OT Sail downwind faster than the wind!

On Jul 30, 2:24 pm, Jim Thompson <To-Email-Use-The-Envelope-I...@On-My-
Web-Site.com> wrote:
On Fri, 30 Jul 2010 14:22:54 -0500, John Fields



jfie...@austininstruments.com> wrote:
On 30 Jul 2010 18:54:14 GMT, John Doe <j...@usenetlove.invalid> wrote:

Phil Hobbs <pcdhSpamMeSenseless electrooptical.net> wrote:

it's a hydrodynamics problem.

You ignore the fact that there is negative pressure on the
propeller (and the craft), that is what makes the propeller spin.
Your argument is that you can turn that rearward thrust into a
greater forward thrust. It is a prima facie failure.

---
Think about this:

You have a propeller facing into the wind, and to it you have
connected a shaft which drives the input of a gearbox.

The output of the gearbox is connected to the input of a differential
gear, and the outputs of the differential are connected to axles with
wheels on their ends, resting on the ground.

Now imagine all this mounted to a platform with two extra freewheeling
wheels on it so it can roll along the ground.

If the propeller spins, the driven wheels _must_ turn and the "cart"
_must_ move into the wind.

Other than the wrong ratio in the gearbox, what would keep the prop
from turning?  

Into the wind.

How do you go faster than the wind, with the wind at your back?

If you travel faster than the wind with the wind behind your back, by
definition it's no longer at your back--it's in your face.

I used to race sailboats. A number (esp. cats on hydrofoils) can go
to weather faster than the wind. I think windsurfers too. Downwind?
Nope.

John Larkin <jjlarkin highNOTlandTHIStechnologyPART.com> wrote:

....

You can certainly make a cog railway engine, propeller-driven,
that moves into the wind. Just gear it down until it works.

I am disappointed that even John Larkin would argue something like
that.

John Fields <jfields_at_austininstruments.com> wrote:

John Doe <jdoe_at_usenetlove.invalid> wrote:
Phil Hobbs <pcdhSpamMeSenseless electrooptical.net> wrote:

it's a hydrodynamics problem.

You ignore the fact that there is negative pressure on the
propeller (and the craft), that is what makes the propeller
spin. Your argument is that you can turn that rearward thrust
into a greater forward thrust. It is a prima facie failure.

Think about this:

You have a propeller facing into the wind, and to it you have
connected a shaft which drives the input of a gearbox.

The output of the gearbox is connected to the input of a
differential gear, and the outputs of the differential are
connected to axles with wheels on their ends, resting on the
ground.

Now imagine all this mounted to a platform with two extra
freewheeling wheels on it so it can roll along the ground.

If the propeller spins, the driven wheels _must_ turn and the
"cart" _must_ move into the wind.

Only if there were no headwind, the thing that turns the
propeller. You have headwind resistance against the propeller (and
the craft) that pushes pushes the craft backwards.

On Fri, 30 Jul 2010 14:08:21 -0400, Phil Hobbs
pcdhSpamMeSenseless_at_electrooptical.net> wrote:

Richard Henry wrote:
On Jul 30, 8:39 am, John Larkin
jjlar...@highNOTlandTHIStechnologyPART.com> wrote:
On Fri, 30 Jul 2010 10:54:25 -0400, Phil Hobbs



pcdhSpamMeSensel...@electrooptical.net> wrote:
Richard Henry wrote:
On Jul 30, 7:42 am, John Larkin
jjlar...@highNOTlandTHIStechnologyPART.com> wrote:
On 30 Jul 2010 09:16:40 GMT, John Doe <j...@usenetlove.invalid> wrote:
If you enjoy reading technical argument back and forth (especially
when you suspect that one side is full of it), and have not
already done so, this one is for you.
There is much discussion about a concept called Direct Downwind
Faster Than the Wind (DDWFTTW). The idea of going directly
downwind faster than the wind using only that wind power.
I think you can, as long as you don't insist on steady motion.
Apparently they breed the silliness with the idea that you can
move directly into the wind using only the wind power.
That can definitely be done.
Heh! Only on lawyer's boats.
You do have to zigzag a bit.
Not really. A windmill driving a propeller or a paddlewheel would
work. It's just an impedance matching problem.

