High Speed Boat

Abstract

A boat for operating at high speeds even in water having waves of moderate to large height, comprising a pair of laterally spaced hull sections connected by a body. The rear portion of each hull section has a planing surface, all of the planing surfaces normally being submerged even during high speed travel. The front portion of each hull section has a narrow width and sharp entry angle for cutting into waves instead of riding over them. The body that connects the hull sections normally extends at a large height above the water surface, and it includes a front body portion at the bow to assure that the boat will ride over very large waves.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to water craft.

2. Description of the Prior Art:

Boats with conventional displacement hulls are not satisfactory at high speeds because the large submerged surface results in high drag, due largely to its wave-making tendency. Such drag increases sharply when the Froude number, which equals

exceeds about 0.2 for a typical displacement hull. Planing hulls can be used to achieve considerably lower drag at high speeds because the dynamic (planing) forces acting on the hull tend to lift the boat up on top of the water surface. However, the hulls used heretofore experience pounding when even small waves are encountered. The pounding is largely due to the increase in the effective planing surface (and therefore, an increase in dynamic lift forces), when the hull encounters a wave.

Fully submerged hydrofoil craft have been extensively developed, which can operate efficiently at high speeds, and which avoid pounding. In hydrofoil craft, a hull is supported out of the water during high speed travel, by underwater foils fixed to the lower end of struts that extend from the hull. The hull can be maintained a small distance above the water by employing foils that are normally only partially submerged. However, when waves of even moderate height are encountered, the foils can ride out of the water or too deeply into it, and the boat is subjected to heavy pounding. It is also possible to maintain the foils at a large depth, but then a complex and expensive control system is required to maintain a constant height of the hull above the water. In both types of hydrofoil systems, there is considerable complexity and expense involved in transmitting power from an engine in the hull to propellers mounted on or near the foils.

A boat which had the low drag characteristics of hydrofoil crafts at high speeds, which could operate in at least moderately high seas without complex controls, and which utilized a relatively simple drive train for a propeller or other driving system, would be valuable in a wide range of applications.

SUMMARY OF THE INVENTION

In accordance with one embodiment of the invention, a relatively simple craft is provided which can move smoothly and at high speeds along water having moderately high waves. The craft includes a pair of laterally spaced skeg or hull sections which support a body of the craft above the water. The rear portion of each hull section has a planing surface that supports the craft primarily by dynamic forces during motion through the water, so that a minimum amount of the hull is in the water where it would produce drag. The front or bow portion of each hull section has a narrow width and a sharp entry angle for cutting through waves.

When a wave is encountered, the sharp front portion of each hull tends to cut through the wave instead of producing large dynamic forces that would tend to lift the bow. In addition, the narrow width of the front portion results in small bouyancy, so that a wave does not forcefully lift the bow even by reason of static bouyant forces. Thus, the attitude of the craft does not change drastically when a wave of moderate size is encountered. As the wave encounters the rear portion of each hull, the bouyancy of the rear portion causes it to rise. The planing surface along the rear portion is positioned so that normally all of it is submerged. Thus, no additional planing surface is brought into use by reason of the wave, and only minor changes in dynamic lifting forces are produced as the crest of the wave passes by the rear portion of the craft. The craft therefore, rises and falls smoothly in the waves, and avoids large pitching and vertical accelerations.

The body portion of the craft, which connects the hull sections, extends along most of the length of the craft to form a tunnel therealong. The forward part of the body, which extends between the front parts of the hull sections, is normally high above the water. However, when a large wave is encountered, the wave produces dynamic lifting forces on the body that raise the forward portion of the craft to assure that the craft will ride over the wave and will not dive into it and be submerged. The tunnel can also provide aerodynamic lift forces, particularly where the rear portion of it is blocked by a door or by spray.

