Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B63—SHIPS OR OTHER WATERBORNE VESSELS; RELATED EQUIPMENT
  • B63B—SHIPS OR OTHER WATERBORNE VESSELS; EQUIPMENT FOR SHIPPING 
  • B63B39/00—Equipment to decrease pitch, roll, or like unwanted vessel movements; Apparatus for indicating vessel attitude
  • B63B39/06—Equipment to decrease pitch, roll, or like unwanted vessel movements; Apparatus for indicating vessel attitude to decrease vessel movements by using foils acting on ambient water

Definitions

• HYDRODYNAMIC FIN FOR WATER-BORNE CRAFT The invention is concerned with improvements in or relating to a hydrodynamic fin for water-borne craft, particularly but net exclusively a stabilising fin for a
• fins projecting outwardly from the ship's hull below the water-line to act to correct any tendency for the ship to roll with the movement of the water.
• Such fins will conveniently have a hydrodynamic cross-sectional profile and may resemble that shown in Figure 1 of the drawings, which shows a section of a fin 2 comprising a main Cody portion 4, provided with a movable trailing edge portion 6.
• the fin 2 is adapted to project from a ship's hull 8 as shown in Figure 2 and to be rotated as required about an axis 10 to vary the operating angle.
• the axis ⁇ . " is arranged transvers-eiy to a line extending lengthwise of the ship 8.
• edge portion 6 is hinged so as to be movable with respect to the body portion 4 by an angle greater than that of the rotation of tne latter about axis 10.
• a fin housing 12 is provided in the hull to receive the fin 2 when in a retracted,
• the invention therefore provides a hydrodynamic fin member for use on water-borne craft, comprising an elongate body portion having a generally streamlined cross-section including a tapering portion reducing in a direction from a leading to a trailing zone thereof, a ridge-like member having an at least substantially wedge-shaped cross-section and being provided at a location rearward of said tapering portion, said wedge-shaped cross-section diverging in said direction and terminating in an end wall.
• the end wall may lie at least substantially in a plane transverse to said direction.
• the profile of said end wall may be planar, or may be concave or include an obtuse or acute angle if desired.
• the fin member may be mounted with respect to a hull for rotation about an axis substantially transverse to a line extending fore-and-aft of said hull, said rotation providing a continuously variable operating angle in a predetermined range.
• the angle range may bs ⁇ 20* with respect to zero deflection.
• the fin member may project from the hull in a horizontal or downwardly inclined attitude, at an angle preferably between 0° and 30°.
• diverging surfaces of said ridge-like member are arranged to include an angle between 20" and 90°, in one example the angle being 70°.
• the maximum, heightwise, thickness of the fin may be between 12% and 33% of the overall, fore-and-aft, width of the fin and preferably may be between 21% and 33% of said width, for example 26%.
• the maximum height of the end wall of the ridge-like section may be between 30% and 70% of the thickness of the fin, and preferably may be 50%.
• provision may be made for retracting the fins into an out-of-the-way condition as required, either by being withdrawn into a housing or by being pivoted either foreword or aft to be received in a stowing recess.
• a fin according to the invention may be provided with a tip plate or fence at the outboard end thereof for purposes which will be explained.
• Figure 4 is a perspective view of a fin according to — A —
• Figure 5 is a perspective view of a fin according to the invention.
• Figure 6 illustrates three of the various angular positions available for the fin
• Figure 7 is a graph comparing the position of the chordwise centres of pressure for the fins of Figure 1 (prior art) and of Figure 5 for a range of fin angle values;
• Figure 8 is a diagrammatic view of the position of permanently fixed fins with respect to a ship's hull
• Figure 9 is a diagrammatic view of the position of retractable fins with respect to a ship's hull
• Figure 10 is an outline representation of the cross-sectional profile of a fin as shown in Figure 4.
• Figure 11 is an outline representative of the cross-sectional profile of a fin as shown in Figure 5.
• Figure 4 shows a fin F according to the invention, having a hydrodynamically efficient profile comprising a smoothly rounded leading edge zone 14, an upper surface 16 and a lower surface 18 which converge in a direction towards a trailing zone 20.
• two diverging surfaces 22 and 24 define a ridge-like member 26 having a wedge-shaped cross-section.
• An end wall 28 lies in a plane transverse and substantially perpendicular to a line 30 extending fore-and-aft of the fin (see Figure 10) .
• the fin is adapted to be pivotally adjusted about a transverse axis 32 in a manner similar to the adjustment about axis 10 of the fin of the prior art.
• Figure 5 shows a similar fin to that of Figure 4 with the addition of a plate 34 of the kind commonly known as a tip fence.
• a plate 34 of the kind commonly known as a tip fence.
• Such plates are known to increase the slope of the lift curve for a given operating angle. Thus the required angle may be reduced if a tip fence is present.
• a tip fence assists in increasing maximum lift by suppressing fin tip flow losses.
• Figure 6 illustrates the adjustment of the operating angle of the fin about the axis 32 with a 20° angle of adjustment both above and below a position of zero deflection shown in full lines.
• the centre of pressure for the fin section is located approximately at the zone of maximum thickness t (see Figure 10) .
• Figure 7 shows the movement of the position of the centre of pressure for a range of angular deflections for the prior art fin shown in Figures 1 and 3 (curve A) and for the fin of Figure 5 (curve B) .
• the upper curve A shows the amount of movement of the chordwise centre of pressure (CCp) over the range 5° - 20°
• the lower curve (B) illustrates that the centre of pressure of the fin according to the present invention shows virtually no change in the same range.
• the optimum shaft position (on axis 32) occurs at a zone where the largest diameter shaft can be accommodated. Because three is so little movement of the centre of pressure along the fore-and-aft chord line 30, with increasing fin angle, it will be appreciated that a relatively small torque is required to operate the fin over the preferred operating range.
• Figures 10 and 11 illustrate more clearly a preferred profile or outline for the cross-section of a fin F according to the invention, Figure 11 shown also the provision of a plate 34.
• the value of t as 0.26 c has the advantage that a suitably large structure is available in which to mount a shaft 36 along the axis 32 to sustain the various levels of imposed loads.
• the value of w which is selected to be 50% of that of t gives a compromise between adequate lift and an acceptable level of drag.
• the value for ⁇ is selected bearing in mind that the more shallow the angle the less drag and lift.
• a value of 70° is given by way of the present example, a value as low as 20° may be used.
• the value of w is suitably increased by way of compensation.
• Figure 11 shows the preferred profile of the tip fence plate 34. Since the maximum areas of effective operation of the plate 34 are at the positions X and Y, the outline of the plate 34 has been chosen to reduce its height, dimension D, to a minimum. This facility has. the practical advantage that the mouth opening of the hull recess can be reduced accordingly.