John
The first notch on the bullshit meter is conservation of energy.
It isn't a perpetual motion machine, it's a hydrodynamics problem.
Given a solid substrate, it isn't even difficult. No energy
conservation issues.

Cheers

Phil Hobbs

You'd need a hull that's very slippery, so the wind doesn't push much
on it. That's easy... keep most of the hull underwater. Now the
question is how much power the windmill makes for some amount of wind
load on the structure; the water propeller has to generate more thrust
than that. Marine propellers are very efficient, so gear it down until
you gave more prop thrust than wind load on the windmill. It would be
an ugly boat, but it would work.

John

John Doe wrote:
John Larkin wrote:

....

You can certainly make a cog railway engine, propeller-driven,
that moves into the wind. Just gear it down until it works.

I am disappointed that even John Larkin would argue something
like that.

Why not?

He's perfectly right. Given a windmill with shaft speed Omega
shaft torque Gamma, and drag force F, by balancing the work done
against drag with the available shaft power, you get a maximum upwind speed

Gamma Omega
Vmax = -----------
F

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs
Principal
ElectroOptical Innovations
55 Orchard Rd
Briarcliff Manor NY 10510
845-480-2058
hobbs at electrooptical dot net
http://electrooptical.net



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Message-ID: <4C5341EC.9000803 electrooptical.net
Date: Fri, 30 Jul 2010 17:19:40 -0400
From: Phil Hobbs <pcdhSpamMeSenseless electrooptical.net
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Subject: Re: OT Sail downwind faster than the wind!
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John Larkin <jjlarkin highNOTlandTHIStechnologyPART.com> wrote:

On Fri, 30 Jul 2010 14:08:21 -0400, Phil Hobbs
pcdhSpamMeSenseless electrooptical.net> wrote:

Richard Henry wrote:
On Jul 30, 8:39 am, John Larkin <jjlar...
highNOTlandTHIStechnologyPART.com> wrote:
On Fri, 30 Jul 2010 10:54:25 -0400, Phil Hobbs



pcdhSpamMeSensel... electrooptical.net> wrote:
Richard Henry wrote:
On Jul 30, 7:42 am, John Larkin <jjlar...
highNOTlandTHIStechnologyPART.com> wrote:
On 30 Jul 2010 09:16:40 GMT, John Doe <j...
usenetlove.invalid> wrote:
If you enjoy reading technical argument back and forth
(especially when you suspect that one side is full of
it), and have not already done so, this one is for you.
There is much discussion about a concept called Direct
Downwind Faster Than the Wind (DDWFTTW). The idea of
going directly downwind faster than the wind using only
that wind power.
I think you can, as long as you don't insist on steady
motion.
Apparently they breed the silliness with the idea that
you can move directly into the wind using only the wind
power.
That can definitely be done.
Heh! Only on lawyer's boats.
You do have to zigzag a bit.
Not really. A windmill driving a propeller or a paddlewheel
would work. It's just an impedance matching problem.

John

The first notch on the bullshit meter is conservation of
energy.

It isn't a perpetual motion machine, it's a hydrodynamics
problem. Given a solid substrate, it isn't even difficult. No
energy conservation issues.

Cheers

Phil Hobbs

You'd need a hull that's very slippery, so the wind doesn't push
much on it.

The headwind pushes on the propeller, that is enough to keep the
craft from moving forwards or to make it move backwards.

That's easy... keep most of the hull underwater. Now the
question is how much power the windmill makes for some amount of
wind load on the structure; the water propeller has to generate
more thrust than that. Marine propellers are very efficient, so
gear it down until you gave more prop thrust than wind load on
the windmill. It would be an ugly boat, but it would work.

