초록 ▼

A low drag ship hull generally includes a side air cavity initiated by wetted bow section, bottom air cavity initiated by wetted bottom nosepiece, wetted stem section that closes a lower portion of the side cavity, wetted bottom tailpiece that closes the bottom cavity, stabilizing fin, and propulsor

A low drag ship hull generally includes a side air cavity initiated by wetted bow section, bottom air cavity initiated by wetted bottom nosepiece, wetted stem section that closes a lower portion of the side cavity, wetted bottom tailpiece that closes the bottom cavity, stabilizing fin, and propulsor. The bottom of a catamaran hull cross structure includes bow impact alleviator. Optional flaps in the stabilizing fins, together with optional all-movable canard fins are used for control. Different wetted bow sections and retractable plates are used for starting side cavities. A low drag hull may utilize multiple air cavities. A new low drag hull includes a new upper bottom air cavity that is initiated by an upper bottom wetted nosepiece, and closed by an upper bottom tailpiece. Alternative designs include a shortened forward hull spaced ahead of a shortened aft hull, and a hydrofoil-supported trimaran with low drag hulls.

대표청구항 ▼

We claim: 1. Low drag hull apparatus, comprising a waterborne vessel having at least one vessel-supporting hull, a hull bottom on the hull, at least one side cavity on the hull, at least one bottom cavity on the hull bottom, a wetted bow nosepiece on the hull, a wetted bottom nosepiece on the hull

We claim: 1. Low drag hull apparatus, comprising a waterborne vessel having at least one vessel-supporting hull, a hull bottom on the hull, at least one side cavity on the hull, at least one bottom cavity on the hull bottom, a wetted bow nosepiece on the hull, a wetted bottom nosepiece on the hull bottom, and a wetted bottom tail region on the hull bottom, wherein the at least one side cavity opens at the wetted bow nosepiece for displacing water from a side portion of the hull adjacent the cavity, wherein at least one bottom cavity opens at the bottom nosepiece and at least a part of the at least one bottom cavity closes at the wetted bottom tail region for reducing drag on the hull, wherein the bottom nosepiece is swept-back along the bottom sides, resembling a vee in bottom view, to form the at least one bottom cavity and to separate a significant part of the one or more bottom cavities from adjacent side cavities, and wherein the bottom tail region may be swept forward near each side of the hull bottom to separate a significant part of the one or more bottom cavities from adjacent side cavities, and further comprising wetted regions or fences positioned between side and bottom cavities as needed to assist the bottom nosepiece and the bottom tail region in separating bottom cavities from side cavities. 2. The apparatus of claim 1, wherein the hull has opposite sides, and the at least one side cavity comprises side cavities on the opposite sides of the hull for opening at the wetted nosepiece and displacing water away from the opposite sides of the hull, further comprising a wetted side tailpiece and wherein at least part of the side cavities close at the wetted tailpiece. 3. The apparatus of claim 2, wherein the side cavities further comprise upper and lower portions, wherein the wetted tailpiece is positioned at a lower position of a stern of the hull, wherein the upper side cavity portions close beyond the stern, and wherein the lower side cavity portions close at the wetted tailpiece. 4. The apparatus of claim 1, further comprising at least one step extending across the hull bottom to close a preceding bottom cavity and an air outlet either in or following an after portion of the at least one step to open a following bottom cavity aft of the step by releasing pressurized air from the air outlet. 5. The apparatus of claim 4, further comprising an air intake near a forward portion of the at least one step or near a forward portion of the wetted bottom tail region to help close the preceding bottom cavity. 6. The apparatus of claim 2, further comprising one or more side steps located within the side cavities to initiate additional side cavities in case the outside water flow contacts a hull side under off design conditions, or further comprising one or more bottom steps located within the bottom cavities with associated air supplies to initiate additional bottom cavities in case the outside water flow contacts the hull bottom under off design conditions. 7. The apparatus of claim 1, wherein the pressure in a bottom cavity is less than depth pressure in order to help ensure a stable bottom cavity. 8. The apparatus of claim 1, wherein the lift on the bottom of the hull is approximately equal to the displacement of the cavities and the hull portions that lie above the bottom of the hull and ahead of the stern of the hull. 9. The apparatus of claim 1, wherein the design waterline lies lower on the hull than the at-rest waterline. 10. The apparatus of claim 1, further comprising at least one stabilizing fin mounted on the hull having a vertically-projected area and extending from the hull. 11. The apparatus of claim 10, further comprising at least one flap mounted on the at least one stabilizing fin. 12. The apparatus of claim 1, further comprising at least one canard fin, wherein at least one of the canard fins has upper and lower fin surfaces that may have an air cavity on at least one of the fin surfaces. 13. The apparatus of claim 2, wherein the vessel comprises two or more hulls. 14. The apparatus of claim 13, wherein two or more vessels are linked together as a platform. 15. The apparatus of claim 2, wherein the side cavities are filled with air at approximately atmospheric pressure. 16. The apparatus of claim 2, wherein lower side cavity portions have overall side-to-side cavity widths that increase with depth. 17. The apparatus of claim 2, wherein the hull surface lies a short distance inside the cavity portions near the bow or bottom nosepieces, said short distance reducing or increasing somewhat, and then reducing to zero for cavities that close on the hull. 18. The apparatus of claim 2, wherein the hull sides are relatively streamlined in horizontal cross section. 19. The apparatus of claim 2, wherein one or more steps lie just under the cavities in order to start new cavities in case the outside water flow contacts the steps under off design conditions. 20. The apparatus of claim 2, wherein the hull has side steps spaced along the opposite sides for forming plural side cavities along the opposite sides of the hull wherein one or more of the side cavities may be open to the atmosphere. 21. The apparatus of claim 20, wherein the side steps are either outward formed on the hull sides or inward formed in the sides. 22. The apparatus of claim 20, wherein the side steps are angled to the vertical along the hull. 23. The apparatus of claim 20, wherein cavities near the center of the hull are largest toward the top of the hull, and cavities near the ends of the hull are largest toward the bottom of the hull, thereby reducing wavemaking drag or reducing overall beam. 24. The apparatus of claim 20, wherein the side steps increase in number as the hull bottom is approached. 25. The apparatus of claim 24, wherein the side steps have varied heights, and wherein the steps that begin at the lesser depths have the greater heights. 26. The apparatus of claim 25, wherein the side steps have alternating longer and shorter lengths from a bottom of the vessel for forming additional side cavities near the bottom of the hull. 27. The apparatus of claim 20, wherein at least one side step has an air outlet for assisting in opening new side cavities. 28. The apparatus of claim 20, wherein at least one side step has an air intake for assisting in closing a previous side cavity. 29. The apparatus of claim 1, further comprising fore and aft ballast or fuel tanks in the hull, means to move ballast or fuel between fore and aft tanks, and means to increase or reduce the amount of ballast in the ballast tanks, to help control vessel weight or center of gravity. 30. The apparatus of claim 2, wherein at least a portion of the nosepiece may be swept either way from vertical and may comprise one or more of many different kinds of cross sectional shapes that may change in shape from the top to the bottom of the nosepiece, wherein the shapes have surface changes in a rearward direction that cause the water flow to separate from the nosepiece on opposite sides, and wherein the surface changes may be obtuse angles, increased convex curvatures, steps and notches, and wherein the nosepiece may be a wedge shape with flat sides, convex sides or concave sides, and wherein the nosepiece could be a flat transverse plate. 31. The apparatus of claim 30, wherein the nosepiece has extendable and retractable elements on opposite sides, and wherein the extendable and retractable elements are transverse plates, curved flexible plates, flat rigid plates, extendable supports for the nosepiece, hinged plates, inflatable tubes, slidable bars, and rotatable curved transverse plates, and wherein the amount of extension or retraction may vary along the nosepiece length. 32. The apparatus of claim 2, wherein at least a portion of the nosepiece further comprises a flat forward surface whose width is optionally controllable. 33. The apparatus of claim 2, wherein the nosepiece further comprises at least one attachable strip. 34. The apparatus of claim 33, wherein the attachable strips are attached to either low drag hulls or conventional hulls. 35. The apparatus of claim 2, further comprising attachable steps attachable along sides of either low drag hulls or conventional hulls. 