State of the Art
Smaller rudders e.g. for leisure boats are occasionally made of fibre-reinforced plastic (FRP), while large rudders for container ships and tankers with a size of up to 100m² are nowadays exclusively made of steel, resulting in high weights of hinges, shafts and supports, and correspondingly high loads and energy demands. Increased freedom of design of a composite rudder flap can improve hydrodynamic performance, lifetime and reduce maintenance cost. High loads and a lack of experience in production processes currently inhibit the use of advanced materials.
Objective
This demo case addresses in combination the first load adapted as well as hydro dynamical optimized application on flap-rudders for merchant vessels. The combination and development of these techniques is straightforward in order to obtain recognition and an established role for fibre-composite materials in flap-rudder structures.
Solution
A high performance, multi-material rudder with a lightweight flap was developed, including its multi-material components, manufacturing, joints and joining technique. The solution will provide improved hydrodynamic design up to potentially adaptive flap shapes at equal production and reduced maintenance cost. The demonstration campaign comprises real-life operational validation on board and maintenance/repair tests.
The preferred manufacturing method one-shot infusion on the demo case was specified in high detail and requirements assembly and functionality were determined. The realized design provides an additional weight saving by further substitution of steel parts and solves some stress problems in high loaded interface areas due to the reduction of stiffness changes of different materials. Another significant change applied in difference to the initial design, is the number, distance, and thickness of horizontal stiffeners. A laboratory demonstrator in model scale of 1:6 was developed. The area load was applied by air cushions covering the total lateral surface of the flap, which is a good approximation of the hydrodynamic area load affecting the flap in the propeller slipstream. A sensing network will monitor the testing until break load and validate the fibre layout and FEA (finite element analysis) results.
Potential
The variety of rudders for different types of ships will increase, including those not produced in Europe. Market potential for EU equipment suppliers, many of them small and medium-sized enterprises, will grow.
Positive experiences will trigger applications of FRP e.g. for propulsion improvement devices and adaptive hull structures. Potential synergies to offshore, e.g. renewable energy devices are possible will emerge.