If that were true, there would be a zillion attempts at United
States patents, with at least one successful patent. Not talking
about a silly Internet patent, talking about the United States
patent office that has deflected (millions?) of "perpetual motion
machine" patent attempts.

Phil Hobbs <pcdhSpamMeSenseless electrooptical.net> wrote:

Richard Henry wrote:
John Larkin <jjlar... highNOTlandTHIStechnologyPART.com
Phil Hobbs <pcdhSpamMeSensel... electrooptical.net
Richard Henry wrote:
John Larkin <jjlar... highNOTlandTHIStechnologyPART.com
John Doe <j... usenetlove.invalid> wrote:

If you enjoy reading technical argument back and forth
(especially when you suspect that one side is full of it),
and have not already done so, this one is for you.
There is much discussion about a concept called Direct
Downwind Faster Than the Wind (DDWFTTW). The idea of going
directly downwind faster than the wind using only that
wind power.

I think you can, as long as you don't insist on steady
motion.

Apparently they breed the silliness with the idea that you
can move directly into the wind using only the wind power.

That can definitely be done.

In a fantasy while lounging on an Arizonan beach.

Heh! Only on lawyer's boats.

You do have to zigzag a bit. ;)

Not really. A windmill driving a propeller or a paddlewheel
would work. It's just an impedance matching problem.

The first notch on the bullshit meter is conservation of
energy.
It isn't a perpetual motion machine,

It is generating forward motion out of rearward thrust. A
perpetual motion machine generates motion out of no thrust.
The idea is worse than a perpetual motion machine.

it's a hydrodynamics problem.

You ignore the fact that there is negative pressure on the
propeller (and the craft), that is what makes the propeller spin.
Your argument is that you can turn that rearward thrust into a
greater forward thrust. It is a prima facie failure.

John Larkin wrote:
On Fri, 30 Jul 2010 14:08:21 -0400, Phil Hobbs
pcdhSpamMeSenseless_at_electrooptical.net> wrote:

Richard Henry wrote:
On Jul 30, 8:39 am, John Larkin
jjlar...@highNOTlandTHIStechnologyPART.com> wrote:
On Fri, 30 Jul 2010 10:54:25 -0400, Phil Hobbs



pcdhSpamMeSensel...@electrooptical.net> wrote:
Richard Henry wrote:
On Jul 30, 7:42 am, John Larkin
jjlar...@highNOTlandTHIStechnologyPART.com> wrote:
On 30 Jul 2010 09:16:40 GMT, John Doe <j...@usenetlove.invalid> wrote:
If you enjoy reading technical argument back and forth (especially
when you suspect that one side is full of it), and have not
already done so, this one is for you.
There is much discussion about a concept called Direct Downwind
Faster Than the Wind (DDWFTTW). The idea of going directly
downwind faster than the wind using only that wind power.
I think you can, as long as you don't insist on steady motion.
Apparently they breed the silliness with the idea that you can
move directly into the wind using only the wind power.
That can definitely be done.
Heh! Only on lawyer's boats.
You do have to zigzag a bit.
Not really. A windmill driving a propeller or a paddlewheel would
work. It's just an impedance matching problem.

John
The first notch on the bullshit meter is conservation of energy.
It isn't a perpetual motion machine, it's a hydrodynamics problem.
Given a solid substrate, it isn't even difficult. No energy
conservation issues.

Cheers

Phil Hobbs

You'd need a hull that's very slippery, so the wind doesn't push much
on it. That's easy... keep most of the hull underwater. Now the
question is how much power the windmill makes for some amount of wind
load on the structure; the water propeller has to generate more thrust
than that. Marine propellers are very efficient, so gear it down until
you gave more prop thrust than wind load on the windmill. It would be
an ugly boat, but it would work.

John




"Very efficient" != "efficient enough". Depending on how the math
comes out, it may need an efficiency of 1000%, or maybe it's 50%.

you can't power a mostly-submerged hull that way, because you need the
centre of buoyancy way above the centre of mass in order not to capsize
due to the polar torque due to the drag of the ruddy great windmill.