36. The apparatus of claim 2, further comprising a propulsor positioned near a wetted side tailpiece or a wetted bottom region, the propulsor further comprising a propeller and rudder, or a pump with an inlet in the wetted side tailpiece or bottom region, and having a steerable water jet. 37. The apparatus of claim 2, wherein the side cavities comprise one or more open side cavities that cover a stern region of the hull at or near the water line, one or more closed cavities below the open side cavities, additional closed cavities on each side below the one or more closed cavities, and optionally even more additional closed cavities below each of the additional closed cavities, and wherein the side cavities are mismatched vertically and horizontally to minimize wavemaking drag. 38. The apparatus of claim 2, further comprising at least one fence in a fore and aft direction for separating the at least one bottom cavity into separate port and starboard bottom cavities. 39. The apparatus of claim 38, wherein at least one step extends across each bottom cavity, including injecting pressurized air at or behind each step to form at least four separate bottom cavities. 40. The apparatus of claim 39, further comprising means to vary the cavity pressure or airflow rate within each of the at least four bottom cavities to maintain good cavity coverage under off-design conditions or to provide limited control over hull pitch, heave or roll. 41. The apparatus of claim 2, further comprising one or more approximately-parallel fences on the sides of the hull in the at least part of the side cavities which close at the wetted tail piece for separating the side cavities into plural layers of side cavities. 42. The apparatus of claim 41, further comprising steps on the hull for creating multiple fore and aft cavities within each cavity layer. 43. The apparatus of claim 42, wherein the pressure within each cavity layer increases with depth. 44. The apparatus of claim 41, including means to provide pressurized air to each side cavity below the upper fence, further including means to control the airflow rate or air pressure into each pressurized cavity as a function of hull speed, depth or other variables. 45. The apparatus of claim 2, wherein hull shapes are relatively streamlined in horizontal cross sections except for nosepiece protuberances and step protuberances, and wherein the side cavities are mismatched vertically and horizontally to minimize wavemaking drag. 46. A vessel comprising: a navigation deck; passenger or cargo compartments; a propulsion system; one or more low drag hulls, each hull having opposite sides and a bottom; one or more side cavities on each side of the one or more low drag hulls; a wetted bow nosepiece for starting the one or more side cavities; a wetted side tailpiece for closing at least a portion of the one or more side cavities; wherein the hull and cavities together provide a transverse cross section that resembles an hour glass which may have unequal top and bottom widths; and wherein at least most of the cavities in the lower part of the hour glass-like cross section comprise closed side cavities. 47. The vessel of claim 46, wherein the cavities cover up to about 90% of a below water line area of the vessel. 48. The vessel of claim 46, further comprising a wetted stern tailpiece for closing at least a portion of the one or more side cavities. 49. The vessel of claim 46, further comprising one or more bottom cavities on the one or more low drag hulls; a wetted bottom nosepiece for starting the one or more bottom cavities; a wetted bottom tail region for closing the one or more bottom cavities; and edge fences or wetted regions as needed for assisting the bottom nosepiece and the wetted bottom region for dividing the one or more bottom cavities from the one or more side cavities on the one or more low drag hulls. 50. The vessel of claim 46, further comprising at least one stabilizing fin having a vertically-projected area extending from the one or more low drag hulls. 51. The vessel of claim 50, further comprising fin cavities on at least one surface of the at least one stabilizing fin to reduce drag. 52. The vessel of claim 50, wherein the at least one stabilizing fin comprises more than one stabilizing fin on one or more sides of the one or more low drag hulls. 53. The vessel of claim 52, further comprising closed cavities on opposite surfaces of the stabilizing fins. 54. The vessel of claim 50, further comprising control surfaces on the stabilizing fins or other means to control the fins. 55. The vessel of claim 46, further comprising one or more canard fins having a vertically-projected area extending from submerged forward portions of the hulls. 56. The vessel of claim 46, further comprising a bow impact alleviator hull. 57. The vessel of claim 46, wherein the side cavities are at atmospheric pressure. 58. The vessel of claim 46, wherein the side cavities are open near the water surface, and closed elsewhere. 59. The vessel of claim 46, further comprising controls mounted on the one or more hulls for controlling one or more of pitch angle, altitude, direction and depth of the hulls. 60. The vessel of claim 46, further comprising one or more steps along the sides for opening and closing and for separating cavities along sides of the one or more hulls. 61. The vessel of claim 46, wherein at least a portion of the wetted bow nosepiece for initiating side cavities is wedge shaped. 62. The vessel of claim 46, wherein at least a portion of the wetted bow nosepiece for initiating side cavities has rearward increases in surface curvature to separate the water flow and start a cavity. 63. The vessel of claim 46, wherein at least a portion of the wetted bow nosepiece for initiating side cavities has steps for separating water flow and/or ducts for flowing air into the side cavities. 64. The vessel of claim 46, wherein at least a portion of the wetted bow nosepiece for initiating side cavities has a combination step and notch. 65. The vessel of claim 46, wherein at least a portion of the wetted bow nosepiece for initiating side cavities has a convex lateral bow surface. 66. The vessel of claim 46, wherein at least a portion of the wetted bow nosepiece for initiating side cavities has a concave lateral surface. 67. The vessel of claim 46, wherein at least a portion of the wetted bow nosepiece for initiating side cavities is flat. 68. The vessel of claim 46, wherein at least a portion of the wetted bow nosepiece for initiating side cavities is retractable. 69. The vessel of claim 46, wherein a bottom nosepiece and one or more a spaced bottom steps are used as cavity initiators to initiate bottom cavities. 70. The apparatus of claim 3, wherein at least one approximately horizontal fence is placed in the lower side cavity portions on each side, and the airflow rates into side cavities below the at least one fence are controlled. 71. Low drag hull apparatus, comprising a waterborne vessel having at least one vessel-supporting hull, an open side cavity on each side of the hull at approximately atmospheric pressure, a wetted nosepiece on the hull, and a hull bottom, wherein the side cavity opens at the wetted nosepiece for displacing water from a side portion of the hull adjacent the cavity, wherein the hull bottom is convex in a longitudinal cross section and in a transverse cross section, and wherein at least a majority of the hull bottom is at a pressure greater than atmospheric pressure and less than depth pressure. 72. The apparatus of claim 71, wherein the vessel is a monohull. 73. The apparatus of claim 72, wherein the majority of the hull volume lies below the waterline. 74. The apparatus of claim 71, wherein the vessel is a catamaran or a trimaran, wherein the at least one vessel-supporting hull comprises a center hull or each of two side hulls. 75. The apparatus of claim 2, wherein the side of at least a portion of a nosepiece is moved outward to form a larger cavity. 76. The apparatus of claim 4, further comprising one or more underlying bottom steps that lie under design bottom cavities that form at design speed, and wherein under an off-design condition, a new bottom cavity is formed behind at least one underlying bottom step. 77. The apparatus of claim 4, wherein the bottom nosepiece or one or more bottom steps are moved outward to form larger cavities. 78. The apparatus of claim 2, further comprising one or more spaced approximately parallel fences on the sides of the hull for separating each of the side cavities into plural layers of side cavities, further comprising steps on the hull for creating multiple fore and aft cavities within each cavity layer, wherein the upper layers of cavities comprise either large center cavities and small end cavities, or small center cavities and large end cavities, or combinations thereof, and the lower layers of cavities comprise either small center cavities and large end cavities or large center cavities and small end cavities, or combinations thereof, wherein the mismatch between cavity sizes in the upper and lower layers reduces wavemaking drag. 79. The apparatus of claim 78, further comprising large center cavities and small end cavities above an upper fence, and small center cavities and large end cavities below a lower fence, a forward step that angles down and back from a region near the front end of the upper fence to a region near the center of the hull bottom, further comprising an aft step that angles upward and rearward from a region near the lower end of the forward step to a region near the aft end of the upper fence, and wherein a side cavity below each fence may be pressurized. 80. The apparatus of claim 2, further comprising either a forward step that angles down and back from a region near the nosepiece to a region near the hull bottom, or an aft step that angles down and forward from a wetted stern region near the stern of the hull to a region near the hull bottom, wherein the nosepiece, step and wetted stern region are designed to form upper and lower side cavities that are mismatched to reduce wavemaking drag. 81. The apparatus of claim 80, wherein all side cavities are at atmospheric pressure. 82. The apparatus of claim 80, wherein at least a portion of the hull nosepiece is angled down and forward from the water surface, or at least a portion of the hull stern is angled down and rearward from the water surface. 83. The apparatus of claim 80, wherein both the forward step and an aft step angle down to a middle region of the hull bottom. 84. The apparatus of claim 2, wherein the nosepiece is enlarged in order to open wide side cavities, and wherein a cross section of the nosepiece resembles a cutoff hydrofoil nose section. 