The novel features of the invention are set forth with particularity in the appended claims. The invention will be best understood from the following description when read in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a boat constructed in accordance with one embodiment of the invention, shown during high speed travel on water, the superstructure of the boat being shown in a simplified form;

FIG. 1A is a bottom perspective view of the boat of FIG. 1, with the planing surface emphasized with diagonal lines, and without the superstructure;

FIG. 2 is a side elevation view of the boat of FIG. 1;

FIG. 3 is a plan view of the boat of FIG. 1;

FIG. 4 is a front elevation view of the boat of FIG. 1;

FIG. 5 is a rear elevation view of the boat of FIG. 1;

FIGS. 6A through 6E are contour views showing the configurations of the boat at various stations along the length of the boat as indicated in FIG. 2, but not showing boat portions behind the stations;

FIG. 7 is a partial sectional view taken on the line 7--7 of FIG. 1;

FIG. 8 is a sectional view of a door attachment which can be utilized with the boat of FIG. 1 to close the tunnel therein;

FIG. 9 is a simplified pictorial view of an automatic tab control system which can be utilized with the boat of FIG. 1;

FIG. 10 is a bottom view of a boat with a convex planform planing surface;

FIG. 11 is a bottom view of a boat with a concave planform planing surface;

FIG. 12 is a side elevation view of a boat constructed in accordance with another embodiment of the invention;

FIG. 13 is a partial plan view of the boat of FIG. 12;

FIG. 14 is a front elevation view of the boat of FIG. 12;

FIGS. 15 through 19 are sectional views showing the outline configurations at various stations along the length of the boat as indicated in FIG. 12;

FIG. 20 is a simplified side elevation view of a boat constructed in accordance with yet another embodiment of the invention;

FIG. 21 is a bottom view of the boat of FIG. 20;

FIGS. 22 through 26 are partial sectional views taken at various stations along the length of the boat as indicated in FIG. 21;

FIG. 27 is a side elevation view of a boat constructed in accordance with still another embodiment of the invention;

FIG. 28 is a sectional view of only the right half of the boat of FIG. 27, taken on the line 28--28 of FIG. 27;

FIG. 29 is a side elevation view of a boat constructed in accordance with yet another embodiment of the invention;

FIG. 30 is a view showing the planform of one planing surface of the boat of FIG. 29;

FIG. 31 is a perspective view of a boat constructed in accordance with yet another embodiment of the invention; and

FIG. 32 is a sectional end view of a boat constructed in accordance with a further embodiment of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 shows a small boat 10 constructed in accordance with the invention, moving rapidly over water W. The boat has a pair of identical laterally spaced hull sections 12, 14 connected by a body 16. The hull sections 12, 14 have very narrow forward portions 18 that normally ride out of the water, and wider rearward portions 20 whose lower regions are normally submerged in the water. The lower surface 22 of each rearward portion is flat and serves as a planing surface that supports nearly all of the weight of the boat when it moves at high speed through the water. Generally, all of the planing surface 22 is submerged even at high speed travel. FIGS. 2 through 7 illustrate details of the boat configuration.

The use of planing surfaces 22 to support most of the boat weight at high speeds, allows for a minimum of submerged boat surface and therefore low drag and high efficiency. Of course, this is characteristic of vessels which utilize airfoil or planing type surfaces to support most of a craft weight at high speeds. However, unlike many other types of such craft, the boat 10 is able to operate well in seas with moderate waves. When a moderate wave is encountered, such as one which has a crest-to-trough height one-third the height H of the boat (as measured perpendicular to the length of the boat, between the top of the bow and the planing surface), the front portion 18 of each hull section cuts through the wave. That is, the sharp entry angle of the hull sections produces a minimum dynamic force that would tend to lift the bow. In addition, the narrow width and therefore, small volume of the front portions 18 results in a minimum of additional static bouyancy, so there is a minimum of static forces that tend to lift the bow. As a result, the bow tends to remain almost level rather than pitching up.

