US3331347A - Boats comprising means for introducing air to submerged portions of the boat bottom - Google Patents

Description

ERGED July 18, 1967 E. J. VON HEIIDENS'QI'AM BOATS COMPRISING MEANS FOR INTRODUCING AIR TO SUBM PORTIONS OF THE BOAT BOTTOM 5 Sheets-Sheet 1 Filed June 23, 1965 Fig.3a

y 1967 E. J. VON HEIDENSTAM 3,331,347

BOATS COMPRISING MEANS FOR INTRODUCING AIR TO SUBMERGED PORTIONS OF THE BOAT BOTTOM Filed June 25, 1965 5 Sheets-Sheet 2 Flg 8 Fig 9 l 71 10 72 75 73 73 y 13, 1967 E. J. VON HEIDENSTAM 3,331,347

BOATS COMPRISING MEANS FOR INTRODUCING AIR TO SUBMERGED PORTIONS OF THE BOAT BOTTOM Filed June 23, 1965 5 Sheets-Sheet 5 y 1967 I E. J. VON HEIDENSTAM 3, 3

BOATS COMPRISING MEANS FOR INTRODUCING AIR TO SUBMERGED PORTIONS OF THE BOAT BOTTOM Filed June 23, 1965 5 Sheets-Sheet 4 --."""IIIIIZ 2 8 July 18, 1967 E. J. VON HEIDENSTAM 3,331,347

BOATS COMPRISING MEANS FOR INTRODUCING AIR TC SUBMERGED PORTIONS OF THE BOAT BOTTOM Filed June 25, 1965 s Sheets-Sheet s United States Patent 2 Claims. (Cl. 114-67) Several types of partly air-borne boats are known in the art in which the boa-t when moving over a water surface is to an essential part supported by a cushion of compressed air or other gas enclosed between portions of the boat bottom and the water.

The invention consists primarily of the provision of means to make air or other gas used for reducing friction between the boat and the water flow along the boat botmm in such a manner that essential portions of the bottom are entirely carried by the intermediary of an air cushion.

One object of my invention is by said means to increase the speed of high speed boats or, respectively, to diminish the motor force required for a certain speed.

A further object of the invention is to provide means greatly improving the properties and behavior of a high speed boat which is in part carried by air supplied to the space underneath portions of the boat bottom when the boat moves at high speed on wavy sea, and to distribute air introduced underneath the boat bottom so as to obtain favorable support and friction diminishing characteristics of the air.

With these and other objects in view my invention is directed to a high speed boat of the type comprising bottom surfaces, the portions of which in contact with water have at least in part a V-shape or a shape similar thereto, such portions of the bottom thus enclosing an angle with the center longitudinal vertical plane of the boat which is less than 90. More specifically, a boat according to the invention relates to the type of high speed boat comprising a forward bottom portion which, adjacent said center longitudinal vertical plane, terminates in a step separating the forward bottom portion from a rearward bottom portion, the latter adjacent the step, being located at a higher level than the forward bottom portion adjacent the step, said boat further comprising means for admitting gas to the space below said rearward bottom portion.

According to the present invention, said step extends from said longitudinal vertical plane obliquely rearwardly towards the sides of the boat on each side of said vertical plane at least over part of the range between said plane and each side. Further, this step terminates at a distance from the side walls of the boat, the forward bottom portion thus merging, without astep being present, in the rearwardbottom portion at least at the extreme lateral parts of the rearward bottom portion.

In the following description the word air will be used for the cushion of gas introduced underneath the rearward portion of the bottom, although it will be understood that such gas may consist of a mixture of pressurized air and exhaust gases, or other gases or gas mixtures.

With the arrangement of the bottom step as defined above, several improvements are obtained in comparison to known air cushion boats.

With a boat comprising a bottom step as defined above, certain disadvantageous phenomena which have shown to be present with boats comprising means for supplying.

air to the bottom thereof, are essentially eliminated, this being mainly due to the fact that the supporting air cushion obtains a considerable size as compared with the size 3,331,347 Patented July 18, 1967 of the boat bottom surface within the outer limits of the bottom surface in contact with the water during running, and this without air leakage which is necessarily present with partly airborne boats.

