Sorry Jax, sometimes you get it right, but this time your habit of
stating absolutes where not appropriate is showing again. The
underwater lawn sprinkler is an imperfect model for the mechanics of a
boat's prop and rudder. Now, a prop in reverse creates very little
water movement past the rudder compared to one in forward, but very
little is not the same as none. As long as there is water being moving
past and deflected by the rudder there will be some lateral force
generated. Not much in this case, but some. This can be readily
demonstrated as another poster pointed out.

JAXAshby wrote:
The exercise was
repeated in reverse hanging off a bow line, proving (contrary to jaxie's
claim)
the affect works in reverse,


geezus kriste, jeffies, you claim to have a degree in physics and have NEVER --
to this moment -- heard of classic "under water lawn sprinkler" paradox that
ALL physics students learn.

Get your wife to explain it to you. It is impossible to steer by *pulling*
water over a rudder with a prop. Can't be done, except when under the
influence of hard drugs.



--
Dan Best - (707) 431-1662, Healdsburg, CA 95448
B-2/75 1977-1979
Tayana 37 #192, "Tricia Jean"
http://rangerbest.home.comcast.net/TriciaJean.JPG

sorry, Dan. don't try to noodle this one out. It is a fact of physics that
you can NOT control using rudder by *pulling* water over it. you MUST push.

lay people often don't that know, for intuitively it doesn't seem "right". but
jeffies has in the past claimed specifically not to be a layperson regarding
physics.

Sorry Jax, sometimes you get it right, but this time your habit of
stating absolutes where not appropriate is showing again. The
underwater lawn sprinkler is an imperfect model for the mechanics of a
boat's prop and rudder. Now, a prop in reverse creates very little
water movement past the rudder compared to one in forward, but very
little is not the same as none. As long as there is water being moving
past and deflected by the rudder there will be some lateral force
generated. Not much in this case, but some. This can be readily
demonstrated as another poster pointed out.

JAXAshby wrote:
The exercise was
repeated in reverse hanging off a bow line, proving (contrary to jaxie's
claim)
the affect works in reverse,


geezus kriste, jeffies, you claim to have a degree in physics and have
NEVER --
to this moment -- heard of classic "under water lawn sprinkler" paradox
that
ALL physics students learn.

Get your wife to explain it to you. It is impossible to steer by *pulling*
water over a rudder with a prop. Can't be done, except when under the
influence of hard drugs.



--
Dan Best - (707) 431-1662, Healdsburg, CA 95448
B-2/75 1977-1979
Tayana 37 #192, "Tricia Jean"
http://rangerbest.home.comcast.net/TriciaJean.JPG

On 25 Mar 2004 19:07:46 GMT, (JAXAshby) wrote:

It is a fact of physics that
you can NOT control using rudder by *pulling* water over it. you MUST push.

===================

Absolutely not true.

If there is water moving past the rudder, regardless of direction or
cause, it can be used to create a directed thrust simply by angling
the rudder away from the flow direction.

The confusion arises because the prop in forward pushes a large flow
across the rudder, whereas the prop in reverse pulls only a relatively
small amount of water across the rudder. Small, but not zero.

You don't need a degree in physics to understand this, just a little
common sense. Richard Feynman would no doubt find the discussion
amusing however.

wayne, you are out of your league.

*push* is required under the laws of physics. If you can't see that, just take
Feynman's word for it.

It is a fact of physics that
you can NOT control using rudder by *pulling* water over it. you MUST
push.

===================

Absolutely not true.

If there is water moving past the rudder, regardless of direction or
cause, it can be used to create a directed thrust simply by angling
the rudder away from the flow direction.

The confusion arises because the prop in forward pushes a large flow
across the rudder, whereas the prop in reverse pulls only a relatively
small amount of water across the rudder. Small, but not zero.

You don't need a degree in physics to understand this, just a little
common sense. Richard Feynman would no doubt find the discussion
amusing however.

You're absolutely wrong about this jaxie. Feynman would think you're a complete
fool for invoking his "sprinkler paradox" in this case. The boat is not turned
directly by the propeller, it is turned because a water flow is pressing against
the rudder. "Push" and "pull" are irrelevant, and the water flow could even
come from a current, or the wash from another boat. For a variety of reasons,
the affect is far more powerful in foreword, but it is still there in reverse.