That means a lot of free surface and a lot of freeboard.

I don't know if it can be done or not.

On Fri, 30 Jul 2010 14:22:54 -0500, John Fields



jfie...@austininstruments.com> wrote:
On 30 Jul 2010 18:54:14 GMT, John Doe <j...@usenetlove.invalid> wrote:

Phil Hobbs <pcdhSpamMeSenseless electrooptical.net> wrote:

it's a hydrodynamics problem.

You ignore the fact that there is negative pressure on the
propeller (and the craft), that is what makes the propeller spin.
Your argument is that you can turn that rearward thrust into a
greater forward thrust. It is a prima facie failure.

---
Think about this:

You have a propeller facing into the wind, and to it you have
connected a shaft which drives the input of a gearbox.

The output of the gearbox is connected to the input of a differential
gear, and the outputs of the differential are connected to axles with
wheels on their ends, resting on the ground.

Now imagine all this mounted to a platform with two extra freewheeling
wheels on it so it can roll along the ground.

If the propeller spins, the driven wheels _must_ turn and the "cart"
_must_ move into the wind.

Other than the wrong ratio in the gearbox, what would keep the prop
from turning?  

Into the wind.

How do you go faster than the wind, with the wind at your back?

On Fri, 30 Jul 2010 17:28:04 -0400, Phil Hobbs
pcdhSpamMeSenseless_at_electrooptical.net> wrote:

John Larkin wrote:
On Fri, 30 Jul 2010 14:08:21 -0400, Phil Hobbs
pcdhSpamMeSenseless_at_electrooptical.net> wrote:

Richard Henry wrote:
On Jul 30, 8:39 am, John Larkin
jjlar...@highNOTlandTHIStechnologyPART.com> wrote:
On Fri, 30 Jul 2010 10:54:25 -0400, Phil Hobbs



pcdhSpamMeSensel...@electrooptical.net> wrote:
Richard Henry wrote:
On Jul 30, 7:42 am, John Larkin
jjlar...@highNOTlandTHIStechnologyPART.com> wrote:
On 30 Jul 2010 09:16:40 GMT, John Doe <j...@usenetlove.invalid> wrote:
If you enjoy reading technical argument back and forth (especially
when you suspect that one side is full of it), and have not
already done so, this one is for you.
There is much discussion about a concept called Direct Downwind
Faster Than the Wind (DDWFTTW). The idea of going directly
downwind faster than the wind using only that wind power.
I think you can, as long as you don't insist on steady motion.
Apparently they breed the silliness with the idea that you can
move directly into the wind using only the wind power.
That can definitely be done.
Heh! Only on lawyer's boats.
You do have to zigzag a bit.
Not really. A windmill driving a propeller or a paddlewheel would
work. It's just an impedance matching problem.

John
The first notch on the bullshit meter is conservation of energy.
It isn't a perpetual motion machine, it's a hydrodynamics problem.
Given a solid substrate, it isn't even difficult. No energy
conservation issues.

Cheers

Phil Hobbs
You'd need a hull that's very slippery, so the wind doesn't push much
on it. That's easy... keep most of the hull underwater. Now the
question is how much power the windmill makes for some amount of wind
load on the structure; the water propeller has to generate more thrust
than that. Marine propellers are very efficient, so gear it down until
you gave more prop thrust than wind load on the windmill. It would be
an ugly boat, but it would work.

John



"Very efficient" != "efficient enough". Depending on how the math
comes out, it may need an efficiency of 1000%, or maybe it's 50%.

Marine props are typically about 75% efficient, but that doesn't
actually matter. It would work with a 10% efficient prop... just use a
higher gear ratio and move more slowly into the wind. It's like the
cog railway, but we lose some power to prop inefficiency. So we go
slower into the wind is we use a prop instead of a cog.



Also
you can't power a mostly-submerged hull that way, because you need the
centre of buoyancy way above the centre of mass in order not to capsize
due to the polar torque due to the drag of the ruddy great windmill.