With a shape of the bottom step as mentioned above and the essentially continuous merging of the forward portions of the bottom strakes with the rearward ones adjacent the boat sides, the water seal along the edges of the air cushion underneath the rearward part of the boat bottom is greatly improved, such a seal being essential for the creation of a large air cushion causing a favorable relation between boat speed and driving force, the force necessary for creating the air cushion bein taken into account as well.

Furthermore, the shape of the step and the termination thereof adjacent or at a distance from the boat sides to letthe forward bottom portion laterally merge into the aft portion of the bottom diminishes the risks of frictionincreasing water motion along and in contact with the bottom rearwardly of the step and wingwards.

Due to the small resistance caused by the boat hull in contact with the water and the gas cushion, the resulting drag of the boat is extremely small. Further the friction resistance is very small due to the fact that the bottom skin portions which are in contact with the water during running essentially constitute only .a minor sealing surface or even sealing line, the boat supporting forces being essentially created by the air cushion pressure. Tests have evidenced, that a boat according to the invention show the property, not usual for planing boats, of obtainin g a very low total resistance force over a comparatively large range of speed. Further, it has very good steering properties, the shape of the step aiding in holding the supporting air cushion enclosed underneath the bottom to an extent essentially reducing the total resistance force.

Various features and advantages of the invention will be described in detail in connection with accompanying drawings, in which:

FIG. 1 is a longitudinal side view of a first embodiment of a boat according to the invention;

FIG. 2 is a plan view of the boat shown in FIG. 1;

FIGS. 3ae are vertical cross sections in planes along lines IIIa, I111), I110, H112 and IIIe, respectively, of FIG. 2;

FIG. 4 illustrates, by way of an example, a shape of the step of the boat as viewed from aft towards stem, FIG. 4 illustrating the starboard part of the boat bottom and side;

FIG. 5 is an inverted plan view of a further embodiment of a boat according to the invention;

FIG. 6 is a section taken on line VI-VI of FIG. 5;

FIG. 7 is an inverted plan view of a further embodiment of a boat comprising two steps;

FIGS. 8 and 9 schematically illustrate means for supplying air to the space underneath the boat bottom rearward of the step;

FIG. 10 illustrates still another embodiment of a boat according to the invention;

FIG. 11 is a side view of a boat comprising a plurality of steps;

FIG. 12 is an inverted plan view of the boat illustrated in FIG. 11;

FIG. 13 is a vertical section of the bottom skin of the boat illustrated in FIGS. 11 and 12 taken on line XIII XIII of FIG. 12;

FIG. 14 is a vertical section of the bottom surface taken on line XIV-XIV of FIG. 12;

FIG. 15 is a vertical section of the bottom taken on line XV-XV of FIG. 12;

XVI of FIG. 12;

FIG. 17 is a vertical cross sectional view of still anoth embodiment of a boat;

F G. 18 is an inverted plan view of the boat illustrated in FIG. 17;

FIG. 19 is a cross sectional view of the boat illustrated in FIGS. 17 and 18 taken on line XIX-XIX of FIG. 18; and

FIGS. 20 and 21 are cross sections through bars connecting portions of steps of the boat illustrated in FIGS. 17-19.

FIGS. 1 to 3 illustrate a first embodiment of a boat with a step according to the invention. In FIGS. 1 to 3 there is shown a hull 1 of the boat having a bottom 2 rearwardly of the step, a bottom 3 forwardly of the step, bilge lines 4 and a stern 5. The water level with the boat at rest is shown at 6-6. An air supply distribution duct 7 is fed from an air duct 8. A boat driving motor 9 drives a fan 10. Numeral 11 represents side Walls of the hull and 12 designates the step between the rearward portion 2 and the forward portion 3 of the bottom. A space 13 is formed for an air cushion rearwardly of the step. Lines 1414 represent the water level with the boat running at speed. 15 is the wetted range of the forward portion of the bottom during running, 15a being the wetted portion of lateral parts of the rearward bottom portion constituting lateral sealing surfaces or lines during running, 15b being the wetted aft bottom surface. Water is discharged during running over smooth water along path 16 the bounds of which are shown by dash-dot lines 16a16a, during running over waves water is discharged along path 17.

