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

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


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

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]

Derek Rowell wrote in message
news:E4o9c.108024$1p.1536914@attbi_s54...

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.

Yes, in reverse there is a torque on the rudder. But (if I read
your hinges correctly) it may be caused by a solely fore and aft
force on the rudder. Either would certainly explain the rudder
kick I have experienced.

What we're actually looking for is a net force at right angles to
the centreline of the boat, so the proper hinge for this
experiment would be parallel to the boat centreline, above the
flow. We'd then look to see if the paper was still deflected.

Just nipping off to play with some bits of wire and card . . .

JimB

On 26 Mar 2004 21:44:34 GMT, (JAXAshby) wrote:

Intuitively, most people sense that water "pulled" over a rudder will cause a
rudder to change direction of a boat in much the same way as water "pushed"
over a rudder does. However, intuition misses some things along the way.
[...]
end) to port. However, the water drawn over the rudder's port side hits that
side and is deflected towards port. Then the rudder would push the boat
(after end) to starboard. And equal and opposite reaction. Net, net, the boat
does not turn. The pressure on each side of the rudder is equal. Nada.


Jox, since you're such an "expert" on Feynman inverse sprinkler problem
and how to misapply it to any situation, maybe you can answer a question
about it. While it's true that the sprinkler won't turn when water is
being sucked in, it's not true that no net force is generated by sucking
the water in. In fact, there is a net force generated. It's just not
in a direction that will turn the sprinkler.

In relation to your discussion about about equal and opposite, net net,
no net force, etc., how do you reconcile that with the fact that it's
not true for the inverse sprinkler problem?

Steve

wtf are you talking about? it's awfully early in the day to be so incoherant
from alcohol.

Intuitively, most people sense that water "pulled" over a rudder will cause
a
rudder to change direction of a boat in much the same way as water "pushed"
over a rudder does. However, intuition misses some things along the way.
[...]
end) to port. However, the water drawn over the rudder's port side hits
that
side and is deflected towards port. Then the rudder would push the boat
(after end) to starboard. And equal and opposite reaction. Net, net, the
boat
does not turn. The pressure on each side of the rudder is equal. Nada.


Jox, since you're such an "expert" on Feynman inverse sprinkler problem
and how to misapply it to any situation, maybe you can answer a question
about it. While it's true that the sprinkler won't turn when water is
being sucked in, it's not true that no net force is generated by sucking
the water in. In fact, there is a net force generated. It's just not
in a direction that will turn the sprinkler.

In relation to your discussion about about equal and opposite, net net,
no net force, etc., how do you reconcile that with the fact that it's
not true for the inverse sprinkler problem?

Steve

On 29 Mar 2004 17:33:21 GMT, (JAXAshby) wrote:

wtf are you talking about? it's awfully early in the day to be so incoherant
from alcohol.

Bzzzt!!! Wrong answer jox. Try again. It's clear you don't understand
the sprinkler problem. While you're cogitating on why you're wrong in
applying feynman's sprinkler problem to this arena, here's another,
simpler question for you:

Say you have a wind tunnel with a rudder mounted at the test point.
First case is a blower at one end forcing air though the tunnel and past
the rudder at 1mph. You turn the rudder at a 45 degree angle to the
airflow. Is there a lateral force generated by the rudder?

Second case is a blower at the other end of the tunnel but now it's
sucking air through the tunnel past the rudder at 1mph. You turn the
rudder at a 45 degree angle to the airflow. Is there a lateral force
generated by the rudder?


Intuitively, most people sense that water "pulled" over a rudder will cause
a
rudder to change direction of a boat in much the same way as water "pushed"
over a rudder does. However, intuition misses some things along the way.
[...]
end) to port. However, the water drawn over the rudder's port side hits
that
side and is deflected towards port. Then the rudder would push the boat
(after end) to starboard. And equal and opposite reaction. Net, net, the
boat
does not turn. The pressure on each side of the rudder is equal. Nada.


Jox, since you're such an "expert" on Feynman inverse sprinkler problem
and how to misapply it to any situation, maybe you can answer a question
about it. While it's true that the sprinkler won't turn when water is
being sucked in, it's not true that no net force is generated by sucking
the water in. In fact, there is a net force generated. It's just not
in a direction that will turn the sprinkler.

In relation to your discussion about about equal and opposite, net net,
no net force, etc., how do you reconcile that with the fact that it's
not true for the inverse sprinkler problem?