85. The apparatus of claim 2, wherein the pressure on at least a portion of the wetted nosepiece is less than the pressure in the cavity that lies behind the nosepiece. 86. The apparatus of claim 2, further comprising grooves or ridges attached to the hull that start inside each side cavity upstream of a design cavity closure location, and end either near or aft of the design cavity closure location, and that are approximately aligned in the direction of the local cavity wall water flow wherein energy is saved at cavity closure because the grooves reduce forward splash at cavity closure. 87. The apparatus of claim 86, wherein the grooves or ridges are placed near the wetted bottom tail region or a wetted region on the hull sides. 88. The apparatus of claim 86, wherein the grooves or ridges are placed near steps on the sides or near the end of the one or more bottom cavities. 89. Low drag hull apparatus, comprising a waterborne vessel having at least one vessel-supporting hull, at least one side cavity on each side of the hull, a wetted nosepiece on the hull, wherein at least one side cavity opens at the wetted nosepiece for displacing water from each side of the hull adjacent the cavity for reducing drag on the hull, further comprising a hull bottom, at least one bottom cavity on the hull bottom, a sweptback bottom nosepiece to open at least one bottom cavity, a wetted bottom tail region to close at least a part of one bottom cavity, wherein the sweptback bottom nosepiece separates a significant part of one or more bottom cavities from one or more side cavities, and additionally comprising a dynamic lifting surface connected to the hull. 90. The apparatus of claim 89, wherein the vessel is an aircraft, the dynamic lifting surface is a wing, and wherein after takeoff the hull bottom supports no portion of the weight of the vessel. 91. The apparatus of claim 89, wherein the vessel is a WIG, and the dynamic lifting surface connected to the hull is a ground effect wing. 92. The apparatus of claim 89, wherein the vessel is a ship, and the dynamic lifting surface is at least one hydrofoil. 93. The apparatus of claim 92, wherein the vessel is a catamaran ship, the at least one hull comprises parallel catamaran hulls, and the at least one hydrofoil may extend between the catamaran hulls. 94. The apparatus of claim 89, wherein the at least one hull comprises a main hull of a trimaran, wherein the two auxiliary hulls may have nosepieces for opening auxiliary hull cavities. 95. Submarine apparatus comprising at least one hull having non-circular cross sections whose beams are greater then their heights having a bow and a stern, a wetted nosepiece extending rearward or sideward from the bow and a wetted tailpiece that comprises a wetted tail region that extends forward or sideward from the stern, upper and lower gas cavities between the nosepiece and the tailpiece and respectively above and below the hull, wherein the wetted nosepiece and the wetted tailpiece separate at least a significant part of the upper and lower gas cavities, further comprising wetted regions or fences for assisting the wetted nosepieces and tailpieces in fully separating the upper and lower cavities as needed. 96. The apparatus of claim 95, further comprising one or more pressurized gas sources in the hull and conduits from the sources to the cavities for supplying the upper cavity with gas at a first pressure and supplying the lower cavity with gas at a second, higher pressure and maintaining a pressure differential between the cavities. 97. The apparatus of claim 95 further comprising at least one stabilizer with either a horizontally-projected area or a vertically-projected area extending from the hull. 98. The apparatus of claim 95 further comprising at least one control connected to the submarine for controlling the submarine. 99. The apparatus of claim 98 wherein the control comprises at least one flap that connected to or including at least a part of the tailpiece, the nosepiece or the at least one stabilizer. 100. The apparatus of claim 98 wherein the control comprises a movable tailpiece, a movable nosepiece or at least one moveable stabilizer. 101. The apparatus of claim 95, wherein the hull comprises an internal main pressure hull or one or more pressure or non-pressure hulls. 102. The apparatus of claim 95, wherein the hull, the nosepiece and the tailpiece have a delta-like planform, narrow at the nosepiece and wide at the tailpiece. 103. The apparatus of claim 95 further comprising means to halt the gas flow into cavities and-smooth the water flow over the submarine surfaces in order to eliminate cavities for operating the submarine quietly or efficiently in a fully wetted condition without the cavities. 104. The apparatus of claim 95 further comprising a sonar array incorporated in the nosepiece, hull or tailpiece. 105. The apparatus of claim 10, wherein the vessel comprises two hulls, further comprising one or more dynamically-lifting hydrofoils, wherein at least one of the one or more hydrofoils may be attached between the two hulls near their bottoms. 106. The apparatus of claim 105, wherein the one or more hydrofoils has a cavity on at least one surface. 107. The apparatus of claim 105, further comprising at least one canard fin mounted on each hull. 108. The apparatus of claim 106, further comprising at least one fin, and wherein at least one of the one or more hydrofoils and the at least one fin has an air cavity on one or both surfaces to reduce drag. 109. The apparatus of claim 105, wherein the hydrofoil is movable fore and aft to adjust for changes in longitudinal center of gravity. 110. The apparatus of claim 92, wherein at least one hydrofoil is attached to the hull by means of one or more struts to lift the hull at least partly out of water at design speed. 111. The apparatus of claim 110, wherein the at least one hydrofoil is a low drag hydrofoil having a cavity on at least one surface to reduce drag, and may be either unswept or swept either way. 112. The apparatus of claim 110, further comprising a bow lifting means attached near the bow of the hull to provide bow height stabilization. 113. The apparatus of claim 110, wherein the low drag hull helps reduce drag during takeoff, and reduces the effects of wave impacts when the vessel travels in waves. 114. The vessel of claim 110, in which the vessel is a trimaran, further comprising low drag outer hulls to help support the at least one hydrofoil. 115. A method of water supported vessel operation comprising providing a waterborne vessel, providing at least one vessel-supporting hull, providing at least one side cavity on each side of the hull, providing a wetted bow nosepiece on the hull, and providing a wetted stern tailpiece on the hull, opening the at least one cavity at the wetted bow nosepiece, displacing water from a side portion of the hull adjacent the cavity, closing at least a part of the at least one cavity at the wetted stern tailpiece, and further comprising shaping the hull to form cavities wherein at least a portion of the hull and cavities together provide a transverse cross section that resembles an hour glass that has equal or unequal top and bottom widths, and reducing drag on the hull. 116. The method of claim 115, further comprising providing a hull bottom on the hull, providing at least one bottom air cavity on the hull bottom, providing a bottom nosepiece on the hull bottom for opening a bottom cavity, supplying pressurized air into the at least one bottom cavity behind or through the bottom nosepiece, and providing a wetted bottom tail region on the hull bottom, and closing at least a part of a bottom cavity at the wetted bottom tail region. 117. The method of claim 116, further comprising providing the bottom nosepiece with sweepback along the sides of the hull bottom having a vee-like shape in bottom view, optionally providing the wetted bottom tail region with forward sweep along the sides of the bottom, and providing wetted side regions or fences extending from the hull bottom for assisting the bottom nosepiece and the wetted bottom tail region in separating bottom cavities from side cavities. 118. The method of claim 116, further comprising extending at least one bottom step across the hull bottom, closing a preceding bottom cavity at the at least one bottom step, and opening a following bottom cavity aft of the at least one bottom step. 119. The method of claim 116, further comprising generating one or more additional side cavities in case the outside water flow would otherwise contact a hull side under off design conditions, or further comprising initiating one or more additional bottom cavities in case the outside water flow would otherwise contact the hull bottom under off design conditions. 120. The method of claim 116, further comprising providing pressure in at least one bottom cavity at less than depth pressure and helping ensure a stable bottom cavity. 121. The method of claim 115, further comprising providing at least one stabilizing fin having a vertically-projected area mounted on the hull and extending from the hull, wherein the at least one fin may or may not have a cavity on one or both sides to reduce drag. 122. The method of claim 121, further comprising providing at least one flap mounted on the at least one stabilizing fin. 123. The method of claim 115, further comprising providing at least one canard fin on the hull which may or may not have a cavity on one or both sides to reduce drag. 124. The method of claim 115, further comprising providing two or more hulls, and linking the hulls together. 125. The method of claim 115, further comprising providing side steps along the hull. 126. The method of claim 125, further comprising providing a cavity formed behind each side step, and providing a mismatch in side cavities by providing a center side cavity largest toward a top of the hull, and providing end cavities largest toward the bottom of the hull, reducing wavemaking drag, or reducing overall beam. 127. The method of claim 125, further comprising providing more side steps as the hull bottom is approached, providing more steps for a hull that operates at a low design volumetric Froude number, or providing more steps that underlie design cavities for retaining side-cavity coverage under off design conditions. 