2 blade or 3 blade propeller

[ddilman]

I need help deciding between a 2 blade or 3 blade propeller
for a Catalina 36 with a wing keel. Planning to do little
or no racing and I''m non experienced in docking.
How practical is the 3 blade when docking? And is it worth
the extra drag when sailing?
Thank You
Danny

[RichardElliott]

Spend the money on a three blade Max Prop and forget the drag issue and smile broadly while you are backing up.

[mgiguere]

I don''t think you are evaluating the right issue. Cruising has been my primary activity and an extra 1/2 knot makes a big difference if your sailing for 4-5 hours. The main thing is matching your diesel engine to the size and pitch of the prop. When you run full throttle, you don''t want to engine to "over rev" at one extreme (too little bite out of the prop) and you don''t want to kick out black smoke (too much bite). You should be able to size a two blade prop that will fit into these extremes. That''s what I did and my 27 hp diesel pushes my Apache 37 at 6.9 knots at 2900 rpms full throttle with a two blade prop. With a decent breeze, the boat goes its hull speed of 7.5 knots.

Remember, an extra 1/2 knot in 8 hours of sailing gets you 4 miles further.

Good luck,

Moe Giguere

[capttb]

Your main concern seems to be docking, I really think we tend to adapt to either prop when doing slow speed moves around the dock. A little practice will allow you to learn the boats'' characteristics. The first concern is usually propwalk, you either use it to advantage or compensate for it. RH props pull the stern right in forward and left in reverse. If you want to minimize walk you give short burst to get boat moving then go to neutral, to use walk let the prop run longer at idle. Most cruisers seem to prefer 3 blades, I think the stuff growing on your boat when it''s due for cleaning probably causes more drag then a third blade. I really can''t advise you in making a choice, people have personal preferences but I think you will learn to work with either. One mentor once told me "Never approach a dock any faster than you are willing to hit it, you shouldn''t have to depend on reverse preventing catastrophe".