US3537412A

US3537412A - Stabilizer for marine vessels

Info

Publication number: US3537412A
Application number: US842785A
Authority: US
Inventors: Homer I Henderson
Original assignee: Individual
Current assignee: Individual
Priority date: 1969-06-30
Filing date: 1969-06-30
Publication date: 1970-11-03
Anticipated expiration: 1987-11-03

Description

United States Patent Inventor Homer 1. Henderson 2220 Live Oak St., San Angelo, Texas 76901 Appl. No. 842,785 Filed June 30, 1969 Continuation of Ser. No. 727,894, May 9,

1968, abandoned. Patented Nov. 3, 1970 STABILIZER FOR MARINE VESSELS 10 Clalrns, l4 Drawing Figs.

US. Cl

Int. Cl

Fleld of Search References Cited UNITED STATES PATENTS 2,889,795 6/1959 Parks 2,939,291 6/1960 Schurmanetal......l...... 114/06 3,349,740 10/1967 Field 114/05 Primary Examiner- Trygve M. Blix Attorney- Horn er I. Henderson ABSTRACT: A stabilizer for a marine vessel having pipes termed buoy pipes," of relatively large diameter secured on each side and each end of the vessel; the pipes projecting downwardly into the water for a distance that is many times the draft of the vessel and the lower end of said pipes being open while the upper end is closed. Air is pumped into the buoy pipes to displace water therefrom. The resultant pressure of the air corresponds to the head of water displaced. The air pressure within the buoy pipe generates an upward force on the closed top of the openended buoy pipe, which force is a product of the pressure within the buoy pipe and the buoy pipe's internal area. A sufficient number of pipes, of sufficient area, and depth of submersion, are used so as to actually pneumatically jack the vessel above the water's surface a sufficient distance as to be above the crest of surface water waves. Each cubic foot of water displaced by air gives a lift equivalent to the weight of 1 cubic foot of water.

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Patented Nov. 3, 1970 Shoot 1 of 3 FIG.I4

38 INVENTOR.

HOMER l. HENDERSON FIG.4

Patented Nov. 3, 1970 3,537,412

Shut 2 of 3 r 1% 36 1: WM, 40 437 42 37 r H; V 23 534 I F l G. 7 36 mmvron HOMER I. HENDERSON Patented Nov. 3, 1970 Sheet '5 0:3

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INVENTOR HOMER I. HENDERSO N STABILIZIIR FOR MARINE VESSELS This application is a continuation of 0.8. Pat. application Ser. No. 727,894 filed May 9, i968 and now abandoned.

The buoy pipes on either side of the vessel, port and starboard, may be connected at their tops to equalize the pressure in these pipes and consequently since the lift is proportional to air pressure, it makes the boat passive to those waves causing roll. The fore and aft buoy pipes may be connected to make the vessel passive to those waves causing pitch. An anchoring system is disclosed which system anchors the vessel and the lower ends of the aforementioned buoy pipes to prevent roll or pitch caused by shifting cargo, waves, etc.

An embodiment is disclosed that automatically pumps air from the high-side buoy pipe of a listing boat and into the lowside buoy pipe to correct any list and level the boat. A similar arrangement for the fore and aft buoy pipes is used to correct a pitching boat.

DESCRIPTION Since history's earliest recordings of marine transportation, mariners have been disturbed, aggravated, made seasick and hindered in their activities because of the seemingly incessant oscillation of their vessel due to wind-driven waves. Many attempts have been made to reduce the wave-caused oscillations, and some have succeeded, to a large degree, but the size and cost of such successful attempts are prohibitive for most operations. An example of a present day stabilizer vessel is one built for marine drilling of deep earth bores, and such successfully stabilized vessels have been built, but their size is enormous, because two hulls are required, one being submerged for stabilization, and their cost is many millions of dollars. They are not self-propelled, and must be towed by large high-powered tugs, themselves costing around SI ,000,000 each. Once on the site for the proposed hole, this vessel must be securely anchored, and then partially submerged to gain stability and both of these operations are costly and time consuming.

