Title: Low drag submerged asymmetric displacement lifting body
Abstract: Low drag underwater submerged lifting bodies which can be used as underwater displacement portions of a vessel whose main hull is at sea level are asymmetrical and have improved lift to drag ratios. The lifting bodies have outer surfaces whose shapes are defined in plan and elevation by generally parabolic curves which are different on opposite sides of the lifting bodies.
Patent Number: 7,004,093 Issued on 02/28/2006 to Loui, et al.
| Inventors:
|
Loui; Steven (Honolulu, HI);
Shimozono; Gary (Kapolei, HI);
Keipper; Troy (Honolulu, HI)
|
| Assignee:
|
Navatek, Ltd. (Honolulu, HI)
|
| Appl. No.:
|
834930 |
| Filed:
|
April 30, 2004 |
| Current U.S. Class: |
114/61.3; 114/274 |
| Current Intern'l Class: |
B63B 1/00 (20060101) |
| Field of Search: |
114/613,274
|
References Cited [Referenced By]
U.S. Patent Documents
| 3157145 | Nov., 1964 | Farris.
| |
| 3347197 | Oct., 1967 | Scherer.
| |
| 3429287 | Feb., 1969 | Uram.
| |
| 3885514 | May., 1975 | Lauenborg.
| |
| 3947906 | Apr., 1976 | McLane.
| |
| 4819576 | Apr., 1989 | Shaw.
| |
| 4919063 | Apr., 1990 | Hall.
| |
| 4981099 | Jan., 1991 | Holder.
| |
| 5046444 | Sep., 1991 | Vorus.
| |
| 5433161 | Jul., 1995 | Loui.
| |
| 5477798 | Dec., 1995 | Ness.
| |
| 5522333 | Jun., 1996 | Lang.
| |
| 5544610 | Aug., 1996 | Harding.
| |
| 5645008 | Jul., 1997 | Loui.
| |
| 5794558 | Aug., 1998 | Loui.
| |
| 6263819 | Jul., 2001 | Gorustein et al.
| |
Primary Examiner: Olson; Lars A.
Attorney, Agent or Firm: Fitzpatrick, Cella, Harper & Scinto
Parent Case Text
This application claims the benefit of U.S. Provisional Application No. 60/466,787,
filed May 1, 2003.
Claims
What is claimed is:
1. A three dimensional low drag underwater lifting body for operation in a submerged
state, said lifting body having a fore and aft axis and an outer surface whose
shape conforms a) in plan on one side of said fore and aft axis to a first parabolic
curve whose vertex is located on the fore and aft axis, and on the other side of
said axis to a second different parabolic curve whose vertex is also located on
the fore and aft axis; said parabolic curves together defining a leading edge for
the lifting body when viewed in plan and b) in longitudinal cross-sectional planes
parallel to the fore and aft axis, to symmetrical and graduated generally parabolic
foil curves having vertices lying on the leading edge defined by said first and
second parabolic curves and which extend aft predetermined distances, with the
thickness of the parabolic foil shaped longitudinal cross-sectional planes decreasing
from the fore and aft axis of the lifting body to the leading edge of the lifting body.
2. A low drag underwater lifting body as defined in claim 1 wherein the lifting
body's beam, transversely of the fore and aft lifting body axis, is equal to or
greater than its thickness perpendicular to the beam and fore and aft axis.
3. A low drag underwater lifting body as defined in claim 2 wherein said body
has a predetermined length along said fore and aft axis and a stern portion defined
by a segment of a third parabolic curve transverse to the lifting body's length
on said one side of said axis.
4. A low drag underwater lifting body as defined in claim 3 wherein the substantially
parabolic foil shape of the lifting body at each of said planes intersecting the
lifting body parallel to the fore and aft is symmetrical to the shapes of the lifting
body at the planes parallel thereto but each is smaller at positions further from
the fore and aft axis of the lifting body.
5. A low drag underwater lifting body as defined in claim 2 wherein said body
has a bow and a stern, a side periphery as viewed in plan, a predetermined length,
and a stern section, said stern section having a progressively decreasing height
dimension in cross-section parallel to the fore and aft axis of the lifting body
from a point at each plane intersecting the lifting body parallel to the fore and
aft axis which is about two-thirds of the length dimension from the intersection
of such plane with said side periphery to the stern.
6. A low drag underwater lifting body as defined in claim 5 wherein said stern
is defined by a segment of a third parabolic curve transverse to the length of
the lifting body and located on one side of the fore and aft axis.
7. A low drag underwater lifting body as defined in claim 1 wherein the lifting
body has port and starboard hull sections on opposite sides of said fore and aft
axis and the hull section defined by said second parabolic curve is shaped as one
half of a parabolic body of revolution.
8. A low drag underwater lifting body as defined in claim 2 wherein the maximum
thickness of said lifting body is between 10% and 33% of the lifting body's length.
9. A low drag underwater lifting body as defined in claim 8 wherein the lifting
body has an aspect ratio of 10% to 150%.
