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On 25 Mar 2004 01:32:19 -0800, (Bob Whitaker)
wrote:
I wasn't quite sure what you were driving at until I read your last
sentence and then it all became crystal clear. So the answer is "yes"
I would understand what you were saying and "yes" it would help me
understand the concept. But even though the term "thrust" is easy for
most people to understand, the concept of a "vector" (magnitude and
direction) may not be. But only you know who your target audience is,
and whether they would understand what a vector is.
===============================

From a teaching standpoint, I think it might be more clear, and to a
wider audience, if you referred to the concept as "directed thrust",
i.e., using the rudder to direct the prop thrust to port or starboard.
It means the same thing but to me it's more intuitive.

I think the most difficult concept to visualize is "prop walk". It's
not instantly clear what is generating the side force, or in which
direction. Prop walk is important to understand because it seems to
cause much of the consternation when backing a single screw. I like
to think of it as a jet of water created between the prop tips and the
hull, but I'm not sure if that's an accurate visualization or not. If
true, it would imply that deeply mounted props, away from the hull,
should generate less "walk" but I'm not sure if that is valid.

It seems to be a consensus among experienced twin screw captains that
leaving the rudders amidship is good practice for most maneuvers.
There are exceptions of course but having the rudders amidship leads
to more predictable response in my experience.

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