US3488783A

US3488783A - Long spar buoy

Info

Publication number: US3488783A
Application number: US697402A
Authority: US
Inventors: George S Lockwood Jr
Original assignee: Global Marine Inc
Current assignee: Global Marine Inc
Priority date: 1968-01-12
Filing date: 1968-01-12
Publication date: 1970-01-13
Anticipated expiration: 1987-01-13

Description

fi 1970 G. s. LOCKWOOD, JR 3,488,783

LONG SPAR BUOY Filed Jan. 12, 1968 United States Patent 3,488,783 LONG SPAR BUOY George S. Lockwood, Jr., Carmel Valley, Calif., assiguor to Global Marine Inc., Los Angeles, 'Calif., a corporation of Delaware Filed Jan. 12, 1968, Ser. No. 697,402

Int. Cl. B63b 21/52 U.S. Cl. 9-8 14 Claims ABSTRACT OF THE DISCLOSURE A long spar buoy adapted to float in a body of water in a substantially vertical attitude. At least a portion of the buoy adjacent the end thereof piercing the water surface is constructed of a flexible, non-metallic material. Stiffening means are provided to limit deflection of the body adjacent the water surface under lateral loads imposed on the buoy.

BACKGROUND OF THE INVENTION Field of the invention This invention concerns an improved long spar buoy having at least a portion thereof constructed of a relatively elastic, non-metallic material to enable the body to deflect under lateral loads without developing unduly high stresses in the body.

State of the prior art Recently, the interest in obtaining more knowledge about the oceans, their water currents, temperatures and conditions, and associated weather conditions has focused attention upon spar buoys of great length, sometimes as long as several thousand feet, which are vertically disposed in the water. Long spar buoys are exceptionally stable in that they are relatively unaffected by both wave action and weather conditions in comparison to more conventional displacement buoys which are of rather shallow draft. Long spar buoys are, therefore, ideally suited for use in oceanographic instrumentation and data acquisition programs.

Previous proposals suggested that long spar buoys be constructed of sections of steel pipe, such as drill pipe or oil well casing, for example, suitably secured to each other in an end-to-end relation. The use of steel pipe is desirable since it gives the buoy the necessary strength particularly at great depths where hydrostatic pressure on the buoy is substantial. However, there are disadvantages to the use of heavy steel pipe'or tubing, most prominent among them being the great weight and relative stiffness of such structural elements.

Surprisingly, the high stiffness of steel pipe of the size contemplated for practical use in long spar buoys subjects the buoy to stresses over its length in response to bending moments imposed on the buoy by its environment. The most troublesome bending stresses which may be encountered in a long spar buoy are those attributable to currents which impose lateral loads of difierent magnitude and direction upon different vertically spaced portions of the buoy. Generally, the larger the buoy, the more serious becomes the matter of current-caused stresses. These loadings are greatest in the upper portions of a long spar buoy. The cost of constructing a long spar buoy which is able to withstand such stresses may become prohibitive.

It has, therefore, been proposed to construct a long spar buoy in sections jointed to each other by moment-free connectors which isolate bending moments to single sections and do not transmit the moments developed in one section to adjacent sections. Although moment-free connectors succeed in reducing stresses in the long spar buoy from bending moments, in some cases their use is not prac- Patented Jan. 13, 1970 tical since the uppermost section of the buoy must have positive buoyancy, which in turn requires the section of the buoy above the upper moment-free connector to be of appreciable length, with the result that it may not be possible to obtain the benefit of a moment-free connection in the portion of the buoy where its use is most required. Moreover, moment-free connectors are relatively expensive and are subject to wear and corrosive forces which shorten their useful life.

SUMMARY OF THE INVENTION Briefly, a long spar buoy constructed in accordance with the present invention includes an elongated, positively buoyant tubular body having a length many times greater than the average transverse dimension thereof. The body is adapted to float in a vertical attitude in a body of water. At least a portion of the length of the body is constructed in at least substantial part of an elastic, nonmetallic material having a modulus of elasticity substantially less than about 30x10 pounds per square inch.

Preferably, the elastic material used in the construction of the buoy is a thermoplastic resin material such as polyethylene, polypropylene, or vinyl polymers and copolymers. Such materials are not only lightweight and relatively inexpensive, they are easily handled and worked on in the field. They can be welded together or out quickly during repair or initial construction of the buoy at its location of use without the need for special and expensive machinery. Moreover, thermoplastic resin materials of the types mentioned are essentially inert to salt water and resist corrosion from it to a much greater extent than does steel.