This invention is adapted for, but not limited to, much smaller vessels, that are normally self-propelled, and of such a size as is used for marine exploration by shallow hole drilling (holes up to 3,000 ft. deep] searching for minerals or geological information. In such an operation a relatively low-weight drill is used, and hence is accommodated by a lower displacement vessel, but the need to move to a new location every few hours, or days, necessitates a self-propelled vessel, and a much more economical vessel, in original cost, and in operation. The usefulness of this invention is not limited to shallow drilling, or any size of vessel; it may be used for any operation, for work, or pleasure, wherein an anchored, stabilized, vessel is desirable, either a self-propelled vessel, or a towed platform.

It is therefore an object of my invention to make a floating marine vessel stable, or passive, to surface water waves.

A further object of my invention is to stabilize a marine vessel without submerging it in part.

A further object of my invention is to stabilize a marine vessel without adding greatly to its cost, or its weight.

A further object of my invention is to provide a stabilized vessel which is automatically self-righting to correct for upsetting moments caused by shifting cargo or other loads.

Another object of my invention is to provide a drilling vessel wherein an earth bore hole can be drilled through a "well" in the center of the vessel and upon completion of the hole, the holes casing, or drill pipe, can be left extending above the water's surface, and the drilling vessel can be raised by pneumatic jacks "buoy pipes, of this invention to a height sufficient to clear said casing, or drill pipe; and thereupon the vessel is moved free from'said casing, or drill pipe, leaving the casing extending above the water's surface for production purposes, or the drill pipe is left extended to serve as a semipermanent lighted marker of the hole s location.

Another object of my invention is to provide a stabilized vessel that is passive to wave action and as a consequence removes the well-known "walking-the-anchor" effect of anchored normal vessels wherein the upward down-wind momentum given to the vessel by a wave crest imposes impulses on the anchor line characterized by abnormally high forces.

Another object of my invention is to' anchor a marine vessel in place by anchors connected to the vessel's hull and to anchor the vessel in trim by anchors connected to the lower end of the buoy pipes of this invention.

Other objects and a fuller understanding of the invention may be had by referring to the following description and claims taken in conjunction with the accompanying drawings in which:

FIG. I is a vertical rear-end view of a catamaran-type drilling vessel on which this invention may be utilized.

FIG. 2 is a vertical view showing this invention employed on a catamaran vessel.

FIG. 3 is a plan view showing one embodiment of this invention employed on a catamaran vessel.

FIG. 4 is a fragmentary cross-sectional view taken on line 4-4 of FIG. 3.

FIG. 5 is a vertical view showing a different embodiment of the invention employed on a catamaran vessel.

FIG. 6 is a vertical view showing one anchoring and stabilizing means for the embodiment of FIG. 5.

FIG. 7 is a plan view showing the anchoring system employed on the FIG. 5 embodiment.

FIGS. 8, 9, and 10 are diagrammatical end views to show the comparative effects of waves to their respective vessels: without this invention, (FIG. I), the embodiment of FIG. 2, and the embodiment of FIG. 5.

FIG. I] is a plan view showing the embodiment of FIG. 5 with additional air pipes to keep the vessel in trim: fore-aft, and port-starboard.

FIG. 12 is a vertical end view showing the automatic leveling scheme employed in FIG. 11.

FIG. 13 is a fragmentary sectional view showing a modified form that may be used for buoy pipes.

FIG. 14 is a diagrammatic view of the buoy pipe to indicate the nature ofthe forces within, and without, the buoy pipe.

Referring now to FIG. I, there is shown a catamaran-type vessel, that can be employed for drilling operations and can profitably use this invention, and it is designated generally as 20. For flotation this vessel 20 uses pontoons 21. These are rigidly connected by trusses 24, and have a living and working enclosure 25. The drilling mast 26 would normally be lowered while in transit. When drilling the drill pipe 27 may extend through a well" in the center of the boat, to centralize the high forces that may occur when pulling stuck drill pipe. The surface of the water is referred to as 22. The decking 23, has extensions to receive the buoy pipes of this invention. The vessel is preferably self propelled by twin screws 28.

