Choosing a Sailboat Propeller for your boat you would consider factors like;
- Drag under sail
- Speed & Power in forward
- Stopping power in reverse
For the racer you are primarily looking for a low drag propeller, for the cruiser however a small increase in drag is well worth the better handling under power.
- Propeller hand. A right handed propeller is one that turns clockwise in forward.
- Propeller Pitch is defined as how far the propeller advances with one full revolution of the shaft. Think of a screw and how far it goes in with one full turn.
- Number of blades. Two blade props are far less powerful than 3 blades. A two blade prop has only one blade working in clean water while the other blade is in disturbed water from the keel. With a three bladed prop you have two blades working all the time.
- Propeller Balance; 3 or more blades have better balance than two blades, more metal evenly spread around, which reduces vibration.
- Propeller clearance; the distance between the blade tip and the hull.
- Propeller Diameter; The diameter of the prop plays a big role in how much power it produces, but hull shape restricts available space.
- Blade area; More blades increase the blade area.
Types of Sailboat propellers
Fixed blade propellers
- Pros; Cheap, Good power in forward, Reliability
- Cons; Low power in reverse, High Drag, Weed catcher
If you are looking for a propeller for a sail boat and are particularly interested in sailing performance, a folding propeller may be best. Many performance sail boats specify a folding prop as it will produce the least drag under sail, better than a fixed prop by far as mentioned above and slightly better than a feathering prop.
- Pros; Low Drag, Low profile shape does not catch weed
- Cons; Cannot change pitch (except Gori does have overdrive which is a different pitch), Low power in reverse
Folding propeller models include;
- Pros; Low Drag, Good power in forward and reverse, Minimal vibration, Adjustable pitch
- Cons; Blades catch weed etc, Maintenance & installation, Expensive
Feathering propeller models include
- Max Prop
- Kiwi Prop
Another feature of the Max Prop is the ability to adjust the pitch. Part of the assembly requires you set the pitch. The correct pitch is set to load the engine at max RPM. Most engine mechanics can tailor the correct pitch for you.
Conclusion & References
If you were unsure of the differences between all the various sailboat props, hopefully we have helped clear the air. There is no single prop that performs the best in all conditions so you need to make some choices when picking the best prop for your boat.
All of the feather/folding propeller options will reduce drag and increase performance between 1/2 and 1 knot over a similar sized and number of blades fixed prop. So for performance sailing and a prop with the least drag a Folding prop like the Flexofold is a good choice. For a low drag prop with good handling under power a feathering prop works well. For just the benefits under power some argue the Autoprop is best.
References These articles show test data of all the prop types in a variety of conditions
As for the choice between 2 and 3 blades in either of the folding/feathering types. The difference in drag is something a cruiser will not notice. A racer will but it is just a few %. However the advantages of a 3 blade prop in maneuverability, stopping and the reverse power make the 3 blade the best choice. Three blades however does offer a greater chance of fouling with weed or a pot etc.
Sailboat Propeller Cost comparison
2 blade fixed prop costs around
- $400 2 blade flexofold costs
- $1,115 2 blade Max prop costs
- $1,630 for 16 inch blades.
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