10. A watercraft as defined in claim 3 wherein the substantially parabolic foil
shape of the lifting body at each of said planes intersecting the lifting body
parallel to the fore and aft of the hull is symmetrical to the shapes of the lifting
body at the planes parallel thereto but each is smaller at positions further from
the fore and aft axis of the lifting body.
11. A three dimensional low drag underwater lifting body for operation in a submerged
state, said lifting body having a fore and aft axis and an outer surface whose
shape conforms a) in plan on one side of said axis to a first parabolic curve whose
vertex is located on the fore and aft axis, and on the other side of said axis
to a second different parabolic curve whose vertex is also located on the fore
and aft axis; said parabolic curves together defining a leading edge for the hull
when viewed in plan and b) in longitudinal cross-sectional planes parallel to the
fore and aft axis, to symmetrical and graduated generally parabolic foil curves
having vertices lying on the leading edge defined by said first and second parabolic
curves and which extend aft predetermined distances, with the thickness of the
parabolic foil shaped longitudinal cross-sectional planes decreasing from the fore
and aft axis of the lifting body to the leading edge of the lifting body; said
lifting body having a bow and a stern and a predetermined length extending from
the bow to the stern, said first parabolic curve increasing in width from said
bow to said stern with said stern being defined by a segment of a third parabolic
curve transverse to the lifting body's length extending from the widest portion
of the first parabolic curve to said axis.
12. A low drag underwater lifting body as defined in claim 11 wherein the lifting
body's beam transversely of the fore and aft lifting body axis is equal to or greater
than its thickness perpendicular to the beam and fore and aft axis.
13. A low drag underwater lifting body as defined in claim 12 wherein the substantially
parabolic foil shape of the lifting body at each of said planes intersecting the
lifting body parallel to the fore and aft axis is symmetrical to the shapes of
the lifting body at the planes parallel thereto but each is smaller at positions
further from the center line for and aft axis of the lifting body.
14. A low drag underwater hull as defined in claim 12 wherein the lifting body
has port and starboard hull sections on opposite sides of said fore and aft axis
and the hull section defined by said second parabolic curve being shaped as one
half of a parabolic body of revolution.
15. A low drag underwater hull body as defined in claim 12 wherein said lifting
body has a bow and a stern, a side periphery as viewed in plan, a predetermined
length, and a stern section, said stern section having a progressively deceasing
height dimension in cross-section parallel to the fore and aft axis of the lifting
body from a point at each plane intersecting the lifting body parallel to the fore
and aft axis which is about two-thirds of the length dimension from the intersection
of such plane with said side periphery to the stern.
16. A low drag underwater lifting body as defined in claim 12 wherein the maximum
thickness of said lifting body is between 10% and 33% of the lifting body's length.
17. A low drag underwater lifting body as defined in claim 16 wherein the lifting
body has an aspect ratio of 10% to 150%.
18. A three dimensional low drag underwater lifting body for operation in a submerged
state, said lifting body having a fore and aft axis and an outer surface whose
shape is defined by a) a leading edge for the lifting body when viewed in plan
and b) in longitudinal cross-section by symmetrical generally parabolic foil curves
having vertices lying on the leading edge of the lifting body and lying in planes
parallel to the fore and aft axis, said lifting body having first and second hull
sections on opposite sides of said fore and aft axis and a midship section between
said first and second hull sections and located to one side of said fore and aft
axis, said first and second hull sections conforming in plan to first and second
different parabolic curves whose vertexes are located on said leading edge on opposite
sides of said midship section; the midship section having a parabolic foil shape
in longitudinal cross-section which is uniform in planes parallel to the fore and
aft axis between the first and second hull sections across the width thereof; and
wherein the foil curves of said first and second hull sections decrease in thickness
from the fore and aft axis of the lifting body to the edge thereof.
19. A low drag underwater lifting body as defined in claim 18 wherein the lifting
body's beam transversely of the fore and aft hull axis is equal to or greater than
its thickness perpendicular to the beam and fore and aft axis.
20. A low drag underwater lifting body as defined in claim 19 wherein said lifting
body has a bow and a stern and a predetermined length along said fore and aft axis
and a stern portion defined by a segment of a third parabolic curve transverse
to the lifting body's length on the side of said axis opposite said midships section.
21. A low drag underwater lifting body as defined in claim 20 including a stern
portion on said midships section which extends transversely to said fore and aft axis.
22. A low drag underwater lifting body as defined in claim 21 wherein the substantially
parabolic foil shape of the lifting body in said first and second hull section
at each of said planes parallel to the fore and aft planes is symmetrical to the
shapes of the lifting body at the planes parallel thereto but each is smaller at
positions further from the center line for and aft axis of the lifting body.
23. A low drag underwater lifting body as defined in claim 22 wherein the hull
section on the side of the lifting body containing said midships section is shaped
as one half of a parabolic body of revolution whose parabolic formula is the same
as that of said midship section.