128. The method of claim 115, further comprising providing spaced approximately parallel fences on the sides of the hull, separating each of the side cavities into plural layers of side cavities, and optionally increasing pressure within each cavity layer with depth. 129. A vessel operating method, comprising providing a navigation deck, passenger or cargo compartments, providing a propulsion system, providing one or more low drag hulls, each hull having opposite sides and a bottom, providing one or more side cavities on the one or more low drag hulls, providing one or more bottom cavities on the one or more low drag hulls, providing a wetted bow nosepiece on the one or more hulls, starting the one or more side cavities at the bow nosepiece, providing a wetted swept-back bottom nosepiece having a vee-like shape in bottom view and whose leading edges lie near the sides of the hull bottom to form the at least one bottom cavity and to separate a significant part of the one or more bottom cavities from any adjacent side cavity, further comprising providing a wetted bottom tail region on the bottom of the hull to close the at least one bottom cavity wherein the wetted bottom tail region may be swept forward near each side of the hull bottom to separate a significant part of the one or more bottom cavities from any adjacent side cavity, providing edge fences or wetted regions to assist the bottom nosepiece in dividing the one or more bottom cavities from the one or more side cavities on the one or more low drag hulls, and further providing the at least one bottom cavity with air at greater than atmospheric pressure but at less than depth pressure outside the bottom cavity. 130. The method of claim 129, further comprising providing a wetted stern tailpiece and closing at least a portion of the one or more side cavities at the stern tailpiece. 131. The method of claim 130, further comprising providing longitudinal grooves or ridges attached to the hull that start inside at least one cavity upstream of a cavity closure location, and end at or aft of the design cavity closure location, and saving energy at the cavity closures by reducing forward splash at the cavity closures. 132. The method of claim 129, further comprising providing a dynamic lifting surface connected to the hull. 133. The method of claim 132, wherein the vessel comprises two hulls, further comprising providing at least one a hydrofoil that is attached to at least one hull near its bottom. 134. The method of claim 132, wherein the hull is a center hull of a trimaran vessel, and further comprising providing at least one hydrofoil that is attached to at least the center hull for supporting a part of the vessel weight. 135. A submarine operating method comprising providing an outer hull having a bow and a stern, providing a nosepiece at the bow that may extend rearward from the bow on each side of the hull and a tailpiece that may extend either forward or aft from the stern, providing upper and lower gas cavities between the nosepiece and the tailpiece and respectively above and below the hull, providing at least one pressurized gas source in the hull and conduits from the at least one source to the cavities, and supplying the upper cavity with gas at a first pressure and supplying the lower cavity with gas at a second, higher pressure and typically maintaining a pressure differential between the cavities. 136. The method of claim 135, further comprising providing one or more pressure hulls located inside the outer surface of the outer hull, and providing a floodable region between the outer hull and the one or more pressure hulls. 137. The method of claim 135, wherein the outer hull has a delta-like platform, narrow at the nosepiece and wide at the tailpiece. 138. The method of claim 135, wherein at least a part of the nosepiece or tailpiece is controllable. 139. The method of claim 135, wherein at least a part of the nosepiece comprises a flat plate in a longitudinal cross-section. 140. The method of claim 135, further providing at least one or more cavities on one or more sides of one or more of the following: a vertically-extending stabilizer, a horizontally-extending stabilizer, a conning tower, and propulsor blades. 141. The method of claim 135, wherein the nosepiece extends rearward over a majority of the length of the submarine. 142. The apparatus of claim 2, further comprising at least one hydrofoil having a vertical-projecting area connected to the hull and extending outward from the hull and providing dynamic lift to the hull when underway. 143. The apparatus of claim 142, the hull further comprising at least one stabilizing fin having a vertically-projected area extending outward from the at least one hull. 144. The apparatus of claim 142, wherein the hull further comprises catamaran hulls and wherein the at least one hydrofoil optionally extends between the catamaran hulls. 145. The apparatus of claim 2, further comprising at least one canard fin placed near the bow of the hull. 146. Low drag hull method, comprising providing a waterborne vessel having at least one vessel-supporting hull, providing at least one side cavity on each side of the hull, providing a wetted nosepiece on the hull, opening the side cavities at the wetted nosepiece, displacing water from each side of the hull adjacent the cavity, widening the nosepiece to widen the side cavities, and reducing the resulting added cavity drag by adding convexity to the sides of the widened nosepiece to reduce the surface pressure over a portion of the nosepiece below the local depth pressure and to reduce the outward angle of cavity walls at the end of the nosepiece with respect to the hull centerline. 147. The method of claim 146, further comprising shaping the wetted nosepiece to provide a region on the nosepiece where the pressure is less than the pressure in a cavity behind the nosepiece. 148. Low drag hull method, comprising providing a waterborne vessel having at least one vessel-supporting hull, providing a wetted nosepiece on the hull, opening side cavities at the wetted nosepiece, displacing water from each side of the hull adjacent the cavity, and further providing closed side cavities over at least a portion of the hull depth, wherein underwater hull transverse cross sections resemble an isosceles triangle with a base near the hull bottom and a cut-off upper tip near the design waterline. 149. The method of claim 148, wherein the overall width of the side cavities in a lower portion of the closed-cavity region near the hull bottom reduce in a downward direction. 150. The method of claim 148, further providing at least one bottom cavity on a bottom of the hull. 151. Low drag hull method, comprising providing a waterborne vessel having at least one vessel-supporting hull, providing a wetted swept-back nosepiece on a bottom of the hull, having a vee-like shape in bottom view, opening at least one bottom cavity at the wetted nosepiece having a pressure less than depth pressure, displacing water from the bottom of the hull, and further providing shaping and sizing the bottom of the hull to close at least one bottom cavity, wherein the bottom surface of the at least one bottom cavity is convex in any vertical longitudinal cross section and is convex in at least one portion of any transverse cross section, and wherein no lower cavity is constrained by a side keel. 152. The method of claim 151 further comprising providing side cavities over at least a portion of the hull depth wherein at least a portion of the side cavities are open. 153. The method of claim 152, where the hulls are relatively streamlined in horizontal cross sections. 154. The method of claim 152, wherein the displacement of a hull and its adjacent cavities approximately equals the weight supported by the hull. 155. The method of claim 115, further providing relatively streamlined hull shapes in at least most horizontal cross sections. 156. Low drag hull method, comprising providing a waterborne vessel having at least one low-drag vessel-supporting surface piercing hull that uses cavities to reduce hull drag, and that supports at least part of the weight of the vessel at some design speed, providing at least one side cavity on each side of the hull, providing a wetted nosepiece on the hull, opening the side cavities at the wetted nosepiece, displacing water from each side of the hull adjacent the cavity, and reducing drag on the hull, providing a hull bottom, and providing at least one dynamic lifting surface connected to the hull that supports part of the weight of the vessel at some design speed. 157. Low drag hull method, comprising providing a waterborne vessel having at least one vessel-supporting low-drag surface piercing hull that uses cavities to reduce hull drag at some design speed, providing a wetted nosepiece on the hull, opening the side cavities at the wetted nosepiece, displacing water from each side of the hull adjacent the cavity, and further providing at least one fin or at least one dynamically-lifting hydrofoil attached to the hull. 158. The method of claim 157 wherein the at least one fin on the hydrofoil is controllable. 159. The method of claim 157, further providing a propulsor having blades, and further providing a cavity on at least one side of either the at least one fin, the hydrofoil or the propulsor blades. 160. The method of claim 157, further providing a hull bottom with at least one bottom cavity. 161. Low drag hull method, comprising providing a waterborne vessel having at least one vessel-supporting hull that comprises an upper hull, providing a lower hull having an upper side and a lower side attached to a bottom of the upper hull, and further providing a wetted sweptback lower hull nosepiece on the lower hull having a vee-like shape in plan view that extends rearward from a bow on one or both sides for forming a cavity an the upper side or the lower side of the lower hull, wherein the lower hulls are non-circular or non-tandem, and provide mostly displacement lift or remain submerged at rest. 162. The method of claim 161, further comprising providing a wetted upper hull nosepiece on the upper hull, and providing one or more side cavities on each side of the upper hull, wherein the upper hull nosepiece is angled or not angled to the vertical. 