Hydrodynamically-contoured towable load-supporting float, including as permits high-speed controlled-depth towing of a seismic air gun

Abstract

A float having symmetrical fore-aft and port-starboard cross sectional surfaces in the shape of multiple, above- and below-centerline, ellipsoids is hydrodynamically-contoured to support suspended devices, typically a seismic air cannon, at even height/depth in the water, and at even attitude (roll, pitch and yaw). The float places nearly constant force on the tow line over a broad range of tow speeds from at least 3 to 12 knots during sea states from 0 to 6 and in the presence of variable direction surface winds to 25 knots. The float transitions easily and smoothly from displacement to hydroplaning operational modes, permitting that seismic equipment may be towed smoothly and at even depth in the water even at high speeds, thus accelerating seismic surveys. The preferred fore-to-aft contour of the lower surface is in the substantial shape of an ellipsoidal surface of from 4-10 feet, and most commonly 7 feet, in length with a height of from 6-14 inches, and most commonly 10 inches. The hydrodynamic aspect ratio is thus in the range from 9-13, and is most commonly approximately 11.4. The port-side to starboard-side ellipsoidal contour of the lower surface has a major axis, or width of the float, of from 1-3 feet and most commonly 2 feet, and a minor axis, or thickness, from 6-14 inches and most commonly 10 inches. The hydrodynamic aspect ratio is thus in the range from 2-4.4 and is most commonly approximately 3.2. The top surface is preferably substantially flat.

What is claimed is:  
     
         1 . A marine flotation device comprising: 
 a flotation body in the shape of a hydrodynamic lifting body with substantial fore-aft and port-starboard symmetry, the hydrodynamic body providing be definition lifting, as well as flotation force, by movement through the water; and    fins affixed to the aft of the flotation body.    
     
     
         2 . The marine flotation device according to  claim 1   wherein the flotation body is towable from the fore.    
     
     
         3 . The marine flotation device according to  claim 1   wherein the flotation body exhibits perfect fore-aft and port-starboard symmetry.    
     
     
         4 . The marine flotation device according to  claim 1  wherein the flotation body has as the fore-to-aft contour of a lower surface in the substantial shape of an ellipsoidal surface.  
     
     
         5 . The marine flotation device according to  claim 4  wherein the flotation body has as the fore-to-aft contour of a lower surface in the substantial shape of an ellipsoidal surface from 4-10 feet in length.  
     
     
         6 . The marine flotation device according to  claim 4  wherein the flotation body has as the fore-to-aft contour of a lower surface in the substantial shape of an ellipsoidal surface from 6-14 inches in height.  
     
     
         7 . The marine flotation device according to  claim 1  wherein the flotation body has a fore-to-aft hydrodynamic aspect ratio in the range from 2 to 4.4.  
     
     
         8 . The marine flotation device according to  claim 1  wherein the flotation body has as the port-side to starboard-side contour of a lower surface in the substantial shape of an ellipsoidal surface.  
     
     
         9 . The marine flotation device according to  claim 8  wherein the flotation body has as the port-side to starboard-side contour of a lower surface in the substantial shape of an ellipsoidal surface from 1-3 feet in length.  
     
     
         10 . The marine flotation device according to  claim 8  wherein the flotation body has as the port-side to starboard-side contour of a lower surface in the substantial shape of an ellipsoidal surface from 6-14 inches in height.  
     
     
         11 . The marine flotation device according to  claim 1  wherein the flotation body has a port-side to starboard-side hydrodynamic aspect ratio in the range from 2 to 4.4.  
     
     
         12 . The marine flotation device according to  claim 1  wherein the flotation body has substantially flat top surface.  
     
     
         13 . The marine flotation device according to  claim 1  used to tow a seismic air gun.  
     
     
         14 . A marine float CHARACTERIZED IN THAT 
 the shape of the float as a hydrodynamic lifting body permits the float permit it to transition from (i) a stationary state where only displacement buoyancy is provided and towing force increases with increased tow speed, to (ii) a state planning upon the surface of the water where lifting force is provided and towing force at least regionally momentarily decreases with increased tow speed, with but insignificant change, less than 10%, of a depth of the float in the water;    wherein the float differs from common planing bodies where the goal of going on plane is to lift onto the surface of the water, and at diminished depth in the water, so as to produce greater speed from equal propulsion force.    
     
     
         15 . The marine float according to  claim 14  used to tow a seismic air gun.