24. A low drag underwater lifting body as defined in claim 19 wherein said body
has a bow and a stern, a side periphery as viewed in plan, a predetermined length,
and a stern section, said stern section having a progressively deceasing height
dimension in cross-section parallel to the fore and aft axis of the lifting body
from a point at each plane intersecting the hull parallel to the fore and aft axis
which is about two-thirds of the length dimension from the intersection of such
plane with said side periphery to the stern.
25. A low drag underwater lifting body as defined in claim 24 wherein said stern
is defined by a third parabolic curve transverse to the hull length on the side
of said fore and aft axis opposite said midship section.
26. A low drag underwater lifting body as defined in claim 19 wherein the maximum
thickness of said hull is between 10% and 33% of the hull length.
27. A low drag underwater lifting body as defined in claim 26 wherein the hull
has an aspect ratio of 10% to 150%.
28. A watercraft including a first hull having a surface waterline, at least
one strut depending from the first hull and a three-dimensional underwater submerged
lifting body secured to said strut beneath the waterline during operation of the
watercraft, said lifting body having a fore and aft axis and an outer surface whose
shape conforms a) in plan on one side of said fore and aft axis to a first parabolic
curve whose vertex is located on the fore and aft axis, and on the other side of
said axis to a second different parabolic curve whose vertex is also located on
the fore and aft axis; said parabolic curves together defining a leading edge for
the hull when viewed in plan and b) in longitudinal cross-sectional planes parallel
to the fore and aft axis, to symmetrical and graduated generally parabolic foil
curves having vertices lying on the leading edge defined by said first and second
parabolic curves and which extend aft predetermined distances, with the thickness
of the parabolic foil shaped longitudinal cross-sectional planes decreasing from
the fore and aft axis of the lifting body to the leading edge of the lifting body.
29. A watercraft as defined in claim 28 wherein the lifting body's beam, transversely
of the fore and aft lifting body axis, is equal to or greater than its thickness
perpendicular to the beam and fore and aft axis.
30. A watercraft as defined in claim 29 wherein said body has a predetermined
length along said fore and aft axis and a stern portion defined by a segment of
a third parabolic curve transverse to the lifting body's length on said one side
of said axis.
31. A watercraft as defined in claim 30 wherein the substantially parabolic foil
shape of the lifting body at each of said planes intersecting the lifting body
parallel to the fore and aft axis is symmetrical to the shapes of the lifting body
at the planes parallel thereto but each is smaller at positions further from the
fore and aft axis of the lifting body.
32. A watercraft as defined in claim 29 wherein said body has a bow and a stern,
a side periphery as viewed in plan, a predetermined length, and a stern section,
said stern section having a progressively decreasing height dimension in cross-section
parallel to the fore and aft axis of the lifting body from a point at each plane
intersecting the lifting body parallel to the fore and aft axis which is about
two-thirds of the length dimension from the intersection of such plane with said
side periphery to the stern.
33. A watercraft as defined in claim 32 wherein said stern is defined by a segment
of a third parabolic curve transverse to the length of the lifting body.
34. A watercraft as defined in claim 28 wherein the lifting body has port and
starboard hull sections on opposite sides of said fore and aft axis and the hull
section defined by said second parabolic curve is shaped as one half of a parabolic
body of revolution.
35. A watercraft as defined in claim 28 wherein the maximum thickness of said
lifting body is between 10% and 33% of the lifting body's length.
36. A watercraft as defined in claim 35 wherein the lifting body has an aspect
ration of 10% to 150%.
37. A watercraft as defined in claim 28 including at least two struts depending
from the first hull and a pair of said three dimensional underwater submerged lifting
bodies respectively secured to said struts.
38. A watercraft as defined in claim 37 wherein the fore and aft axes of said
lifting bodies diverge from each other toward the bow of the watercraft.
39. A watercraft as defined in claim 37 wherein the fore and aft axes of said
lifting bodies converge toward each other in the direction of the bow of the watercraft.
40. A watercraft as defined in claim 38 including a foil shaped fin connecting
said lifting bodies.
41. A watercraft as defined in claim 40 wherein said foil shaped fin is joined
to said lifting bodies as a blended wing body wherein the thickness of the foil
at its junctures with the lifting bodies is substantially the same as the thickness
of the lifting bodies at said junctures.
42. A watercraft as defined in claim 38 wherein said watercraft has a bow and
a stern, said lifting bodies being mounted in the rear portion of the ship forward
of the stern.
43. A watercraft as defined in claim 42 including a three dimensional symmetrical
low drag underwater lifting body mounted on the forward portion of the watercraft
rearward of the bow.
44. A watercraft as defined in claim 42 including a second pair of lifting bodies
mounted amidship of the watercraft.
45. A watercraft as defined in claim 42 wherein said watercraft is a monohull
vessel with a fore and aft keel, said second pair of lifting bodies being respectively
connected by cross foil support members to the hull of the watercraft adjacent
said keel.
46. A watercraft as defined in claim 29 including a three dimensional symmetrical
low drag underwater lifting body mounted on the forward position of the watercraft
at the bow.
