Re: Sailing, sailing....

On Nov 7, 4:08 am, "Cwatters"
<colin.wattersNOS...@xxxxxxxxxxxxxxxxxxxxxxxxx> wrote:
"Edward Green" <spamspamsp...@xxxxxxxxxxx> wrote in message

news:36f63adc-32c8-4483-a8b3-7cdda9488f52@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxx

A thought problem (I don't know the answer):

Given a still body of water, a wind over the water, and a boat.  The
boat has an air turbine (fan/screw) and a water turbine (fan/screw)
connected by a mechanical linkage.  Can the boat, without any external
source of power, sail directly into the wind?

Yes and it's not too hard to understand how it can work.

First thing to understand is that the windmill and turbine DONT travel
directly into the wind. The blades take a helical path not that unlike a
regularsailingboat tacking in 3D.

Imagine asailingboat towing a barge. Thesailingboat has to tack but the
barge can go directly upwind with suitable application of the rudder. After
a few hours the center of gravity of the system will have moved many miles
upwind. The rest is engineering.

Imagine the same set up with twosailingboats on oposite tacks. They cross
back and forth in front of the barge which now needs no rudder input to
travel directly upwind. Then imagine the wind turbine and propeller only
have two blades. As they rotate there will be a point where the blades are
vertical. Freeze frame and compare with thesailingboat case. The wind
turbine blades are directly comparable to the sails. The water prop blabes
are directly comparable to the center boards of thesailingboats.

From a work/energy perspective.. The energy extracted is proportional to the
LIFT produced by the blades/wings of the turbine. However the energy
expended moving through the air is proportional to the DRAG of the blades..
Since the LIFT/DRAG ratio of a modern wing can be very high - it works.

Nice analysis -- and you are not the only one to take this tack. But
I think Dave Typinksi's energy/momentum analysis was by far the
simplest -- and essentially correct.

I see why one of the illustrate examples had a pivoting wind turbine:
you can sail in other directions as well, while maintaining efficiency
of your power source. Ironically, the worst direction to sail would
be directly _down_ wind. It's sort of an anti-square rigger.
.

Relevant Pages

  • Re: DNA = Information
    ... the fewer blades one would want. ... turbine on the stern of a sail boat that had just one blade, ... A wind turbine has an upper limit on the amount of energy it can ...
    (talk.origins)
  • Re: DNA = Information
    ... the fewer blades one would want. ... A wind turbine has an upper limit on the amount of energy it can ... We design our machines to sit on that optimum most of the time. ...
    (talk.origins)
  • Re: Storm and wind turbines.
    ... the wind turbine would shut down. ... If the blades are variable pitch controlled by a governer they could change angle and take on 200mph winds if they wished, being inline with wind direction at 0degrees pitch. ...
    (uk.media.tv.misc)
  • Re: Sailing, sailing....
    ... boat has an air turbine and a water turbine ... Can the boat, without any external ... sail directly into the wind? ... directions). ...
    (sci.physics)
  • Re: Domestic wind turbines
    ... Blades 'flew off' wind turbine ... and flew over his house before crashing to the ground. ...
    (uk.business.agriculture)
Quantcast