As the crest of the wave reaches the rearward portions 20 of the hull sections, the greater width and therefore, volume and bouyancy of the rearward portions causes them to rise in the water, largely by reason of static bouyant forces. The fact that all of the planing surface 22 is already submerged means that no additional planing surface is brought into use and there is a minimum of additional dynamic forces tending to lift the rear portion of the boat. Also, the portion of the hull immediately above the planing surface has substantially vertical sides so it produces a minimum of dynamic forces and therefore substantially no change in dynamic forces as it moves down into a wave or up out of it. The rear portion therefore begins to rise smoothly on the crest of the wave. It is not thrown out of the water and therefore can smoothly lower into the trough of the wave, the planing surface 22 generally remaining submerged throughout the rise and fall. Even if the boat pitches up substantially or does not fall quite fast enough into the trough of the wave, only the forward part of the planing surface will be out of the water. This forward part has a small width, since the planing surface is triangular. Therefore, there is a minimum change of dynamic lifting force even if the forward part of the planing surface rises out of the water and resubmerges.

As shown in FIGS. 2-6, the body 16 merges into the hull sections 12, 14 to form a tunnel that extends through the middle of the craft. The smooth arch transition from hull section to body provides a progressively greater response to large waves to prevent bow immersion at high or low speeds, and it also contributes to an attractive appearance. However, hull sections which are vertical or nearly vertical at their inner sides can be used, as will be more fully explained below.

The front body portion 24 that extends between the front hull portions 18 at a location normally high above the water, is useful in preventing swamping in very high waves. If a wave is encountered which is nearly as high or higher than the height H of the boat, it will reach the lower surface 24S of the front body portion. The surface 24S is upwardly inclined, that is, a line 26 parallel to the surface 24S near the bow, and in the same plane as a side elevation view, makes an angle A of at least several degrees with the horizontal. Accordingly, as the surface 24S contacts a large wave, a dynamic lifting force is produced which lifts the bow. The large area of the front body portion surface results in a large dynamic lifting force. This plus the large bouyancy of the body raises the front of the craft and prevents it from being submerged. As the wave passes along the tunnel formed by the body, it lifts the rest of the body by reason of dynamic and static bouyant forces. While such an encounter with a large wave produces large pitch and heaving motions, the lifting does prevent swamping and therefore contributes to safety under conditions of very heavy seas. The provision of a front body portion 24 also helps to insure proper response to waves when the boat is stationary or moving at low speed; for example, it keeps waves from breaking over the deck under such conditions by raising the bow over them. When the boat is stationary, the boat assumes the position indicated in phantom lines at 10A in FIG. 2, so the deck is close to the waterline 29. When the boat moves at high speed, it lies higher above the waterline 29 as shown at 10 in FIG. 2, with a trim angle of the planing surface of between about 2.degree. and about 10.degree. at high speed.

The tunnel created by the body 16 and hull sections 12, 14 also contributes to lift of the craft, and therefore allows a smaller area to remain in the water where it produces drag. It is believed that the air trapped in the tunnel particularly when spray from the hull sections closes off the rear end of the tunnel, creates air pressure that increases lift. The spray can, however, appreciably increase drag. It has been found that an installation of door means such as a panel 28 of the type shown in FIG. 8, which can pivot about an axis 30 to substantially close the rear end of the tunnel, can produce slightly greater speed.

