摘要 |
<p>The manually operated drive for propelling a surf board on light craft in water, has a handle with a set of blades attached to it. All the blades are secured by couplings at right angles to the handle, acting as hinges so that they can be swung from a vertical closed position to a horizontal open position. When the blades are closed, the drive can be used as a paddle, all the blades forming a single large area surface. Alternatively a pair can be used as oars, and in another method, the handle can be reciprocated vertically forming a pumping action, the blades being raised and lowered.</p> |