US 3316874 A
Abstract available in
Claims available in
Description (OCR text may contain errors)
H. D. CANAZZI May 2; 1967 BOAT HULLS 2 Sheets-Sheet 1 Filed Oct. 9, 1964 INVENTOR fenr r DonaZci aznazzt A'Z'T NEK H. D. CANAZZI May 2, 1967 BOAT HULLS 2 Sheets-Sheet 2 Filed Oct. 9, 1964 & mw
7 I'll ll v V/ INVENTOR JfrnyfimzaZ'dCaflaZZi United States Patent 3,316,874 BOAT HULLS Henry Donald Canazzi, 178 Jewett Parkway, Buffalo, N.Y. 14214 Filed Oct. 9, 1964, Ser. No. 402,769 Claims. (Cl. 114-67) This invention relates to boat hulls. More particularly, it relates to a novel planing type of boat hull designed to skim on the surface of the water with maximum speed and economy and to operate with maximum efficiency.
Generally, boat hulls designed for use in small pleasure craft can be divided into two distinct classes. One type, such as that commonly used in skiffs, dorys and the like is designed to move through the water, displacing an amount of water equal to the weight of the boat. Boats of this type are referred to as displacement hulls and such hulls are not capable of developing high speeds. Generally, hulls of this type have a maximum speed of about mph. and no significant improvement in performance results by increasing the motor power on a hull of this yp In order to obtain increased speeds, modern outboard utilities, runabouts, cruisers and the like have hulls de signed on different principles. The stern area on such boats is great enough so that when speed is increased and the bow lifts, the pressure of the moving water thereon will sustain the weight of the boat. Such boats are known as planing hulls.
The planing hull at higher speeds skims the surface of the water. The only things that hold it back are the drag of the water and air resistance. Thus the speed of such a hull can be increased by reducing the resistance to forward motion due to the contact with the water passing over the surface of the hull.
Many theories and various hull designs have been proposed for reducing the surface friction of the water against the hull so that increased speeds may be obtained. Thus, it has been recognized that the frictional resistance can be reduced by reducing the wetted surface of the hull. One way in which this has been accomplished is to introduce a lateral break or step about midway between the bow and the stern. Such a stepped hull structure concentrates the weight of the boat, once a fairly high speed has been reached, on a relatively small area of the hull bottom adjacent the stern, thereby reducing the wetted surface and so providing less water resistance to forward motion.
While such stepped hulls do reduce the frictional resistance of water on the hull, the demand for higher boat speeds requires that water resistance be further reduced. With a stepped hull, regions of reduced pressure tend to form immediately aft of the step or steps thereby creating drag. Such drag is present and troublesome even before true planing conditions are reached, i.e. at 'low speeds. As a result, the stepped hull is more ineflicient than any other type at low speeds.
It is, therefore, an object of the present invention to provide a planing type of boat hull having a minimum amount of surface friction between the water and the hull.
Another object of the present invention is to provide a planing type of boat hull, having one or more lateral steps, which is capable of developing high speeds and which has very high efliciency at both high and low speeds.
Another object of this invention is to provide a stepped boat hull having means for reducing the surface friction of water on the hull and drag resulting from the step.
Another object of the invention is to provide a planing type of boat hull, having one or more lateral steps, which is free of excessive drag and in which the surface friction of the water against the hull is reduce-d when operated at both high and 'low speeds.
These and other objects and advantages of the invention will become apparent from the following detailed description and drawings of one embodiment of the invention in which:
FIGURE 1 is a side elevational view of a boat hull according to the present invention;
FIGURE 2 is a bottom plan view of the hull construction illustrated in FIGURE 1;
FIGURE 3 is a cross-sectional view taken through section line 3-3 in FIGURE 2;
FIGURE 4 is a sectional view taken along section line 4-4 in FIGURE 3; and
FIGURE 5 is a top plan view taken along line 55 in FIGURE 4.
The present invention provides a planing type of boat hull having one or more lateral steps. While the hull as illustrated and described hereinafter has two lateral steps, it will be understood that the hull according to the present invention may have one, two or more lateral steps. The stepped hull of the present invention is provided with a plurality of laterally spaced openings or vents in the steps and means for discharging air through such vents. In this manner, as will be described in detail hereinafter, air is discharged from the vents to provide a cushion of air beneath the hull. This discharge of air reduces the surface friction of water against the hull, thereby enabling the boat to plane more readily and to achieve greater speeds when the boat is in the planing position. In addition, the discharge air prevents the formation of regions of reduced pressure adjacent the steps, thus further decreasing the drag on the hull.