The planing surface 22 of each hull section which extends from the point 32 to the rear end of the hull section, is flat and has a triangular shape. As best seen in FIG. 5, the planing surface is oriented at an angle of about 15.degree. from the horizontal. This dihedral or deadrise resists outward rolling in a turn, and in some configurations causes the boat to bank into a turn, thereby to minimize sideward forces on passengers. A variety of planing surfaces can be used, including those with a dihedral that varies along the length, to produce a "warped plane" bottom, and those with a concave or convex camber so that the trim angle varies along the length. The planform of the planing surface is preferably of a generally triangular shape, so that the width of the planing surface generally increases towards the rear, at least during the first half of the planing surface length behind the beginning point 32. This minimizes variation of planing surface even if the front portion of the planing surface should rise out of the water. Concave or convex sides can be used for the generally triangular shape, or combination concave-convex sides (e.g. the forward part concave and the rearward part convex or vice versa). It has been found that planing surfaces with fuller forward parts, i.e., with a convex planform as shown in FIG. 10, have greater pitch damping than straight-sided triangular surfaces. Planing surfaces with fuller rearward parts, i.e., with a concave plan-form as shown in FIG. 11, have less wetted area for the same lift and therefore have greater efficiency; however, they are harder to stabilize. Greater stability can be obtained by employing small foils near the rear of the boat, which provide greater pitch damping. Other types of planing surfaces which may be used include those which form a V in section.

It is important that the front portions 18 of each hull section that lie in front of the planing surface, have a narrow or sharp entry angle to cut into waves, so that they are subjected so only negligible dynamic forces when they encounter a wave. While the bows of ordinary boats may have angles of perhaps 60.degree. at a height above water of about one-third the total height of the bow above water, the hull sections of boats of the present invention are much more sharply angled. As shown in FIG. 7, two points 31 and 33 spaced behind a bow point 35 by a distance equal to the height H of the bow of the craft, where all points 31, 33 and 35 are at a height of about H/3 above the water surface (when planing at high speed), form an entry angle B of less than 10.degree.. As contrasted with an ordinary hull, the entry angles of the hull sections of the boats of this invention are generally less than 20.degree. and preferably less than 10.degree.. Where the height H of the boat is indefinite, the angle B may be measured at a point above the waterline at high speed (when most of the lift is dynamic lift on the planing surface) equal to one-half the minimum height T of the centerline of the tunnel (see FIG. 4). An entry angle of this fineness should also be present at the waterline at high speeds. A sharp entry angle which is less than 20.degree. and preferably less than 10.degree. both at the waterline and up to a height of one-third the height of the boat above the waterline at high planing speeds, provides a relatively smooth ride even in fairly rough seas.

While the boat 10 does not require a complex stabilization system, a tab system 34 can be employed behind each skeg 36 as a boat leveler to control pitch attitude, which is influenced by center of gravity location and wind over the deck. The tab system includes a tab 38 pivotally mounted on the skeg along an axis 40 that extends at the same angle (15.degree.) from the horizontal as the planing surface. A hydraulic cylinder 42 has one end mounted on a bracket 44 on the skeg and another end mounted on a bracket 46 that is fixed to the tab. The hydraulic cylinder can be operated to pivot the tab to any position between 7.degree. up and 30.degree. down from a neutral position where it lies as an extension of the planing surface 22 of the hull section. The tab system can be used to trim the boat in roll, or to roll the boat to help initiate a turn. The tab system has the advantage that it does not protrude outside of the lines of the hull. Also, the fact that it lies in a high pressure area, and is generally deflected down to produce a control moment, results in freedom from cavitation even at high speeds. It is possible to locate the tabs at the rear of the hull sections instead of behind them, so that the tabs are less likely to be damaged. In this case, the tabs would generally lie flush with the planing surface until it was desired to change the boat attitude.

FIG. 9 is a simplified view of an automatic tab control system which moves two tabs 48, 50, in response to turning of a steering wheel 52 (which also pivots the outboard engines and their mounts 53 that primarily steer the boat). The tabs move in different directions, one up and the other down, to bank the boat into the turn, to reduce the effects of centrifugal forces on the occupants. The steering wheel operates hydraulic cylinders 54, 56 that force hydraulic fluid through lines to the tabs 48, 50. In turning to the left, tab 48 moves down while tab 50 moves up, while in turning to the right the movements are reversed. The tabs 48, 50 can also be controlled together by an automatic trim system that senses the speed of the boat and/or the wind, to adjust for an optimum trim angle.

