| 摘要 |
A propulsion unit for driving water craft, particularly those of the floating lounge type, is disclosed as including a fin made from a flexible material with a first end formed to define a foil into which the lower end of an oscillatory drive member projects downwardly in a fixedly secured relationship and with a second flexible fin end that extends from the foil end to provide a flapping movement through the water upon oscillation of the drive member in order to propel the water craft. Movement of the drive member through the water is facilitated by the foil shape of the first fin end which is also more rigid than the second flexible end so as to increase the moment arm about the drive member where the flexible flapping movement is concentrated. Flexible sheet plastic is preferably used to form the fin with a folding operation at a score line to define the foil shape. A journal in the form of a tube receives an intermediate portion of the drive member to provide mounting thereof and is connected to the first end of a mounting bar which has a pair of spaced mounts for securing the unit to the frame of a water lounge. One of the mounts includes a saddle-like member and a cooperable fastener for securing the first end of the mounting bar to the frame. The other mount may include either a flattened hook shape portion of a second end of the mounting bar and a cooperable fastener or a flattened portion of the second mounting bar end which is inserted within a hole in the lounge frame. A foot actuator bar for the unit is secured to the upper end of the drive member either by a welded connection or a hollow T-shaped connector. Best results are achieved when the length of the flexible fin end is between about 1.4 and 1.8 times the length of the foil fin end.
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