FIG. 2 is a partial end view showing the buoy pipes 30 of this invention employed on the vessel of FIG. 1. The buoy pipes may be 3 ft. in diameter, for small vessels, and preferably of aluminum. These buoy pipes are accommodated in the extensions of the decking 23. These buoy pipes are open ended and are suspended vertically in the water when the vessel 20 has reached its drilling site and is anchored. These pipes have sufficient volume to provide enough buoyancy when filled with air, to float the vessel 20, plus the additional buoyancy required to permit the maximum pull on the drill pipe 27. An air compressor, not shown, maintains a required air pressure in the receiver 29, via the tube 53. The receiver is connected to each buoy pipe via the tube, or hose, 32. This tube 32, has a valve 33, which is opened when the buoy pipe is placed in place and it is desired to displace the water in the pipe to some required depth to procure the desired buoyancy, or lift. Knowing the required depth, the operator computes the corresponding pressure and sets the regulator 34 to maintain this pressure.

FIG. 3 shows a plan view of the buoy pipes and their abovedeck piping. It will be noted that these buoy pipes are operated in pairs, foreaft, and port-starboard, with the pair members being diameterically opposite each other, vesselcenter-of-weight-wise, and with the length of the moment arm being considered in determining the relative sectional areas of the pipes. Also that each pipe has its own pressure regulator so that eccentric loading of the vessel can be accommodated by increasing, or decreasing, the air pressure in the required buoy pipe.

The drilling well" 37, through which the drill pipe descends is norm ally located at midship.

FIG. 4 is a partial sectional view showing one way to secure the buoy pipes to the decking 23. The buoy pipes may be in i ft. lengths for easy handling and can be connected by flanges 3!. The deck 23 is slotted as at 38, FIG. 3, to receive the buoy pipes, but will not pass the flange 31. The buoy pipes may be handled with a small crane, (or equivalent) and they are connected one joint at a time while resting in the slot 38. After each joint is connected it is moved outboard to clear the slot and is then lowered into the water one joint length, and again rested in the slot, and another joint connected until the desired total length is in the water. Whereupon the sealing cap 36, carrying the airhose 32, is placed over the flange 3] of the topmost pipe. The sealing may be an O-ring, gasket, or sealing dope, since the maximum pressure is nominal (usually under p.s.i.). It is noted that the cap 36 is relatively thick and extends over the pontoon and decking a considerable distance to distribute the stress imposed upon it by the air pressure within the pipe 30.

FIG. 14 shows diagrammatically the nature of the forces associated with the buoy pipes when active, with the bottom end open, the top end closed, and partially filled with air. In this diagram the length S indicates the depth of water displacement within the pipe 30. The character W, indicates the weight supported by the buoy pipe. The three forces, F, are all equal (neglecting the negligible weight of the air column). The upper force F is balanced by the weight W. The two forces F at the air-water interface are equal and opposed, one being the downward force of the air on the interface, and the other being the equal upward force of water on the interface. The upward force of water at the interface is transmitted by the air pressure to the plate 36. Therefore F W Pa where P is the air pressure within the buoy pipe, and a is the internal area of the buoy pipe. If the vessel is in sea water, the pressure is 0.445 p.s.i. per foot of depth. Should the displacement S be 30 ft., then the pressure P would be SL445) or I335 p.s.i. Should the internal diameter of the pipe be 35% inches the area a" would be 1,004 square inch. It follows that the force: F P0 l3.35Xl,004 l3,400 lbs., therefore W H.400 lbs. it is realized that the air pressure is proportional to depth of submergence (S) and the force equal to Pa hence F S(0.445)a volume ofdisplacement times specific weight ofthe water. it is noted that the walls of this open-ended pipe, do not see the forces F, but only the hoop stress due to the Pressure P. Column stresses are nonexistent. It is preferable to use thin wall aluminum pipes. It is of interest that if one computes the displacement of a vertical, closed, empty, pipe of the same diameter and length S. the buoyancy obtained is again l3,400 lbs. in the latter case, however, the force of 13,400 lbs. is due to the pressure of 13.35 p.s.i. on the bottom plate of the sealed pipe, and is transmitted not by gas under pressure within the pipe, but by the pipe walls themselves to the plate 36; hence the pipe acts as a column with the walls under compressional stress and it has the undesirable characteristics of a column.

It may be a misnomer to call pipes 30 buoy pipes" but this term is understood in the marine art and the amount of upward force due to pressure is the same as would result from the buoyance of such a closed end pipe, hence the decision to term them "buoy pipes.