47. A watercraft as defined in claim 37 wherein said struts are foil shaped and
each is joined to its associated lifting body as a blended wing body wherein the
thickness of the foil at its junctures with the lifting body is substantially the
same as the thickness of the lifting body at that juncture.
48. A watercraft as defined in claim 45 wherein said cross foil members are each
joined to their associated lifting bodies as a blended wing body.
49. A watercraft as defined in claim 43 wherein the fore and aft axes of said
lifting bodies diverge from each other toward the bow of the watercraft.
50. A watercraft as defined in claim 49 including a foil shaped fin connecting
said lifting bodies.
51. A watercraft as defined in claim 50 having at least one hull having a surface
waterline and a fore and aft axis, and a three dimensional low drag underwater
lifting body secured to said hull beneath the waterline for operation in a submerged
state, said lifting body having a first side, when viewed in plan, extending in
the fore and aft direction relating to said hull and being secured to the hull,
said lifting body having an outer wetted surface whose shape is defined by a) a
leading edge for the lifting body when viewed in plan and b) in longitudinal cross-section
by symmetrical generally parabolic foil curves having vertices lying on the leading
edge of the lifting body and lying in planes parallel to the fore and aft axis,
said lifting body having first and second sections, said first section conforming
in plan to a segment of a first parabolic curve whose vertex is located at the
fore of said leading edge; and said second section joined to said first section
having a parabolic foil shape in longitudinal cross-section which is uniform in
planes parallel to the fore and aft axis across the width thereof; said second
section including said first side of the lifting body; and wherein the foil curves
of said first section decrease in thickness along the width thereof to the edge thereof.
52. A watercraft as defined in claim 49 wherein said watercraft has a bow and
a stern, said lifting bodies being mounted in the rear portion of the ship forward
of the stern.
53. A watercraft as defined in claim 52 including a three dimensional symmetrical
low drag underwater lifting body mounted on the forward portion of the watercraft
rearward of the bow.
54. A watercraft as defined in claim 52 including a second pair of said lifting
bodies mounted amidship of the watercraft.
55. A watercraft as defined in claim 54 wherein said watercraft is a monohull
vessel with a fore and aft keel, said second pair of lifting bodies being respectively
connected by cross foil support members to the hull of the watercraft adjacent
said keel.
56. A watercraft as defined in claim 55 wherein the lifting body's beam transversely
of the fore and aft axis of the hull is equal to or greater than its thickness
perpendicular to the beam and fore and aft axis.
57. A watercraft including a first hull having a surface waterline, at least
one strut depending from the first hull and a three-dimensional underwater submerged
lifting body secured to said strut beneath the waterline during operation of the
watercraft, said lifting body having a fore and aft axis and an outer surface whose
shape conforms a) in plan on one side of said axis to a first parabolic curve whose
vertex is located on the fore and aft axis, and on the other side of said axis
to a second different parabolic curve whose vertex is also located on the fore
and aft axis; said parabolic curves together defining a leading edge for the hull
when viewed in plan and b) in longitudinal cross-sectional planes parallel to the
fore and aft axis, to symmetrical and graduated generally parabolic foil curves
having vertices lying on the leading edge defined by said first and second parabolic
curves and which extend aft predetermined distances, with the thickness of the
parabolic foil shaped longitudinal cross-sectional planes decreasing from the fore
and aft axis of the lifting body to the leading edge of the lifting body; said
lifting body having a bow and a stern and a predetermined length extending from
the bow to the stern, said first parabolic curve increasing in width from said
bow to said stern with said stern being defined by a segment of a third parabolic
curve transverse to the lifting body's length and located at the widest portion
of the first parabolic curve.
58. A watercraft as defined in claim 57 wherein the lifting body's beam transversely
of the fore and aft lifting body axis is equal to or greater than its thickness
perpendicular to the beam and fore and aft axis.
59. A watercraft as defined in claim 58 wherein the substantially parabolic foil
shape of the lifting body at each of said planes intersecting the lifting body
parallel to the fore and aft planes intersecting the lifting body parallel to the
fore and aft axis is symmetrical to the shapes of the lifting body at the planes
parallel thereto but each is smaller at positions further from the center line
for and aft axis of the lifting body.
60. A watercraft as defined in claim 58 wherein said body has a bow and a stern,
a side periphery as viewed in plan, a predetermined length, and a stern section,
said stern section having a progressively decreasing height dimension in cross-section
parallel to the fore and aft axis of the lifting body from a point at each plane
intersecting the lifting body parallel to the fore and aft axis which is about
two-thirds of the length dimension from the intersection of such plane with said
side periphery to the stern.
61. A watercraft as defined in claim 60 wherein said stern is defined by a third
parabolic curve transverse to the length of the lifting body.
62. A watercraft as defined in claim 58 wherein the maximum thickness of said
lifting body is between 10% and 33% of the lifting body's length.
63. A watercraft as defined in claim 62 wherein the lifting body has an aspect
ration of 10% to 150%.
64. A watercraft as defined in claim 60 including at least two struts depending
from the first hull and a pair of said three dimensional underwater submerged lifting
bodies respectively secured to said struts.
