| 摘要 |
As herein illustrated, the device comprises a central, elongate, hollow core embodying oppositely-diverging, truncated cones integrally-connected at their smaller ends to each other, an annular gripping portion disposed about the core intermediate the opposite ends defining with the core an annular chamber about the core and a plurality of radial fins disposed in the chamber about the core connected at their opposite ends to the core and the annular gripping portion. The annular gripping portion is of generally spherical configuration and is connected at its opposite ends to the core by annular flanges. Desirably, the annular gripping portion is in the neutral area of the aero slip stream created by the ends of the leading and trailing cone ends.
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