Returning now to FIG. 2, wherein is shown the port-starboard buoy pipes filled with air to some depth "S". Both would be at the same depth only if the total loading had a center of mass at the midpoint between the buoy pipes, otherwise one, or the other, pipe would have a deeper air column to supply a counter torque to offset the eccentric loading. The normal displacement of the pontoons 21 is shown as D. It is seen that dimensionwise, S is many times greater than D. Shown dashed is a surface wave W, having an amplitude A. As this wave moves across the vessel the starboard buoy pipe may be sensing the crest of the wave as shown. The bottom of the starboard buoy pipe sees" an increase of water pressure due to the effective increase in submergence A, and as a consequence water flows into the bottom of this buoy pipe compressing the air within. The ratio of the pressure increase at the bottom of the buoy pipe is AIS. if the air column within the pipe were of the same length, 5, its shortening due to the increased pressure would be in the same ration A/S but since it is slightly longer its shortening ratio would be slightly longer. However, the loss of head due to frictional flow, and due to momentum effects, reduces slightly the pressure increase within the pipe to less than that outside the pipe. Since the cap 36, "sees" only the air pressure within the pipe, the actual rolling moment is slightly lessened (dampened) by the frictional flow, and the momentum lag. Further, the air column has a large cushioning effect. For practical engineering purposes the shortening of the air column can be assumed to be A, as shown.

Since the port buoy pipe is in the trough of the wave it will experience a decrease of pressure and the ratio will likewise be A/S, and will have an increase in air column length of approximately A. It will be noted that this vessel without buoy pipes will be rolled with a moment proportional to AID while the same vessel with the buoy pipes will be rolled with a moment proportional to AIS. Also that the ratio of roll moment between the vessel with the buoy pipes/vessel without buoy A 2 S D S moment with buoy pipes is only It) percent of the same vessel without buoy pipes.

It will be understood that the fore-aft set of buoy pipes will have a similar function to reduce pitching of the vessel.

FIG. 5 depicts a modification of this invention. It will be seen that FIG. 5 is quite similar to H0. 2, except that the port and starboard pipes are interconnected by a large, open flow, pipe, or tube, 39. in H6. 5 the valve 33 controls the air feed from the receiver, while the regulator 34 controls the pressure in the buoy pipes and the valve 35 is to bleed the pipes of air.

Pipe 39 has a valve 54 which is normally open when the buoy pipes are active. Consider the reaction when a surface wave W, passes under the vessel equipped with this modification. When the crest is at the starboard pipe, the bottom of the pipe senses an increase of pressure due to the effective increase in submergence A. Correspondingly water flows into the bottom of the starboard pipe until the air-water interface rises by substantially A. This would compress the air in the starboard pipe, except this air is free to flow through the tube 39 into the port buoy pipe. The port buoy pipe is experiencing the trough of the wave and the bottom end of the port pipe senses a decrease in head A, and a corresponding decrease in pressure at the bottom of the pipe and water flows out of the pipe, reducing the air pressure. Simultaneously, the connecting pipe 39, transmits the crest-induced pressure increase of the starboard pipe to the trough-induced pressure decrease in the port pipe. As a consequence, the pressure in both pipes remains almost constant, therefore the lift per square inch, at each pipe stays constant, and the vessel with this embodiment of the invention is passive to surface waves. These pipes may be of unequal sectional areas to compensate for unequal loading. The pipe 39 needs to be of sufficient diameter to transmit a volume of air (which volume is the product of amplitude and the pipe area "0") in the time of one quarter period of the pipes is: Hence, ifS is 10 times D the roll wave, and do so with negligible friction loss. The Encyclopedia Britannica, copyrighted 1962, Volume 23, page 4428 gives for surface water waves: the ratio of length, L/double amplitude (2A) as 1311. Computing for a 10-foot wave (amplitude Sfeet) results in a wave length of feet. This Hence for L I30 feet the period P=/ 2 5.1 sec., and one quarter period 1.25 sec. The volume of air to be passed by the pipe 39 in 1.25 see. is the inside sectional sq. ft.

tiplied by the amplitude, A feet. Therefore the volume to be passed in one quarter period is 6.97X5 34,85 cu. ft. in

%)(3435: 1670 cu. ftJmin. Computations indicate that a 30 foot length of 8-inch diameter pipe will transmit air at this rate with a frictional pressure drop of less than 0.05 p.s.i., which is negligible.

