# US 5,704,309 A · Hybrid boat and underwater watercraft > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 5,704,309 A - Document ID: US5704309A - Status: Granted - Kind: A - Application number: 08/568,270 - Filed: 1995-12-06 - Granted: 1998-01-06 - Earliest claimed: 1995-12-06 - Assignees: SEAmagine Hydrospace Corporation - Inventors: William Kohnen - Web page: https://patentgrep.com/patent/US5704309A ## CPC - B63G 8/22: Adjustment of buoyancy by water ballasting; Emptying equipment for ballast tanks ({conduits for emptying or ballasting on vessels in general B63B13/00;} stabilising vessels using ballast tanks B63B43/06) - B63G 8/16: by direct use of propellers or jets - B63G: OFFENSIVE OR DEFENSIVE ARRANGEMENTS ON VESSELS; MINE-LAYING; MINE-SWEEPING; SUBMARINES; AIRCRAFT CARRIERS (means of attack or defence in general, e.g. turrets F41H) ## Abstract A hybrid boat and underwater craft and method for operating an underwater craft having positive buoyancy, a three-point stabilization system and vertical thruster and a system for enhanced buoyancy at the surface. ## Claims ### Claim 1 An underwater watercraft having a structure for mounting components, a positive buoyancy when submerged under the surface of a body of water and a center of gravity, the watercraft comprising: a front end; a rear end opposite the front end; a three point stabilization system comprising: a front buoyancy element having a center of buoyancy and imparting a buoyant force on the watercraft, effectively at a center of buoyancy of the front buoyancy element, wherein the center of buoyancy of the front buoyancy element is between the front end and the center of gravity; a tail buoyancy element imparting a buoyant force on the watercraft, effectively at the center of buoyancy of the tail buoyancy element, wherein the center of buoyancy of the tail buoyancy element is between the rear end and the center of gravity; and a vertical thruster system wherein the depth of the watercraft below the surface of the water is adjusted using the vertical thruster system. ### Claim 2 An underwater watercraft having a center of gravity, the watercraft comprising: a front end; a rear end opposite the front end; a three point stabilization system comprising: a front buoyancy element having a center of buoyancy and imparting a buoyant force on the watercraft, effectively at a center of buoyancy of the front buoyancy element, wherein the center of buoyancy of the front buoyancy element is between the front end and the center of gravity; and a tail buoyancy element imparting a buoyant force on the watercraft, effectively at the center of buoyancy of the tail buoyancy element, wherein the center of buoyancy of the tail buoyancy element is between the rear end and center of gravity. ### Claim 3 (depends on 1) The watercraft of claim 1 wherein the buoyant force imparted by the front buoyancy element exceeds the buoyant force imparted by the tail buoyancy element. ### Claim 4 (depends on 1) The watercraft of claim 1 wherein the front buoyancy element comprises water impermeable structure defining an interior space. ### Claim 5 (depends on 1) The watercraft of claim 1 wherein the front buoyancy element comprises a structure defining an interior space for carrying any of passengers, equipment and cargo. ### Claim 6 (depends on 1) The watercraft of claim 1 wherein the front buoyancy element includes: at least one counterweight; and a structure defining an interior space for carrying any of passengers, equipment and cargo. ### Claim 7 (depends on 1) The watercraft of claim 1 wherein the tail buoyancy element includes: at least one buoyant element; and at least one counterweight. ### Claim 8 (depends on 1) The watercraft of claim 1 wherein the tail buoyancy element includes a movable counterweight. ### Claim 9 (depends on 1) The watercraft of claim 1 wherein the vertical thruster system imparts a vertical thrust having a center of thrust and the center of thrust is between the front and tail buoyancy elements. ### Claim 10 (depends on 3) The watercraft of claim 3 wherein the vertical thruster system includes a single vertical thruster. ### Claim 11 (depends on 3) The watercraft of claim 3 wherein the vertical thruster system includes a plurality of vertical thrusters. ### Claim 12 (depends on 1) The watercraft of claim 1 wherein the vertical thruster system imparts a vertical thrust having a center of thrust and the center of thrust is between the respective centers of buoyancy of the front and tail buoyancy elements. ### Claim 13 (depends on 1) The watercraft of claim 1 wherein the vertical thruster system imparts a vertical thrust at a center of thrust and the center of thrust is situated at the center of gravity. ### Claim 14 (depends on 1) The watercraft of claim 1 wherein the sum buoyant forces of the front and tail buoyancy elements exceeds the weight of the watercraft. ### Claim 15 (depends on 1) The watercraft of claim 1 wherein the watercraft descends to a greater depth when the downward force imparted by the vertical thruster system exceeds the difference between the sum of the buoyant forces imparted by the buoyant elements, including the front buoyancy element and the tail buoyancy element, and the weight of the watercraft. ### Claim 16 (depends on 1) The watercraft of claim 1 wherein the watercraft ascends to a lesser depth when the downward force imparted by the vertical thruster system is less than the difference between the sum of the buoyant forces imparted by the buoyant elements, including the front buoyancy element and the tail buoyancy element, and the weight of the watercraft. ### Claim 17 (depends on 1) The watercraft of claim 1 having a depth limiting means for diminishing the thrust output by the vertical thruster system when the watercraft is at a desired depth below the surface. ### Claim 18 (depends on 1) The watercraft of claim 1 further comprising: a forward thruster providing thrust optionally in a forward or reverse direction; and a tail thruster for providing thrust to move the tail end left or right. ### Claim 19 The watercraft of