US2597048A - Watercraft - Google Patents

Description

y 1952' B. K. L..ALMQVIST ET AL 2,597,048

WATERCRAFT Filed Dec. 28, 1948 FIG]. E

Patented May 20, 1952 Olof Elgstriim, -Alvsjo, "Sweden, assignors to Aktiebolaget Supermarin, Stockholm, Sweden,

a corporation of Sweden Application December 28, 1948, Serial No. 67,602 In Sweden May 24, 194 8 3 Claims. (01. iii-6.6.50

This invention relates to hydrodynamically supported watercraft in-which the hull at normal speed rises entirely clear of the water. More specifically, the invention relates to such Watercraft in which the substantial part of the craft is supported by one or more hydrodynamical sustainers, while the remaining weight is supported by a. forwardly placed planing surface or surfaces adapted at normal speed to rest on the surface of the water even if the water surface is disturbed by waves, for the purpose serving as a stabilizer.

One object of the invention is to construct the stabilizer so that the same has both a.- longitudinal and a latitudinal stabilizing effect on the hull.

Further objects of the invention will be better understood from the description hereinbelow, by reference to the annexed drawings which show embodiments of the device according to the invention.

Fig. 1 is a side elevation illustrating the hull of a watercraft with a hydrofoil and a forward stabilizer attached thereto and showing the hull supported clear of the surface of the water.

Fig. 2 shows in the same manner as Fig. 1 a watercraft having two hydrofoils attached thereto.

Fig. 3 showsthe hull of the watercraft according to Fig. 1 in top view.

Fig. 4' is a section taken on the line IVIV in Fig. 1.

Fig. 5 is a section taken on the line VV in Fig. 4.

Fig. 6 is a section taken on the line VIVI in Fig. 1.

Fig. 7 shows in the same way as Fig. 6. a modifi embodiment of the stabilizer.

Figs. 8, 9 and 1 0 are sections taken on the lines VIII-VIII, IX IX, and XX respectively in Fig. 6.

Fig. 11 is a diagrammatical section taken on the line IV-IV in Fig. 1 illustrating the latitudinal stabilizing force of the hydrofoil. The full lines show the watercraft in normal position, while the dotted lines show the craft tilted by a foreign force.

Fig. 12 is a diagrammatical section taken on theline VIVI in Fig. 1 illustrating the latitudinal stabilizing force of. the forward stabilizer. The full lines show the watercraft in normal position, while the dotted linesshow the craft tilted by a foreign force.

In the. drawing l indicates the hull of a waterby G. A hydrofoil 3 for instance of known type 2 is attached to the hull by means of supports 2. It will be seen from Fig. 5 that the lower face of the hydrofoil is plane and has an inclination 1) towards the horizontal plane of about 3. The hydrofoil is arranged behind the centre of gravity G.

At the forward part of the hull, preferably at the how, there is arranged a stabilizer a adapted at normal speed of the craft to rest upon the surface of the water and thus hold the forward part of the hull clear of said surface, as shown in Figs. 1 and 6, the hydrofoil 3 maintaining at the same time the aft part of the hull above the water level. i

The stabilizer consists in the embodiment according to Figs. 1 and 6 of a central portion forming two planing surf- aces 5 and 6, one at each side of the hull. The forward edge of surfaces 5 and 6 is horizontal. At the outer end of each of; the horizontal parts 5 and 6 there is an upwardly inclined portion, 1 and 8 respectively, extending above the water surface when the central portion of the stabilizer is resting thereon.

The two surfaces 5 and 6 are connected with each other and with the hull respectively by means of upwardly and inwardly inclined plates l2 extending longitudinally of the hull. The surfaces 5 and 6- are further connected with the hull by means of supports 9 and ID.

As will be seen from Fig. 8, the parts 5 and 6 have a longitudinal cross section of a shape similar to that of the hydrofoil. The parts 5 and 6, however, have preferably a longer extension in longitudinal direction of the hull than the hydrofoil 3. Moreover, the lower side of the parts 5 and 6 facing the water, which side is plane or concave, has an inclination 1; towards the horizontal plane which is greater than 3, preferably about 5; The planing surface of the parts 5 and B have thus an angle of attack to the water which is greater than the angle of attack to the water of the hydrofoil 3. The forward edge of the parts 5, 6 is preferably sharp and the profile (Fig. 8-) is, as will be seen in the drawing, of modified hydrofoil type.

