Semi-submerged vessel adaptable to sailing
United States Patent 3866557

A vessel having a superstructure supported above water on streamlined struts extending from fully submerged hulls. Portions of the struts are hinged to act as rudders and submerged vanes provide stability in pitch, and control pitch and roll. The form of structure illustrated is particularly suitable for small sail boats and is easily disassembled for transportation. In one form the superstructure is composed of buoyant hulls differing in size from the submerged hulls, the hulls being readily made interchangeable to adjust the buoyancy of the vessel to different loads.

Application Number:
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Filing Date:
Primary Class:
Other Classes:
International Classes:
B63B1/12; B63B7/02; B63H25/10; (IPC1-7): B63B1/12
Field of Search:
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US Patent References:
3696451TUBE FLOAT OR BOAT1972-10-10Thompson
3648635MARINE TRANSPORT1972-03-14Hashemi
3580207METHOD AND MEANS FOR MOORING1971-05-25Pangalila
3120829Boat rudder with planing angle trim plates1964-02-11Chew et al.
2858788Water craft1958-11-04Lyman

Primary Examiner:
Spar, Robert J.
Assistant Examiner:
Underwood, Donald W.
Attorney, Agent or Firm:
Brown & Martin
1. A semi-submerged vessel, comprising,

2. A semi-submerged vessel according to claim 1, wherein the major portions of said rear struts rearward of the hulls are hinged between the lower

3. A semi-submerged vessel according to claim 2, and including control vanes pivotally mounted on the lower portions of said rudders and extending substantially horizontally inboard therefrom toward the center of the boat,

4. A semi-submerged vessel according to claim 1, wherein said superstructure includes a pair of elongated upper hulls secured to said

5. A semi-submerged vessel according to claim 4, and including releasable

6. A semi-submerged vessel according to claim 4, and including a front cross bar detachably secured between said front struts, and a rear cross bar detachably secured between said rear struts with releasable fastener

7. A semi-submerged vessel according to claim 4, wherein said upper and lower hulls are of different cross sectional sizes and are interchangeable

8. A semi-submerged vessel according to claim 1, wherein said lower hulls have rigid portions secured to said struts, a bar member interconnecting the lower ends of said rigid portions, and an inflatable body supported by

9. A semi-submerged vessel according to claim 1, wherein certain of said struts are tapered vertically, with the narrower portions at the lower

10. A semi-submerged vessel, comprising,

11. A semi-submerged vessel according to claim 10, and including a front cross bar interconnecting said front struts, and a rear cross bar interconnecting said rear struts,


Conventional types of ships are limited in speed by wave and surface drag on the considerable hull surface necessary for support. In heavy seas, conventional vessels are subject to all motions of the water, and their stability and performance is reduced. To overcome this, various means have been devised to lift the bulk of the vessel clear of the water as much as possible.

High performance vessels using hydrofoils are efficient at high speeds, but their hulls rest in the water at speeds below the lifting speed of the foils. Air cushion supported vessels are completely clear of the water when the air cushion is operating, but are very bulky for their load capacity and are not particularly seaworthy when the air cushion is inoperative.

Another type of vessel utilizes one or more submerged buoyant hulls to support a superstructure above the water line. In one form the submerged hull is large and comprises the payload section, with only a small control structure above water. In another form, typified in U.S. Pat. No. 3,623,444, the bulk of the vessel is above the water, supported well clear of the surface by submerged hulls, the configurations shown being primarily adaptable to large vessels.


The vessel structure described herein, while adaptable to a wide range of sizes, is particularly suitable for small craft such as powered by sails, outboard motors or manual means. The structure comprises a pair of submerged hulls in spaced parallel relation, each having upwardly extending streamlined struts at opposite ends to support a superstructure above the water line. In the form illustrated, the superstructure includes a pair of hull members, each mounted on and being parallel to one of the submerged hulls, the hull members being connected at opposite ends by cross bars which set the width of the vessel. Any suitable deck or supporting surface may be attached to the hull members and cross bars, depending on the intended use of the vessel. The hulls are detachably secured to the struts and the cross bars plug into the struts, making the structure easy to disassemble for storage and transportation.

Portions of the rear struts, at least, are hinged to serve as rudders, and vanes are mounted on the submerged structure for roll and pitch stabilization and control. A simple control system operates the movable surfaces.

With the knock-down type of structure, it is practical to make the upper and lower hull units interchangeable and of different sizes. Thus either size may be used for the submerged hulls, providing a variable buoyancy to suit the load to be carried by the vessel.

The struts extend forwardly and rearwardly beyond the hulls to provide maximum length with minimum hull structure, the center of gravity being generally near the center of the vessel between the struts. The hulls are streamlined longitudinally between the struts to reduce drag and the struts provide an "area ruling" effect at high speeds to minimize wave drag. In larger sizes of the vessel, it may be desirable to use a third strut on each side, between the front and rear struts.

Various materials may be used for the structure, such as metal, fiberglass, or plastics, with parts or all of the components filled with buoyant foam material for safety and rigidity. For maximum portability, portions of the hulls may be inflatable.

