Particularities of hydrodynamic of hull of high-nautical gliding boat at gas cavity

While motion at still water, hull of high-nautical gliding boat at gas cavity (HNGBGC) operates as follows. While motion at every speed range, thanks to downwards bendings of keel line 12 at bow and keel line 14 of bottom 1 stern section, ram-shape projection 16 of hull bow is always submerged into the water. At that, thanks to almost vertical position of stem 10 line of ram-shape projection 16, running WL 9 length remains constant in spite of its certain at transition onto plane. Due to ram-shape projection 16, the general area of moistened surface increases. Simultaneously, this increase is being decreased by the artificial gas cavity that is formed under the bottom 1 while vessel motion.

Hull bottom 1 flow is carried out along the generating lines 17 of cylindrical insert 27 that are to be strictly parallel. This parallelism contributes to creation of stable gas cavity with its smooth locking at the bottom 1 in the area of transom 24. Hence, there is assurance of minimum gas carrying out supplied under pressure into the bottom groove for formation of artificial gas cavity, and hence, maximum excessive pressure inside it what, in turn, lets achieve the maximum surface area of bottom 1 of HNGBGC hull covered by the artificial gas cavity. Surface area of hull bottom 1 is filled by the groove for artificial gas cavity formation with the top 25 located in the hull bow and exceeds the auxiliary area of moistened surface of the constantly immersed ram-shape projection 16. As a result, ultimate area of moistened hull surface is greatly less of the one of the hull of the traditional gliding boat with the equal displacement.

Thus, at every speed range of this hull motion, on the one hand, there is support of its running WL 9 length that due to relative speed increase provides for the minimum value of its wave impedance. On the other hand, there is support of minimum area of moistened hull surface that provides for the minimum value of its friction drag. Ultimately, all this provides for considerable propulsion increase of the HNGBGC hull.

While motion at heavy sea, the offered HNGBGC hull interacts with aquatic environment as follows. Ram-shape projection 16 of hull bow meets the wave and easily enters it with minimum resistance thanks to the minimum butt angle of its extended water lines 17 near the stem 10 to the CL and thanks to its wedge-shaped frames 18 with the keel 12 acute angle. At that, its bow emergence that is specific for traditional hull configuration gliding boats does not occur under the influence of auxiliary buoyancy force which is acquired after its dipping into the wave; or it occurs with a very slight acceleration. It is caused by the following: on the one hand, the auxiliary volume of dipping hull bow of the above mentioned HNGBGC hull is not so great. On the other hand, even this slight auxiliary buoyancy force is totally or partially got balanced by oppositely directed vertical component resultant of velocity head from the counter-current flow of incoming wave; this resultant arises at the ram-shape projection 16 upper edge 19, auxiliary chine 8 steps 15, and at the lower section of cone cavities 21 in the sides 2 of the offered HNGBGC hull bow. As a result of composition of these two forces, they cancel or arises a relatively slight resultant directed upwards. Thanks to this resultant, the offered hull, while motion at heavy sea, does not feel any vertical overloads, or feels insignificant vertical overloads much slighter than the vessels with traditional hull configuration.

After analysis of particularities of the offered HNGBGC hull configuration and hydrodynamic, one can conclude the following: by joining two fruitful ideas in the contemporary shipbuilding - artificial gas cavity and "wave-piercing" technology - we managed to get a brand new type of ship's lines of high-speed gliding boat. HNGBGC hull configuration joins the advantages of both these ideas and eliminates their defects. The offered HNGBGC hull configuration is very effective for achievement of HSGB high navigability and contains a great potential for its following development.