FIGS. 12 through 19 illustrate a larger boat 60 constructed with an overall design somewhat similar to the boat of FIG. 1. In this boat, the entire length of the boat is utilized for passengers and/or cargo, with the bridge 62 located near the bow and with much of the volume of the hull sections 64, 66 behind the narrow forward portions 68 utilized for storage. It may be noted, particularly from FIG. 14 and FIG. 19, that the rear portions 70 of the hull are not vertical along the entire height of their outer surfaces. Instead, these surfaces bulge out at the lower end near the planing surface, which provides a wide planing surface. A spray rail 72 is located above the waterline of each hull section to deflect spray away from the sides of the boat and keep them dry. Such rails can also be placed on the inner surface of each hull section.

FIGS. 20 through 26 illustrate a craft constructed in accordance with yet another embodiment of the invention. In this craft, the body 90 extends horizontally and the hull sections 92, 94 have vertical inner surfaces 96 that meet the body at right angles instead of merging with it. The parallel-sided tunnel which is thus produced minimizes spray in the tunnel, and therefore the drag that results when the spray hits the tunnel surface. The tunnel has a substantially constant cross-section, which minimizes pitch-up during acceleration by minimizing wave-making. This boat has a minimum response to waves of moderate size, although once waves reach the top of the tunnel there is a sudden change in response. In this configuration, no attempt is made to add aerodynamic lift by closing the rear of the tunnel by spray or a door.

As shown in FIG. 26, the bow of each hull is very narrow for cutting through waves to provide a soft ride. FIGS. 25 and 24 show the beginning of a downwardly angled chine flare or chine region 98 on the outer surface of the hull section. The chine 98 helps to direct spray away from the boat to keep the sides dry. It also reduces porpoising and helps to prevent tripping on turns (uneven sideward movement out of the turn) and assure inboard heeling (leaning) on turns. At the more rearward stations shown in FIGS. 23 and 22, the planing surface becomes more horizontal, this type of surface generally being referred to as a warped plane. The warped bottom can help to maintain a stable trim, but can lead to a somewhat harder ride. It may be noted that strips of material can be fastened to the hull sections instead of forming chine regions in the hulls, but this generally increases the number of steps required in production. Hulls have been tested with inboard chine strips, and they further reduce spray in the tunnel and reduce any tendancy to dig in on turns, but these problems were not present in an appreciable degree so the additional cost of including them may not be justified.

Thus, the invention provides boats which have surfaces for producing dynamic lifting forces at high speeds, that support most of the boat out of the water to thereby reduce drag. These surfaces, which are referred to herein as planing surfaces, are at the bottoms of the hull sections to assure submersion of the surfaces. Two spaced hull sections are utilized, each with a planing surface, to provide stability. Each hull section has a forward portion with a sharp entry angle and narrow width to minimize dynamic and static bouyant forces when it encounters a wave, so that it can cut through the wave. The planing surface is substantially completely submerged so that the amount of active planing surface does not change substantially when the boat heaves or pitches. In addition, the planing surface is basically triangular in planform, i.e., its width increases towards the rear of the boat, so that the front portion of the surface is narrow; thus, even if the front portion of the planing surface rises out of the water, there is only a small decrease in effective planing surface. The planing surface preferably has an angle B' (see FIG. 3) at its leading edge, as seen in substantially a planform view, which is less than about 20.degree.. Also, at least about 80 percent, and preferably close to 100 percent of the planing surface is normally (in small waves) submerged even at high speed (i.e., when most of the lift is due to dynamic forces on the planing surface rather than to bouyancy forces).

