Final answer:
For best performance on a slow-speed boat, the propeller should have a larger diameter, more pitch, and typically a three-blade design for efficiency. Material choice and matching propeller characteristics with boat hull design and engine power are essential to reduce drag and enhance efficiency.
Step-by-step explanation:
Features of a Propeller for Best Performance on a Slow-Speed Boat
For a slow-speed boat, the propeller design is crucial for achieving the best performance. A propeller with a larger diameter and more pitch (the distance the propeller would move in one revolution if it were moving through a solid) is usually preferable. This design allows the propeller to displace more water with each revolution, which increases efficiency and therefore performance, particularly at lower speeds. Additionally, the number of blades on the propeller can affect performance. Generally, a three-blade design is considered the most efficient for slow-speed boats, as it offers a balance between smooth operation and the power required to turn the propeller.
Another important feature is the material from which the propeller is made. Materials that resist corrosion and wear, such as bronze or stainless steel, ensure longevity and consistent performance. The propeller's moment of inertia also plays a role in its start-up acceleration and overall performance. Moreover, torque and the power being provided to the propeller are important considerations. For instance, a boat engine operating at a given power will exert a certain torque on the propeller shaft, as outlined in the example provided, where an engine at 9.0 × 104 W operating at 300 rev/min delivers a specific torque to the shaft.
It's essential that the propeller is well-matched to the boat's hull design and engine power to minimize drag and ensure efficient movement through the water. The Bernoulli's principle calculation, although approximate due to the effects of turbulence, helps in assessing the force the propeller will exert and whether it is effective for propelling the boat.