65. A watercraft as defined in claim 60 wherein the fore and aft axes of said
lifting bodies converge toward each other in the direction of the bow of the watercraft.
66. A watercraft as defined in claim 61 wherein said foil shaped fin is joined
to said lifting bodies as a blended wing body wherein the thickness of the foil
at its junctures with the lifting bodies is substantially the same as the thickness
of the lifting bodies at said junctures.
67. A watercraft as defined in claim 61 wherein said symmetrical low drag underwater
lifting body has a bow and a stern position, the bow of said first hull being secured
to the stern position of said symmetrical low drag lifting body.
68. A watercraft as defined in claim 60 wherein said stern is defined by a segment
of a third parabolic curve transverse to the length of the lifting body.
69. A watercraft as defined in claim 68 wherein said foil shaped fin is joined
to said lifting bodies as a blended wing body wherein the thickness of the foil
at its junctures with the lifting bodies is substantially the same as the thickness
of the lifting bodies at said junctures.
70. A watercraft including a monohull vessel having a surface waterline, a three
dimensional underwater submerged lifting body secured to the bow of said monohull
beneath the waterline during operation of the watercraft, said lifting body having
a fore and aft axis and an outer surface whose shape conforms a) in plan on one
side of said axis to a first parabolic curve whose vertex is located on the fore
and aft axis, and on the other side of said axis to a second different parabolic
curve whose vertex is also located on the fore and aft axis; said parabolic curves
together defining a leading edge for the hull when viewed in plan and b) in longitudinal
cross-sectional planes parallel to the fore and aft axis, to symmetrical and graduated
generally parabolic foil curves having vertices lying on the leading edge defined
by said first and second parabolic curves and which extend aft predetermined distances,
with the thickness of the parabolic foil shaped longitudinal cross-sectional planes
decreasing from the fore and aft axis of the lifting body to the leading edge of
the lifting body; said lifting body having a bow and a stern and a predetermined
length extending from the bow to the stern, said first parabolic curve increasing
in width from said bow to said stern with said stern being defined by a segment
of a third parabolic curve transverse to the lifting body's length and located
at the widest portion of the first parabolic curve; wherein said stern of said
lifting body being defined by a third parabolic curve transverse to the length
of the lifting body; the maximum thickness of said lifting body is between 10%
and 33% of the lifting body's length, and a stern lifting body secured to said
monohull below the stern thereof.
71. A watercraft including a first hull having a surface waterline, at least
one strut depending from the first hull and a three-dimensional underwater submerged
lifting body secured to said strut beneath the waterline during operation of the
watercraft, said lifting body having a fore and aft axis and an outer surface whose
shape is defined by a) a leading edge for the lifting body when viewed in plan
and b) in longitudinal cross-sectional by symmetrical generally parabolic foil
curves having vertices lying on the leading edge of the lifting body and lying
in planes parallel to the fore and aft axis, said lifting body having first and
second hull sections on opposite sides of said fore and aft axis and a midship
section between said first and second hull sections and located to one side of
said fore and aft axis, said first and second hull sections conforming in plan
to first and second different parabolic curves whose vertices are located on said
leading edge on opposite sides of said midship section; the amidship section having
a parabolic foil shape in longitudinal cross-section which is uniform in planes
parallel to the fore and aft axis between the first and second hull sections across
the width thereof; and wherein the foil curves of said first and second hull sections
decrease in thickness from the fore and aft axis of the lifting body to the edge thereof.
72. A watercraft as defined in claim 71 wherein the lifting body's beam transversely
of the fore and aft lifting body axis is equal to or greater than its thickness
perpendicular to the beam and fore and aft axis.
73. A watercraft as defined in claim 72 wherein the substantially parabolic foil
shape of the lifting body at each of said planes intersecting the lifting body
parallel to the fore and aft planes are symmetrical to the shapes of the lifting
body at the planes parallel thereto but each is smaller at positions further from
the center line for and aft axis of the lifting body.
74. A watercraft as defined in claim 72 wherein said body has a bow and a stern,
a side periphery as viewed in plan, a predetermined length, and a stern section,
said stern section having a progressively decreasing height dimension in cross-section
parallel to the fore and aft axis of the lifting body from a point at each plane
intersecting the lifting body parallel to the fore and aft axis which is about
two-thirds of the length dimension from the intersection of such plane with said
side periphery to the stern.
75. A watercraft as defined in claim 72 wherein the maximum thickness of said
lifting body is between 10% and 33% of the lifting body's length.
76. A watercraft as defined in claim 75 wherein the lifting body has an aspect
ration of 10% to 150%.
77. A watercraft as defined in claim 74 including at least two struts depending
from the first hull and a pair of said three dimensional underwater submerged lifting
bodies respectively secured to said struts.
78. A watercraft as defined in claim 77 wherein the fore and aft axes of said
lifting bodies diverge from each other toward the bow of the watercraft.
79. A watercraft as defined in claim 74 wherein the fore and aft axes of said
lifting bodies converge toward each other in the direction of the bow of the watercraft.