Steve

schlackoff, you are using a constrained airflow? know what that means? know
how it is different from unconstrained.

get some sleep, schlackoff, and you will feel better by tomorrow afternoonn.

wtf are you talking about? it's awfully early in the day to be so
incoherant
from alcohol.

Bzzzt!!! Wrong answer jox. Try again. It's clear you don't understand
the sprinkler problem. While you're cogitating on why you're wrong in
applying feynman's sprinkler problem to this arena, here's another,
simpler question for you:

Say you have a wind tunnel with a rudder mounted at the test point.
First case is a blower at one end forcing air though the tunnel and past
the rudder at 1mph. You turn the rudder at a 45 degree angle to the
airflow. Is there a lateral force generated by the rudder?

Second case is a blower at the other end of the tunnel but now it's
sucking air through the tunnel past the rudder at 1mph. You turn the
rudder at a 45 degree angle to the airflow. Is there a lateral force
generated by the rudder?


Intuitively, most people sense that water "pulled" over a rudder will
cause
a
rudder to change direction of a boat in much the same way as water
"pushed"
over a rudder does. However, intuition misses some things along the way.
[...]
end) to port. However, the water drawn over the rudder's port side hits
that
side and is deflected towards port. Then the rudder would push the boat
(after end) to starboard. And equal and opposite reaction. Net, net, the
boat
does not turn. The pressure on each side of the rudder is equal. Nada.


Jox, since you're such an "expert" on Feynman inverse sprinkler problem
and how to misapply it to any situation, maybe you can answer a question
about it. While it's true that the sprinkler won't turn when water is
being sucked in, it's not true that no net force is generated by sucking
the water in. In fact, there is a net force generated. It's just not
in a direction that will turn the sprinkler.

In relation to your discussion about about equal and opposite, net net,
no net force, etc., how do you reconcile that with the fact that it's
not true for the inverse sprinkler problem?

Steve

On 29 Mar 2004 23:27:42 GMT, (JAXAshby) wrote:

schlackoff, you are using a constrained airflow? know what that means? know
how it is different from unconstrained.

Interesting that you think it makes a difference. Ok, try it again but
this time with a theoretical infinitely sized wind tunnel, or a physical
one large enough that the difference between constrained flow and
unconstrained flow is negligable, like a 1 mile diameter wind tunnel and
a 1" rudder. In one case the air in an infinite wind tunnel is being
pushed at 1mph past the rudder and in the other case it's being drawn
past the rudder at 1mph. In both cases, air is flowing past the rudder
at 1mph and the rudder is at a 45 degree angle. Does the rudder
generate a lateral force in both cases?

Steve

wtf are you talking about?

Bzzzt!!! Wrong answer jox. Try again. It's clear you don't understand
the sprinkler problem. While you're cogitating on why you're wrong in
applying feynman's sprinkler problem to this arena, here's another,
simpler question for you:

Say you have a wind tunnel with a rudder mounted at the test point.
First case is a blower at one end forcing air though the tunnel and past
the rudder at 1mph. You turn the rudder at a 45 degree angle to the
airflow. Is there a lateral force generated by the rudder?

Second case is a blower at the other end of the tunnel but now it's
sucking air through the tunnel past the rudder at 1mph. You turn the
rudder at a 45 degree angle to the airflow. Is there a lateral force
generated by the rudder?


Intuitively, most people sense that water "pulled" over a rudder will
cause
a
rudder to change direction of a boat in much the same way as water
"pushed"
over a rudder does. However, intuition misses some things along the way.
[...]
end) to port. However, the water drawn over the rudder's port side hits
that
side and is deflected towards port. Then the rudder would push the boat
(after end) to starboard. And equal and opposite reaction. Net, net, the
boat
does not turn. The pressure on each side of the rudder is equal. Nada.


Jox, since you're such an "expert" on Feynman inverse sprinkler problem
and how to misapply it to any situation, maybe you can answer a question
about it. While it's true that the sprinkler won't turn when water is
being sucked in, it's not true that no net force is generated by sucking
the water in. In fact, there is a net force generated. It's just not
in a direction that will turn the sprinkler.

In relation to your discussion about about equal and opposite, net net,
no net force, etc., how do you reconcile that with the fact that it's
not true for the inverse sprinkler problem?

Steve