US2896565A - Hydraulic flow control plate - Google Patents

Description

July 28, 1959 s. E. STEVENS 2,

HYDRAULIC mow CONTROL PLATE Filed Nov. 28, 1956 lf l'32 I l: ./28

52 40 26 54 I8 3844 58 J i 56 42 Fig. 2

INVENTOR. GEORGE E. STEVENS United States Pa HYDRAULIC FLOW CONTROL PLATE George E. Stevens, Watertown, Mass. Application November 28, 1956, Serial No. 624,771

4 Claims. (Cl. 11542) This invention relates to boats having screw type propellets at the stern ends of the vessels and more particularly to hoods or plates mounted at the propellers for improving control and. operation of boats.

In the operation 'of motor boats propelled from the stern, the bow tends to rise and the stem to settle deeper into the water in increasing proportions as the thrust exerted by the propeller and speed of the boat increases. As this condition becomes more pronounced, it results in several undesirable characteristics. It makes the boat more sensitive to pounding of the waves, increases the pitching of the boat so as to generally increase the roughness of the ride. Another undesirable result is that the boat becomes less maneuverable in that side slip of the boat during a turn is increased so as to make controlled turning more diflicult.

Pursuant to the present invention, these undesirable characteristics have been overcome and other desirable features and advantages have been achieved. Among the other features and advantages achieved by the present invention is an improvement in maneuverability and steering characteristics at all speeds of boat travel. At low speeds as well as high speeds, the boat can be turned with less side slip and greater precision. Another advantage is that of improving utilization of propulsive power of the propeller.

Accordingly a primary object of the present invention is the provision of a propeller hood which tends to keep the boat on an even keel at all speeds of travel.

Another object is the provision of a propeller hood 7 which provides a stern lifting force which is sufficient to counteract the prow lifting force by the water as the speed of the boat increases.

A further object is the provision of a propeller hood which cooperates with the rudder to increase directional response of the boat to the rudder.

A still further object is the provision of a propeller hood which increases thrust efficiency of the propeller.

And another object is the provision of a propeller hood which protects the propeller from contact with foreign objects and can withstand heavy impact without injury to the boat hull.

And a further object is the provision of an extremely simple propeller hood structure which is both relatively inexpensive to manufacture and to install at the propeller.

These features, objects and advantages are achieved generally by providing a cylindrical plate section in proximate relation to and above the propeller blades: with the axis of the hood tilted to provide lift for the stern during forward motion of the boat.

By placing the hood substantially in line with the apex of the prow of the boat, a proper transverse direction of the hood for the desired amount of lift at the stem is achieved.

By providing a spacer between the hood and keel and bolts passing through the hood, spacer and keel, very Patented July 28, 1959 rugged mounting is achieved which can withstand heavy shock loads without damage to the boat hull.

By providing a brace along each end of the hood and fixed to the sides of the keel, further rigidity of the hood is achieved as well as additional protective shielding for the propeller.

These and other features, objects and advantages will become more apparent from the following description taken in connection with the accompanying drawings of a preferred embodiment of the invention and wherein:

Fig. 1 is a side view of a portion of a'boat with a propeller hood in accordance with the present invention;

Fig. 2 is an end view taken on the line 2-2 of Fig. 1 to moreclearly show construction of the propeller hood.

Referring to Fig. 1 in more detail, a boat incorporating the present invention, only segments ofwhich appear in the drawing, is designated generally by the numeral 10. At the stern end 12 of the boat 10 ismounted a conventional propeller 14 having a drive shaft 16 passing through a sleeve 18 into the hull of the boat for engagement with a conventional driving motor (not shown). To the rear of the propeller 14 is a conventional rudder 20 mounted to a rudder shaft 22, the bottom end. ofwhich may, if desired, be pivotally anchored in a keel extension 24.

The upper end of the rudder shaft 22may pass upwardly the spacer 28 and keel planking 34 of the boat 10. The

hood 26 may be further anchored in place by a pair of bars36 and 38, one at each side of the hood 26. Each of the bars 36 and 38 may be anchored at one end to the "hood '26 and at the other end tothe boat keel 40 as by screws 42. The bars 36 and 38 may be of rectangular cross section and preferably bent and twisted so that the body portion 44 between each of the ends lies at right angles to the ends and parallel to the top 46 of the hood 26. The top 46 of the hood 26 is in transverse relation to the axis of the shaft 16 and is preferably on a line 47 running to apex 48 of prow 50 of the boat 10.