Use a very long, skinny keel with a big weight at the bottom, like
some racing boatd have. If the drag slows you down, you'll just be
movint into the wind a little slower.

That means a lot of free surface and a lot of freeboard.

I don't know if it can be done or not.

I think it has been done. Not often, because it would be a silly thing
to do to a sailboat.

http://en.wikipedia.org/wiki/Windmill_ship#Points_of_sail


John

On Fri, 30 Jul 2010 10:54:25 -0400, Phil Hobbs





pcdhSpamMeSensel...@electrooptical.net> wrote:
Richard Henry wrote:
On Jul 30, 7:42 am, John Larkin
jjlar...@highNOTlandTHIStechnologyPART.com> wrote:
On 30 Jul 2010 09:16:40 GMT, John Doe <j...@usenetlove.invalid> wrote:

If you enjoy reading technical argument back and forth (especially
when you suspect that one side is full of it), and have not
already done so, this one is for you.
There is much discussion about a concept called Direct Downwind
Faster Than the Wind (DDWFTTW). The idea of going directly
downwind faster than the wind using only that wind power.
I think you can, as long as you don't insist on steady motion.

Apparently they breed the silliness with the idea that you can
move directly into the wind using only the wind power.
That can definitely be done.

Heh!  Only on lawyer's boats.

You do have to zigzag a bit.  ;)

Not really. A windmill driving a propeller or a paddlewheel would
work. It's just an impedance matching problem.

John- Hide quoted text -

- Show quoted text -

John Larkin wrote:
On Fri, 30 Jul 2010 17:28:04 -0400, Phil Hobbs
pcdhSpamMeSenseless_at_electrooptical.net> wrote:

John Larkin wrote:
On Fri, 30 Jul 2010 14:08:21 -0400, Phil Hobbs
pcdhSpamMeSenseless_at_electrooptical.net> wrote:

Richard Henry wrote:
On Jul 30, 8:39 am, John Larkin
jjlar...@highNOTlandTHIStechnologyPART.com> wrote:
On Fri, 30 Jul 2010 10:54:25 -0400, Phil Hobbs



pcdhSpamMeSensel...@electrooptical.net> wrote:
Richard Henry wrote:
On Jul 30, 7:42 am, John Larkin
jjlar...@highNOTlandTHIStechnologyPART.com> wrote:
On 30 Jul 2010 09:16:40 GMT, John Doe
j...@usenetlove.invalid> wrote:
If you enjoy reading technical argument back and forth
(especially
when you suspect that one side is full of it), and have not
already done so, this one is for you.
There is much discussion about a concept called Direct Downwind
Faster Than the Wind (DDWFTTW). The idea of going directly
downwind faster than the wind using only that wind power.
I think you can, as long as you don't insist on steady motion.
Apparently they breed the silliness with the idea that you can
move directly into the wind using only the wind power.
That can definitely be done.
Heh! Only on lawyer's boats.
You do have to zigzag a bit.
Not really. A windmill driving a propeller or a paddlewheel would
work. It's just an impedance matching problem.

John
The first notch on the bullshit meter is conservation of energy.
It isn't a perpetual motion machine, it's a hydrodynamics problem.
Given a solid substrate, it isn't even difficult. No energy
conservation issues.

Cheers

Phil Hobbs
You'd need a hull that's very slippery, so the wind doesn't push much
on it. That's easy... keep most of the hull underwater. Now the
question is how much power the windmill makes for some amount of wind
load on the structure; the water propeller has to generate more thrust
than that. Marine propellers are very efficient, so gear it down until
you gave more prop thrust than wind load on the windmill. It would be
an ugly boat, but it would work.

John



"Very efficient" != "efficient enough". Depending on how the math
comes out, it may need an efficiency of 1000%, or maybe it's 50%.