USSailing, and Boat/US both describe this on their websites.
http://www.videos.sailingcourse.com/...pring_line.htm
http://www.boatus.com/seaworthy/swlines.asp
And the Coast Guard
http://www.uscg.mil/hq/g-o/cgaux/Pub...crew/ch10d.pdf



"JAXAshby" wrote in message
...
wayne, you are out of your league.

*push* is required under the laws of physics. If you can't see that, just
take
Feynman's word for it.

It is a fact of physics that
you can NOT control using rudder by *pulling* water over it. you MUST
push.

===================

Absolutely not true.

If there is water moving past the rudder, regardless of direction or
cause, it can be used to create a directed thrust simply by angling
the rudder away from the flow direction.

The confusion arises because the prop in forward pushes a large flow
across the rudder, whereas the prop in reverse pulls only a relatively
small amount of water across the rudder. Small, but not zero.

You don't need a degree in physics to understand this, just a little
common sense. Richard Feynman would no doubt find the discussion
amusing however.

BG Jeff, you still wasting time on that imbecile? The odds on him
knowing anything about real world boat handling fall into the "minuscule
to none" category.

otn


Jeff Morris wrote:
You're absolutely wrong about this jaxie. Feynman would think you're a complete
fool for invoking his "sprinkler paradox" in this case. The boat is not turned
directly by the propeller, it is turned because a water flow is pressing against
the rudder. "Push" and "pull" are irrelevant, and the water flow could even
come from a current, or the wash from another boat. For a variety of reasons,
the affect is far more powerful in foreword, but it is still there in reverse.

USSailing, and Boat/US both describe this on their websites.
http://www.videos.sailingcourse.com/...pring_line.htm
http://www.boatus.com/seaworthy/swlines.asp
And the Coast Guard
http://www.uscg.mil/hq/g-o/cgaux/Pub...crew/ch10d.pdf



"JAXAshby" wrote in message
...

wayne, you are out of your league.

*push* is required under the laws of physics. If you can't see that, just

take

Feynman's word for it.


It is a fact of physics that
you can NOT control using rudder by *pulling* water over it. you MUST

push.

===================

Absolutely not true.

If there is water moving past the rudder, regardless of direction or
cause, it can be used to create a directed thrust simply by angling
the rudder away from the flow direction.

The confusion arises because the prop in forward pushes a large flow
across the rudder, whereas the prop in reverse pulls only a relatively
small amount of water across the rudder. Small, but not zero.

You don't need a degree in physics to understand this, just a little
common sense. Richard Feynman would no doubt find the discussion
amusing however.

Yea, but he always gets an "A" in the trolling category.

--


Keith
__
What did you forget?
"otnmbrd" wrote in message
.net...
BG Jeff, you still wasting time on that imbecile? The odds on him
knowing anything about real world boat handling fall into the "minuscule
to none" category.

otn

over the nee, you be a stew pid as jeffies.

go ahead. TRY to back that thing up.

BG Jeff, you still wasting time on that imbecile? The odds on him
knowing anything about real world boat handling fall into the "minuscule
to none" category.

otn


Jeff Morris wrote:
You're absolutely wrong about this jaxie. Feynman would think you're a
complete
fool for invoking his "sprinkler paradox" in this case. The boat is not
turned
directly by the propeller, it is turned because a water flow is pressing
against
the rudder. "Push" and "pull" are irrelevant, and the water flow could
even
come from a current, or the wash from another boat. For a variety of
reasons,
the affect is far more powerful in foreword, but it is still there in
reverse.

USSailing, and Boat/US both describe this on their websites.
http://www.videos.sailingcourse.com/...pring_line.htm
http://www.boatus.com/seaworthy/swlines.asp
And the Coast Guard
http://www.uscg.mil/hq/g-o/cgaux/Pub...crew/ch10d.pdf



"JAXAshby" wrote in message
...

wayne, you are out of your league.

*push* is required under the laws of physics. If you can't see that, just

take

Feynman's word for it.