When at rest, the boat is displacing, the entire portion 2 of the boat bottom rearwardly of the step and major parts of the front portion 3 of the bottom, as well as portions of the side walls 11 above the bilges 4 then being submerged as indicated by water level line 6-6 in FIG. 1. When the motor 9, and thus the fan as well, is started, air is supplied through duct 8 to the air distribution duct 7, which extends along the step 12 or a great part thereof. From the air distribution duct 7 the air enters the space 13 rearwardly of the step and underneath the rearward bottom portion 2, said air constituting an air cushion within the space 13. Air supplied when the boat is at rest will then be expelled along the boat sides. When the screw of the boat (not illustrated) is then coupled to the motor, the boat starts moving forward while air is supplied to the space 13. When the boat obtains its full speed or other high speed at which the boat is normally intended to be used, the boat and in particular the rearward parts thereof will occupy a higher position relative to the water level, as illustrated by water level line 1414.

The fan 10 is so dimensioned, that, when the boat is running at speed, the fan delivers compressed air required for compensating the inavoidable leakage of air from the air cushion. The leakage of air arises for several obvious reasons, one object of the invention as mentioned above being to provide means to restrict such leakage and consequently the energy consumed for generating the compressed air to an acceptable value, without jeopardizing other valuable characteristics of the boat as, for instance, stability and maneuverability on smooth water as well as in rough sea.

One such cause of loss of air and one which is present also when the boat is moving over a smooth water surface, is that the air, even if the pressure of the air cushion is held very small, will be sucked out backwardly by the water streaming towards the rear bottom portions under a very small angle of attack.

In the most common situation the water surface is, however, not completely smooth, which brings about an increase of air loss not only in a rearward and in a lateral direction, but incidentally in the direction of movement of the boat as well.

When the water surface is smooth, the wetted surface is of the shape illustrated at for the forward portion of 4 the bottom and at 15a and 15b for the lateral and the rearmost parts, respectively, of the rearward portion 2 of the bottom. The water discharge from the boat when it moves on smooth water surface, is illustrated by path 16. When the forward portion of the bottom loses its contact with the water locally, a second type of water discharge will arise as well, this water discharge being schematically illustrated by path 17 in FIG. 2. Tests in practice have shown that such discharge of water into the space of the air cushion is directed outwardly and upwardly, so as to strike the lateral parts of the rearward bottom portion 2 at a small angle. With the construction of the boat bottom as described, the resistance caused by such inward water discharge as illustrated by the path 17 is greatly reduced.

FIG. 4 illustrates by way of example the shape of a step 12 as viewed from stern to stem, showing how the height of the step decreases laterally towards the bilge 4 to vanish entirely at or a short distance from the bilge. Experiments in practice have proven that, if H is the largest step height within the center part of the bottom over about one third of the boat breadth, the height of the step should preferably decrease so as to obtain a value h=H 3 or less within about the outermost /5 of the boat breadth. The angle B between the forward and rearward bottom portions adjacent the step should be less than 30 and preferably less than 20.

Further improvements of the properties of a boat according to the invention and in particular the properties of such a boat when running a high speed over a rough water surface will be evident from the following description of further embodiments of a boat according to the invention.

FIGS. 5 and 6 illustrate an embodiment comprising a plurality of further steps 12a, 12b and 120 extending from a recess 34 in the bottom surface exending rearwardly of the front step 2 and connecting to a compressed air duct 37. The rearward part of the bottom comprises a center portion 33 located at a higher level than the inner parts of lateral portions 31, the raised center portion 33 causing a concentration of the air exit to the center portions of the stern and at a level to diminish the possibility for the air to be sucked downwardly by the screw or screws when running in rough sea. The lateral portions 31 together constitute a V-shaped structure aiding in hydrodynamic stability of the boat.

FIG. 7 shows a boat comprising two steps, a step 35 of essentially the same shape as the front step 12 being arranged rearwardly of the step 12. The step 35 is arranged at such a level that normally, that is when the boat is moving over a smooth water surface, it does not contact the water, but it aids in guiding water jets hitting the bottom skin between the two steps to cause the water again to leave the skin and restore the air cushion. 16 and 17 represent the water discharge paths where the boat moves respectively over smooth and rough water.

FIG. 8 schematically illustrates the fan 10 for supplying air to the space beneath the bottom rearward of the step and means to prevent water from entering the fan under conditions for which the pressure underneath the boat may exceed the pressure of the fan. For this purpose, the outlet of the fan 10 connects to the air cushion space 13 by means of a duct 71 containing a non-return valve 72.

