Join Date: Oct 2004
Thanked 0 Times in 0 Posts
Rep Power: 11
Should transmission be in gear when sailing?
While the reasons for putting the transmission in gear are correct, in my humble opinion, but reinforced by a lifetime as a mechanic and the past 20 years as a marine mechanic, there is another good reason that I read some 20 or so years ago in Practical Sailor, which I tested myself.
The report had to do with conflicting theories of drag from the propellor, and this is what they found:
A free-spinning prop quickly enters it''s intended range of efficiency where it gets a full mechanical grip on the water. If the props RPM''s 200 or 300 or even 400, imagine how hard you would be working to do that by hand. That''s horsepower and it translates into considerable drag. They had numbers. I forget them.
A locked prop produces some drag at slower speeds that is a tiny bit higher than a slowly spinning prop, but once you start making more than 3 knots, the spinning prop makes more drag. At speeds approaching five knots, locked props begin to cavitate, significantly reducing drag. Yes, there''s still drag - you don''t get cavitation without pumping horsepower into it, but it''s far less than a fully spinning prop that has a secure grip on the water your trying to slip through.
Just my 2 cents.
Fair winds and fine seas, all.