The hulls are preferably spaced at least two hull widths apart, the vessel being a wide stable platform in any reasonable sea state. Only the sides of the struts are exposed to the immediate surface wave action, the supporting hulls being below the surface and the bulk of the superstructure generally clear of the water, at rest or at any speed of the vessel. By making the upper hulls buoyant, additional support is provided when the upper hulls are partially in the water, as when rolling under sail, or under heavy load conditions.

The primary object of this invention, therefore, is to provide a new and improved semi-submerged vessel.

Another object of this invention is to provide a new and improved semi-submerged vessel having submerged hulls which support an above water superstructure on streamlined struts.

Another object of this vessel is to provide a new and improved semi-submerged vessel structure which is particularly adaptable to small craft use and is readily assembled and disassembled.

A further object of this invention is to provide a new and improved semi-submerged vessel capable of high performance with low power and having high stability in a wide range of sea states.

Other objects and advantages of the invention will become more apparent upon reading the following description together with the drawings, in which like reference numerals refer to like parts throughout, and in which:

FIG. 1 is a perspective view of the complete basic structure of the vessel, the deck being omitted for clarity.

FIG. 2 is a longitudinal center line sectional view of the vessel.

FIG. 3 is a sectional view taken on line 3--3 of FIG. 2.

FIG. 4 is an exploded perspective view of a typical hull and strut connection.

FIG. 5 is an enlarged sectional view taken on line 5--5 of FIG. 2.

FIG. 6 is a top plan view of the vessel with a modified stabilizing surface arrangement.

FIGS. 7a and 7b are perspective views of an alternative strut configuration.

FIGS. 8a and 8b and 8c are cross sections of alternative hull shapes.

FIG. 9 is a side elevation view of a form of the vessel with an inflatable hull section.

FIG. 10 is an enlarged sectional view taken on line 10--10 of FIG. 9.

FIG. 11 is a side elevation view of a vessel with an added center strut.


In the basic configuration of the vessel, illustrated in FIGS. 1-5, the structure includes a pair of elongated lower hulls 10 and 20, a pair of upper hulls 12 and 22, front struts 14 and 24, rear struts 16 and 26, and rudders 18 and 28. Front strut 14 is streamlined in cross section from front to rear, with a reasonably sharp water penetrating leading edge 30. The forward end of lower hull 10 has a cavity 32 shaped to receive the lower rear portion of front strut 14 with a close fit. The forward end of upper hull 12 has a similar cavity 34 to fit the upper rear portion of the front strut. At the rear end of the lower and upper hulls 10 and 12 are similar cavities 36 and 38, respectively, to fit the forward portions of rear strut 16. As illustrated, the main structural components are of plastic material filled with buoyant foam 40, but other types of construction may be used.

The upper and lower hulls are secured to the struts by fasteners 42, which may be screws or quick release pins passing through the hull walls and seating into suitable receiving sockets 44 in the struts. More than one fastener may be used at each joint if required. The hulls 10 and 12 and struts 14 and 16 are thus joined to form a rigid left hull assembly 46.

Fixed to the rear top portion of upper hull 12 is a top hinge plate 48, which extends rearwardly and has a downwardly projecting hinge pin 50. Fixed to the lower rear portion of lower hull 10 is a rearwardly extending bottom hinge plate 52, with an upwardly projecting hinge pin 54. Rudder 18 is pivotally mounted between hinge pins 50 and 54 when the structure is assembled and forms the streamlined rear portion of rear strut 16.

The left hull assembly 56, comprising hulls 20 and 22 and struts 24 and 26, is identical in structure and has the same hinge arrangement for its rudder 28.

The two hull assemblies are connected in spaced parallel relation by a front cross bar 58 and a rear cross bar 60. Each cross bar has downwardly turned ends 62, each fitted with a non-circular plug 64. As illustrated, the plug portion is a square tube element, welded or otherwise secured to the cross bar. The ends of the front cross bar 58 plug into sockets 66 in the top portions of front struts 14 and 24, forward of the upper hulls, and are held by removable fasteners 68. The ends of rear cross bar 60 pass through openings 70 in top hinge plates 48 and into sockets 72 in rear struts 16 and 26, and are also held by fasteners 68. By making the plug and socket connections square or otherwise non-circular, the structure is prevented from twisting. For heavy load conditions, auxiliary struts or bracing wires can be used, or rigidity provided by deck structure secured between the cross bars. The deck structure, indicated in broken line at 74, may be of any suitable type to suit the specific use of the vessel. If the upper and lower hulls are to be interchangeable, bottom hinge plates 52 would also have openings 70 for the cross bar ends.

The vessel rides in the water with the lower hulls and approximately one half of the height of the struts submerged, depending on the load. A typical waterline is indicated at 76 in FIG. 2. The center of gravity 78 of the vessel is preferably slightly above the water line and longitudinally near the center of the vessel, between the front and rear struts. This configuration is extremely stable as long as the metacentric height of the vessel is positive, the metacenter being above the center of gravity. It has been found that the metacentric height should be at least 10 percent of the vessel beam width in roll and about 10 percent of the vessel length in pitch, but any positive value makes the vessel statically stable. When heavily loaded, or when rolling under sail, portions of one or both upper hulls may be in the water at times. It is thus an advantage to have the upper hulls water tight and buoyant to provide additional support when required.

