1. Field of the Invention
The present invention relates generally to a propeller for use in a boat and more specifically, to a propeller that can increase the propulsive force of the boat.
2. Description of the Related Art
FIGS. 1 and 2 show a propeller 10 according to a prior art. The propeller 10 includes a hub 12, a plurality of blades 14 equiangularly disposed on an outer periphery of the hub 12, and an end cover 16 engaged with a tail 122 of the hub 12 and having an outer periphery defining with a center axis 124 of the hub 12 a distance gradually increasing away from the tail 122.
When the propeller 10 is driven by an engine to rotate, vortices will be generated by the rotation of the blades 14 and shed downstream, and simultaneously the waste gas produced from the engine will be exhausted out of an outlet 128 of the hub 12 through a center hole 126 of the hub 12.
However, because the end cover 16 is gradually expanded in its external diameter, the water flowing along the outer periphery of the end cover 16 will interfere with the waste gas exhausted out of the outlet 128 to cause turbulence, resulting in increase of drag and decrease of thrust force for propulsion of a watercraft when the propeller 10 rotates. Further, the end cover 16 and the hub 12 are manufactured individually and engaged with each other, resulting in that the propeller 10 has high manufacturing cost, and the end cover 16 may be disengaged from the hub 12 after a long time of use because the junction of the end cover 16 and the hub 12 will corrode in seawater. Thus, it is desirable to provide a propeller that can eliminate the aforesaid drawbacks.