The boats basically provide efficient high speed operation and resistance to the effects of waves that is characteristic of fully submerged hydrofoil craft. However, this is achieved without the complexity and cost of such a hydrofoil craft. It has been found, moreover, that whereas a typical hydrofoil craft can operate smoothly only in waves up to about one-tenth its length, the boats of the present invention can operate smoothly in waves of up to about one-fourth their length (or for a typical boat, in waves nearly equal to the height of the boat). It may also be noted that in boats of the present invention, there is no distinct change between planing and non-planing modes of operation, as occurs with hydrofoil craft, and any operating speed up to the maximum can be chosen that seems appropriate. The boats of the present invention also have the advantage that they can be designed without struts and other members that can snag on objects in the water or be damaged if run aground. The simplicity of design results in light weight and therefore large payload.

Many variations in boat design can be employed. As shown in FIG. 27, an up-stepped region 102 can be added at the rear of the boat, with a lower surface 104 higher than the planing surface 106. This up-stepped region 102 may be low enough to add bouyancy at the rear when the boat is stationary or moving at low speed. Yet it does not substantially affect lift during high speed operation, when the boat is supported primarily by the planing surface 106 and the up-stepped region 104 may be completely out of the water or almost completely out of the water. The up-stepped region 102 also reduces drag caused by wave-making, when the boat is moving at lower speeds (when most of the lift is due to bouyancy). FIG. 28 which illustrates one of the hull sections, shows the inside surfaces I of the hull sections (the hull sections are identical). Waves are created in the narrowing space between the hull sections. The pressure at P.sub.1 of the waves creates a drag component D.sub.1 tending to retard forward motion. The boatail or rearward converging region 102 utilizes the pressure at P.sub.2 of the waves along the rear of the boat to provide a propulsive component D.sub.2 which aids forward motion. Thus, the up-stepped portion 102 uses the waves to reduce drag at low speeds.

Another variation in design, shown in FIG. 29, utilizes a discontinuous planing surface, including a forward portion 110 and a rearward portion 112. As shown in FIG. 30, which shows the planform of the planing surface, this design provides a large planing area at the forward and rearward ends of the planing surface, but a smaller planing area at the center. This results in better pitch stability than for a simple triangular planform, in much the same manner as a longer wheel base provides a more even ride in an automobile; that is, a shift in the center of lift to adjust to a change in weight distribution, wind forces, etc., is accomplished with a smaller change in pitch attitude. To further reduce the planing effectiveness of the center region 112 (which is the front of the rear portion 114), it is stepped up from the forward portion 110.

Still another variation of the boat, shown in FIG. 31 has a body without a front portion to connect the bow portions of the hulls. As mentioned earlier, a bow or front portion of the body can be useful in preventing swamping in very high waves. However, it has been found that the aerodynamic lift of the bow portion has a substantial effect on the attitude of the boat. This is because the bow is a substantial distance from the center of gravity of the boat and therefore forces on it produce a large pitch moment. This pitch moment can change greatly when the boat turns to head into the wind after heading downward. In some situations, this necessitates frequent adjustments in the trim (pitch) of the boat. To avoid this, the front body portion is eliminated. This may reduce safety in case an unexpectedly large wave is encountered, but it reduces changes in trim and also reduces the amount of pitching when moderately large waves are encountered which just reach the top of the tunnel.

FIG. 32 illustrates a cross-sectional view of yet another variation of design of a boat. In this boat, the hull portions 120, 122 immediately above the planing surfaces 124, 126 are narrower than the planing surface, to minimize the amount of wetted surface and therefore to reduce drag. However, the forces of the hull portions 120, 122 are vertical immediately above the planing surfaces to minimize dynamic lift forces, so there is a minimum variation of dynamic lift with variation depth of submersion.

Many other variations in boat shape and in attachments can be made. For example, a third hull section could be added to form two tunnels, or the planing surfaces could be located on separate members attached to the bottom of each side of the boat so that each hull section includes a separate planing member that forms the planing surface. The boats can be driven by a variety of propulsion systems, including water jet propulsion or water ram jet. In any case, however, high efficiency and smooth travel make it preferable to have the planing surfaces substantially completely submerged and the front portions of the hull sections constructed with a sharp entry angle approaching 0.degree..

