Prop choices
Hi Nigal, No one prop is going to satisfy your every need. For sailboats, a folding or feathering prop is in my opinion the only way to go. Fixed propellers just add too much drag, but if motoring is the main focus, it would be suitable. There are many choices of brands once you get into varietal propellers, it all depends on what your looking to improve on the boat. In folding propellers, there are basically two well known choices; Martec and Gori. Both fold under sail, so are going to provide the absolute best in minimal drag. The two bladed non-geared martec is in my opinion too poorly made to withstand the harshest environment on earth(marine), in addition the fact that there are no gears makes deployment not always a given. They also now have a 3 blade folder, called Autostream i think. Good prop from what I hear, but check the durability factor again. Gori two bladers are the industry standard over in Europe, they are geared, and will provide excellent ahead motoring due to their shape(curved blades). They also now have a 3 blade folder, which also passes all the way through itself to be the same shape in forwars as reverse.This means incredible reverse performance, and also around 11% better effeciency in ahead than flat bladed props. Many high profile boats now sport these, and production yachts like hinckley, Swann, and Halberg Rassey put them on as standard. The price is also incredible, as they are 20-30% less than competitors. Feathering props have two basic leaders as well. Maxprop, has been the industry standard for over 25 years here in the states, and they are very durable and well made. They have flat blades, which will provide excellent reverse power, and great under sail. There are two major drawbacks, however. One is that the pitch needs to be adjusted on the unit once it is installed. Just because they give settings for many yachts, does not mean that you won't have to tweak for your preferences. They have a VP model, which allows external adjustments, but it is pretty pricey. The other problem is that Max props are very ineffecient in ahead motoring. The blades have no curve or camber to them, they are planar or flat. This creates poor loading along the blades, which means you will need to give high rpms to the engine to get cruising speeds. This will mean increased fuel consumption, and poor low end power from the prop. Maybe not the choice for underpowered boats, but if you have enough horsepower, probably not a problem for you. The Autoprop is a self pitching unit that continually optimizes its pitch. This will provide the best motoring of any prop in forward or reverse, but the drag is a little greater than Maxprop. These units also don't fit on every boat, as they have some sort of fore and aft clearances required. Also, I don't really know how durable they or how user friendly they are in terms of maintenance; they haven't been around that long. This prop would be a better choice for those who factor motoring at the top of their wish list. Without getting too long winded, in regards to two versus three blade, cost is the first factor, then size of boat and engine, or fit constraints. Your best bet is to size your boats propeller area first, determining the maximum size diameter. Usually the largest diameter chosen for your engine and transmission is the way to go, and play with pitch after. This will help get the right size, then brand is up to you and your needs.(not to mention budget.) Hope this helps! Fair Winds.....