Also the upwardly inclined lateral portions 1, 8 of the stabilizer have an inclination rearwards and downwards from their forward edge. This inclination 0 Fig. 9, is preferably greater than that of the parts 5, 6, for instance about 7. On the other hand, the plane lower sides of the parts I2 have no inclination in the longitudinal direction of the craft (Fig. 10)

Fig. '7 shows a modified embodiment of the stabilizer. The lateral portions ll, I8 thereof incline in this case in a curve upwards from the central surfaces of the stabilizer which latter also in this case have a horizontal forward edge and slide on the water surface.

The stabilizer is preferably made of metal and thus does not have any innate buoyancy.

It will be understood that the parts 5, B may be made so as to extend uninterruptedly in transverse direction underneath the hull, whil according to other embodiments they may be divided into more than two parts.

Fig. 2 shows a watercraft having two stabilizers 4 of the kind shown in Fig. 1, the hull being provided with two hydrofoils 3. If desired, three or more hydrofoils may be arranged. The dynamic sustaining system created by the hydrofoils is located so that the upwardly directed resultant force R of said system is located aft of the centre of gravity G of the watercraft. One

or more of the hydrofoils 3' may be assumed to be of such a type as has no latitudinal stabilizing force of its own.

The stabilizer or forward planing surface or system of surfaces, in the following called foreplane, has five distinct functions when used on a dynamically sustained watercraft.

(1) Automatic control of the angle of attack of the hydrofoil (dynamic sustaining systems): The action of the foreplane in planing on the surface of the water in running position provides an automatic check on the angle of attack to the water of the hydrofoil or hydrofoils, which are fixed at a given angle to the hull-of the watercraft, in the following manner: should the foreplane, for example, be lifted upwards by the ction of a wave or some other similar surface irregularity in the water, this upward movement of the foreplane is transferred to the bow of the hull and thence to the hydrofoil, causing an automatic increase of the angle of attack to the water of the hydrofoil, simultaneously increasing the lifting force on said hydrofoil and thereby raising the stern of the boat to a somewhat lesser degree than, but in direct proportion to, the lift of the bow. The result is a decrease in the pitching motion characteristic of a displacement boat or a planing boat in disturbed water. (The same process in reverse naturally is the result of a sudden drop in the foreplane resulting in a decrease in the angle of attack of the hydrofoil). (2) Shock absorbing effect in disturbed water: The sharp profile and wing form of the foreplane, plus its lack ,of innate buoyancy, enable it to proceed in a plane with the average surface of the water rather than with the constantly changing levels of minor fluctuations in that surface caused by waves or other similar disturbances. The leading edge of the planing surface thus cuts through the tops of the smaller waves and gives the boat a smooth horizontal course. The entire structure of the foreplane is also a protection against the bouncing or slapping so common in fast boats of the planing type (i. e.: racing boats) operating in Water which is not perfectly calm. If the bow of a dynamically sustained boat equipped with a foreplane should rise clear of the water just after a wave top, and then fall toward the water surface in the following trough, the foreplane structure provides a shock absorber for the hull; the resistance of the foreplane to vertical passage through the water being pronounced, but not as great as the corresponding resistance of a displacement or planing hull. The result in the case of the foreplane-equipped boat is a breaking of the impact 4 and a gradual braking of the fall a the combined foil and planing eifects of the foreplane take effect and prevent more than a momentary contact of the hull itself with the water before normal running position is resumed. The sharp jar which accompanies such a manoeuvre in a displacement or planing hull is eliminated.

(3) Function as a hydrofoil during the moment of lift: The hydrofoil profile of the foreplane, acting under water before acceleration has proceeded to the point where the actual hydrofoils or dynamic sustainers have enabled the hull to free itself from the surface, enables the foreplane to act at these low speeds as a dynamic sustainer in itself and to contribute a strong lift of its own to the forward portion of the boat. By reason of the foreplanes greater surface area as compared to the hydrofoils, this lift is more effective than that of the foils and thereby (see point 1) increases the angle of attack of the foils, simultaneously increasing their capacity for lift and freeing the entire hull sooner than would otherwise be the case. The action of the foreplane in rising quickly to the surface, even at low speeds, and beginning to plane, raises the forward portion of the boat out of the water, decreasing the total water resistance of the boat, enabling it to accelerate faster, and thereby hastening the completion of the lifting process additionally.

(4) Longitudinal stabilizing function: The nature of a hydrofoil operating entirely or partly under water is such that it has no stabilizing effect along the longitudinal axis of the boat to which it is attached and which it supports wholly or partially. In order to achieve such a longitudinal stability some means of orienting the boats progress to a plane of reference parallel with the plane of the waters surface is necessary. This orientation is provided by the foreplane, which follows the water surface itself and prevents the boat, if the foreplane is placed according to the drawing with respect to the center of gravity of the boat, from either nosing down or rearing on the water.