Although particular embodiments of the invention have been described and illustrated herein, it is recognized that modifications and variations may readily occur to those skilled in the art and, consequently, it is intended that the claims be interpreted to cover such modifications and equivalents.

Claims

What is claimed is:

1. A boat adapted to operate at high speeds in water having waves of at least moderate height comprising:

a pair of laterally spaced hull sections, each having a sharp entry angle at its bow portion, and a planing surface along its rear portion; and

a body connecting said hull sections, said body normally extending above the water to define a tunnel normally above the water between said hull sections;

said planing surface of each hull section being at the bottom of the hull section, and said planing surface of each hull section gradually increasing in width from a point spaced behind the bow to the rear of the planing surface, whereby there is a minimum variation of planing surface even if the boat's attitude changes considerably.

2. The boat described in claim 1, wherein:

each of said planing surfaces has a convex planform, whereby to provide greater pitch damping.

3. The boat described in claim 1, wherein:

each of said planing surfaces has a concave planform, whereby to further increase efficiency.

4. A boat for movement at high speeds comprising:

a pair of hull sections; and

a body portion lying above the water surface and connecting said hull sections;

each of said hull sections having a narrow forward hull portion with a sharp entry angle immediately above the water of less than about 10.degree. and a hull portion behind it with a normally substantially completely submerged bottom planing surface, said planing surface being of primarily triangular planform to generally increase in width at stations progressively nearer the rear of the boat.

5. The boat described in claim 4 wherein:

said body portion includes a bow part extending between the front portions of said hull sections, said bow part having a lower surface whose center is upwardly inclined, whereby to ride over large waves.

6. The boat described in claim 4 including:

a pair of tabs extending rearwardly from the rear of each planing surface; and

means for pivoting said tabs to change the attitude of the boat.

7. A boat for movement at high speeds comprising:

a hull having a narrow bow portion and a planing surface along the bottom of at least part of its rear portion, said planing surface gradually increasing in width along most of its length from a point spaced behind the bow, and said planing surface located so that substantially all of it is submerged even at a speed where the dynamic forces of water on said planing surface supplies more lift than is supplied by buoyant forces on the hull.

8. The boat described in claim 7 wherein:

said bow portion has an entry angle of less than about 10.degree. immediately above the waterline when the dynamic forces of water on said planing surface begin to exceed buoyant forces on the hull.

9. The boat described in claim 7 wherein:

the sides of the hull immediately above said planning surface extend substantially vertical, so they supply substantially no dynamic lifting forces, whereby to minimize variations in dynamic lift with small variations in depth of submersion.

10. A boat adapted to operate at high speeds in water having waves of at least moderate height comprising:

a pair of laterally spaced hull sections, each having an entry angle of less than about 20.degree. as measured between a point on the tip of the bow at a height above the water approximately one-third the height of the bow above the water and a pair of points on opposite sides of the hull surface and spaced behind said bow point by a distance equal to the height of the bow above the water, and each hull section having a planing surface along its rear portion;

a body connecting said hull sections, said body normally extending above the water to define a tunnel normally above the water between said hull sections; and

means for propelling said hull sections at a speed at which a majority of the weight of the boat is supported by planing forces on said planing surfaces.

11. The boat described in claim 10 wherein:

said entry angle is less than about 10.degree..

12. A boat adapted to operate at high speeds in water having waves of at least moderate height comprising:

a pair of laterally spaced hull sections, each having a sharp entry angle at its bow portion, and a planing surface along its rear portion, the planing surface of each hull section being tilted outwardly from a horizontal plane along substantially its entire area;

a body connecting said hull sections, said body normally extending above the water to define a tunnel normally above the water between said hull sections; and

means for propelling said hull sections at a speed at which a majority of the weight of the boat is supported by planing forces on said planing surfaces.