Customised functions for maximum efficiency and safety.

Improved rudder efficiency and minimised risk of cavitation

Strong rotational flows from the propeller create areas of low pressure on the rudder blade. For symmetric rudders this can result in erosion and energy loss. A twisted rudder equalises the pressure distribution on the rudder and reduces cavitation, which leads to an increase in rudder efficiency.

The twisted leading edge on rudders is a core element of modern maritime technology that was introduced by Becker Marine Systems and has now been tried-and-tested for over 20 years. The idea behind it is to align the rudder profile to the asymmetrical flow generated by the rotation of the propeller. 

With a twisted leading edge rudder, the upper half of the rudder blade is orientated in one direction, the lower half in the opposite sense. This special design results in two key benefits. Firstly, by aligning the rudder profile to the propeller wake a significant reduction in rudder drag is achieved, which brings improved overall powering performance. Secondly, the equalised pressure distribution decreases the likelihood of cavitation on the rudder blade, reducing vibration, erosion damage and cavitation losses.

The key to large full spade rudders

Becker Marine Systems has developed the King Support technology to allow manufacture of full-spade rudders with an area of up to 130 square metres and maintaining a slender rudder profile. This design extends the rudder trunk and stock into the rudder blade so that the main neck bearing is positioned as close as possible to the centre of force of the rudder. Due to the reduced lever arm, this significantly reduces the stresses and bending moments in the rudder stock and trunk. As a result, the reaction forces on the neck and support bearings are significantly lower, resulting in an exceptionally stable rudder structure.

The King Support technology represents the state-of-the-art in rudder manufacture without size limitations, and its single main bearing requires less maintenance compared to similar semi-spade rudders. Unlike conventional designs, a Becker rudder with King Support does not require additional castings, such as a rudder horn, which could cause cavitation problems and complicate installation within the hull structure.

In addition, a rudder with King Support offers an extended active steering surface, which significantly improves manoeuvrability in lower speeds. The reduced bending moments created by the King Support allow for a more streamlined rudder profile, increasing the overall efficiency of the vessel.

Illustation Systematic of King Support Technology

1. The conventional semi-spade rudder blade and the rudder horn are replaced.
2. An optimised, streamlined headbox is placed on top of the full spade rudder blade.
3. The rudder trunk extends from the steering gear deck through the headbox down into the full spade rudder.
4. View of the inside of the rudder trunk: Only one support bearing (neck bearing) is required inside the rudder blade.
5. The full spade rudder blade and the rudder stock are connected by a hydraulic conical connection.

Effective rudder control for offshore vessels and workboats

Standard heel pintle arrangements are compatible with all Becker Marine Systems rudder solutions. This configuration allows the rudder to be optimally aligned with the heel arm installed by the shipyard. In particular, smaller vessels such as fishing boats, offshore vessels, workboats and tugs benefit from this design as it provides additional stability and reduces the risk of interaction between the rudder and ropes or nets.

Maximum safety and durability, even in icy conditions, make the rudder a reliable choice. Becker rudders with heel pintle are particularly suitable for small and slow-moving vessels. Fishing vessels, tugs and research vessels are ideal areas of application.

Advantages of the Becker Rudder with heel pintle:

• Minimum steering gear size
• Highest safety against cyclic stresses
• Durable in ice
• Reduced bending moment at rudder stock connection
• Slender rudder blade

More efficiency through targeted flow control

The rudder bulb from Becker Marine Systems is an advanced solution for increasing the propulsive efficiency of vessels. Correctly designed, a rudder bulb will eliminate the strong hub vortex which is shed from the propeller. This vortex leads to significant energy losses and increases the likelihood of impact cavitation damage on the leading edge of the rudder blade. By guiding the flow more smoothly along the propeller hub to the rudder, the rudder bulb enables a more efficient flow, which leads to a significant reduction in losses. 

The design of the geometry of the rudder bulb in combination with a twisted leading edge of the rudder ensures optimum energy recovery from the propeller slipstream. The transition between the bulb and propeller hub is bridged by an optimised propeller cap design that further increases hydrodynamic efficiency and minimises energy losses downstream of the propeller hub by eliminating flow separation and reducing fluid turbulence.

Computational Fluid Dynamics (CFD) calculations and tank tests have confirmed direct power savings of up to 1.5% when using a rudder bulb, depending on the type of vessel and propeller. This energy-saving device is particularly suitable for vessels with large propeller hub sizes and high thrust loads, such as, container ships, Ro-Ro vessels and cruise ships, but can also be adopted to oil and chemical tankers as well as bulk carriers. A rudder bulb can be installed in both new-buildings and existing ships (retrofitting).

Advantages of the rudder bulb

• Energy savings of up to 1.5% 
• No hub cavitation due to reduced hub vortex strength
• Customised design according to the propeller 
• Applicable for both CPP and FPP propellers

Closed connecting linkage for demanding environments

The closed linkage flap rudder is an option for the use of rudders in demanding environmental conditions. Its ingenious design incorporates the advantages of a flap mechanism protected in a hydrodynamically moulded upper part of the rudder blade with a smooth and progressive flap angle ratio. This protects the linkage from ice and sand and still allows optimum manoeuvrability. 

For additional safety, the rudder flap is equipped with overload protection, which prevents damage to the mechanism and deactivation of the rudder due to a blocked flap or an obstacle. The integrated slip clutch protects the flap from external damage. If the rudder flap is hit, the clutch slips and yields to the overload. The flap centres itself when the rudder is steered hard to port and starboard.

The closed linkage is designed for durability and protection against excessive forces. In addition, the closed linkage system reduces hydrodynamic radiated noise, ideal for vessels with sensitive acoustic requirements.