Derek Rowell wrote:
Would you all agree that in areas of dispute the truth may be revealed by an
experiment?

Yes, if the experiment is setup properly, and the data is
*accurately* analyzed and interpreted.

Please try the following:
Take a fan, say a large house cooling fan (that's your propellor). Take a
flat surface, for example a stiff lightweight book (thats the rudder).
Turn the fan on and hold the rudder at an angle on the outflow side
(transmission in forward). Does the flow exert a torque (turning effect) on
the rudder? Let go one corner and see. Is there a sideways thrust that
you have to oppose to keep the rudder in position?

Clearly. f=ma, i.e. force is the product of Mass times
acceleration. In this case the mass of accelerated air will apply
disproportionate force to the 'book' as a function of aspect
ratio. Basically, the book will "weathervane" until the force
applied to each side equalizes.

Repeat the experiment with the "rudder" on the inlet side of the fan
(transmission in reverse). Is there a turning effect (torque) or not? Is
there a sideways thrust on the "rudder"?
You tell me - I just did it. The answers to all four questions is yes.

And...irrelevant! YES there is force on the 'vane', just as there
was on the downstream side. Less due to the the wider flow pattern
on the suction side, but still significant.

However, in the context of the boat model, this force is virtually
irrelevant. In the first case, water is forced over the rudder at
an angle to the boat centerline. It's a simple vector equation.
Water moves to starboard, reaction force is thus to port, the boat
turns starboard.

In REVERSE, the water flow, *irrespective of rudder position* is
along the centerline of the boat, thus the reaction force is
parallel to the keel line, and the boat moves straight back
(ignoring the precessional forces that result in 'prop walk' that
is). It's only when the boat moves through the water that the
rudder can have an effect - another simple vector equation. There
must be additional non-parallel force applied in order to produce
a turn, and that is caused by *additional* water flow past the
rudder caused by boat movement.

Aero/hydrodynamic lift/drag is determined by the flow patterns over surfaces
(Bernoulli effects, etc), not by the simple minded pseudo-science that is
being thrown around here.

Lift and drag are irrelevant. Consider, what is the effect of lift
on the rudder? Heeling action, not turning action. You appear to
be confusing hdyrodynamics with simple force/vector equations.

It's a VERY complex situation.

Not at all. Oh the precessional effects are definitely complex,
all the more so when hydrodynamic effects are added in the
equation, but precession, while important to why your stern always
drifts one way in reverse (i.e. force applied to a spinning object
- the propeller - will be translated 90° in the direction of
rotation, creating a turning force), is not a factor in why the
rudder is ineffective in reverse.

We all agree
that in practice the effect is much, much weaker in reverse but it is still
present. (The reason that it is weaker is that only a small fraction of
the in-flow to the propellor actually passes over the rudder in reverse.)

Sorry, but that's just not accurate.

Keith Hughes

ubject: push vs pull vis a vis rudders
From: (JAXAshby)
Date: 03/27/2004 15:41 Pacific Standard Time
Message-id:

sclackoff, nice flip-flop.

I'll give you credit for one thing. You can come up with more ways of saying
"duh I ain't got no intelligent response and wouldn't know the answer anyway".

Shen

ject: push vs pull vis a vis rudders
From: "Derek Rowell"
Date: 03/27/2004 15:26 Pacific Standard Time
Message-id: E4o9c.108024$1p.1536914@attbi_s54

Would you all agree that in areas of dispute the truth may be revealed by an
experiment? Please try the following:
Take a fan, say a large house cooling fan (that's your propellor). Take a
flat surface, for example a stiff lightweight book (thats the rudder).
Turn the fan on and hold the rudder at an angle on the outflow side
(transmission in forward). Does the flow exert a torque (turning effect) on
the rudder? Let go one corner and see. Is there a sideways thrust that
you have to oppose to keep the rudder in position?
Repeat the experiment with the "rudder" on the inlet side of the fan
(transmission in reverse). Is there a turning effect (torque) or not? Is
there a sideways thrust on the "rudder"?
You tell me - I just did it. The answers to all four questions is yes.

