GB1604462A - Means with which to reduce resistance of surface marine vessels - Google Patents

Description

(54) MEANS WITH WHICH TO REDUCE RESISTANCE OF SURFACE MARINE VESSELS (71) 1, ANTHONY HUGH ORR, 395 Wandsworth Road, London S.W.8, British, do hereby declare the invention, for which I pray that a patent may be granted to me, and the method by which it is to be performed, to be particularly described in and by the following statement:- The invention relates to improvements in the hulls of marine surface vessels, and has the aim of reducing hull resistance.

In particular the invention comprises a displacement hull of the type which when viewed in plan at any horizontal through the hull has a bow and stern region in which the side walls of the hull respectively diverge and then converge aftwardly, and in which two water guide fins are arranged symmetrically one on each side throughout the stern region, characterised in that each fin comprises at least two longitudinally extending non-coplanar parts arranged athwartships one another, the inboard part of each fin having its aftward termination in the same horizontal as or adjacently above the lower-most level of the keel line in the stern region, whilst the outboard part extends outwardly beyond the adjacent side wall when viewed in plan at the datumn waterline, and in that one said part of each fin lies in a substantially horizontal plane.

The water guide fins are preferably integral with the hull's stern region and may be of buoyant construction.

It is strongly prefered for the water guide fins to extend afiwardly at least as far as the aft perpendicular of the hull.

In a hull as described the water streamlines beneath the water guide fins are restricted from converging towards the centerline of the hull or upward to the surface. The extent of streamline convergence being dependant upon the location of the fins inboard part above the lower-most keel level in the hull's stern region. But streamline convergence would not be to the same extent as if the fins were absent. Where the fins occupy the same horizontal as the lower-most level of the keel outward convergence of the streamlines beneath the water guide fins does not occur.

Moreover it is believed that a reduction in turbulence both above and below the fins is obtained.

When an upright hull according to the invention moves at low speed the waterline will be near to the hull's static waterline. It is expected that in this low speed range the water that flows into contact with the stern region of the hull will be restricted by the fins to that water laterally outward of the hull above the fin's upper surface. As the hull speed increases the waterline throughout the stern region drops, until most of the hull surface above the fin is no longer in contact with the water. This appears to result in reduced resistance.

At low speed it is preferable that a laterally unrestricted flow of water is available to the hull's stern region above each fin. In order to optimise this flow the outboard part of each fin may be hinged longitudinally, and operable from within the hull.

It is further believed that the hull experiences an upward thrust from the hydro-static pressure acting along the under surface of the water guide fins, when the waterline above the fins has dropped below that level when the hull is stationary. This upward thrust combined with the dynamically derived upward thrust from the bow region is responsible for the reduction in hull draft and a subsequent reduction in resistance. This reduction in resistance is in addition to the aforementioned reduction derived from the water separation over the hulls stern region.

The invention is described by way of diagramatic example with reference to the accompanying drawings in which Figure I, is an isometric view of a first hull according to the invention where water guide fins are located in the same horizontal with the lower-most level of the keelline. Figures 2, 3, and 4 are transverse sectional views of the hull shown in Figure I, on the lines A-A, B-B, and C-C, Figure 5, is an isometric view of a second hull according to the invention. Figures 6 and 7 are transverse sectional views on the lines A-A, B-B, of the hull shown in Figure 5. Figure 8, is a plan view of the hull shown in Figure 5.

With reference to the first embodiment shown in Figures IQ, each fin comprises two parts 3, and 4, the inboard one of which 3 has its aft termination in the same horizontal as the keel line and extends horizontally outward. Part 3 extends outwardly to be adjacent the maximum waterline beam of the hull, and extends aftwardly to terminate in transverse alignment with the hulls aft perpendicular. The part 4, is planar and is hinged to the outer edge of the part 3. Means are provided within the hull (not shown) to pivot the part 4.

Refering now to the second hull shown in Figures 5--8, each water guide fin comprises three fixed parts, 3, 6 and 4. Parts 3 and 4 being horizontal with part 6 being inclined downwardly outward when viewed in transverse section. Again each fin terminates in transverse alignment with the hull's aft perpendicular.

WHAT I CLAIM IS: 1. A displacement hull of the type which when viewed in plan at any horizontal through the hull has a bow and stern region in which the side walls of the hull respectively diverge and then converge aftwardly, and in which two water guide fins are arranged symmetrically one on each side throughout the stern region, characterised in that each fin comprises at least two longitudinally extending non-coplanar parts arranged athwartships one another, the inboard part of each fin having its aftward termination in the same horizontal as or adjacently above the lower-most level of the keel line in the stern region, whilst the outboard part extends outwardly beyond the adjacent side wall when viewed in plan at the datumn waterline, and in that one said part of each fin lies in a substantially horizontal plane.

2. A boat hull as claimed in Claim I where-in the fins are integral with the hull's stern region.

3. A boat hull as claimed in claim I, wherein each fin comprises only two parts the outer one of which is hinged to the inner part.

4. A boat hull as claimed in any one of claims 1-3 wherein each fin terminates at the aft perpendicular.

5. A boat hull as claimed in claim I, wherein each fin comprises three parts the intermediate part being inclined downwardly outward, and where the inboard and outboard parts lie in respective horizontal planes.

6. A boat hull substantially as herein before described with reference to and shown in Figures 14 and Figures 5--8 of the accompanying drawings.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (6)

**WARNING** start of CLMS field may overlap end of DESC **. shown in Figures IQ, each fin comprises two parts 3, and 4, the inboard one of which 3 has its aft termination in the same horizontal as the keel line and extends horizontally outward. Part 3 extends outwardly to be adjacent the maximum waterline beam of the hull, and extends aftwardly to terminate in transverse alignment with the hulls aft perpendicular. The part 4, is planar and is hinged to the outer edge of the part 3. Means are provided within the hull (not shown) to pivot the part 4. Refering now to the second hull shown in Figures 5--8, each water guide fin comprises three fixed parts, 3, 6 and 4. Parts 3 and 4 being horizontal with part 6 being inclined downwardly outward when viewed in transverse section. Again each fin terminates in transverse alignment with the hull's aft perpendicular. WHAT I CLAIM IS:

1. A displacement hull of the type which when viewed in plan at any horizontal through the hull has a bow and stern region in which the side walls of the hull respectively diverge and then converge aftwardly, and in which two water guide fins are arranged symmetrically one on each side throughout the stern region, characterised in that each fin comprises at least two longitudinally extending non-coplanar parts arranged athwartships one another, the inboard part of each fin having its aftward termination in the same horizontal as or adjacently above the lower-most level of the keel line in the stern region, whilst the outboard part extends outwardly beyond the adjacent side wall when viewed in plan at the datumn waterline, and in that one said part of each fin lies in a substantially horizontal plane.

2. A boat hull as claimed in Claim I where-in the fins are integral with the hull's stern region.

3. A boat hull as claimed in claim I, wherein each fin comprises only two parts the outer one of which is hinged to the inner part.

4. A boat hull as claimed in any one of claims 1-3 wherein each fin terminates at the aft perpendicular.

5. A boat hull as claimed in claim I, wherein each fin comprises three parts the intermediate part being inclined downwardly outward, and where the inboard and outboard parts lie in respective horizontal planes.

6. A boat hull substantially as herein before described with reference to and shown in Figures 14 and Figures 5--8 of the accompanying drawings.