FIG. 9 schematically illustrates a duct system which utilizes the exhaust gases of the boat motor as a source of compressed gas. The exhaust gas duct 73 connects to the space 13 via a non-return valve 72. A branch duct 74 of duct 73 between the exhaust gas manifold of the motor and non-return valve 72 connects to open air via a further non-return valve 75 to prevent creation of a vacuum sucking water into the motor.

FIG. 10 illustrates an embodiment according to the invention comprising a front step of conventional construction in the front portion 3 of the bottom. This step is arranged at a level such that when the boat is moving at speed over calm water surface the step is raised over sea level, while it improves the longitudinal stability when the boat is moving over waves by the front bottom surface 81 occasionally contacting the water, the step 80 aids in causing the water to hit the front bottom portion 3 adjacent the step 12 at an angle of attack essentially corresponding to the one prevailing when the boat is moving over calm water. In this embodiment, the bilge line 4 has a point of inflection 82 and is curved to correspond essentially to the water level downstream of the stem when the boat moves over calm water in the highest speed range to provide as far as possible an ideal sealing line or surface between boat bottom and water. Forward of the inflection point 82 the bilge line is concave, viewed from above, and rearwardly of the point of inflection it is convex, the rearmost porton of the rearward bottom portion 2 ending in a V-shaped portion having a keel line 61 and the front part of the rearward bottom portion 2 having a section in lateral vertical planes which is essentially convex upwardly.

Figs 11 and 12 illustrate a further development of a boat according to the invention by which the properties of the boat when moving over a rufiled sea is further greatly improved. In this embodiment a number of further steps 112114 are arranged rearward of the step 12 and extend from the longitudinal vertical center plane obliquely forwardly towards the bilge line 4 to terminate at or before reaching the bilge line. Preferably, these steps 112-114 are curved so as to have a concave shape as viewed from the stem of the boat. In tin's embodiment the air duct 8 from fan 10 connects the air ducts 107 extending in the longitudinal direction of the boat and having air outlet apertures 108 opening in the air cushion space adjacent and rearward of each step.

The steps 112-114 are arranged at such a level that, in principle, they have no effect or action when the boat is moving at high speed over a calm sea level. When the boat moves over a ruffied water surface by which water jets 17 of the type described above are discharged rearwardly of the front step 12, said jets are taken care of by a successive concave step towards which the jets originally leaving the front step 12 .are essentially perpendicular or at least constitute an angle not far from 90. Although steps of the kind described in connection FIGS. 5-7 essentially improve the running characteristics of the boat on ruffled sea, a still more favorable result is obtained with a shape of the steps as illustrated in FIGS. 11 and 12.

As mentioned above FIGS. 13-15 illustrate sections taken on the lines XIII, XIV and XV, respectively, of FIG. 12. In FIG. 15, a is the angle of attack of a normally wetted part of the rearward bottom portion 2 when the boat is running on calm water. The size of angle a should be between 3 and 12, and preferably between 6 and 9.

FIG. 16, which is a section on the curved line XVI of FIG. 12 along step 113, illustrates the air channel 107 extending between an internal bottom plating 104 and the rearward bottom portion 2, which in FIG. 16 is represented by step 113. FIG. 16 illustrates how the steps terminate at a point 139 located a distance from the bilge line 4, leaving a rim surface 132 on the rearward bottom portion 2 constituting a continuous extension to the forward bottom portion 3 laterally of the front step 12.

FIGS. 17-19 illustrate an embodiment essentially corresponding the one illustrated in FIGS. 1116, in which,

however, a central air distribution channel 215 extends centrally of the boat. This channel 215 opens downwardly over its entire length and extends sufiiciently far in the forward and rearward direction, so that air is admitted to all the spaces beneath the rearward bottom portion 2 and between each two successive steps. As evident from the section illustrated in FIG. 19, this embodiment makes it possible to construct the boat bottom in one continuous shell. The compressed air duct 8 opens into the roof 216 of channel 215. The steps 211-214 which are concave as viewed from the stem, are located rearwardly of the convex step 12 and bridge over the channel 215, constituting thereat flat bars 218, the lower surfaces of which have an angle of attack making the bars suitable to act either as hydrofoils, as illustrated by a section of a bar shown in FIG. 20 or as a step, as illustrated by the bar section shown in FIG. 21. In the latter case, the bar has a downstream end wall essentially perpendicular to the direction of motion of the boat.