Marine props are typically about 75% efficient, but that doesn't
actually matter. It would work with a 10% efficient prop... just use a
higher gear ratio and move more slowly into the wind. It's like the
cog railway, but we lose some power to prop inefficiency. So we go
slower into the wind is we use a prop instead of a cog.



Also
you can't power a mostly-submerged hull that way, because you need
the centre of buoyancy way above the centre of mass in order not to
capsize due to the polar torque due to the drag of the ruddy great
windmill.

Use a very long, skinny keel with a big weight at the bottom, like
some racing boatd have. If the drag slows you down, you'll just be
movint into the wind a little slower.

That means a lot of free surface and a lot of freeboard.

I don't know if it can be done or not.

I think it has been done. Not often, because it would be a silly thing
to do to a sailboat.

http://en.wikipedia.org/wiki/Windmill_ship#Points_of_sail


John


No, there's definitely a lower limit for the boat case on account of the
limited viscosity of water. Your analysis leaves the water out of the
picture, and it would apply equally to a sailplane, which is obviously
wrong. Kites, yes. Sailplanes, no. Boats, maybe.

Cheers

Phil Hobbs

I think it is more basic, not just 'impedance matching'.
When the boat's speed increases, then, at some point,
it will move the same speed as the wind.

Not if we're going *into* the wind. The apparent wind, what drives the
windmill, is increasing.

John

On 30 Jul 2010 19:30:46 GMT, John Doe <jdoe_at_usenetlove.invalid
wrote:

John Fields <jfields_at_austininstruments.com> wrote:

John Doe <jdoe_at_usenetlove.invalid> wrote:
Phil Hobbs <pcdhSpamMeSenseless electrooptical.net> wrote:

it's a hydrodynamics problem.

You ignore the fact that there is negative pressure on the
propeller (and the craft), that is what makes the propeller
spin. Your argument is that you can turn that rearward thrust
into a greater forward thrust. It is a prima facie failure.

Think about this:

You have a propeller facing into the wind, and to it you have
connected a shaft which drives the input of a gearbox.

The output of the gearbox is connected to the input of a
differential gear, and the outputs of the differential are
connected to axles with wheels on their ends, resting on the
ground.

Now imagine all this mounted to a platform with two extra
freewheeling wheels on it so it can roll along the ground.

If the propeller spins, the driven wheels _must_ turn and the
"cart" _must_ move into the wind.

Only if there were no headwind, the thing that turns the
propeller. You have headwind resistance against the propeller (and
the craft) that pushes pushes the craft backwards.


Gearboxes can have more output torque than input torque.
Any amount,
actually. If there's 1000 pounds of wind force on the windmill,
adjust
the gear ratio for 2000 pounds of thrust at the wheels. Or 200,000
pounds. All you lose is speed.

In any given situation, there is some
best gear ratio that will give you the max speed into the wind;
it's
an impedance matching problem.

John

On Jul 30, 8:39 am, John Larkin
jjlar...@highNOTlandTHIStechnologyPART.com> wrote:
On Fri, 30 Jul 2010 10:54:25 -0400, Phil Hobbs



pcdhSpamMeSensel...@electrooptical.net> wrote:
Richard Henry wrote:
On Jul 30, 7:42 am, John Larkin
jjlar...@highNOTlandTHIStechnologyPART.com> wrote:
On 30 Jul 2010 09:16:40 GMT, John Doe <j...@usenetlove.invalid
wrote:

If you enjoy reading technical argument back and forth
(especially
when you suspect that one side is full of it), and have not
already done so, this one is for you.
There is much discussion about a concept called Direct Downwind
Faster Than the Wind (DDWFTTW). The idea of going directly
downwind faster than the wind using only that wind power.
I think you can, as long as you don't insist on steady motion.

Apparently they breed the silliness with the idea that you can
move directly into the wind using only the wind power.
That can definitely be done.

Heh! Only on lawyer's boats.

You do have to zigzag a bit. ;)

Not really. A windmill driving a propeller or a paddlewheel would
work. It's just an impedance matching problem.

John

The first notch on the bullshit meter is conservation of energy.