There is no easy way to prove this one way or the other by hand waving
for one reason: it depends on the propeller. Large ship propellers
are sometimes more efficient freewheeling, but this is not the case
for 3-blade yacht props. I suspect the the difference has to do with
the pitch, and whether or not the flow is stalled - Ship props often
high a large pitch compared to yacht props.

BTW, it worth while lining up one blade of a 3-blade with the hull
when you lock it.



Flemming Torp wrote:
My brother in law, and I have had a discussion of whether it
is best - from a pure speed point of view (no consideration
to the mechanics/oil/maintenance/gearbox etc. here ...)
whether you should let your "fixed three bladed propeller"
run/turn or keep it fixed (like put into gear) when sailing
just for the wind with your sails in a 34 feet cruiser
weighing roughly 5 T ... We have - unsuccesfully - tried to
find out using the log ... the results were not conclusive -
or one of us would not admit, that the other was right ... I
think we need a testimony from someone, that has a
'scientific based valid answer' ... or just knows for sure
...

The assumption is: There is no way to move, turn, 'collapse'
anything on the propeller - the 'blades' are fixed ... (hard
to explain in a language, that is not your own ... hope you
get my point).

Anybody in this group that can convince one of us, that he
is not right? ...