2010 at 4:53 PM, YES NOPE9 <yesspamKILLspamnope9.com> wrote:
> After watching this video ....
> www.youtube.com/watch?v=k-trDF8Yldc&NR=1
> I feel my grip on reality is more tenuous than before
> ( especially during the latter parts of the video )
> gus in Denver

Try http://www.youtube.com/watch?v=E7vcQcIaWSQ&feature=related instead
- exactly the same principle, but with less moving parts it's somewhat
easier to understand. Fundamentally what's happening here is that when
the cotton reel rolls to the right, the bottom of the inner part also
moves to the right, but slower than the reel does.- not hard to
analyse that as it's basic gears, with the very top of the outside of
the reel moving fastest to the right and the bottom where it's
touching the ground stationary, with a linear continuity between.
Therefore when there's a force to the right on the bottom of the inner
part, that moves to the right, with the reel itself moving to the
right at a faster rate.

Now I wonder what would happen if you could make paddles attached to
the underneath of the inner part of the reel which would completely
stop the wind, and then direct a jet of air onto them...

The truck in the video you linked works in _exactly_ the same way -
the only difference is that they're using the big wheel to move the
point of application of force from underneath the centre of the reels
to on top. The top of the big wheel moves to the right at exactly the
same speed as the bottom of the inner part of the reel. The only
difference being that it seems a lot more complicated, but if you can
understand the example with a single reel you're most of the way
there.

To come back to the original ddwfttw machine, the principle this
starts from is that a sailing yacht can travel to a point directly
downwind of where it starts faster than the a balloon floating in the
wind. It does this not by going straight, but by travelling on broad
reaches and using the "gearing" power of the wind on the sail, to
drive it downwind faster than the wind - you just need to gybe at some
point to go directly downwind. All you need to do to go directly
downwind is continuously gybe!

The ddwfttw machine kind of combines these principles. The propellor
is effectively acting like a sail on a boat on a broad reach -
extracting energy from the wind despite moving downwind faster than
the wind. The cotton reel examples above also illustrate the
principle, that when the vehicle attached to the prop moves downwind,
the prop itself also moves downwind, but the surfaces of the prop
effectively move downwind slower than the vehicle because the prop is
spinning.

http://www.youtube.com/watch?v=7xL8gRJ5F6k&feature=related shows the
principle at work quite neatly - I wonder how hard it is to make one
(goes to check out instructables).

Chri

2010\11\06@201235 by Chris McSweeny

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On Sat, Nov 6, 2010 at 11:40 PM, Chris McSweeny <.....cpmcsweenyKILLspamspam.....gmail.com> wrote:
> I wonder how hard it is to make one
> (goes to check out instructables).

Not on instructables maybe, but I found the answer to my own question
http://www.youtube.com/watch?v=T-ArigMKhi4&fmt=18

Chri

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