In the world of larger sailboats, a prop is as common as a main sail. While a prop is indispensable for moving the boat safely when sails would be too dangerous it quickly becomes a liability once the sails are raised. It not only creates drag but also makes the boat more difficult to sail. There are two solutions to eliminate, or at the very least, significantly reducing the negatives a prop brings to a sailboat. One is a
feathering prop and the other a
folding prop. The obvious question is which does a better job and retaining the benefits of a prop while reducing the negatives.
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The folding props are considerably less expensive than the feathering props. This is primarily due to the folding props being less complex and hence requiring less machining. The price difference can be as much a $1,000 to $1,500.
Folding props developed a bad reputation for not being very effective in reverse. This reputation was earned in large part to the early non-gear folding props that when in reverse failed to open completely. New folding gear-driven props, such as the Flex-O-Fold, have reverse performance equaling many fixed props however still not as much as a feathering prop. In this regard the feathering prop outperforms the folding prop. Even still, if you are please with the reverse performance of your fixed prop you wouldn't be disappointed with that of a gear-driven folding prop.
Man it's a drag to have a prop once under sail. This is the primary reason for a feathering or folding prop - to reduce drag. Comparatively the folding prop really shines in this regard. Both will significantly reduce drag over a fixed prop however the folding prop can reduce drag up to 3:1 over the feathering prop. It might be noted that at this level of reduced drag one could argue that this difference is not significant and I would tend to agree. Both perform well in reducing drag over fixed props.
It's not all about just drag and the resulting loss of speed, but what drag will do to your sailing experience. Since the prop is in front of the rudder this "prop drag" creates turbulent water which reduces the efficiency and consistency of rudder control. Owners of these props indicate they are able to sail closer to the wind and at greater speeds.
So it's not just about increased speed but how much increase in speed can you expect from a feathering or folding prop? It's a good question with no real way to answer it with any level of accuracy. Those who have swapped out their fixed props to one of these report anywhere from .25 to 1.25 knots of increased speed. Of course, the adage "your mileage will vary" applies here as there are many factors that are in play besides prop drag.
Lastly, installation and maintenance should always be a consideration. From the reading I've been able to do installation of a folding prop is much easier than that of a feathering prop. From a maintenance standpoint one could argue that the folding prop may require more attention since it's gears are exposed whereas the feathering prop gears are encased. I wasn't able to find any real-world experience that indicated that either would be a maintenance issue.
My conclusion is based on expense, drag reduction and ease of installation. From all that I've been able to research the gear-driven folding prop is the better choice. If money was not an issue and installation was going to hired out the feathering prop would be the better choice only if maximum drag reduction wasn't the primary goal. This would especially true if reverse pull power was very important.
With either prop you'll have to make the decision of which prop manufacturer is producing the best of the field. Then you'll have to decide 2 blade or 3 blade prop.
