Performance Propellers

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(published April 2017)

What does an extra knot of boat speed mean under sail? On a day run of 30 miles, it will cut almost an hour off the time under way. On a coastal passage of 250 miles you will save seven hours. And, on a 1,500 mile passage from the East Coast to the Caribbean you will save yourself a full day at sea.

There is another way of thinking about enhancing your boat’s sailing performance, too, safety. If you are trying to outrun an approaching cold front and make harbor before the wind and rain hit you, an extra knot might make the critical difference. Plus, if you like sailing, knowing that you are getting the best from your boat is always a good feeling.

That’s what feathering and folding props will do for you. Feathering propellers operate exactly as the name implies; when the engine is shut down or put into neutral, the propeller blades feather in the passing stream of water like a sail positioned head-to-wind and thus present the smallest profile. This reduces drag and enhances sailing performance.

A folding prop, doesn’t feather when it is put into neutral; instead, the force of the water flowing by the blades folds them together behind the prop’s hub to reduce drag. Here’s a sample of the most popular folding and feather props on the market.

FEATHERING
The granddad of feathering props is the two and three bladed MaxProps, made in Italy and distributed in North America by PYI. Since the introduction of the first two blade Max Prop Classic in the early 1970s, more than 40,000 Max Props have been sold. In addition to the Classic, they offer the newer Easy, in three and four-blade models, and the new Whisper, which has five blades and is the smoothest, quietest feathering prop out there. The blade pitch of Max Props is adjustable; you have to haul the boat to adjust the Classic, but the Easy and Whisper can be adjusted by a diver with the boat still in the water.

The Variprop and VariProfile feathering props are made in Germany and distributed in North America by AB Marine. These elegant, finely tuned machine props have infinite, minute blade pitch adjustments that are separate for forward and reverse so you can accurately match the pitch to the engine’s gear box. The Variprop has the shortest hub length of all feathering props so it works well with boats that have small keel-rudder apertures. The Variprofile has new, high performance blades that enhance performance under power.

The British made Autoprop is unique among feathering props because its three L-shaped blades automatically adjust their pitch to meet the demands of the engine and gearbox. When full throttle is applied, the blades deploy fully and then as you reach cruising speed and less torque is required, the blades fold partially. When sailing, the blades feather to reduce drag. Autoprops are also distributed in North America by King Marine.

J-Props from Italy are distributed in America by Beta Marine. These technically sophisticated props have highly efficient blades that offer excellent performance in both forward and reverse due to the 180 degree rotation when the direction changes. J-Props have a simple and easy to use way to adjust the blade pitch that can be done quickly and while the boat is in the water. This allows an owner to experiment with blade pitches until the right one for the boat, engine and transmission is found.

FOLDING
The leader in the folding prop world is Gori from Denmark which is distributed in the U.S. by AB Marine. These beautifully designed and machined props have unique hydrodynamic blades and a massive gearing system that gives them extra power in forward and reverse. Plus, the three and four-blade models have a unique overdrive function for higher torque and performance at lower engine rpms. The two blade Gori racing props are used by all of the Volvo Ocean Race boats, 90 percent of the Vendee Globe boats and many other offshore competitors. Last year, Gori introduced a new cruising prop that does not have the overdrive function.

Varifold, also from Denmark, is similar in many ways to the Gori designs and has shown to be a competitor in powering performance in both forward and reverse. The three-blade prop’s hub is one of the largest and the way the blades fold together combine to raise the drag when under sail. The two blade racing prop has efficient blades that fold cleanly for minimum drag when sailing.

Seahawk in Australia, produces finely engineered stainless steel folding props under the Slipstream brand. These are distributed in the U.S. by Martec Marine. The stainless props are robustly built and will stand up to many years of hard use. The large blades offer excellent motoring performance and when folded, a low profile for minimum drag.

Author: Blue Water Sailing

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