On Mon, 6 Jun 2005 22:17:44 +0200, "Flemming Torp"
fletopkanelbolle2rp.danmark wrote:


My intuition tells me, however, that if you 'let the
propeller go', the total resistance/drag will be less and if
you start braking the turning propeller, the resistance/drag
gets bigger...

Fluid dynamics is tough on the intuition.

But if you cannot decide between two different opinions,
you *could* do what fluid dynamicists do when uncertain:
run a test.

One way:

find a spinning lure and tow it on a swivel so it can turn, behind a
boat at moderate speed (you could even do this in the bath, maybe?)
and check the drag with an ounce spring scale.

Then fix the spinner, and rerun the test.
Is the drag greater or less?

You will be surprized I expect.

[Usual disclaimer: fluid dynamics people and naval engineers know
there are scale effects as between boat sized props and little fish
size spinners.

Still, in comparing results at constant speed and constant spinner
size, you *can* get useful results.... ]

Brian Whatcott Altus, OK.