To provide for control and stabilization in pitch and roll, horizontal control vanes 80 and 82 are mounted on the inside of rubbers 18 and 28, respectively, well below the water line. The mounting is illustrated in FIG. 5, wherein vane 82 is fixed on a pitch shaft 84 which is pivotal in a bearing 86 in the rudder. Pitch shaft 84 has a radial arm 88 from which a link rod 90 extends upwardly through the top of the rudder. Vane 80 is mounted in a similar manner. To reduce cost in a simple sail boat, the vanes could be fixed, or have means for limited adjustment to a preset pitch angle to suit the particular conditions and performance of the vessel.

Various types of controls may be used to operate the movable surfaces. The system illustrated is an example adapted to the simple structure of the vessel and should not be considered limiting. On the top rear portion of each rudder is a hinge fitting 92, the hinge fittings being connected by tie rods 94 and 96 to a central coupling sleeve 98. The tie rods are secured in any suitable manner to maintain a fixed length and thus parallelism of the rudders, but are free to rotate individually on their axes. Tie rod 94 has an arm 100 connected to the link rod 90 of vane 80 and tie rod 96 has a similar arm connected to the link rod of vane 82. On the central portion of rear cross bar 60 is a tiller bar 102 pivoted to swing about a generally vertical axis, and attached to coupling sleeve 98 to move both rudders by tiller action. Telescopically mounted in the forward end of the tiller bar is a control rod 104 with control hangle 106 pivoted to swing vertically. On one side of handle 106 is a downwardly extending arm 108, coupled by a link rod 110 to an arm 112 fixed below the tie rod 94. On the other side of handle 106 is an upwardly extending arm 114, coupled by a link rod 116 to an arm 118 fixed above tie rod 96.

An upward motion of handle 106 causes link rod 110 to be pulled forwardly and link rod 116 to be pushed rearwardly, both actions causing arms 100 to be lifted and vanes 80 and 82 to be moved to a negative pitch angle. A downward motion of handle 106 produces a corresponding positive pitch motion of vanes 80 and 82. Thus lifting the control handle tends to raise the bow, providing a natural pitch control. If roll control is required, the control rod 104 can be slid forward or backward in tiller bar 102 to produce opposite twisting action on tie rods 94 and 96, and corresponding opposite pitch motion of the vanes.

For some conditions it may be desirable to minimize torque on the structure caused by operation of the vanes. This can be accomplished by extending pitch shafts 84 through the rudders and attaching external vanes 120, as in FIG. 6. The external vanes should be kept as short as possible to avoid damage against a dock or other structure. Additional control in heave and pitch may be provided by forward control vanes 122 mounted on front struts 14 and 24, and suitably coupled to the control system, or set at a predetermined pitch angle.

When interchangeability of the hulls is not required, the drag of the vessel can be reduced by reducing the cross sectional area of the struts below the water line. This can be accomplished as in FIG. 7a by tapering the strut 124 in width while retaining a constant thickness for strength. In FIG. 7b, the strut 126 is of constant width but is reduced in thickness.

The hulls are shown as having a square or rectangular cross section for simplicity. However, they could be circular as in FIG. 8a, or elliptical as in FIG. 8b. FIG. 8c shows a rectangular cross section with the large dimension horizontal, to obtain maximum volume of the hull with minimum draft clearance. It should be noted that the left and right hull assemblies could be permanently secured as units, with the knock-down limited to the interconnection of the hull asssemblies by the superstructure.

The vessel can be powered by a sail 128 supported by a mast 130, which is held in a socket 132 on the front cross bar 58, as in FIG. 1. Other mountings for the sail may be used, such as on the deck structure 74 in FIG. 11. Alternatively, an outboard motor 134 may be attached to rear cross bar 60, as in FIG. 9, or to any other suitable portion of the structure. With the flat bottomed lower hulls as shown, the vessel will be capable of planing on the lower hulls at high speed with sufficient power.

In FIG. 9, a modified lower hull 136 is illustrated, all other structure being as described above. The hull 136 has front and rear rigid portions 138 and 140 for attachment to the respective struts, the rigid portions being joined by a lower connecting bar 142. The body of the hull between the rigid portions is formed by an inflatable bag 144 of suitable material.

The configuration illustrated in FIG. 11 is suitable for larger sizes of vessels and incorporates the same arrangement of upper and lower hulls and front and rear struts, but includes a central strut 146 between the hulls for added support. With widely spaced front and rear struts, the streamlined center strut also reduces wave drag. If additional directional control is required, a rear portion of each front strut may be hinged to form a rudder 148.

In all forms described the vessel is stable, capable of high speed with low power due to low drag, and has been found to ride waves of considerably size with a minimum of disturbance. With the major portion of the buoyancy provided by submerged hulls, the vessel has good damping characteristics in heave, pitch and roll.