In article , "Flemming
Torp" fletopkanelbolle2rp.danmark says...
I agree, that the practical difference might be dismissal
... but in a race every second counts per NM ... and it is
not easy to get a fixed propeller out of the water ;-) - and
I'm pretty curious of knowing the correct answer to my
question - preferably backed by solid science as I'm not a
scientist ...

When cruising, I would always lock the propeller - or follow
Larry's advice - use the energy generated ... that is
something I will consider ti implement in the future ...

--
Flemming Torp





Well, if you are racing and can't get the prop out of the water I can
see where it may be of concern but if you're looking for a solid science
answer I'd have to venture to say that there are so many variables
involved only a practical application with the boat involved would work.

Drag is drag and if you can set a straight course with a constant speed,
difficult under sail even in ideal conditions but still do able, just
locking and unlocking the prop and seeing what it does to your speed
should provide the answer.

However, I'd have to opine that there is a difference between a free
wheeling prop and one that is not only spinning but driving an
generator/alternator. There is no free ride. A prop working a generator
requires more energy then a free wheeling one and the only place that
energy can come from is the forward speed of the boat.

Again, the difference may be negligible but if you are concerned with
thousands of a second, as you would be if racing, you have now
introduced one more variable that has to be considered.

I'm afraid you can't really get a "just speed" answer and expect an
answer backed by science without considering conservation of energy,
every action has an......... and so on.

I can't prove it but my money would be on a truly free spinning prop. A
fixed prop wants to spin and is going to use energy trying to do so.
It's going to fight forward motion harder then a free spinning prop. A
prop with a generator on it will spin but not without the loss of energy
required to also turn the generator, a free spinning prop requires only
the energy required to spin it. It'll, pardon the pun, go with the flow.
Some energy penalty but less then the first two scenario's

Again, the only place the energy required can come from is the forward
motion of the boat.

--
Mike G.
Heirloom Woods

www.heirloom-woods.net