(5) Latitudinal stabilizing function; A bowed hydrofoil, such as that shown in the drawing, provides a strong latitudinal stabilizing force of its own, but this force does not take effect until tipping has reached a point where the perpendicular joining the lines representing the weight of the watercraft at the center of gravity and the line representing the lift at the center of lift of the foil is sufiiciently large to produce an effective stabilizing moment. (See Fig. 11.) This may not occur before a tilt of several degrees is achieved. The foreplane, however, provides an immediate latitudinal stabilizing force at the first incidence of tilting. The upwardly inclined lateral portions 1, 8 of the foreplane-whose angle of attack to the water is greater than that of the normal planing surfaces 5, 8are placed in contact with the water during tilt and immediately provide a stabilizing force perpendicular to their lower faces (see Fig. 12). The V-shaped gap formed by the plates l2 in the central portion of the foreplane has the effect of quickly shifting the center of lift of the system further to the down side of the system during tilt, thus producing a rapid righting tendency.

The said function of the foreplane even if same is combined with a hydrofoil having a latitudinal stabilizing effect of its own, is of special importance at relatively low speed of the craft, since the stabilizing tendency of the bowed hydrofoil does not reach its full efiiciency before considerable running speed is reached, while the described effects of the foreplane are pronounced even at low speeds.

It will be seen from the aforesaid that the mode of operation of the watercraft, both when starting and during running in disturbed water, is attained by means of members (hydrofoil and a forwardly placed stabilizer) which are rigidly attached to the hull. Thus, movable members are superfluous. The combination of the forwardly placed stabilizer of the above-described construction with at least one hydrofoil having a latitudinal stabilizing force of its own will make the watercraft insensitive to horizontal variations of the position of the centre of gravity arising through forward, aftward or lateral displacements of the watercrafts variable load.

As will be seen from the drawing the centre of gravity G of the craft itself including the machinery is situated at a relatively short distance forward of the upwardly directed resultant force of the dynamic sustaining system and at a considerable distance aft of the stabilizer.

What we claim is: l

1. In a dynamically supported watercraft with hull rising clear of the water, a dynamic sustaining system comprising at least one hydrofoil and located such that the upwardly directed resultant force of said system is located near to and aft of the center of gravity of the craft so as to carry the main portion of the weight of the craft, and a stabilizer spaced from the hull and located forwardly of the center of gravity at a considerably greater distance therefrom than said sustaining system so as to carry a small amount only of said weight, said stabilizer having a central portion adapted at normal speed to rest on the surface of the water, and lateral portions having upwardly inclined faces extending above the surface of the water when said central portion is resting thereon, the central portion of said stabilizer forming two planing surfaces, one at each side of the longitudinal axis of the craft, inwardly and upwardly inclined plates extending longitudinally of the craft and constructed and arranged to connect said planing surface to each other.

2. In a dynamically supported watercraft with hull rising clear of the water, a dynamic sustaining system comprising at least one hydrofoil and located such that the upwardly directed resultant force of said system is located near to and aft of the center of gravity of the craft so as to carry the main portion of the weight of the craft, and a stabilizer spaced from the hull and located forwardly of the center of gravity at a considerably greater distance therefrom than said sustaining system so as to carry a small amount only of said weight, said stabilizer having a central portion forming at least one planing face adapted at normal speed to rest on the surface of the water, and lateral portions having upwardly inclined faces extending above the water level when said central portion is resting thereon, the angle of attack to the water of said planing face being smaller than the angle of attack to the water of said upwardly inclined portions.

3. In a dynamically supported watercraft with hull rising clear of the water, a dynamic sustaining system comprising at least one hydrofoil and located such that the upwardly directed resultant force of said system is located near to and aft of the center of gravity of the craft so as to carry the main portion of the weight of the craft, and a stabilizer spaced from the hull and. located forwardly of the center of gravity at a considerably greater distance therefrom than said sustaining system so as to carry a small amount only of said weight, said stabilizer having a central portion adapted at normal speed to rest on the surface of the water, and lateral portions having upwardly inclined faces extending above the surface of the water when said central portion is resting thereon, th central portion of said stabilizer forming two planing surfaces, one at each side of the longitudinal axis of the craft, inwardly and upwardly inclined plates extending longitudinally of the craft and constructed and arranged to connect said planing surfaces to the body of the hull.

BO KARL LORITZ ALIVIQVIST. BJGRN OLOF ELGSTROM.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,976,046 Tietjens Oct. 9, 1934 2,139,303 Grunberg Dec. 6, 1938 2,257,405 Von Burtenbach Sept. 30, 1941 2,257,406 Von Burtenbach Sept. 30, 1941 FOREIGN PATENTS Number Country Date 517,518 Germany Feb. 4, 1931

Images