Referring now more particularly to the drawings, numeral 10 generally designates the hull construction of the present invention. The internal and superstructure of the boat form no part of the invention and will not be described. The hull 10 is generally rectangular in outline with generally parallel side surfaces @11 extend ing from the aft part of the forward or bow portion '12 to the stern portion 13. The sides '11 are inclined slightly inwardly from top to bottom and are substantial- -ly straight relative to their longitudinal length from the transom 36 throughout the stern portion '13 of the hull, while in the bow portion 12 they converge to form a relatively sharp prow 14. Forward, the hull has an overhanging deck 15 which extends a substantial distance outwardly and aft from the prow. Each of the side surfaces .11 has an outwardly projecting gunwale 16 along the upper edge thereof and an integral, outwardly projecting spray rail 17 that extends longitudinally about midway between the top and bottom edges of the side surfaces.
The bottom 18 of the hull, which carries a keel 19, extends between the sides L11 and comprises outer, fiat, longitudinally extending portions 20 adjacent the sides and a depressed, central, longitudinally extending portion 22 which is divided laterally by the keel 19. The bottom portions 20 and the sections of the depressed central portion 22 of the bottom on either side of the keel 19, which bisects the latter, slope downwardly toward the centerline of the hull at an angle of the order of 10. The portions 20 of the bottom are substantially flat for the major portion of the hull length but narrow and curve upwardly toward the bow merging with the portion 22 into the prow 14. longitudinally extending, downwardly directed deflector rails 21 are formed along the chines on each side of the hull, these rails serving to deflect downwardly water thrown outwardly and upwardly from the central bottom portion 22. Retaining rails 23 are provided along the outer edges of the central depressed bottom portion 22. These tend to retain air introduced below the bottom portion 22 as hereinafter described.
The bottom portion 22 is provided with two longi tudinally spaced lateral steps, a forward step 25 and an aft step 26- that extend substantially across the width thereof. The forward step 25 is preferably positioned about midway between the bow and the stern and the aft step 26 is preferably positioned about midway between the step 25 and the stern. The steps 25 and 26 extend inwardly from points adjacent the outer edges of the depressed bottom portion 22 and, according to a preferred embodiment, the risers 27 and 28, respectively at the aft edges thereof shaped as a widely spread V with the bottom of the V being directed toward the stern. In a preferred embodiment the riser 27 of step 25 is about 1 inch in height and the riser 28 of step 26 is about /8 inch in height. However, the position, shape and rise of the steps may vary according to the size of the hull and other design factors.
Each of the risers 27 and 28 is provided with a plurality of slots 29 and 30, respectively. These slots extend laterally and are laterally spaced, the size and spacing being such that substantially the full lengths of the step risers are vented. The slots 29 and 30 serve to introduce air beneath the bottom of the hull.
In order to supply air to the slots 29 and 30, the floor 33 of the boat is supported a substantial distance above the bottom 18 of the hull to provide an enclosed air chamber 34 which extends substantially the entire length of the hull. A spacing member 35, transversely corrugated to form longitudinal channels, is positioned Within the air chamber 34 to provide support for the floor 33. The member 35 preferably extends from the bow portion 12 of the hull adjacent the prow 14 to the transom 3'6 and for substantially the full width of the hull bottom. Alternate channels in the spacing member 35 are closed by the hull bottom 18 and the floor 33, thus providing longitudinally extending air passages 38 in the depressed center portion 22 of the bottom.
As best shown in FIGURE 4, the slots 29 and 30 in the step risers communicate with the air passages 38. At the forward end of the air chamber 34 there is provided an air inlet to supply air to the passages 38. In the illustrated embodiment the air inlet is formed as a pipe or conduit 39 extending upwardly from the air chamber 34 through the floor 33 to a point above the water line of the boat. A rotary disc valve 40 is provided at the outer end of the conduit 39 to control the admission of air and this valve may be operated by suitable means such as a rod 41 attached to operating arm 42 of the valve.
According to the present invention, when the valve 40 is open and the boat is moved through the water, the reduced pressure in the regions just aft of the steps 25 and 26 causes air to -fiow through the passages 38- and the slots 29 and 30, thus reducing drag on the hull. The air emitted through the slots forms a cushion under the hull bottom, thus reducing the surface friction of the water on the hull. This results in further reduction of drag and causes the hull both to plane more easily and to achieve higher speeds when planing than would ordinarily be obtained with a particular application of power. Much greater efiiciency and economy may thus be obtained with the present invention. It has also been found that stopping the flow of air through the slots 29 and 30, as by closing the disc valve 40, has a significant effect .in slowing the boat, this effect being especially noticeable at higher speeds.