claim I wherein the tail buoyancy element comprises tail shell enclosing a buoyant material. ### Claim 20 (depends on 1) The watercraft of claim 1 further comprising a supplemental buoyancy system wherein the supplemental buoyancy system includes: at least one supplemental buoyancy chamber for imparting a buoyant force to the watercraft when the weight of the watercraft exceeds the sum of the buoyant forces imparted by the front buoyancy element and the tail buoyancy element; and wherein the buoyant force supplied by the supplemental buoyancy system exceeds the difference between the weight of the watercraft and the sum of the buoyant forces imparted by the front buoyancy element and the tail buoyancy element. ### Claim 21 (depends on 20) The watercraft of claim 20 wherein the supplemental buoyancy system includes: a movable counterweight in the tail buoyancy element. ### Claim 22 An underwater watercraft having a positive buoyancy when submerged under the surface of a body of water and having a center of gravity, the watercraft comprising: a front end; a rear end opposite the front end; a plurality of buoyancy imparting elements; and a vertical thruster wherein the depth of the watercraft below the surface of the water is adjusted using the vertical thruster; wherein the plurality of buoyancy imparting elements include: a front buoyancy element having a center of buoyancy and imparting a buoyant force on the watercraft, effectively at a center of buoyancy of the front buoyancy element, wherein the center of buoyancy of the front buoyancy element is between the front end and the center of gravity; and a tail buoyancy element imparting a buoyant force on the watercraft, effectively at the center of buoyancy of the tail buoyancy element, wherein the center of buoyancy of the tail buoyancy element is between the rear end and the center of gravity. ### Claim 23 (depends on 22) The watercraft of claim 22 having a boat mode of operation wherein the watercraft is floatable on a surface of a body of water, and an underwater mode of operation wherein the watercraft is submergible below the surface of the body of water, the watercraft further comprising a boat section between the front end and the rear end, the boat section including an air permeable top, side walls and a bottom surface wherein the top of the boat section can emerge above the surface of the water when the watercraft is in boat mode. ### Claim 24 An underwater watercraft having a structure for mounting components, the watercraft having a boat mode of operation wherein the watercraft is floatable on a surface of a body of water and an underwater mode of operation wherein the watercraft is submergible below the surface of the body of water, the watercraft comprising: a surface-buoyancy supplementing system including: a boat section defined in the structure, wherein the boat section includes air permeable top, side walls and a bottom surface wherein the top of the boat section can emerge above the surface of the water when the watercraft is in boat mode; and draining means for draining water from the boat section when the top of the boat section is above the surface of the water; a front end; a rear end opposite the front end; and a three point stabilization system including: a front buoyancy element having a center of buoyancy and imparting a buoyant force on the watercraft, effectively at a center of buoyancy of the front buoyancy element, wherein the center of buoyancy of the front buoyancy element is between the front end and center of gravity; and a tail buoyancy element imparting a buoyant force on the watercraft, effectively at the center of buoyancy of the tail buoyancy element, wherein the center of buoyancy of the tail buoyancy element is between the rear end and the center of gravity. ### Claim 25 (depends on 24) The watercraft of claim 24 further comprising a supplemental buoyancy system wherein the supplemental buoyancy system includes: at least one supplemental buoyancy chamber for imparting a buoyant force to the watercraft when the weight of the watercraft exceeds the sum of the buoyant forces imparted by the front buoyancy element and the tail buoyancy element; and wherein the buoyant force supplied by the supplemental buoyancy system exceeds the difference between the weight of the watercraft and the sum of the buoyant forces imparted by the front buoyancy element and the tail buoyancy element. ### Claim 26 (depends on 24) The watercraft of claim 24 wherein the watercraft has a positive buoyancy when submerged under the surface of a body of water, the watercraft comprising: a vertical thruster wherein the depth of the watercraft below the surface of the water is adjustable using the vertical thruster; and the vertical thruster system is mounted on the structure between the center of buoyancy of the front buoyancy element and the rear buoyancy element. ### Claim 27 An underwater watercraft having a center of gravity, and having: a boat mode of operation wherein the watercraft is floatable on a surface of a body of water; and an underwater mode of operation wherein the watercraft is submergible below the surface of the body of water; and wherein the watercraft comprises: a structure for mounting components, wherein the structure includes: a boat section including an air permeable top, side walls and a bottom surface wherein the top of the boat section can emerge above the surface of the water when the watercraft is in boat mode, a front end; a rear end opposite the front end; a three point stabilization system comprising: a front buoyancy element having a center of buoyancy and imparting a buoyant force on the watercraft, effectively at a center of buoyancy of the front buoyancy element, wherein the center of buoyancy of the front buoyancy element is between the front end and the center of gravity; and a rear buoyancy element imparting a buoyant force on the watercraft, effectively at the center of buoyancy of the rear buoyancy element, wherein the center of buoyancy of the rear buoyancy element is between the rear end and the center of gravity.