80. A watercraft as defined in claim 78 including a foil shaped fin connecting
said lifting bodies.
81. A watercraft as defined in claim 78 wherein said watercraft has a bow and
a stern, said lifting bodies being mounted in the rear portion of the ship forward
of the stern.
82. A watercraft as defined in claim 81 including a three dimensional symmetrical
low drag underwater lifting body mounted on the forward portion of the watercraft
rearward of the bow.
83. A watercraft as defined in claim 81 including a second pair of said lifting
bodies mounted amidship of the watercraft.
84. A watercraft as defined in claim 83 wherein said watercraft is a monohull
vessel with a fore and aft keel, said second pair of lifting bodies being respectively
connected by cross foil support members to the hull of the watercraft adjacent
said keel.
85. A watercraft as defined in claim 80 wherein the lifting body's beam transversely
of the fore and aft axis of the hull is equal to or greater than its thickness
perpendicular to the beam and fore and aft axis.
86. A watercraft as defined in claim 84 wherein the lifting body's beam transversely
of the fore and aft axis of the hull is equal to or greater than its thickness
perpendicular to the beam and fore and aft axis.
87. A watercraft having at least one hull having a surface waterline and a fore
and aft axis and a three dimensional low drag underwater lifting body secured to
said hull beneath the waterline for operation in a submerged state, said lifting
body having a first side, when viewed in plan, extending in the fore and aft direction
relative to said hull, said first side being secured directly to the hull, said
lifting body having a leading edge and an outer wetted surface whose shape conforms
a) in plan to a segment of a first parabolic curve whose vertex is located where
the foremost part of the first side of the lifting body joins the hull and b) in
longitudinal cross-sectional planes parallel to the fore and aft axis of the hull,
to symmetrical and graduated generally parabolic foil curves having vertices lying
on the leading edge of the lifting body and which extend aft predetermined distances,
with the thickness of the parabolic foil shaped longitudinal cross-sectional planes
decreasing from the first side of the lifting body to the leading edge of the lifting body.
88. A watercraft as defined in claim 87 wherein the lifting body's beam, transversely
of the fore and aft axis of the hull, is equal to or greater than its thickness
perpendicular to the beam and fore and aft axis.
89. A watercraft as defined in claim 88 wherein said body has a predetermined
length in the fore and aft direction and a stern portion defined by a segment of
a second parabolic curve transverse to the lifting body's length and extending
from said hull.
90. A watercraft as defined in claim 88 wherein said lifting body has a bow and
a stern, a side periphery as viewed in plan, a predetermined length, and a stern
section, said stern section having a progressively decreasing height dimension
in cross-section parallel to the fore and aft axis of the hull from a point at
each plane intersecting the lifting body parallel to the fore and aft axis which
is about two-thirds of the length dimension from the intersection of such plane
with said side periphery to the stern.
91. A watercraft as defined in claim 90 wherein said stern is defined by a segment
of a second parabolic curve transverse to the length of the lifting body and extending
from said hull.
92. A watercraft as defined in claim 88 wherein the maximum thickness of said
lifting body is between 10% and 33% of the lifting body's length.
93. A watercraft as defined in claim 92 wherein the lifting body has an aspect
ratio of 10% to 150%.
94. A watercraft as defined in claim 87 including a pair of said lifting bodies
secured on opposite sides of said hull along their respective first sides.
95. A watercraft as defined in claim 87 including a pair of laterally spaced
parallel hulls having surface water lines and fore and aft axes, and at least one
pair of said lifting bodies secured respectively to said hulls along their respective
first sides and extending towards each other.
96. A watercraft as defined in claim 95 wherein said lifting bodies are each
shaped as one half of a parabolic body of revolution.
97. A watercraft having at least one hull having a surface waterline and a fore
and aft axis, and a three dimensional low drag underwater lifting body secured
to said hull beneath the waterline for operation in a submerged state, said lifting
body having a first side, when viewed in plan, extending in the fore and aft direction
relative to said hull, said first side being secured to the hull, said lifting
body having an outer wetted surface whose shape is defined by a) a leading edge
for the lifting body when viewed in plan and b) in longitudinal cross-section by
symmetrical generally parabolic foil curves having vertices lying on the leading
edge of the lifting body and lying in planes parallel to the fore and aft axis,
said lifting body having first and second sections, said first section conforming
in plan to a segment of a first parabolic curve whose vertex is located at the
fore of said leading edge; and said second section joined to said first section
having a parabolic foil shape in longitudinal cross-section which is uniform in
planes parallel to the fore and aft axis across the width thereof; said second
section including said first side of the lifting body secured to the hull; and
wherein the foil curves of said first section decrease in thickness along the width
thereof to the edge thereof.
98. A watercraft as defined in claim 97 wherein the lifting body's beam transversely
of the fore and aft axis of the hull is equal to or greater than its thickness
perpendicular to the beam and fore and aft axis.
99. A watercraft as defined in claim 98 including a stern portion on said second
section of the lifting body which extends transversely to said fore and aft axis.
