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Full speed astern!
The manoeuvring efficiency of rudders is usually based on the deflection of the propeller wash. However, when moving astern, no propeller wash hits the rudder blades. With the rudders at full deflection, a ship moving astern will respond hardly at all. In some situations a set of rudders in front of the propeller will provide a solution. They are known as flanking rudders.
Specially suited to pushers!
Normally speaking, manoeuvrability when moving astern is not much of a problem. River barges tend to have bow thrusters to provide additional manoeuvrability. The same applies to seagoing coasters. Ocean-going vessels manoeuvre in port with the use of tugs. However, things are different for pusher combinations. Large convoys with many pushed barges that have no power of their own are a plaything of the wind, and pusher combinations find it difficult to move straight astern or negotiate short bends in reverse. This can present a danger to other shipping. In situations like these De Waal likes to recommend its flanking rudders.
Independent control
Flanking rudders are controlled by an independent steering system, allowing the helmsman to operate two sets of rudders independently. This makes it easy to keep convoys on course. When running ahead, normally the rudders are fixed in the neutral centre position.
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Rudder dynamics
The shape and cross-section of the flanking rudders resemble those of the balance rudders. However, their dimensions and proportions make them a bit different. Ahead: no drag. Astern: optimised deflection of the propeller wash. The number of rudders required and their location and size are all accurately determined for each individual ship by the engineers of De Waal.
Features
- Specially designed for large pusher combinations
- Designed and built to measure
- Ample experience with flanking systems
- No drag when moving ahead
- Optimised water deflection when moving astern
- Excellent conservation process
- Heavy-duty bearings
- Features unique shrink ring
- Available for any classification