Referring to Fig. 2, assuming the propeller rotates in a clockwise direction as shown by the arrow 52, the side of the hood 54 on the uprnoving side of the propeller 14 is preferably below the centerline 56 of the propeller 14. The other side 58 of the hood 26 which is on the down moving side of the propeller 14 may be above the centerline 56.

' The hood 26 is found to operate best when its front ends 60 precedes the propeller 14 to about the front end 62 of the propeller hub 64. The hood 26 also preferably has a length 66 approximately equal to the diameter 68 of the hood 26. Also, it is important to the proper operation of applicants hood that the back end 70 of the hood 26 terminate before it reaches the rudder 20.

In operation of the boat 10, during rotation of the propeller 14 in the direction 52, the hood 26 will tend to cause a maximum amount of water to move axially of the propeller 14 so as to increase the thrust generating efficiency of the propeller 14. During forward motion of the boat 10, the hood 26 will also tend to lift the stern 12 to counteract the normal tendency for the stem 12 to draw downward while the vessel is underway. Also, the constraining of the flow of the water from the propeller 12 in the direction axially of the shaft 16 and hood 26 in the direction of the rudder 20- has the effect of improving the steering qualities of the boat 10 even at low forward speeds.

This invention is not limited to the specific details of thestern of the boat; the flow control plate having substantially the shape of a portion of a cylinder over said propeller, including two curved sides, a front and back ends, the curved sides of the plate circumscribing the propeller to substantially a horizontal plane through the axis of the propeller, the front end of the plate extending forward of the propeller and the back end extending rear ward of the propeller and terminating at the rudder, a brace at each side of the plate fixed to the plate and the keel, said plate being tilted diagonally to said boat on a line with the apex of the prow and having an area proportioned for providing substantial hydraulic stern lift during forward motion of the boat.

2. A hydraulic flow control plate for a boat having a prow with an apex at the extreme forward end of the boat, a keel plank centrally thereof, a propeller and a rudder behind the propeller at the stern of the boat; the flow control plate comprising a plate in the form of a half cylinder of revolution with a radius about one tenth larger than the radius of the propeller radius and a length approximately equal to twice the radius of the plate; said plate including a front end extending forward of the propeller and a back end terminating at the rudder; mounting means rigidly fixing said plate to said boat at an angle such that the plate is substantially on a line with the apex of the prow.

3. A hydraulic flow control plate for a boat having a prow with an apex at the front end, a keel centrally thereof, a propeller and a rudder behind the propeller at the stern of the boat; the flow control plate comprising a plate in the form of a portion of a cylinder of revolution with a radius slightly larger than the radius of the propeller and a length equal to substantially twice the radius of the plate; said plate having a front and back ends, two sides and a top; the front end extending for- Ward of the propeller and the back end terminating on the propeller side of the rudder; one of the plate sides extending below the center line of the propeller and the other plate side above the centerline of the propeller; a spacer between the keel and plate for anchoring the plate to the boat; the plate being against the spacer and diagonally to the boat on a line with the apex of the prow; a pair of bolts through the keel, spacer and the plate for rigidly fixing the plate and spacer in place; and a brace at each side of the plate fixed to the respective plate side and the boat.

4. A hydraulic flow control plate providing stern lift tending to maintain level movement with respect to the water line during forward motion of a boat having a propeller at the stern of the boat, said flow control plate being fixed over the propeller of the boat and having a hydraulic deflecting surface substantially the shape of a portion of a cylinder with a front and back ends and a. length therebetween, the front end extending forward of the propeller and the back end extending rearward of the propeller and below the front end so that the length therebetween is at an angle with respect to the water line, said angle and length being proportioned for causing said stern lift. 1

References Cited in the file of this patent V UNITED STATES PATENTS 436,817 lWelch Septi'23, 1890 904,313 Davis Nov. 17, 1908 983,587 Watkins Feb. 7, 1911 2,306,840 Waterval Dec. 29, 1942 7 2,784,691 MacMillan Mars 12, 1957 FOREIGN PATENTS 762,747 France Ian. 29, 1934

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