163. The method of claim 161, further providing a cavity on each side of the lower hull, and further providing at least one stabilizing fin having a vertically-projected area attached near an end of either the lower hull or the upper hull. 164. The method of claim 162 wherein a centerline of the upper hull nosepiece lies in an approximately vertical plane. 165. The method of claim 161 further providing a wetted lower hull tailpiece closing a cavity on the upper side or the lower side of the lower hull. 166. The method of claim 161 further providing an open cavity on the lower side of the lower hull. 167. The method of claim 161 wherein the lower hull is a hydrofoil. 168. The method of claim 167 wherein the hydrofoil provides dynamic lift. 169. The method of claim 161 wherein the displacement of the lower and upper hulls and their associated cavities is approximately equal to the weight supported by the hull. 170. The method of claim 161 wherein the wetted lower hull nosepiece is approximately flat in a longitudinal cross-section. 171. The method of claim 161 further providing attaching two hulls together with a cross structure forming a catamaran, or attaching two side hulls to a low drag hull to form a trimaran. 172. The method of claim 162 wherein the at least one cavity comprises one or more upper cavities on the upper side of the lower hull, and further providing a fence or a wetted region between the one or more upper cavities and the side cavities if their pressures are different. 173. The method of claim 172, further providing a wetted lower hull tailpiece on the lower hull wherein the forming at least one cavity comprises providing upper and lower cavities on the lower hull that close at the wetted lower hull tailpiece wherein the lower hull nosepiece and tailpiece separate at least much of the upper and lower cavities, providing additional wetted regions or fences for further separating the upper and lower cavities on the lower hull as needed, and further providing a pressure difference between the upper cavities and lower cavities for producing an upward force at a design speed and at a design lower hull depth. 174. The method of claim 173, further providing for an off-design lower hull centerline depth that is approximately equal to the design lower hull centerline depth multiplied by the square root of the ratio of an off-design speed to the design speed. 175. The method of claim 162 further providing one or more upper cavities an on the lower hull having a pressure that is essentially the same as a pressure in an adjacent side cavity on the upper hull. 176. The method of claim 161, further providing at least one additional upper hull that is attached to the lower hull, wherein the upper hulls are spaced longitudinally apart. 177. The method of claim 176 wherein the at least one additional upper hull is wetted. 178. The method of claim 176, further comprising providing each upper hull with at least one cavity on each side. 179. The apparatus of claim 71, wherein the vessel is a catamaran or the at least one hull is the main hull of a trimaran. 180. Low drag hull method, comprising providing a waterborne vessel having at least one vessel-supporting hull having opposite sides, providing a wetted nosepiece on the hull, providing side cavities on the opposite sides of the hull, opening the side cavities at the wetted nosepiece, providing wetted side steps on the opposite sides behind the nosepiece wherein more side steps are provided in a lower region on each side than in an upper region, opening additional side cavities at the wetted side steps, and displacing water from each side of the hull adjacent each cavity. 181. The method of claim 180 wherein the side cavities are filled with air at approximately atmospheric pressure. 182. The method of claim 180, wherein the opening side cavities further comprise opening upper side cavities which further comprise larger center cavities and smaller end cavities, and opening lower side cavities which further comprise smaller center cavities and larger end cavities, and wherein mismatches between the upper and lower side cavities reduce wavemaking drag. 183. The method of claim 180, wherein the opening side cavities further comprise opening upper side cavities which further comprise smaller center cavities and larger end cavities, and opening lower side cavities which further comprise larger center cavities and smaller end cavities, and wherein mismatches between the upper and lower side cavities reduce wavemaking drag. 184. The method of claim 180 wherein the side cavities have upper and lower regions of the side cavities that are mismatched with respect to fore-and-aft area distribution for reducing wavemaking drag. 185. The method of claim 180 wherein the nosepiece or the one or more side steps are attachable to the hull. 186. The method of claim 180, further providing at least one approximately-horizontal fence on each side of the hull between the water surface and the hull bottom. 187. The method of claim 186 wherein the side cavities are at approximately atmospheric pressure. 188. The method of claim 186 wherein upper and lower regions of the side cavities are mismatched with respect to fore-and-aft area distribution for reducing wavemaking drag. 189. The method of claim 186 wherein cavity pressures increase under each fence. 190. The method of claim 189 wherein the steps and fences provide cavity regions with a mismatch between upper and lower cavity regions with respect to fore-and-aft area distribution for reducing wavemaking drag. 191. The method of claim 189, further comprising providing a forward step that is angled down and back, providing an aft step positioned behind the forward step that is angled down and forward for forming a larger center cavity and smaller end cavities in upper regions of the side cavities and a smaller center cavity and larger end cavities in lower regions of the side cavities for providing a mismatch in cavity shapes between upper and lower cavity regions to reduce wavemaking drag. 192. The method of claim 180, further comprising providing a forward step that is angled down and back, an aft step positioned behind the forward step that is angled down and forward to form a larger center cavity and smaller end cavities in an upper region of the side cavities and a smaller center cavity and larger end cavities in a lower region of the side cavities to provide a mismatch in cavity shapes between upper and lower cavity regions and reducing wavemaking drag. 193. The method of claim 180, further comprising adding more wetted side steps in the lower region as depth increases. 194. The apparatus of claim 20, further comprising at least one step extending across the hull bottom to close a preceding bottom cavity and an air outlet either in or following an after portion of the at least one step to open a following bottom cavity aft of the step by releasing pressurized air from the air outlet, wherein one or more of the following are attachable and removable from the hull: bow nosepiece, bottom nosepiece, one or more side steps, and one or more bottom steps. 195. The apparatus of claim 5, further comprising recycling the air and releasing the air behind the bottom nosepiece or at least one bottom step. 196. The method of claim 115, further comprising providing grooves or ridges attached to the hull that start inside at least one side cavity upstream of a design cavity closure location, and end either near or behind the design cavity closure location of the at least one side cavity, and are approximately aligned with the water flow along the local cavity wall, for saving energy at cavity closure by reducing forward splash at cavity closure with the grooves or ridges. 197. The method of claim 116, further comprising providing grooves or ridges attached to the hull that start inside the at least one closed side cavity or the at least one closed bottom cavity upstream of a design cavity closure location, and end either near or behind the design cavity closure location of the at least one closed side cavity or the at least one closed bottom cavity, and are approximately aligned with the water flow along the local cavity wall, for saving energy at cavity closure by the grooves or ridges reducing forward splash at cavity closure. 198. Low drag hull method, comprising providing a waterborne vessel having at least one vessel-supporting hull, providing a hull bottom on the hull, providing at least one closed cavity on at least one hull side or the hull bottom, and further providing grooves or ridges attached to the hull that start inside the at least one closed cavity upstream of a design cavity closure location, and end either near or behind the design cavity closure location of the at least one closed cavity, and are approximately aligned with the water flow along the local cavity wall, for saving energy at cavity closure by the grooves or ridges reducing forward splash at cavity closure. 199. The low drag hull method of claim 198 wherein at least some of the grooves or ridges are provided by attaching a film that is attachable to the hull. 200. The method of claim 115 wherein the hull is a main hull of the vessel, further comprising providing at least one side hull attached to the main hull. 201. The method of claim 200 wherein the vessel is a trimaran, further comprising providing a side hull attached to each side of the main hull, and further comprising providing at least one a hydrofoil attached to at least one side hull or to the main hull. 202. The method of claim 200 further comprises providing air cavities on at least one side of the at least one side hull. 203. The method of claim 202 wherein the vessel is a trimaran, and wherein the providing a side hull further comprises providing at least one cavity attached to each side of the main hull. 204. The apparatus of claim 2 wherein the wetted tailpiece is controllable. 205. The method of claim 130 wherein the side tailpiece is controllable. 