100. A watercraft as defined in claim 99 wherein the first section of the lifting
body is shaped as one half of a parabolic body of revolution whose parabolic formula.
101. A watercraft as defined in claim 98 wherein said lifting body has a bow
and a stern, a side periphery as viewed in plan, a predetermined length, and a
stern section, said stern section having a progressively deceasing height dimension
in cross-section parallel to the fore and aft axis of the lifting body from a point
at each plane intersecting the lifting body parallel to the fore and aft axis which
is about two-thirds of the length dimension from the intersection of such plane
with said side periphery to the stern.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to ships and watercrafts having improved efficiency
and seakeeping from underwater submerged displacement hull(s) attached to and part
of a vessel that operates at sea level.
2. Background of the Invention
In recent years interest in the use of small waterplane area ships (SWAS vessels)
has substantially increased because such vessels have improved hydrodynamic stability,
low water resistance and minimal ship motion. Generally such vessels have at least
one waterline located below its design draft with a waterplane area that is significantly
larger than the waterplane area at its design draft. One form of such vessel is
known as a small waterplane area twin hull vessel (a SWATH vessel) which generally
consists of two submerged hulls, originally formed of uniform cross-section, connected
to a work platform or upper hull by elongated struts which have a cross-sectional
area along any given waterplane area that is substantially smaller than a waterplane
area cross-section of the submerged hulls. Thus, at the design waterline such vessels
have a small waterplane area.
The interest in such vessels has increased in large part because of the development
work conducted by Pacific Marine Supply Co., Ltd. A variety of such vessels have
been produced using twin submerged hulls or a plurality of submerged hulls, such
as shown, for example, in U.S. Pat. No. 5,433,161. In the course of the development
work for these vessels, further improvements were made and a so-called Mid-Foil
SWAS vessel was developed, as disclosed in U.S. Pat. No. 5,794,558. Such vessels
use a submerged underwater displacement hull or lifting body to provide lift to
the craft in conjunction with any other parts of the vessel which generate lift.
The lifting body differs from a hydrofoil in that the enclosed volume of the lifting
body provides significant displacement or buoyant lift as well as hydrodynamic
lift whereas the lift of a hydrofoil is dominated by only hydrodynamic lift. In
the course of continuing development work, the particular shape of such lifting
bodies was studied in detail in order to improve their performance and adapt and
integrate their use to a wide range of marine craft.
More specifically, as disclosed in U.S. Pat. No. 6,263,819, it was found that
the submerged bodies of marine vessels, when operated at shallow submergence depths,
such as is the case for SWAS and Mid-Foil vessels, can be adversely effected by
the displacement of the free water surface caused by the body's volume and dynamic
flow effects. The interaction of that displacement of the free surface relative
to the body's shape had not been adequately accounted for in the prior art structures.
It is believed that this inadequacy of existing prior art submerged bodies for
marine vessels is the result of the fact that submerged and semi-submerged marine
vessels have historically been designed to operate at great depths relative to
their underwater body thickness, as with submarines or hydrofoils.
A typical submarine is essentially a body of revolution-shaped hull which has
three
dimensional waterflow about it, but which is designed to operate normally several
hull diameters or more below the free water surface. Thus, the displacement of
the free surface of the water by operation of the hull at such depths is minimal
and does not effect the operation of the body. On the other hand, hydrofoils are
simply submerged wings with predominately two-dimensional flow and are designed
typically to produce dynamic lift as opposed to buoyant or hydrostatic lift.
The displacement of water at the free surface by a submerged body is detrimental
to a marine vessel's hydrodynamic performance with the impact varying as a function
of the body's shape, submergence depth, speed and trim. For example, the free surface
effects can significantly reduce lift in the body or even cause negative lift (also
referred to as sinkage) to occur. Resistance to movement through the water by free
surface effects is generally greater than if the submerged hull were operating
at great depths; and pitch movements caused by the displacement of the free water
surface vary with speed and create craft instability. With the advent in recent
years of marine vehicles (such as the SWAS, SWATH, and Mid-Foil vessels) which
use a shallowly submerged body the detrimental effects of free surface water displacement
on submerged hulls has been recognized.
Prior to the invention as disclosed in U.S. Pat. No. 4,263,819, submerged displacement
watercraft hull body shapes were generally cylindrical or tear-drop shaped bodies
of revolution. The simplest variations are bodies with generally elliptical cross-sections,
such as are shown, for example, in U.S. Pat. No. 4,919,063 or 5,433,161. Others
were simply shaped in a manner similar to an airplane wing, as shown for example,
in U.S. Pat. No. 3,347,197. On the other hand, hydrofoil dynamic lift shapes are
generally thin-foils with little or no, buoyancy and symmetric foil sections having
straight leading and trailing edges. In plan these foils are generally straight,
or are swept forward or rearwardly and/or are trapezoidal in shape. Additionally,
they can have dihedral or anhedral canting from the horizontal. It was found that
the performance of vessels using these shapes is adversely effected by the displacement
of the free surface of the water above the bodies during operation of the vessel.
