US3530815A - Catamaran-type ships - Google Patents

Catamaran-type ships Download PDF

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Publication number
US3530815A
US3530815A US714978A US3530815DA US3530815A US 3530815 A US3530815 A US 3530815A US 714978 A US714978 A US 714978A US 3530815D A US3530815D A US 3530815DA US 3530815 A US3530815 A US 3530815A
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United States
Prior art keywords
ship
spandeck
catamaran
vessel
pitching
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Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
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US714978A
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English (en)
Inventor
George Richard Grant Lewison
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National Research Development Corp UK
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Nat Res Dev
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Filing date
Publication date
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    • 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
    • B63B39/061—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 by using trimflaps, i.e. flaps mounted on the rear of a boat, e.g. speed boat
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B63—SHIPS OR OTHER WATERBORNE VESSELS; RELATED EQUIPMENT
    • B63B—SHIPS OR OTHER WATERBORNE VESSELS; EQUIPMENT FOR SHIPPING 
    • B63B1/00—Hydrodynamic or hydrostatic features of hulls or of hydrofoils
    • B63B1/16—Hydrodynamic or hydrostatic features of hulls or of hydrofoils deriving additional lift from hydrodynamic forces
    • B63B1/24—Hydrodynamic or hydrostatic features of hulls or of hydrofoils deriving additional lift from hydrodynamic forces of hydrofoil type
    • B63B1/28—Hydrodynamic or hydrostatic features of hulls or of hydrofoils deriving additional lift from hydrodynamic forces of hydrofoil type with movable hydrofoils
    • B63B1/285—Hydrodynamic or hydrostatic features of hulls or of hydrofoils deriving additional lift from hydrodynamic forces of hydrofoil type with movable hydrofoils changing the angle of attack or the lift of the foil