206. Low drag hull apparatus, comprising a waterborne vessel having at least one vessel-supporting hull comprising at least one surface-piercing upper hull and at least one lower hull attached to the bottom of the at least one upper hull, wherein the length of the at least one upper hull may range from a strut-like length to a length that approximates the length of the lower hull, and further comprising at least one upper cavity on an upper side of the at least one lower hull, at least one lower cavity on a lower side of the lower hull, a pressurized air source that supplies air to at least one of the lower hull cavities at a pressure greater than atmospheric pressure, a lower hull nosepiece near the bow of the lower hull that is swept back along opposite sides of the lower hull to open one or more upper or lower cavities on the lower hull and to separate a significant part of the lower cavities from the upper cavities, and a wetted tail region or tailpiece near the tail of the lower hull to close one or more upper or lower cavities. 207. Submerged hull apparatus comprising a bow and a stern, a hull beam and a hull height, a wetted nosepiece extending rearward from the bow, a wetted tailpiece extending sideward from the stern, at least one upper and one lower gas cavity between the nosepiece and the tailpiece and respectively above and below the hull, wherein the hull beam is greater than the hull height, wherein the pressure in the upper cavities are lower than the pressure in the lower cavities, wherein the wetted nosepiece and the wetted tailpiece separate the upper and lower gas cavities, and further comprising wetted regions or fences as needed for assisting the wetted nosepieces and tailpieces in separating the upper and lower cavities. 208. A submerged hull operating method comprising providing a hull having a bow, a stern, a beam, and a height, wherein the hull beam is greater than the hull height, providing a nosepiece at the bow that extends rearward from the bow on each side of the hull and a tailpiece that extends sideward from the stern, providing one or more upper and lower gas cavities between the nosepiece and the tailpiece and respectively above and below the hull, providing a at least one pressurized gas source in the hull and conduits from the at least one gas source to the cavities, and supplying the upper cavities with gas at a first pressure and supplying the lower cavities with gas at a second and higher pressure and maintaining a pressure differential between the upper and lower cavities. 209. A method of water supported vessel operation comprising providing a waterborne vessel, providing at least one vessel-supporting hull, providing at least one closed cavity, or a partially-closed cavity, having a cavity thickness on the side or the bottom of the hull, providing a wetted tailpiece on the hull side or the hull bottom, wherein the cavity thickness is designed to vary somewhat, either way, from a nosepiece step thickness to zero cavity thickness at a wetted tailpiece or a wetted tail region, wherein the cavities taper to zero thickness at the wetted tailpieces with either low or minimum cavity contact angles in order to minimize cavity drag at cavity closure. 210. The method of claim 180 wherein the side steps are provided either outward formed on the hull sides or inward formed in the sides, and wherein the side steps in side view are provided angled to the vertical along the hull. 211. The method of claim 115, further providing a bottom on the hull wherein lift on the bottom of the hull is approximately equal to displacement of the cavities and hull portions that lie above the bottom of the hull and ahead of a stern of the hull. 212. The method of claim 151 wherein lift on the bottom of the hull is approximately equal to the displacement of the cavities and hull portions that lie above the bottom of the hull and ahead of a stern of the hull. 213. The method of claim 115 wherein the providing the nosepiece further comprises providing extendable and retractable elements on opposite sides of the nosepiece, and wherein the amount of extension or retraction may vary along the nosepiece length. 214. The method of claim 151 wherein the providing the side or bottom nosepieces further comprises providing extendable and retractable elements on opposite sides of the nosepiece, and wherein the amount of extension or retraction may vary along the nosepiece length. 215. The method of claim 115 wherein the nosepiece may be swept either way from vertical in one or more different kinds of cross sectional shapes that change in shape from the top to the bottom of the nosepiece, and wherein the shapes have surface changes in a rearward direction for causing water flow to separate from the nosepiece on opposite sides, and wherein the surface changes are obtuse angles, increased convex curvatures, steps and notches, and wherein the nosepiece is a wedge shape with flat sides, convex sides or concave sides, or a flat transverse plate. 216. The method of claim 129 wherein the side and bottom nosepieces may comprise one or more of many different kinds of cross sectional shapes that change in shape along the nosepiece, wherein the shapes have surface changes in a rearward direction for causing the water flow to separate from the nosepiece on one or both sides, and wherein the surface changes on at least one side are obtuse angles, increased convex curvatures, steps and notches, and wherein the nosepiece is an angled plate with flat sides, convex sides or concave sides, or a flat or curved plate. 217. The method of claim 215 wherein a thickness of at least a portion of the nosepiece is increased under off design conditions to form a larger cavity. 218. The method of claim 216 wherein a thickness of at least a portion of the nosepiece is increased under off design conditions to form a larger cavity. 219. The method of claim 128, further comprising providing an air injector on or behind nosepiece portions that lie below the one or more fences for flowing air into the cavities. 220. The method of claim 118, further comprising providing an air injector on or behind the at least one bottom step for flowing air into the bottom cavity. 221. The method of claim 128, further comprising providing an air intake for assisting in closing the at least one side cavity or for recycling the air to conserve power. 222. The method of claim 220, further comprising providing an air intake on or ahead of the at least one bottom step for assisting in closing a previous cavity or for recycling the air to conserve power. 223. A method of water supported vessel operation comprising providing a waterborne vessel, providing at least one vessel-supporting, low drag planing hull that has at least one closed cavity on its planing surface to reduce drag, providing one or more inwardly or outwardly extending fences whose inner ends are positioned below and approximately parallel to a high speed waterline on each side of the planing hull when the planing hull is planing, supplying pressurized air to form a pressurized gas cavity on each side of the hull below each fence, and further providing wetted regions on the hull to close each cavity. 224. A waterborne vessel comprising a low drag planing hull that has at least one closed cavity on its planing surface to reduce drag, one or more inwardly or outwardly extending fences positioned below a high speed waterline on each side of the hull, the inner ends of the fences lying approximately parallel to a high speed waterline when the hull is planing, supplying pressurized air below each fence to form a pressurized gas cavity on each side of the hull below each fence, and further comprising wetted regions on the hull to close each cavity. 225. Low drag hull apparatus, comprising a waterborne vessel having at least one vessel-supporting upper hull, a wetted nosepiece on the upper hull, side cavities on the opposite sides of the upper hull for opening at the wetted nosepiece and displacing water away from the opposite sides of the upper hull, and further comprising a lower hull attached to the upper hull below the side cavities that provides the majority of displacement or remains submerged at rest, has non-circular cross sections, and wherein the beam of the lower hull is significantly greater than its height. 226. The apparatus of claim 225, further comprising a wetted lower-nosepiece on the lower hull for opening a lower cavity on the lower hull, and a wetted lower tailpiece on the lower hull for closing the lower cavity on the lower hull. 227. The apparatus of claim 225, further comprising a wetted upper nosepiece on the lower hull for opening an upper cavity on the lower hull, and a wetted upper tailpiece on the lower hull for closing the upper cavity on the lower hull. 228. The apparatus of claim 225, wherein the lower hull has a nose and a tail at opposite longitudinal ends, at least one lower cavity on the lower hull and at least one upper cavity on the lower hull, and further comprising a wetted lower hull nosepiece extending rearward from the nose of the lower hull, and a wetted lower hull tailpiece extending forward from the tail of the lower hull, wherein the lower hull nosepiece opens at least one lower cavity and at least one upper cavity on the lower hull, the lower hull tailpiece closes at least one lower cavity and at least one upper cavity on the lower hull, and further comprising either wetted regions, or fences extending outward from the lower hull, for assisting the lower hull nosepiece and lower hull tailpiece as needed in separating the lower and upper bottom cavities. 229. The apparatus of claim 180, wherein the steps begin at or near the bottom of each hull side and extend upward without reaching the water surface. 230. The apparatus of claim 229, including ducting means to supply air to cavities formed behind the steps. 231. The apparatus of claim 206, wherein a pressure in the upper cavity is approximately atmospheric. 232. The apparatus of claim 206 wherein the beam of the lower hull significantly exceeds its height, wherein the lower hull in plan view is shaped somewhat like a diamond, triangle, delta, ellipse, oval, closed series of straight and curved lines, or some combination of these shapes, or wherein a tail region of the lower hull deviates somewhat in plan view from these planform shapes, and wherein a lift on the lower hull is approximately the same or greater than the displacement of the upper and lower hulls and their associated cavities. 