Landscapes

• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Combustion & Propulsion (AREA)
• Mechanical Engineering (AREA)
• Ocean & Marine Engineering (AREA)
• Bridges Or Land Bridges (AREA)
• Toys (AREA)
• Hydraulic Turbines (AREA)
• Soil Working Implements (AREA)
• Structures Of Non-Positive Displacement Pumps (AREA)

Applications Claiming Priority (3)

Publications (2)

Family

ID=10687942

Family Applications (1)

Country Status (5)

Cited By (1)

Families Citing this family (4)

Family Cites Families (4)

• 1991
  • 1991-01-04 GB GB919100116A patent/GB9100116D0/en active Pending
  • 1991-12-23 JP JP4502542A patent/JPH06506888A/ja active Pending
  • 1991-12-23 DE DE0571401T patent/DE571401T1/de active Pending
  • 1991-12-23 DE DE69126669T patent/DE69126669T2/de not_active Expired - Fee Related
  • 1991-12-23 WO PCT/GB1991/002310 patent/WO1992012046A1/en not_active Ceased
  • 1991-12-23 EP EP92902381A patent/EP0571401B1/de not_active Expired - Lifetime
• 1993
  • 1993-06-15 GB GB9312342A patent/GB2266073B/en not_active Expired - Fee Related

Non-Patent Citations (1)

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