| 摘要 |
PCT No. PCT/GB91/02148 Sec. 371 Date Jul. 30, 1993 Sec. 102(e) Date Jul. 30, 1993 PCT Filed Dec. 4, 1991 PCT Pub. No. WO92/10396 PCT Pub. Date Jun. 25, 1992.A method of constructing or, modifying a watercraft (10) comprises the step of fitting to a main hull (14) of the watercraft an outer hull structure (15) which includes or which forms an outer hull skin (22) by attaching the outer hull structure (15) to the external surface of the main hull (14) of the watercraft. The outer hull structure (15) provides fluid containment spaces (155) between the outer hull skin (22) and the main hull (14) and a communication is provided for flooding the spaces (155) with water from the body of water within which the craft moves. The fluid containment spaces (155) extend above the waterline of the watercraft and means are provided for supplying a pressurized inert gas and/or for applying vacuum pressures to preselected sections of the outer hull structure (15) so that the water levels in those sections can be brought above or below the waterline of the watercraft to increase the overall ballast effect or the buoyancy or to alter the trim of the watercraft (10 ). |