233. The apparatus of claim 206 wherein the one or more lower cavities are open, and the one or more upper cavities are closed. 234. The apparatus of claim 206 wherein the one or more lower cavities are closed, and wherein the one or more upper cavities are open. 235. The apparatus of claim 206 further comprising a wetted nosepiece on the upper hull, one or more side cavities on the opposite sides of the upper hull for opening at the wetted nosepiece and displacing water away from the opposite sides of the upper hull, and wherein the side cavities are at approximately atmospheric pressure. 236. The apparatus of claim 232 wherein the one or more upper cavities are closed and have pressures greater than atmospheric pressure, and the one or more lower cavities are closed and have pressures that are greater than the upper cavity pressures and less than the depth pressure outside of the lower cavities. 237. The apparatus of claim 235, further comprising underlying steps positioned on surfaces of the upper hull, or on surfaces of the upper side or lower side of the lower hull, that underlie air cavities that form at a specific operating condition, wherein the underlying steps become wetted and form additional cavities at certain speeds and depths that are different from those at the operating condition. 238. The vessel of claim 206 wherein the lower hull cavities form at an operating speed and at an operating lower-hull-centerline depth, wherein the apparatus is controlled to operate at some other depth and some other speed wherein the other depth is proportional to the operating depth multiplied by the square root of the ratio of the other speed to the operating speed. 239. The apparatus of claim 206 further comprising a propulsion system, wherein at least one hydrofoil, stabilizing fin, rudder, or canard fin is attached to the lower hull or to the upper hull, and wherein one or more of these hydrofoils, rudders or fins is controllable to control vessel attitude or to maneuver the vessel. 240. The apparatus of claim 206 wherein at least one hull comprises one or more upper and lower hulls that, together with their cavities, are mismatched in cross sectional area to reduce hull wavemaking drag. 241. The apparatus of claim 240 comprising two upper hulls and one lower hull, wherein the center of the displacement of the upper hulls lies above a center region of the lower hull displacement, and wherein the resulting mismatch in cross-sectional areas reduces the wavemaking drag on the hull. 242. The apparatus of claim 240 comprising a single upper hull and either a tandem lower hull or two lower hulls, wherein the center of displacement of the upper hull lies above a center region between the lower hull centers, and wherein the resulting mismatch in cross-sectional areas reduces the wavemaking drag on the hull. 243. The apparatus of claim 235, further comprising one or more wetted steps or fences positioned along opposite sides of the upper and lower hulls to open a variety of cavities to further reduce wetted area and reduce frictional drag on the hull or to provide a displacement distribution of the hull and its associated cavities to reduce hull wavemaking drag. 244. Low drag hull apparatus, comprising a waterborne vessel having at least one vessel-supporting hull having opposite hull sides, a stern, a wetted bow nosepiece on the hull, an upper hull region and a lower hull region on the hull, a wetted tail region near a stern end of the lower hull region, and one or more vertically-extending spaced steps on each side of the hull, wherein more steps are positioned in the lower hull region than in the upper hull region, wherein at least one side cavity opens on each side at the wetted nosepiece for displacing water from a side portion of the hull adjacent the cavity for reducing drag on the hull, wherein additional side cavities open behind the steps, wherein the hull sides in the upper hull region near the stern are covered by open cavities, and wherein side cavities in the lower hull region near the stern are closed by the wetted tail region. 245. The apparatus of claim 2, wherein a transverse cross section of at least part of the at least one hull resembles an hour glass shape that may have unequal widths at the upper and lower ends. 246. The apparatus of claim 244, wherein a transverse cross section of the at least one hull resembles an hour glass shape with the upper portion at least partially cut off. 247. The vessel of claim 46, wherein the side regions of the wetted bottom nosepiece are swept back, and the side regions of the wetted bottom region are swept forward to divide either most or all of the bottom cavities from the side cavities. 248. The vessel of claim 46, wherein all side cavities are closed. 249. A low drag hull comprising: at least one surface-piercing, vessel-supporting hull, at least one pressurized air source, at least one lower region on the at least one hull, a lower air cavity covering the surface of the at least one lower region, a wetted lower nosepiece or a wetted lower step to open one or more lower cavities in the at least one lower region for displacing water from the hull adjacent each cavity for reducing drag on the hull, wherein the lower nosepiece or the lower step is swept back along at least one side of the one or more lower cavities, further comprising a wetted lower tail region on the hull to close the one or more lower cavities, wherein each lower cavity is filled with air at greater than atmospheric pressure that is delivered from the at least one pressurized air source, wherein the pressure in each lower cavity is less than the outside depth pressure, and wherein the lower surface of each lower cavity is convex in a longitudinal cross section and in at least a portion of a transverse cross section. 250. The apparatus of claim 249, wherein the one or more lower regions comprise a bottom region on the hull, further comprising a side surface on at least one side of the at least one hull that extends upward from the bottom region that is covered by at least one side cavity filled with air at a pressure that is less than the pressure in adjacent cavities in the bottom region, further comprising at least one wetted region, fence, nosepiece or tailpiece to help separate the at least one side cavity from adjacent cavities in the bottom region. 251. The apparatus of claim 249, wherein a transverse cross section of the at least one hull resembles an hourglass shape. 252. Low drag hull method, comprising providing a waterborne vessel having at least one vessel-supporting hull having opposite sides, providing a wetted nosepiece on the hull, providing side cavities on the opposite sides of the hull, opening the side cavities at the wetted nosepiece, providing wetted side steps on the opposite sides behind the nosepiece, opening additional side cavities at the wetted side steps, and displacing water from each side of the hull adjacent each cavity, wherein the side cavities have upper and lower regions wherein the side cavities in the upper regions are mismatched from the side cavities in the lower region with respect to fore-and-aft area distribution for reducing wavemaking drag. 253. The method of claim 191, wherein cavity pressures increase under each fence. 254. Low drag hull apparatus comprising a waterborne vessel having at least one vessel-supporting hull, a hull bottom on the hull, one or more bottom cavities on the hull bottom, wherein the pressure in the bottom cavities is less than depth pressure, and wherein the surfaces of the one or more bottom cavities in a longitudinal plane are convex, further comprising a wetted swept-back bottom nosepiece having a vee-like shape in bottom view and whose leading edges lie near sides of the hull bottom to form at least one bottom cavity to reduce drag, wherein bottom steps may be used to initiate one or more additional bottom cavities or to close one or more bottom cavities, further comprising a wetted bottom tail region on the bottom of the hull to close one or more bottom cavities, wherein the wetted bottom tail region is swept forward near each side of the hull bottom, and further comprising wetted regions or fences positioned between the bottom nosepiece and the wetted bottom tail region to limit the bottom cavities to the bottom of the hull without using downward-extending side keels. 255. The method of claim 148, further providing a stern on the hull, providing a bottom on the hull, closing side cavities in a region at or near the bottom of the hull, providing a swept-back wetted bottom nosepiece at the bottom of the hull, opening a bottom cavity at the wetted bottom nosepiece, extending the bottom cavity rearward beyond the stern of the hull, and providing wetted regions or fences as needed to separate the open bottom cavity from adjacent side cavities. 256. The apparatus of claim 71, further comprising one or more closed bottom cavities on the bottom of the hull. 257. The apparatus of claim 92 wherein the side cavities are open, and further comprising one or more closed bottom cavities on the bottom of the hull. 258. The apparatus of claim 161, further providing a wetted lower hull region closing a cavity on the upper side of the lower hull, providing an open cavity on the lower side of the lower hull, and providing fences or wetted regions as needed for separating the cavities on the upper and lower sides of the lower hull. 259. The apparatus of claim 206 wherein the at least one vessel-supporting hull is a catamaran vessel comprising two parallel surface-piercing upper hulls, each with an attached lower hull. 260. The apparatus of claim 254, wherein a transverse cross section of the at least one hull resembles an hourglass shape that has equal or unequal top and bottom widths. 