Derek, you may be able to show a "force" being exerted on the rudder in this
way.
However, connect that rudder to a boat, and although this "force" may be
sufficient to pull that rudder further over (seen that), it will, EG almost
always, never be sufficient to act as a steering force for the boat to any
degree that is useable.
My apologies if I don't launch into some longwinded scientific dissertation.

Shen

OK. You caught me again! Damn! Yep, I'm the fraudulent plumber who can't
read from yesterday. I spent a long time fabricating that email address.
It gives my ego a huge boost. Just to prove that the address is
fraudulent - go to the MIT web site (http://web.mit.edu) and do a "people"
search on my name.

I simply gave you a simple experiment to do - and you attack me
personally. (Do it yourself, and draw your own conclusions - takes about 5
minutes)

That's not how we do business in science and engineering. We calmly look
at a situation, make hypotheses and conjectures and then think of a set of
experiments to disprove or prove our ideas. We invite others to disprove
our theories, and rejoice when they do, because we learn something.

That's the end of this discussion. No more!

"JAXAshby" wrote in message
...
derek, your fricken fraud. I just now noticed your fiticious email
address of
mit.edu. NObody from MIT would write what you wrote.

geesh, dude. get a life.

From: "Derek Rowell"

brian, Feyman thought it easy. why do you suppose a cyber clown with a fake
MIT address would find it so difficult.

brian, this is EASY stuff. Not intuitive for many people, perhaps, but still
EASY for those who think it through for a couple minutes.

however for sure, brian and derek, should EITHER of you wish to back up a
ruddered boat using the engine to steer, please feel free to do so, as long as
you are not near my boat. Bang into boats and docks and pilings and blame the
current for all we care. Just don't hit don't do it near my boat. I'll
ridicule you in front of the bimbo you have onboard.

idiots. you believe you knew the entire universe of knowledge by the time you
finally got out of junior high school. Haven't learned a thing since.

Derek, or perhaps as a courtesy I should say Professor Rowell,
why would you think a physics graduate (as described)
with a reading knowledge of some Feynman stuff
be impressed by the opinions of an MIT prof of Mech Engineering?

Don't be discouraged. People try to avoid the crack pots as far as
possible, and still get lots of value here.

Brian W

On Sun, 28 Mar 2004 00:35:03 GMT, "Derek Rowell"
wrote:

OK. You caught me again! Damn! Yep, I'm the fraudulent plumber who can't
read from yesterday. I spent a long time fabricating that email address.
It gives my ego a huge boost. Just to prove that the address is
fraudulent - go to the MIT web site (http://web.mit.edu) and do a "people"
search on my name.

I simply gave you a simple experiment to do - and you attack me
personally. (Do it yourself, and draw your own conclusions - takes about 5
minutes)

That's not how we do business in science and engineering. We calmly look
at a situation, make hypotheses and conjectures and then think of a set of
experiments to disprove or prove our ideas. We invite others to disprove
our theories, and rejoice when they do, because we learn something.

That's the end of this discussion. No more!

derek, since when do ME's deal with "fluid flow"?

you fraud. MIT is going to find out a janitor is posting using the MIT info
structure. Be prepared to pay the required taxes on using educational
resources for personal gain.

Derek, or perhaps as a courtesy I should say Professor Rowell,
why would you think a physics graduate (as described)
with a reading knowledge of some Feynman stuff
be impressed by the opinions of an MIT prof of Mech Engineering?

Don't be discouraged. People try to avoid the crack pots as far as
possible, and still get lots of value here.

Brian W

On Sun, 28 Mar 2004 00:35:03 GMT, "Derek Rowell"
wrote:

OK. You caught me again! Damn! Yep, I'm the fraudulent plumber who can't
read from yesterday. I spent a long time fabricating that email address.
It gives my ego a huge boost. Just to prove that the address is
fraudulent - go to the MIT web site (http://web.mit.edu) and do a "people"
search on my name.

