This effect is called canting. For a vessel with a right handed propeller, i. The reverse happens for a left handed propeller. At this stage the bow thruster comes to play. The bow in the first case is given to port so that its swing to starboard is restricted while in the second case it is given starboard.
One might ask why the bow and the stern swings while the ship comes astern? This is because of the transverse thrust and screw race effects which will be dealt with in another chapter. Now bow thrusters are driven by motors.
The power of the bow thruster generally depends upon the power of the motor. It can counter easily offshore winds of Beaufort 11 knots while berthing. Bow thrusters often get a bum rap, particularly from boating purists who view them as somehow cheating when it comes to learning proper seamanship. While that view may be extreme, in the old guard's defense there's nothing more frustrating or entertaining, depending on your vessel's location than watching a boat bump into docks and nearby vessels due to wild manipulations of the bow thruster and a lack of basic boathandling skills.
On the plus side, installation of a bow thruster can mean greater confidence at the helm, safer docking, and more time on the water. If you've been sitting on the fence, here's a look at the basics of bow thrusters to help you decide if installing one is right for you. A bow thruster is simply a propulsion device located at the bow that provides lateral port and starboard thrust, making the vessel more maneuverable.
Bow thrusters often come as standard equipment on newer pleasure boats over 45 feet, but almost any midsize vessel can be retrofitted. The benefits of having a bow thruster are many, particularly for boaters who must routinely deal with gusty winds, strong currents, or crowded docking spaces.
Maneuvering in tight areas is much easier, as a thruster allows the operator to turn the vessel to port or starboard without forward motion. This is particularly helpful with high-windage powerboats or sailing vessels with long, full keels.
Another benefit is the greater level of independence and confidence a thruster can offer, both to beginner and experienced boaters alike. Novice operators are more likely to actually get underway in more challenging conditions, while experienced captains can expand their options sailing solo, for example with greater safety.
In both cases, installing a bow thruster is like recruiting a trusted crewmember, one that's always ready to lend a hand when pushing or fending off from a dock. A wireless control unit adds more convenience, allowing you to move around the boat while controlling the thruster.
Imagine picking up that mooring ball with minimal effort and shouting or boarding without having to pull on a single dockline, bringing the boat to you with the push of a button. As a final plus, you're also likely to enjoy a financial benefit when it's time to sell. Having a bow thruster will make your boat more attractive than similar boats on the market. This is particularly true for new or less experienced boat owners, who may not be comfortable handling larger boats in less-than-ideal conditions.
And unlike other major upgrades such as engines or generators, most buyers don't care when a bow thruster was installed, as long as it works. While the benefits of having a bow thruster installed are numerous, so, too, are the concerns with installing them. The first is cost. In lockstep with the above is the complexity of your particular installation. What's the best location?
Will that water tank under the V-berth have to be shifted aft or relocated altogether? How powerful should it be? Will the extra weight in the bow affect performance?
Will the installation void my hull warranty? All of these are valid concerns you'll want to research and review when considering any installation. This is where the bow thrusters and these tips can come in handy. Questions about bow thrusters? Ask an instructor! If you'd like some bow thruster practice with an instructor aboard, consider a private lesson. The meeting room was quite adequate and the location most convenient, but the course outline and instruction were outstanding.
Modern Sailing is fortunate to have such a well organized instructor in Mr. Stan Lander who teaches very well from a rich professional background.
Lander was generous with his time and patiently in helping students who needed more attention or time in understanding various aspects of the curriculum. It has been wonderful sailing with MSC over the years. Please extend my thanks to the owners, management, and staff for unrequited professionalism and high standards in a charter fleet. I have sailed with several in my years and none nearly hold a candle to the quality of business and staff at Modern Sailing.
Skip to main content. They are:. Single propellers are the simplest, cost the least, and are well-suited to applications with shorter, smaller-diameter tunnels.
Twin tandem propellers move water more efficiently by using two propellers, making them a better choice when higher thrust is desired. Twin counter-rotating propellers provide the most efficiency in moving the most water in a given tunnel diameter.
As the costs to produce are higher, they are mostly used on yachts 50 feet and larger. Thruster propellers are a complex subject as they come with varying numbers of blades, are made of composite and alloy materials, and work within a variety of tunnels.
Those with minimal prop-tip clearance — the distance from the end of the prop to the surface of the tunnel — tend to make a thruster more efficient and powerful. Propellers with more prop-tip clearance are quieter but produce less thrust. In general, prop blades are fairly rigid; if the material is too flexible, there are losses. DC electricity is the most common power source for thrusters on recreational boats and is relatively easy to install for what is normally low-intensity usage when leaving and arriving at the dock.
Proportional controllers for DC thrusters developed by Side-Power provide the ability to apply power on a graduated basis, extending run times while reducing both noise and power draw.
Coupled with joystick products that link thrusters and primary propulsion and maneuvering systems, the popularity of DC power aboard recreational and commercial boats has steadily increased. Hydraulic power has the advantage of unlimited run time, making it a favorite in many commercial applications and on large yachts that use hydraulics for other purposes.
It can be relatively expensive to install, however, especially on a boat being refit if hoses need to be run to the bow.
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