The above indicates that the arrangement of FIG. 5 is excellent for stabilizing a vessel in so far as waves are concerned it is passive to waves. There is, however, an almost complete loss of righting moment; that is, the vessel is stable in any posture. FIGS. 6 and 7 show one way in which a vessel using this embodiment may be stabilized for roll and pitch and yaw. When the vessel reaches a drilling site it may be anchored with four anchors 44, whose lines 45, are secured to the vessel above the deck and said lines are at approximately 45 with the keel line. Winches 41, control the boat and may accurately position the vessel once the anchors 44 are placed. These anchors act to anchor the vessel with a horizontal fix. A vessel that is passive to waves will not walk" an anchor, hence anchors lighter than normal are used.

Once the vessel is positioned, the buoy pipes 30 are lowered to prepare for raising the vessel above the waves via pneumatic hoisting. In this case the lower end of the pipes 30 carry a pulley, or block, 47, that may be attached by a swivel 46. Through the block 47 is a loop of anchor line 43, which line is threaded through a pulley 48 in the anchor 42, to form a conventional block-and-tackle with a mechanical advantage of 2: I with the smaller force at the winch 40, since it has a single line while the anchor-to-buoy pipe has a dual line loop. This assures that the winches 40 can control the rolling, or pitching of the vessel. After the buoy pipes are lowered the tender boat carries the anchors 42 to the required locations and lowers them. The winches 40 are then actuated to make each line 43 snug, when the boat is level. This second set of anchors, acts to anchor the lower ends of the long buoy pipes with a horizontal fix, and thereby it prevents rolling or pitching of the vessel since the deck has a fix due to the anchors 44, consequently the buoy pipes are prevented sweeping in arcs. Thereupon the vessel is slowly raised by admitting air into the buoy pipes and the winches are activated to pay out line and keep the vessel level. The vessel is raised until the pontoons 21 are just above the prevailing wave crests, and earth drilling starts.

The low-powered winches 40 may be electric powered, or hydraulic powered, and are normally manually operated. However, it may be desirable to provide for a parallel automatic operation as shown in FIG. 6. A dual-end mercury level switch 49 may be placed on the deck with its axis perpendicular to the axis of control; in FIG. 5 it is perpendicular to the keel since the roll pipes are involved. The terminals 50, 51 are for electric power. Should cargo be moved toward the portside of the vessel, it will tend to roll the vessel to port. This roll will be resisted by the portside tackle. However, should the portside side tackle be slack for some reason, the roll could exist and the roll would move the mercury in the switch 49 to the portside, closing the electric circuit to the portside motor 52, which would operate the port winch 40 to tighten the tackle and hence right the ship. As the vessel approaches level" the switch opens. With automatic operation the winches 40, should be limited in torque, as by slip clutches, to prevent destructive forces, should the automatic system stick in the on" condition. If desired the switch 49 can be made to activate both portside and starboard side winches to take in the line on the low side of the vessel and to pay out the line on the high side of the vessel. Should the submergence S of the buoy pipes be 30 ft., a considerable righting moment is imposed on the vessel by a pull at the pulley 47, of only 200 lbs. (moment 6,000 ft. lb.).

area of the buoy pipe, a= mull.25 sec. for a flow rate of:

Com a a- Comparative tlvo r ghtwave roll lng moment AID. DIS. Almost nil.

FIGS. II and 12 show one method of providing righting moment to the embodiment of FIG. 5. In this method an additional set of pipes, similar to the buoy pipes, but normally smaller, are provided for the dual purpose of providing primarily trim control, and secondarily additional buoyancy. These pipes 55, I term trim pipes. The buoy pipes 30 are interconnected to reduce their response to wave action to a minimum. The trim pipes will have the same relative wave response as shown for the nonconnected buoy pipes of FIG. 2. However their ability to correct an out-ol'-trim vessel is much greater, as shown below. To achieve this out-of-tt'lm response, say in the case of roll:air is pumped out of the pipe 55 on the high side and pumped into the pipe 55 of the low side. The pump may be a reversible rotary compressor, and it is shown as 56, and it is powered by an automated reversible motor. 60, which motor may be electric or hydraulic.

