STP Twin Propeller
Rudderpropeller with two propellers
The SCHOTTEL Rudderpropeller (SRP) has been setting standards in the field of steerable propulsion systems for decades. Proven in service worldwide, this system converts the engine power into optimum thrust power and also offers the possibility of rotating the underwater part through 360°, thus allowing the full input power to be used for manoeuvring the ship.
More power – For medium speeds
This equally simple and effective principle forms the basis for the SCHOTTEL Twin Propeller (STP). In contrast with the SRP, the SCHOTTEL Twin Propeller is equipped with two propellers rotating in the same direction. The optimum matching of the system components “propellers” and “strut with integrated fins” results in a considerable increase in efficiency as compared with systems incorporating just one propeller. The SCHOTTEL Twin Propeller is thus the successful optimization of the complete Rudderpropeller system and ideally suited as a propulsion system for all ships in the medium speed range with design-related higher propeller loads. This is because the Twin Propeller technology reduces the load acting on each individual propeller by distributing the power over two propellers, thereby increasing the efficiency.
Operating principle of the STP
The STP is equipped with a pull propeller and a push propeller. Their relative arrangement is such that the vortex of the front pull propeller passes between the blades of the rear push propeller without impeding it. Contraction of the slip stream in the pull propeller means that more water reaches the push propeller from the sides, which further enhances the performance. Moreover the strut is hydrodynamically optimized and provided with a fin arrangement. The swirl energy generated in the propeller stream is thus recovered, leading to an increase in efficiency. Additionally, the flow around the fins creates a lift component in the thrust direction, which likewise has a thrust-enhancing effect. The noise and vibration level is significantly reduced, too.
The hydrodynamic principle
- Distribution of the power to 2 propellers results in a low propeller load
- Recovery of the swirl losses of the pull propeller by means of the integrated diffuser system consisting of strut and fins
- Streamlined propeller housing
The mechanical principle
- Both propellers on one shaft rotating in the same direction
- Proven power transmission, as there is no additional gearbox
- Only one additional sealing package
- Substantially higher efficiency than Z drives with a single propeller
- Higher power transmission possible than with a single propeller
- Lower risk of cavitation due to the lower propeller load
- Lower pressure fluctuations and noise emissions
- Lower mechanical losses than contrarotating two-propeller systems
- High reliability due to the small number of moving parts
- Fully steerable (360°)
- High variability of the characteristic curve meets a wide range of operational requirements up to speeds of 21 knots
- Particularly suitable for installations permitting only limited propeller diameters (restricted draught or required tip clearance)