JAXAshby wrote in message
...

jim, please don't make the mistake of saying that wings lift
"because they are
round on one side". you can go to any airshow on the planet
and see aircraft
fly upside down, the round side of the wing towards the ground

Of course I won't make that mistake. What made you think I would?
I repeat the relevant part of my post:

"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."

I said this in response to your statement that pressure change
does not have to be related to a speed change in the
circumstances we're talking about. This seemed to me to violate
the laws of conservation of energy. It was you who called
Bernoulli into it, bless his cotton socks. I quote from your
post:

"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"."

You were here responding to my assumption that if there's a
(mean) pressure differential over the rudder, than there will be
an allied mean change in fluid speed. Just like an airplane wing
creating lift. The fluid speed on the low pressure side will be
faster (caveats for supersonic flow etc - we are talking boats).
I hope you don't disagree with that.

JimB