Each pair of pipes 55, port-starboard and fore-aft, is con nected at each end to the air supplying receiver 29, by a pipe 32 having a pressure regulator 34, with a valve 33 just up stream from it, and a valve 59 just downstream from it. The pump 56 is located between the risers 32 and may have a pres sure gauge on either side thereof to indicate to the operator the pressure in each pipe 55, the difference in these pressures will show a measurement of the righting moment. It is important that air be prevented normally from flowing between the pair of pipes 55. Most pumps 56 will effectively block such flow, but should the pump fail in this respect, a solenoid valve 65 must be placed in this pipe. The valve 35 is to bleed air out of the pipes 55. The tube 53 leads to the main air compressor, not shown. The floating ball 66, is to act as a safety valve to prevent water from being pumped into the pump (compressor) 56.

The motor 60 is shown as a reversing electric motor, and it is powered from the

terminals

63, 64. A dual ended mercury level switch is shown deck mounted at 62. When the vessel lists, the mercury in the switch closes the circuit on the down side, opening the valve 65, and actuating the motor to pump air out of the trim pipe on the high side, and into the trim pipe on the low side. There are available mercury switches capable of carrying the motor starting current herein required, but I prefer to limit the level switch to small currents and use conventional motor-starting relays, housed in the housing 61.

In operation, assume that the load shifted to port, thereby causing a list to port. The mercury in switch 62 moves to port closing the electric circuit that opens the solenoid valve 65, and closes relays in the starter box 61 to energize those motor windings that cause the motor 60 to rotate in the direction to pump air out of the high (starboard) pipe 55, and into the low (port) pipe 55. Assume that the capacity of the compressor is I00 cu. ftJmin, or 1.66 cu.ft./sec. The compressor sees", at the time of start, the same pressure at the intake pipe and at the exhaust pipe therefore there is no need to correct the compressor capacity because the air is under approximately 2 atmospheres (absolute) pressure. As shown above, the total upward force exerted by a buoy pipe is the same as the water displacement of air within the pipe. Consequently when L66 cu. ft. of air is taken out of the high side it reduces the lift of that trim pipe by I .66 multiplied by the specific weight of sea water (64 lbs.) 105 lbs. The addition of I66 cu. ft. of air into the low port pipe displaces l.66 cu. ft. of water and increases its lift by I lbs. This transfer results in a moment couple, and assuming a SO-ft. vessel beam the moment of this couple is 30 l05 3,l$0 ft. lb. In 16 seconds the accumulated couple would be 50,200 ft. lb. This is equivalent to changing the center of mass of a 100,400 lb. vessel by one half ft. As the vessel's list is corrected and it approaches level, the mercury switch opens to stop further air transfer.

It will be apparent that in this latter method the trim pipes can be made, if desirable, as large as the buoy pipes. However, the larger the trim pipes 55, the greater their response to wave action. It will be obvious that this automatic air-transfer method can be incorporated into the embodiment of FIG. 2, by considering the buoy pipes 30, of FIG. 2 as the trim pipes 55 of FIG. 12.

FIG. I3 shows one method of telescoping the buoy pipes (or trim pipes) to facilitate handling, and decrease storage space. In this modification the upper section of buoy pipe 30-A is shown supported by its flange 31 upon the deck 23. Telescoping within the upper section is the next lower section 30-B. The section 30-8 has upon its upper end an outwardly extending flange 68. A dual-V, sealing ring 69 is seated just under the flange 68. When the section 30-B is lowered into the section 30-A it finally comes to rest at the bottom of 30-A, supported by the interior flange 67 of 30-A. The other sections are similar. The lowest section 30-N has a spider 70, incorporating a swivel 7l. Into the stem of the swivel 71, is swaged a cable 72. This cable is to lower and raise the telescoping assembly. The lowest section 30-N has a wide outside flange (or spider) 75 which is attached to its lower end after assembly. This flange 75 is large enough in diameter to extend beyond all sections including section 30-A so that all sections are raised, or lowered, as a unit. A small crane, or equivalent, can be used to raise and lower. The upper end of cable 72 may be secured to a hoisting ring 73. After the assembly is lowered, the ring 72 may be placed on a hook 74 in the wall of the section 30-A so as to be readily available for subsequent hoisting. A stanchion, incorporating a winch, may be placed at each buoy pipe station to permit quick raising and lowering, and provide for upright, in-place stowage during transit.