In instances where the buoy body extends through the water surface so that its upper end is disposed out of water, it is preferred that the above-water portion of the buoy and the portion of the body at and for a selected distance below the water surface incorporate a substantial portion of the elastic material. It is preferred, however, that these portions of the body not be made entirely of the elastic material, but rather that the body through these portions include substantially stiffer materials which give the body greater lateral stiffness than would be provided if the elastic material were used exclusively but less stiffness than if the body were made entirely of steel, for example. Lower portions of the body may be made exclusively of an appropriate elastic material of the type mentioned above.

The present long spar buoy is capable of withstanding substantial bending moments imposed thereon in view of the flexibility of the materials of which it is constructed.

The reduced weight of a buoy constructed in accord with this invention enables it to carry a greater payload compared to a more conventional buoy of the same diameter and length. For a given payload capacity, a buoy of the present invention can be smaller than a comparable steel buoy.

If the buoy extends to great depths at which are encountered hydrostatic loads exceeding the strength characteristics of the non-metallic materials mentioned above, the lower portions of the buoy are constructed of steel or the like. This practice reduces the amount of ballast necessary to maintain the buoy in a stable vertical attitude.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a fragmentary elevation view of a long spar buoy according to the present invention;

FIG. 2 is a cross-section view taken along line 2-2 of FIG. 1;

FIG. 3 is a view similar to FIG. 2 showing another embodiment of this invention; and

FIG. 4 is a view similar to FIG, 2 showing another embodiment of this invention.

3 DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIG. 1, a surface piercing long spar buoy is shown floating vertically in a body of water 12 having a free surface 14. The buoy has an elongated, substantially hollow tubular body 15 comprised of a plurality of similar elongated tubular elements 16. The body may have a diameter of 24 to 36 inches or so and a length of from 100 to several thousand feet; preferably the length-todiameter ratio of the body is at least about 50:1. Lower portions of the body preferably are fabricated from sections of oil well drill pipe or well casing. Each tubular element is as long as is convenient and practical, say from twenty to forty feet and adjacent elements are essentially rigidly secured to each other in end-to-end relation by suitable couplings 17 or by welding. The lower end of the buoy carries a ring 18 by which the buoy is connected to a mooring line 20 secured to an anchor (not shown) resting on the floor of the body of water. The lower end of the buoy, as required, includes ballast 22 such as concrete, water or steel shot.

An upper end 24 of the buoy mounts a transmitting platform 26 which includes a suitable transmitting device, including a vertical antenna 30 extending upwardly from the platform, for relaying data acquired by appropriate instrument transducers 28 to a short-based receiving station and the like. The transducers are spaced along the length of the buoy at suitable locations where pertinent data is to be acquired. Transducer output signals are supplied to the transmitting device via signal conductors 32.

The tubular elements 16' defining a portion 34 of the buoy adjacent the upper end of the body are fabricated of an elastic, non-metallic material, Body portion 34 extends from body end 24 past the water surface 14 to the upper end 36 of the remaining portion of the body defined by steel tubular elements, although the entire length of the body may be defined by non-metallic elements 16 if the body is not of particularly great length. Preferably, tubular elements 16 are composed of a thermoplastic resin such as polypropylene, polyethylene, vinyl polymers and copolymers, of similar plastic materials exhibiting a relatively high degree of elasticity in combination with appropriate levels of structural strength.

If the buoy body is exposed to ocean currents of different magnitudes or directions, it is subjected to bending moments over its length. A buoy fabricated at least in part of tubular elements 16 can be deformed to a considerable extent to accommodate such moments without developing excessive stresses which may result in permanent damage to the buoy. In contrast thereto, rigid steel pipes, when subjected to bending moments of like proportions, experience high bending stresses.

Although the flexibility of the buoy body is highly desirable at those portions of the buoy which are submerged a significant distance below water surface 14, such flexibility in the extreme upper extent of the body, from the transmitter platform to a point some distance below the load waterline of the buoy, can cause undesirable instability and deflection of the body under heavy platform payloads. It is therefore preferred to stiffen that section of the body in those applications in which the buoy carries large platform payloads. Portions of the flexible body which are significantly below the water surface do not experience the above-mentioned instability from the load of the transmitting platform. In a preferred embodiment of this invention, therefore, the stiffening of the body extends from buoy upper end 24 over a length of the body approximately equal to about five to ten times the distance along the body between platform 26 and the load waterline of the buoy. Platform 26 may be disposed about feet or more above the load waterline of the buoy.