What is claimed is:

1. A high speed boat comprising a boat hull having lateral bilge lines and including a bottom having a forward bottom portion and a rear bottom portion, said forward bottom portion terminating rearwardly in a step separatmg sa1d forward bottom portion from the rearward bottom portion, said rearward bottom portion having a foremost part which adjacent the step is located on a higher level than the forward bottom portion adjacent the step, to thereby define a space below the rearward bottom portion, means for generating and admitting compressed gas to the space below said rearward bottom portion, said step extending from the center longitudinal vertical plane of the boat obliquely rearwardly towards the bilge lines of the boat on either side of said vertical .plane at least over the major part of the distance between said plane and each bilge line to terminate laterally adjacent the bilge lmes so that the forward bottom portion merges with the rearward portion at least at the extreme lateral regions of the rearward bottom portion adjacent the bilge lines, said rearward bottom portion adjacent the stern on either side of said vertical plane having surfaces which form angles with said plane less than at least one further step extending over part of the rearward bottom portion rearwardly of the first said step between said forward and rearward bottom portions, each further step extending obliquely forwardly towards the bilge lines and terminating at or before reaching the same.

2. A high speed boat as claimed in claim 1 comprising a central air distribution channel in connection with said means for generating compressed gas, said channel extending centrally of the boat and being open downwardly toward the space below the rearward bottom portion, said further step extending laterally across said channel in the form of a bar having a lower face located at a level beneath the rearward bottom portion on either side of the channel.

References Cited UNITED STATES PATENTS 1,121,006 12/1914 Fauber 114--66.5 2,450,665 10/ 1948 Jutte 114-665 2,555,307 6/1951 Alysworth 114-66.5

FOREIGN PATENTS 418 1877' Great Britain. 1,243,460 9/1960 France.

MILTON BUCHLER, Primary Examiner. A. H. FARRELL, Examiner.

Claims (1)

1. A HIGH SPEED BOAT COMPRISING A BOAT HULL HAVING LATERAL BILGE LINES AND INCLUDING A BOTTOM HAVING A FORWARD BOTTOM PORTION AND A REAR BOTTOM PORTION, SAID FORWARD BOTTOM PORTION TERMINATING REARWARDLY IN A STEP SEPARATING SAID FORWARD BOTTOM PORTION FROM THE REARWARD BOTTOM PORTION, SAID REARWARD BOTTOM PORTION HAVING A FOREMOST PART WHICH ADJACENT THE STEP IS LOCATED ON A HIGHER LEVEL THAN THE FORWARD BOTTOM PORTION ADJACENT THE STEP, TO THEREBY DEFINE A SPACE BELOW THE REARWARD BOTTOM PORTION, MEANS FOR GENERATING AND ADMITTING COMPRESSED GAS TO THE SPACE BELOW SAID REARWARD BOTTOM PORTION, SAID STEP EXTENDING FROM THE CENTER LONGITUDINAL VERTICAL PLANE OF THE BOTTOM OBLIQUELY REARWARDLY TOWARDS THE BILGE LINES OF THE BOAT ON EITHER SIDE OF SAID VERTICAL PLANE AT LEAST OVER THE MAJOR PART OF THE DISTANCE BETWEEN SAID PLANE AND EACH BILGE LINE TO TERMINATE LATERALLY ADJACENT THE BILGE LINES SO THAT THE FORWARD BOTTOM PORTION MERGES WITH THE REARWARD PORTION AT LEAST AT THE EXTREME LATERAL REGIONS OF THE REARWARD BOTTOM PORTION ADJACENT THE BILGE LINES, SAID REARWARD BOTTOM PORTION ADJACENT THE STERN ON EITHER SIDE OF SAID VERTICAL PLANE HAVING SURFACES WHICH FORM ANGLES WITH SAID PLANE LESS THAT 90*, AT LEAST ONE FURTHER STEP EXTENDING OVER PART OF THE REARWARD BOTTOM PORTION REARWARDLY OF THE FIRST SAID STEP BETWEEN SAID FORWARD AND REARWARD BOTTOM PORTIONS, EACH FURTHER STEP EXTENDING OBLIQUELY FORWARDLY TOWARDS THE BILGE LINES AND TERMINATING AT OR BEFORE REACHING THE SAME.

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