JAXAshby wrote in message
...
If you could demonstrate, prove or explain why water speed
should
be identical along each side of the rudder

water speed does not have to be equal or greater or less. This
can be a bit
confusing because "bernoulli" is often -- though erroneously --
given as the
reason sails/wings have "lift".

Sails/wings create lift (a force) by altering the momentum of the
air passing by.

The mechanism creating this lift is a (mean) fluid pressure
difference between one side, and the other, of the sail/wing.

Any pressure change in a freely flowing fluid will be matched to
a change in local fluid speed (barring supersonics, flow
breakaway, and the trivial effects of surface viscosity) to
conserve energy. This is (presumably) the 'bernouili' bit you
claim is often erroneous.

Interesting.

Do you disagree with the concept of conservation of energy? or do
you claim special conditions which make his equations irrelevant?

It might be a bit easier to remember that for the rudder to be
pushed one way,
it (the rudder) must push water the opposite way. If the water
is not
deflected then there is no force on the rudder.

Agree; for the rudder to create yaw, it must deflect water. It
must change the momentum of the water. Many ways of saying the
same thing. That's where I'm stuck. I see the rudder (prop in
reverse, boat static) altering the direction of the water
approaching the prop.

Now, perhaps it doesn't. Or perhaps there's an opposite effect
somewhere else which I haven't yet identified. I'm looking for
education here, not stating a flat opinion.

JimB