It is a fact of physics that
you can NOT control using rudder by *pulling* water over it. you MUST

push.

===================

Absolutely not true.

If there is water moving past the rudder, regardless of direction or
cause, it can be used to create a directed thrust simply by angling
the rudder away from the flow direction.

The confusion arises because the prop in forward pushes a large flow
across the rudder, whereas the prop in reverse pulls only a relatively
small amount of water across the rudder. Small, but not zero.

You don't need a degree in physics to understand this, just a little
common sense. Richard Feynman would no doubt find the discussion
amusing however.

geesh, jeffies, you CLAIM to have a degree in physics, yet it is plainly
obvious you don't even begin to understand what is going on.

You're absolutely wrong about this jaxie. Feynman would think you're a
complete
fool for invoking his "sprinkler paradox" in this case. The boat is not
turned
directly by the propeller, it is turned because a water flow is pressing
against
the rudder. "Push" and "pull" are irrelevant, and the water flow could even
come from a current, or the wash from another boat. For a variety of
reasons,
the affect is far more powerful in foreword, but it is still there in
reverse.

USSailing, and Boat/US both describe this on their websites.
http://www.videos.sailingcourse.com/...pring_line.htm
http://www.boatus.com/seaworthy/swlines.asp
And the Coast Guard
http://www.uscg.mil/hq/g-o/cgaux/Pub...crew/ch10d.pdf



"JAXAshby" wrote in message
...
wayne, you are out of your league.

*push* is required under the laws of physics. If you can't see that, just
take
Feynman's word for it.

It is a fact of physics that
you can NOT control using rudder by *pulling* water over it. you MUST
push.

===================

Absolutely not true.

If there is water moving past the rudder, regardless of direction or
cause, it can be used to create a directed thrust simply by angling
the rudder away from the flow direction.

The confusion arises because the prop in forward pushes a large flow
across the rudder, whereas the prop in reverse pulls only a relatively
small amount of water across the rudder. Small, but not zero.

You don't need a degree in physics to understand this, just a little
common sense. Richard Feynman would no doubt find the discussion
amusing however.

Jax,

I may not be the brightest bulb in the box, and the last physics course
I took was well over twenty years ago (I still break out in a cold sweat
when I hear the words "Virial Theorem"), so if you can explain it to me
I'd appreciate it.

How does the rudder (or the rudder stock & pintles through which the
force is applied to the hull) know whether the water flowing past it is
being pushed or pulled?

Now if you want to argue that the water flow across the rudder is so
small that the effect of the rudder is overpowered by the prop walk,
that I can buy. But to say that the water flowing past the rudder (and
being deflected by it has no effect because it's motion was started by
some mysterious sucking force makes no sense.

Because the water column being pushed aft when in forward is of constant
diameter (at least in gross terms across the distances we are toaling
about), the velocity in the column is for practical purposes constant.
resulting in a high velocity stream being deflected by the rudder and a
large resultant lateral force.

In reverse, however, there is no such water column aft of the prop. The
water is being sucked in from all directions and thus it's velocity
falls off as the square of the distance from the prop (again, we are
taling in gross terms here). This results in a comparatively slow, but
non-zero velocity as it passes the rudder. Movement of the water
(regardless of it's cause) past the rudder, and its' being deflected by
it causes a lateral force.

JAXAshby wrote:
wayne, you are out of your league.

*push* is required under the laws of physics. If you can't see that, just take
Feynman's word for it.


It is a fact of physics that
you can NOT control using rudder by *pulling* water over it. you MUST

push.

===================

Absolutely not true.

If there is water moving past the rudder, regardless of direction or
cause, it can be used to create a directed thrust simply by angling
the rudder away from the flow direction.

The confusion arises because the prop in forward pushes a large flow
across the rudder, whereas the prop in reverse pulls only a relatively
small amount of water across the rudder. Small, but not zero.

You don't need a degree in physics to understand this, just a little
common sense. Richard Feynman would no doubt find the discussion
amusing however.










--
Dan Best - (707) 431-1662, Healdsburg, CA 95448
B-2/75 1977-1979
Tayana 37 #192, "Tricia Jean"
http://rangerbest.home.comcast.net/TriciaJean.JPG