SURFACE-PIERCING PROPELLER TECHNOLOGY
Stormfågeln is based on a patented hull design with two surface-piercing propellers and three points of contact.
Surface-piercing propellers are known and proven technology. This has been successfully used for a relatively long period in boat-racing applications, and more recently, in paramilitary applications, to a certain extent. The area of application has been relatively narrow – lightweight, high-speed boats – and this illustrates both the advantages and the limitations of the technology:
A surface-piercing propeller makes it possible to use a propeller of greater diameter, gives significantly lower water resistance, and minimises cavitation around the propeller blades. These factors allow the boat to achieve higher speeds than those that can be achieved with conventional propeller technology.
- At the same time, it is difficult to achieve planing in boats with surface-piercing propeller technology, and this limits its use to relatively light boats. The surface-piercing propeller, further, has a tendency to lift the stern, and this causes problems with maintaining stable planing, particularly at low speeds. Boats with this technology are also difficult to manoeuvre when reversing.
These disadvantages have constituted a barrier to commercialisation in a wider market segment.
Stormfågeln's solutions of surface-piercing propeller technology – which includes the complete propulsion system and the hull design – allows boats to achieve planing essentially immediately, and this means that the solution can be used with significantly heavier boats. At the same time, the tendency to lift the stern is counteracted, and this gives a more stable planing condition, at all speeds above the planing threshold speed. The reverse-enabled propeller blades eliminate manoeuvre problems previously experienced during reversing. The design of the propulsion means that the motor operates at a low rate of revolution, even at high speeds, and this explains the low fuel consumption of Stormfågeln at these speeds.