Referring to FIG. 2, the stiffening of the upper extent of the body is accomplished by the use of foamed in situ closed cell plastic foam material 39 in the elastic tubular elements 16'. The foamed material preferably is low density, high pressure polystyrene foam or polyurethane foam, The foam cures to an essentially rigid state within the buoy body and inhibits deflection of the body in the area filled by the foam,

Referring to FIG. 3, another embodiment of this in vention is shown to include a rigid center core 40, conveniently a length of steel pipe or a downward extension of antenna 30, disposed interiorly of tubular elements 16 defining the portion of the body to be stiffened. The center core of the buoy is maintained coaxial with the axis of the buoy body by a plurality of axially spaced centering plates 41 secured to the core and intimately engaged around their peripheries with the inner walls of the hollow body.

Referring to FIG. 4, another embodiment of this invention includes a tubular stiffener of fiberglass 42 disposed interiorly of tubular elements 16' along the length of the buoy intended to be stiffened. The stiffener tube preferably has its outer surface intimately engaged with the inner surface of the body and is bonded to the body. This mode of stiffening combines light weight and low cost, and is wholly internal to the buoy.

Referring again to FIG. 1, the upper end of the buoy is stiffened by a series of overlapping external stay 44 and spreader arm 46 assemblies 48 of the type used to stiffen masts on sailing yachts, for example. The stay and spreader assemblies are located symmetrically around the body along the desired stiffened length of the body. The stiffening structure shown in FIG. 1 is characterized by being very light in weight, but it is more susceptible to damage than the other structures illustrated since it is external of the buoy body.

If the long spar buoy is of relatively extreme length, it is preferred that the lower reaches of the buoy be formed of tubular steel elements 16 sized to withstand the hydrostatic loads encountered at such depths. Where steel body elements are used in constructing the lower portion of the buoy, the buoy either has inherent stability or only a small amount of ballast is required to assure that the buoy floats'in a vertical attitude.

In the foregoing description, certain tubular elements employed ,in the construction of a buoy according to this invention have been described as being elastic, nonmetallic elements. The elasticity of a structural member can be evaluated by reference to Youngs modulus. For structural metals, Youngs modulus may have a value in the range of from about 9 10 lbs/in. (aluminum) to about 30 10 lbs./in. (high alloy steels) or more. In contrast to these values, which in terms of this invention represent relatively inelastic materials, the elastic, non-metallic materials comprehended by this invention preferably have values of Youngs modulus at least one order of magnitude lower. As noted above, polyethylene, polypropylene, or vinyl polymers or copolymers, may be used to advantage in the practice of this invention. The values of Youngs modulus for these materials ranges from 0.02 10 lbs/in. (ethylene vinyl acetate copolymer) to 512x10 lbs./in. (filled polypropylene) (see Plastics Properties Chart, Modern Plastics, Encyclopedia Issue, 1965) all of which are substantially lower than the values encountered in structural metals. It is preferred, however, that the material used have a value of Youngs modulus of from about 0.4)(10 lbs/in. to about 5 X 10 lbs./in.

While the invention has been described above with reference to specific structural arrangements, this has been merely by way of example in furtherance of an explanation of presently preferred embodiments of the invention. Modifications and alterations of the described embodiments within the talents of one of ordinary skill in the art to which the invention pertains are also within the scope of the invention. Thus, the foregoing description should not be regarded as limiting the scope of the invention.

What is claimed is:

1. A long spar buoy comprising an elongated and positively buoyant tubular body arranged to float in a vertical attitude in a body of water and having a length many times greater than the average transverse dimension thereof and sufiicient in extent to subject the body to significant lateral bending loads in response to Water current differentials in the region traversed by the body when afloat, the body having an essentially straight positively buoyant upper terminal portion of essentially uniform diameter, the outer peripheral extent of at least the upper portion of the body subject to such bending loads being defined at least in principal part by an elastic, nonmetallic material having a modulus of elasticity substantially of about 30x10 pounds per square inch or less, thereby to produce a spar buoy the body of which develops substantially less stress when subjected to bending deformations than the body of an all metal buoy of equal diameter subjected to equal amounts of deformation.

2. A long spar buoy according to claim 1 wherein said non-metallic material is selected from the group consisting basically of polyethylene, polypropylene, and vinyl polymers and copolymers.