261. Submarine method, comprising providing a submerged hull having upper and lower surfaces, providing at least one cavity on each surface, providing a wetted nosepiece on the hull, opening at least one upper cavity and at least one lower cavity at the wetted nosepiece, displacing water from each side of the hull adjacent each cavity and reducing drag, further providing a wetted tailpiece for closing upper and lower cavities, wherein the upper cavities are filled with gas at a pressure less than depth pressure, and the lower cavities are filled with gas at a pressure greater than the upper cavities, and further providing fences or wetted regions to assist the wetted nosepiece and wetted tailpiece in separating the upper and lower cavities, and wherein the width of the hull is significantly greater than its height. 262. The method of claim 146, further providing a wetted tailpiece for closing the side cavities, wherein the side cavities are one or more upper and lower cavities that close on the tailpiece, and the hull is a submarine vessel wherein the upper cavities are filled with gas at a pressure less than depth pressure, and the lower cavities are filled with gas at a pressure greater than the upper cavities, and further providing fences or wetted regions to assist the wetted nosepiece and wetted tailpiece in separating the upper and lower cavities, and wherein the hull beam is greater than the hull height. 263. Submarine method, comprising providing a submerged hull having upper and lower surfaces, providing at least one cavity on each surface, providing a wetted nosepiece on the hull, opening at least one upper cavity and at least one lower cavity at the wetted nosepiece, displacing water from each side of the hull adjacent each cavity and reducing drag, further providing a wetted tailpiece for closing at least one upper or lower cavity, wherein the upper cavities are filled with gas at a pressure less than depth pressure, and the lower cavities are filled with gas at a pressure greater than the upper cavities, and further providing fences or wetted regions to assist the wetted nosepiece and wetted tailpiece in separating the upper and lower cavities as needed, and wherein the width of the hull is significantly greater than its height. 264. The apparatus of claim 254, further comprising one or more open or closed side cavities on the sides of the at least one hull. 265. The apparatus of claim 264 wherein at least one of the side cavities is open. 266. The method of claim 223, further providing a nosepiece attached to a keel portion lying below each fence, or providing one or more vertically extending steps attached to the planing hull on each side behind a keel portion, and supplying pressurized air behind each nosepiece or step to form one or more pressurized gas cavities on each side of the hull. 267. The vessel of claim 224, further comprising a nosepiece attached to a keel portion lying below each fence, or comprising one or more vertically extending steps attached to the planing hull on each side behind a keel portion, and supplying pressurized air behind each nosepiece or step to form one or more pressurized gas cavities on each side of the hull. 268. The apparatus of claim 244, further comprising air injectors on or behind at least a part of the nosepiece or on or behind at least a part of the steps for flowing air into the cavities. 269. The apparatus of claim 244, further comprising side hull air intakes on or near the tail region or on or near the steps to help close side cavities. 270. The apparatus of claim 249, further comprising a stabilizing fin having a vertically-projected area extending from a side of the hull. 271. The apparatus of claim 270, further comprising controls mounted on or near the hull, the bow nosepiece, or the fin, for controlling the hull. 272. The apparatus of claim 271, further comprising control surfaces on the fin. 273. The apparatus of claim 270, further comprising closed fin cavities on opposite surfaces of the fin. 274. The apparatus of claim 249, further comprising parallel hulls, that may be low drag hulls, connected to the hull. 275. The apparatus of claim 249, further comprising a side surface on each side of the one or more hulls, comprising one or more steps along a side surface for starting one or more side cavities along the hull. 276. The apparatus of claim 249, further comprising a bow nosepiece at the bow of the at least one hull, and comprising at least one side cavity that is formed at or behind the bow nosepiece, and wherein at least a portion of the bow nosepiece is either flat in a cross-section parallel to the water flow, or is wedge shaped and has a streamline surface discontinuity at its aft end selected from the group consisting of obtuse angles, change in surface curvature, concave, convex, flat, notches, and combination step and notch. 277. The apparatus of claim 244, wherein at least one of the side steps is an underlying side step that lies under design cavities that form at design speed, and wherein a new side cavity is formed behind at least one of the underlying side steps under an off-design condition. 278. The apparatus of claim 252, further comprising at least one bottom air cavity on the hull bottom, a bottom nosepiece on the hull bottom for opening the bottom cavity, means for supplying pressurized air into the bottom cavity behind or through the nosepiece, a wetted bottom tail region on the hull bottom for closing a bottom cavity, a wetted region or a fence between the lower side cavities and the bottom cavities to separate these cavities, wherein said wetted region or a fence includes the bottom nosepiece and the wetted bottom tail region. 279. The apparatus of claim 227, further comprising wetted side regions or side fences extending outward from the opposite sides of the upper hull for assisting as needed in separating the side cavities from the upper bottom cavity. 280. The apparatus of claim 225, wherein the lower hull has any of a variety of planform shapes including those resembling a streamlined shape with either a rounded or a wedge-shared or a flat nose, a diamond shape with optional wetted outer tips or with wetted parallel tips, a vee-shaped nose with an included angle lying between 10 degrees and 180 degrees followed by one or more straight sides that may be angled either way, a streamlined fore body followed by a wetted vee-shaped tailpiece, a triangular or delta shape, or a streamlined fore body that flares outward near the stern and ending with a wetted transverse or vee-shaped tailpiece. 281. The apparatus of claim 227, wherein the upper bottom cavity is at atmospheric pressure, and merges with the side cavities. 282. The apparatus of claim 279, wherein the upper bottom cavity is at greater than atmospheric pressure. 283. The apparatus of claim 225, wherein the lower hull has at least one control flap attached to a trailing edge of the lower hull. 284. The apparatus of claim 225, wherein the lower hull terminates with a wetted tailpiece having an overall span that approximately equals or exceeds a preceding lower hull span and helps provide vessel pitch stability, and wherein the lower hull has none or one or more upper cavities and none or one or more lower cavities. 285. The apparatus of claim 284, wherein the lower hull has a control flap attached to its trailing edge for controlling one or more of vessel heave, pitch and roll. 286. The apparatus of claim 225, wherein the lower hull provides dynamic lift. 287. The apparatus of claim 225, wherein the vessel is a catamaran, and wherein at least a portion of the upper hull that lies above each lower hull is divided into a forward hull and an aft hull. 288. The method of claim 261, wherein the hull lies inside the upper and lower cavities, and further providing one or more pressure hulls that lie inside the outer surface of the hull. 289. The method of claim 288 wherein the hull encloses a center pressure hull and two parallel side pressure hulls. 290. The method of claim 261, wherein the nosepiece is retractable for operating the submarine with the hull fully wetted. 291. The method of claim 261, further providing sensors placed inside or near the nosepiece or tailpiece. 292. The method of claim 261, wherein flaps are attached to the tailpiece for controlling the submarine in depth, pitch angle and roll angle. 293. The method of claim 261, wherein the cavity shapes and the underlying hull shapes are developed for a given design speed and depth. 294. The method of claim 293, wherein the submarine operates about equally well at speeds and depths other than at the design speed and depth as long as the speed is approximately in proportion to the square root of submarine depth. 295. The method of claim 291, wherein the sensors are sonar arrays. 296. The apparatus of claim 225, wherein the upper and lower hulls form either each hull of a catamaran or the main hull of a multi-hulled vessel, and further comprising one or more hydrofoils attached to the lower hull for supporting at least a part of a weight of the vessel. 297. The apparatus of claim 296, further comprising side hulls of a trimaran that have side cavities to reduce drag. 298. The apparatus of claim 296, wherein the at least one hydrofoil is fully wetted or has at least one cavity on one side, and is unswept, swept back or forward. 299. The apparatus of claim 296 further comprising at least one stabilizing fin attached to at least one hull. 300. The apparatus of claim 299, wherein at least one hull includes canard fins. 301. The apparatus of claim 296, wherein at least one hull is above water at design speed, and the vessel is controlled in one or more of heave, pitch and roll. 302. The apparatus of claim 299, wherein all hulls, fins and hydrofoils have cavities on each side for reducing drag. 303. The apparatus of claim 297, further comprising fins attached to at least one hull or attached between any two hulls to increase pitch and yaw stability. 304. The apparatus of claim 297, wherein the side hulls are positioned toward a forward end of the vessel to support a forward portion of hull weight and help provide stability in heave, pitch and roll. 305. The apparatus of claim 244, wherein a thickness of at least a portion of the nosepiece or of the at least one side step is increased under off design conditions for forming a larger cavity. 306. The method of claim 263, wherein the at least one upper or lower cavity is open. 307. The apparatus of claim 264, further comprising a wetted stern tailpiece, wherein at least a portion of the side cavities close at the wetted stern tailpiece.