The hull illustrated as an embodiment of the present invention is formed of resin-impregnated glass fabric molded and laminated to give an integral, one piece body by procedures well known in the art. This provides a hull of accurate contour and smooth surface and permits reduction in manufacturing costs. The floor 33 and spacing member 35 may also be formed of resin impregnated glass fabric separately molded and cemented in place. It may here be noted that the spacing member 35, when cemented in place, not only provides air passages 38, but also greatly stiffens the hull bottom 18 and the floor .33. The deck 15 is likewise preferably molded separately and cemented in place.
As previously mentioned,-the present invention comprehends stepped hulls in which there may be provided one or a plurality of steps. Other variations and modifications of the invention are also obviously possible; For example, the air inlet in the bow of the boat maybe changed to draw air from one or more inlets opening through the bow above the Waterline or through the deck 15. The airflow into the air passages 38 may be controlled, if desired, by another type of valve or no valve may be employed. On the other hand, a blower, either hand operated or driven by a suitable motor or engine may be provided to force air through the passages 38 and slots 29 and 30. As further possible structural modifications, may be mentioned the provision of additional air vents on the side surfaces of the steps 25 and 26 and the forming of the spacing member 35 in a plurality of parts which may be used separately or fastened together. It will also be recognized that the hull may be formed of other suitable material in whole or in part.
Even further modification of and variation from the specific preferred details shown and described in possible without departing from the spirit of the invention, and it is, therefore, to be understood that the invention is to be construed as broadly as permitted by the appended claims,
1. A high speed, planing hull having a bow portion and a stern portion and including sides that converge in said bow portion to form a relatively sharp prow and which, in the stern portion are joined to a transom, a bottom, said bottom comprising outer, flat, longitudinally extending portions adjacent said sides and a depressed, central, longitudinally extending portion having a lateral, downwardly projecting step extending substantially across the full width thereof, said step being vented across substantially the full width of the rear surface thereof, said hull being provided with an interior floor and spacing means between said bottom and said floor, said spacing means extending from the bow portion of said hull to said transom and for substantially the full width of said hull bottom and being transversely corrugated to form longitudinal channels, and means within said hull for supplying air to the rear vented portion of said step whereby air is discharged under said bottom to provide a cushion of air that reduces drag on said hull, said means for supplying air being at least in part in said central portion of said bottom and including said spacing means.
2. A high speed, planing hull as set forth in claim 1 in which alternate channels are closed by the hull bottom and said floor.
3. A high speed, planing hull as set forth in claim 2 in which said spacing means is cemented to said hull bottom and to said floor.
4. A high speed, planing hull having a bow portion and a stern portion and including sides that converge in said bow portion to form a relatively sharp prow and which, in the stern portion, are joined to a transom, a bottom, said bottom comprising a relatively flat portion having a lateral, downwardly projecting step of substantially less length than the width of said bottom, said step being vented, by openings therein, across substantially the full width of the rear surface thereof, said hull being provided with an interior floor and spacing means between said bottom and said floor, said spacing means extending for a substantial portion of the length of said hull and being transversely corrugated to form longitudinal channels, and means within said hull for supplying air to the rear vented portion of said step through at least one of said channels whereby air is discharged through said openings under said bottom to provide a cushion of air that reduces drag on the hull.
5. A high speed, planing hull having a bow portion and a stern portion and including sides that converge in said bow portion to form a relatively sharp prow and which, in the stern portion, are joined to a transom, a bottom, said bottom comprising outer, fiat, longitudinally extending portions adjacent said sides and a depressed, central, longitudinally extending, fiat portion, a lateral, downwardly projecting step in and extending substantially entirely across said central portion, said step being vented, by openings therein, across substantially the full width of the rear surface thereof, said hull being provided with an interior floor and spacing means between said bottom and said floor, said spacing means extending from the bow portion of the hull to the transom and for substantially the full width of the hull bottom and being transversely corrugated to form longitudinal channels, and means within said hull for supplying air through said spacing means to the rear vented portion of said step whereby air is discharged through said openings under said hull to provide a cushion of air that reduces drag on the hull.
References Cited by the Examiner UNITED STATES PATENTS MILTON BUCHLER, Primary Examiner. FERGUS S. MIDDLETON, Examiner. T. M. BLIX, Assistant Examiner.