I simply gave you a simple experiment to do - and you attack me
personally. (Do it yourself, and draw your own conclusions - takes about 5
minutes)

That's not how we do business in science and engineering. We calmly look
at a situation, make hypotheses and conjectures and then think of a set of
experiments to disprove or prove our ideas. We invite others to disprove
our theories, and rejoice when they do, because we learn something.

That's the end of this discussion. No more!

Subject: push vs pull vis a vis rudders
From: (JAXAshby)


So, Jax, from this, I see you didn't understand another simple, concise comment
on the subject.
Shame you don't have any practical experience to back up and explain your
typical pontificating.
EG wanna try the inboard/outboard turning prop subject ..... didn't think so

Shen
schlackoff, knock it off. you gibber worse than a gas station attendant
trying
to claim degree from MIT.

[snip all but the important stuff from schlackoff's post]

nice, accurate response, Keith.

From: Keith Hughes
Date: 3/27/2004 7:07 PM Eastern Standard Time
Message-id:

Derek Rowell wrote:
Would you all agree that in areas of dispute the truth may be revealed by
an
experiment?

Yes, if the experiment is setup properly, and the data is
*accurately* analyzed and interpreted.

Please try the following:
Take a fan, say a large house cooling fan (that's your propellor). Take a
flat surface, for example a stiff lightweight book (thats the rudder).
Turn the fan on and hold the rudder at an angle on the outflow side
(transmission in forward). Does the flow exert a torque (turning effect)
on
the rudder? Let go one corner and see. Is there a sideways thrust that
you have to oppose to keep the rudder in position?

Clearly. f=ma, i.e. force is the product of Mass times
acceleration. In this case the mass of accelerated air will apply
disproportionate force to the 'book' as a function of aspect
ratio. Basically, the book will "weathervane" until the force
applied to each side equalizes.

Repeat the experiment with the "rudder" on the inlet side of the fan
(transmission in reverse). Is there a turning effect (torque) or not?
Is
there a sideways thrust on the "rudder"?
You tell me - I just did it. The answers to all four questions is yes.

And...irrelevant! YES there is force on the 'vane', just as there
was on the downstream side. Less due to the the wider flow pattern
on the suction side, but still significant.

However, in the context of the boat model, this force is virtually
irrelevant. In the first case, water is forced over the rudder at
an angle to the boat centerline. It's a simple vector equation.
Water moves to starboard, reaction force is thus to port, the boat
turns starboard.

In REVERSE, the water flow, *irrespective of rudder position* is
along the centerline of the boat, thus the reaction force is
parallel to the keel line, and the boat moves straight back
(ignoring the precessional forces that result in 'prop walk' that
is). It's only when the boat moves through the water that the
rudder can have an effect - another simple vector equation. There
must be additional non-parallel force applied in order to produce
a turn, and that is caused by *additional* water flow past the
rudder caused by boat movement.

Aero/hydrodynamic lift/drag is determined by the flow patterns over
surfaces
(Bernoulli effects, etc), not by the simple minded pseudo-science that is
being thrown around here.

Lift and drag are irrelevant. Consider, what is the effect of lift
on the rudder? Heeling action, not turning action. You appear to
be confusing hdyrodynamics with simple force/vector equations.

It's a VERY complex situation.

Not at all. Oh the precessional effects are definitely complex,
all the more so when hydrodynamic effects are added in the
equation, but precession, while important to why your stern always
drifts one way in reverse (i.e. force applied to a spinning object
- the propeller - will be translated 90° in the direction of
rotation, creating a turning force), is not a factor in why the
rudder is ineffective in reverse.

We all agree
that in practice the effect is much, much weaker in reverse but it is still
present. (The reason that it is weaker is that only a small fraction of
the in-flow to the propellor actually passes over the rudder in reverse.)

Sorry, but that's just not accurate.

Keith Hughes

From: (Shen44)

[snip]