3. A long spar buoy according to claim 1 including means for stiffening said upper terminal portion of the body for a selected distance downwardly from the upper end of the body.

4. A long spar buoy according to claim 3 wherein the stiffening means comprises plastic foam material disposed interiorly of the body along said selected distance and filling the body along such distance.

5. A long spar buoy according to claim 3 wherein the stiffening means comprises an elongated member composed of a material having a modulus of elasticity greater in value than that of said non-metallic material and disposed interiorly of the body along said selected distance.

6. A long spar buoy according to claim 5 wherein said stiffening member has an exterior diameter less than the inner diameter of the body and is disposed coaxially of the body.

7. A long spar buoy according to claim 6 including means spaced along the stiffening member for interconnecting the stiffening member with the body and for maintaining the stiffening member coaxial with the body along said selected distance.

8. A long spar buoy according to claim 3 wherein the upper end of the body is disposed above the surface of said body of water, and said selected distance extends from the upper end of the body downwardly for a distance about equal to from five to ten times the distance the body upper end is disposed above said water surface.

9. A long spar buoy according to claim 1 wherein the upper end of the body is disposed above the surface of said body of water, and said upper terminal portion has a length substantially greater than the distance of the body upper end above the water surface.

10. A long spar buoy according to claim 1 wherein the body has a lower terminal portion in which the body is defined by a plurality of steel tubular elements.

11. A long spar buoy according to claim 1 wherein the non-metallic material has a value of modulus of elasticity in the range of "from about 0.4)(10 to about 5 X 10 pounds per square inch.

12. A long spar buoy comprising an elongated and positively buoyant tubular body arranged to float in a vertical attitude in a body of water and having a length many times greater than the average transverse dimension thereof, at least a portion of the body including an upper terminal portion thereof being constructed at least in substantial part of an elastic non-metallic material having a modulus of elasticity substantially less than about 30 1O pounds per square inch, and means for stiffening the upper terminal portion of the body for a selected distance downwardly from the upper end thereof, saidstiffening means comprising an elongated member composed of a material having a modulus of elasticity greater in value than that of said non-metallic material and disposed interiorly of the body along said selected distance, the elongated stiffening member comprising a tubular fiberglass core having an outer diameter corresponding to the inner diameter of the body and secured to the body along said selected distance.

13. A long spar buoy comprising an elongated and positively buoyant tubular body arranged to float in a vertical attitude in a body of water and having a length many times greater than the average transverse dimension thereof, at least a portion of the body including an upper terminal portion thereof being constructed at least in substantial part of an elastic non-metallic material having a modulus of elasticity substantially less than about 30x10 pounds per square inch, means for stiffening the upper terminal portion of the buoy body for a selected distance downwardly from the upper end of the body, the upper end of the body being disposed above the surface of the body of water, a data acquisition and transmission system mounted to the buoy including a data transmitting station mounted to the upper end of the buoy body, the transmission station including an antenna extending upwardly from the body coaxially thereof and in which the stiffening means comprises a downward extension of the antenna.

14. A long spar buoy comprising an elongated and positively buoyant tubular body arranged to float in a vertical attitude in a body of water and having a length many times greater than the average transverse dimension thereof, at least a portion of the body including an upper terminal portion thereof being constructed at least in substantial part of an elastic non-metallic material having a modulus of elasticity substantially less than about 30x10 pounds per square inch, means for stiffening the upper terminal portion of the buoy body for a. selected distance downwardly from the upper end of the body, the stiffening means comprising a plurality of stay line and spreader arm assemblies connected externally to the body along said selected distance.

References Cited UNITED STATES PATENTS 3,092,852 6/ 1963 Devereux 9-8 3,301,048 l/ 1967 Felsenthal et a1. 9--8 3,378,863 4/1968 Johnson 98 TRYGVE M. BLIX, Primary Examiner CERTIFICATE OF CORRECTION Patent NO- 488,783 Dated January 13, 1970 InventorQg) GEQBGE S LQQKHOOD JR It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

| Column 3, line 26, "short-based" should read --shore-based--.

Column 3, line 45, between "buoy" and "fabricated" insert "'bOdY".

Column 3, line 73, "39" should read -38--.

SKENED AND SEALED JUN 2 31970 Arrest:

Flem'm WILLIAM E. sum, .13. Im gi ()ffi Commissioner of Patents