Throughout this specification most of the description has been concerned with the pair of buoy pipes, or trim pipes, that control roll, that is, the port-starboard pair. It will be understood that the fore-aft pair are equally important and are analogous in properties and operation. Also a "pair" of interacting buoy pipes (or trim pipes) may consist, not only ofa single large pipe on each side, or end, but may consist of multiple pipes on each side, or end, with said multiple pipes connected in parallel.

I claim;

I. In a stabilizer for a marine vessel having dependent buoy pipes, closed at the top and open at the bottom and extending into the water, said buoy pipes being connected in counterpart pairs and arranged around the vessel with one member of a counterpart pair being diametrically opposite its counterpart member in a port-starboard and fore-aft manner, and means for introducing gas into said buoy pipes to cause them to contribute buoyancy to said vessel, the improvement for stabilizing the vessel for local variations in water surface levels such as crest to trough in water surface waves, said improvement comprising: an open, pressure-equalizing conduit connecting the top ends of each member of a counterpart pair to maintain substantially equal pressure in both members of a counterpart pair whereby substantially equal buoyancy per unit sectional area is maintained in each member of the counterpart pair, in combination with a second stabilizing means that stabilizes the vessel for conditions other than variations in local water surface levels, such other conditions as uneven cargo loading, or wind forces.

2. The stabilizer for a marine vessel defined by claim I, wherein in a case of unequal loading the sectional area of each member of a counterpart pair of buoy pipes is proportional to its individual loading.

3. The stabilizer for a marine vessel defined by claim I, wherein each said buoy pipe comprises a series of telescoping, self-sealing sections.

4. A trim stabilizer for a marine vessel to retrim said vessel should i become out of trim due to cargo shift, or to other causes, said stabilizer comprising in combination:

rigid trim pipes having open bottoms and closed tops secured to said vessel and projecting downwardly into the water and having sutficient internal volume below the waters surface as to generate the desired buoyancy forces when such volume is gas filled;

said trim pipes arranged in counterpart pairs, port-starboard, and fore-aft;

a connecting conduit joining the top ends of the two trim pipe members ofeach counterpart pair;

a reversible motor-driven compressor incorporated in each said connecting conduit;

means for injecting air into each trim pipe member of said counterpart pairs until the desired buoyancy is obtained;

sensor means on said vessel to sense out-of-trimness and while the vessel is out of trim to activate said reversible motor-driven compressor to cause it to pump air out of the trim pipe member that is abnormally high and into its counterpart trim pipe that is abnormally low; and

means in said connecting conduits to block fluid flow while the said motor-driven compressor is not activated.

5. A stabilizer for a marine vessel comprising in combination:

a first set of anchors placed on the seas floor around said vessel and with lines connecting said first set of anchors with the vessel, thereby restricting the vessel to a position fix and heading;

rigid pendent members affixed to the vessel and extending downwardly into the water; and

a second set of anchors placed on the seas floor around said vessel and with lines connecting said second set of anchors with said pendant members, with the line con nections being below the connections of said first set of anchors, thereby restricting the vessel from roll and from pitch.

6. The stabilizer for a marine vessel defined by claim 5, in-

eluding:

individual winch means mounted on the vessel to spool the line of each anchor of the second set of anchors;

each anchor of the second set of anchors incorporating a sheave; and

the anchor line of each anchor of the second set of anchors extending from its individual winch, thence through the sheave in the anchor, thence to a connection onto its individual pendent member.

7. The stabilizer for a marine vessel defined by claim 6, ineluding each individual anchor of the second set of anchors connected to its individual pendent member by a block and tackle system with the free end of the line of said block and tackle passing through the said sheave in the anchor and thence to its individual winch, thereby putting a higher force on the pendent member than on the winch.

8. The stabilizer for a marine vessel defined by claim 7, including:

reversible power means for each said individual winch;

and sensor means mounted on the vessel to sense out-oftrimness and in case of out-of-trimness to actuate the power means of the abnormally low winch to cause it to reel in line, thereby generating a righting torque on the vessel.

9. The stabilizer for a marine vessel defined by claim 5, wherein said pendent members are pipe buoys, open at their bottom ends and closed at their top ends, and with means for injecting a gas into the pipe buoys to make them buoyant.

lb. The mbitiuz for a maxim: mm! denim! by Claim, wlwcin said p pe wy: are arrangm in counterpart pain wnh aach member M a wummpan mm being diamelncally up