Definitions

  • This invention relates to catamaran-type ships, that is ships which, to provide great lateral stability, comprise a pair of hulls united into a stiff structure by cross connections. Considerations of strength and stiffness call for the cross connections to extend well fore and aft, and to extend down as close to the water line as possible. Such cross connections may include one or more continuous spandecks from end to end or only at the fore part and stern.
  • wave motion in the space between the hulls of such a vessel and the magnitude of this motion will depend principally on three factors, namely, the speed of the vessel, the force of the sea in which it is traveling, and the direction of the vessel relative to that of the sea. In general, the wave motion in question will increase as the speed of the vessel increases and as the sea becomes heavier, and the highest waves will occur with the vessel traveling into a head sea, other things being equal for each factor.
  • the waves in the space between the hulls are of the greatest height in the neighbourhoodof the fore-end of the vessel and it is customary for this reason to carry the spandeck or the lowest spandeck upwardly towards the fore-end. If the waves strike the underside of this spandeck slamming may occur. In order to avoid slamming, the spandeck must be at such a level that, at the most, only a proportion, say 30 percent, of the waves strike it. This may require the spandeck to be located at such a level as to reduce the stiffness and resistance of the complete structure to stresses, particularly to torsion and racking stresses when the vessel is in an oblique sea.
  • a catamaran-type ship is provided with an anti-pitching member in the form of platelike means extending between the two hulls near the bottom fore-ends thereof, the general plane of the said plate-like means being set at an angle to the horizontal substantially between zero and a small positive angle of incidence.
  • Such a member reduces the relative bow motion between the vessel and the water and so reducing or even eliminating slamming on the underside of the spandeck. It decreases the pitching motion of the ship and the vertical accelerations, thus making for comfort. Finally it provides additional stiffening to the fore part of the ship, especially in torsion thus reducing racking stresses when the ship is in an oblique sea.
  • the member is desirably of hydrofoil section and may be set at zero angle of incidence or at a small positive angle of incidence, say 7, in which case as the speed of the ship increases, so a greater lift is obtained thus counteracting the effect of speed in increasing the wave motion under the spandeck. It would be possible to provide for variation of the angle of incidence but as a rule the advantages do not justify the complication and expense. But it may be worthwhile to provide the member with an adjustable or controllable flap pivoted to the trailing edge of the member. Alternatively other water flow control devices could be used.
  • An anti-pitching member of adequate size to have the above effects is of hydrofoil section and at a small angle of incidence, is found not only to present low additional resistance to propulsion, but in medium to heavy head seas actually to reduce resistance to propulsion.
  • the overall effect in the case of a ship operating mostly in moderate seas, of Beaufort 3-5, say. may be a slight net gain in propulsive efficiency.
  • FIGS. 1 and IA illustrate, in FIGS. 1 and IA, a specific example of a power driven ship according to the present invention tested in model form and, in FIGS. 2 to 12, the results of the tests as applied to the corresponding full size ship in various conditions simulated during the tests.
  • FIG. 13 indicates the meaning to be attached to various symbols used in FIGS. 2 to I2, namely, the absence of an anti-pitching member and the values of the angle ofincidence a of such a member when used.
  • FIG. I more particularly illustrates the forward part of the tested model in longitudinal cross section between the hulls.
  • this figure indicates the port hull at I, the spandeck at 2, and an anti-pitching member at 3.
  • the member 3 was made pivotally adjustable about an axis 4 for testing the effects of different angles of incidence a.
  • FIG. 1A which shows a flap 5 pivoted at 6 to the trailing edge of a member 3A, which is otherwise similar to the member 3 shown in FIG. I and would be similarly positioned and secured.
  • stations 7, 8 and 9 are also indicated in this figure.
  • FIG. I is drawn to a scale such that substantially 1/16 inch in the figure equals 1 foot of actual vessel size.
  • FIGS. 2 to 12 illustrate the test results graphically.
  • Each of these figures, except FIG. 8, indicates the percentage of waves which reached various heights above the construction water line at different ones of the stations 7, 8 and 9 and in different conditions.
  • the station to which any characteristic of the last-mentioned figures relates is denoted by the reference number of the relevant station, and the percentage exceedance and wave heights, the latter in feet, are respectively indicated by reference to the Y-axes and X-axes.
  • the sea conditions simulated during the tests represented by these figures are Beaufort force ,6 head seas.
  • FIGS. 2, 3 and 4 concern the ship without an anti-pitching member in association with respective ship speeds of l0, l2 and I4 knots and resultant wave motions at stations 7, 8 and 9.
  • FIGS. 5, 6 and 7 show respectively corresponding results with use of the member 3 disposed horizontally, or 0, but only for resultant wave motions at stations 7 and 8.
  • FIGS. 9 to 11 show further respectively corresponding results for resultant wave motions at station 8, for different positive angles of incidence for the member 3.
  • FIG. I2 is similar, but concerns station 7.
  • FIGS. 9 to 12 show the corresponding individual characteristics for the case of no anti-pitching member and a horizontal member from FIGS. 2
  • FIG. 8 shows comparative results of the actual vessel speeds achieved in terms of knots for the full size ship for different propellor rotation rates in terms of revolutions per second for the model, the model being self-propelled for this purpose, under different sea conditions, namely calm water and a simulated Beaufort force 6 head sea, with an anti-pitching member at different angles of incidence.
  • the symbols of FIG. 13 are used in the last connection, it being noted that the first set of symbols denote the head sea condition, and the second set of symbols, which correspond to the first set with the additon of a tail" line, denote calm water.
  • the broken line characteristics A and B in FIG. 8 indicate the corresponding results without member 3 in the calm water and head sea conditions, respectively.
  • a catamaran-type ship provided with an anti-pitching member in the form of plate-like means extending between the two hulls only near the bottom fore-ends thereof, the general plane of the said plate-like means being set at an angle to the horizontal substantially between zero and a small positive angle ofincidence.
  • a ship according to claim 2 wherein said member is provided with an adjustable flap pivotally connected to its trailing edge.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Combustion & Propulsion (AREA)
  • Mechanical Engineering (AREA)
  • Ocean & Marine Engineering (AREA)
  • Physics & Mathematics (AREA)
  • Fluid Mechanics (AREA)
  • Other Liquid Machine Or Engine Such As Wave Power Use (AREA)
  • Butt Welding And Welding Of Specific Article (AREA)
  • Auxiliary Methods And Devices For Loading And Unloading (AREA)
US714978A 1967-03-22 1968-03-21 Catamaran-type ships Expired - Lifetime US3530815A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
GB1351667 1967-03-22

Publications (1)

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US3530815A true US3530815A (en) 1970-09-29

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US714978A Expired - Lifetime US3530815A (en) 1967-03-22 1968-03-21 Catamaran-type ships

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US (1) US3530815A (enrdf_load_stackoverflow)
GB (1) GB1226323A (enrdf_load_stackoverflow)

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5787828A (en) * 1996-11-27 1998-08-04 Service Marine Industries, Inc. Swath cargo ship
USD404003S (en) 1997-11-27 1999-01-12 Service Marine Industries, Inc. Swath cargo ship
USD414457S (en) 1997-11-26 1999-09-28 Service Marine Industries, Inc. Swath cargo ship hull
US20060009093A1 (en) * 2004-06-16 2006-01-12 David Murphy Surface effect craft

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5787828A (en) * 1996-11-27 1998-08-04 Service Marine Industries, Inc. Swath cargo ship
USD414457S (en) 1997-11-26 1999-09-28 Service Marine Industries, Inc. Swath cargo ship hull
USD404003S (en) 1997-11-27 1999-01-12 Service Marine Industries, Inc. Swath cargo ship
US20060009093A1 (en) * 2004-06-16 2006-01-12 David Murphy Surface effect craft
US7311057B2 (en) * 2004-06-16 2007-12-25 David Murphy Surface effect craft

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Publication number Publication date
GB1226323A (enrdf_load_stackoverflow) 1971-03-24

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