According to teaching of U.S. Pat. No. 6,263,819 (hereinafter the "'819
patent"), a low drag underwater submerged displacement hull is defined from two
parabolic shapes. The periphery of the hull when viewed in plan is symmetrical
and defined by a first parabolic form (or parabolic equation) with the form defining
the leading edge of the hull. The longitudinal cross-section of the hull is formed
of foil shaped cross-sections which are defined as cambered parabolic foils having
a low drag foil shape and providing a generally parabolic nose for the hull. Generally,
each longitudinal cross-section of the hull parallel to the longitudinal or fore
and aft axis of the hull has a symmetrical cambered parabolic foil shape with the
cross-section along the longitudinal axis of the hull having the maximum thickness
and the cross-section furthest from the centerline of the hull having the minimum
thickness. In plan, the hull has a stern or trailing edge which is defined by either
a straight line, a parabolic line, or a straight line fared near its ends to the
side edges of the plan parabola shape.
In another embodiment the hull shape is a parabolic body of revolution. In a
third
embodiment the hull also has a foil shape in longitudinal cross-section which is
essentially formed by a parabolic body of revolution cut in half and separated
by a uniform midships section, whose longitudinal cross-sections are uniform in
shape and correspond to the parabolic shape of the body of revolution.
These body shapes have benign pressure gradients and small stagnation points
over the body which make the bodies less sensitive to changes in the body angle
of attack relative to the flow so that they are less effected by free water surface
disturbance. Parabolic foil embodiments have high Block coefficients which maximize
their volume to surface area relationship with the result that they have less frictional
drag because of reduced wetted surface area, less structure and thus less cost.
With higher Block coefficients, such as the 60-70% coefficients achieved with the
lifting bodies of the '819 patent, the volume of the foil relative to its surface
area is maximized and, as a result, the foils provide greater buoyancy for the
same surface area as compared to the prior art.
Because of their high Block coefficient, high displacements can be achieved
with hulls having relatively short bodies. This allows these bodies to operate
at high Froude numbers, preferably in excess of 1. This in turn results in less
wave making drag and less friction drag from a thinner boundary layer. Wakes formed
by these bodies are very uniform and result in minimal disturbance beyond the trailing
edge to appendages bodies, or propulsers positioned at the trailing edge or stern.
The symmetrical parabolic foils, at critical design submergence depths, displace
the free surface of the water in a manner which reduces the pressure coefficient
on the bodies and allow higher incipient cavitation speeds. Their dynamic lift
can then be varied as a function of camber (i.e. variation of the surface location
from the design parabola), submergence, speed and angle of attack. As a result,
optimization of lift characteristics for a given craft design speed and draft can
be achieved. Further, dynamic lift of these bodies can be varied by the use of
integrated trailing edge flaps, which will mitigate appendage drag of non-integral
foil stabilizers.
It has been found that the symmetric lifting bodies of the '819 patent operate
very satisfactorily for most applications, even for very large vessels of 2000
tons and up. However, it is advantageous to have lifting bodies which are smaller
relative to the length of the ship and capable of being positioned outboard of
the watercraft hull. Therefore, further development of the lifting bodies of the
'819 patent has occurred, particularly for use with monohull vessels.
The symmetrical lifting bodies as disclosed in the '819 patent were primarily
used generally directly under the hull. However, if the lifting body is located
further from the center of gravity of the ship, it not only can provide lift but
greater dynamic control as a result of maximizing dynamic moment. In addition,
it has been found useful to tailor the shape of the lifting body to conform to
the hull it is used with as well as to accommodate flows under the hull caused
by the hull or other underwater structures. It also has been found that while large
monohull vessels have very good seakeeping ability, the use of the tailored asymmetric
lifting bodies of the present invention with such hulls greatly increase their
seakeeping abilities.
It is an object of the present invention to provide a submerged lifting body
which
can be employed on various marine vessels to maximize performance of the vessel
by creating a high lift to drag ratio (L/D), i.e., low drag, at operational speed,
while increasing dynamic control.
Another object of the present invention is to provide a submerged lifting
body for use on various marine vessels which improves performance of the vessel
at operational speed while creating a dynamically stable vessel.
Yet another object of the present invention is to provide submerged lifting bodies
for use on various marine vessels which can increase the efficiency of these vessels
by reducing hydrodynamic drag.
A further object of the present invention is to adapt these improved submerged
lifting bodies to a variety of watercraft (monohulls, catamarans, trimarans, swath,
semi-swath, planing and displacement vessels) by optimizing their shape, size,
number and location.
Another object of the present invention is to provide submerged lifting bodies
for use on various marine vessels that are shaped to reduce the possibility of
being damaged when docking or coming alongside another structure.
Yet another object of the present invention is to provide submerged lifting bodies
for use on various massive vessels that reduce the wave making and slamming of
a vessel.
Yet another object of the present invention is to provide submerged lifting bodies
for use on various marine vessels that improve the seakeeping by reducing the vessel's
motions while at rest as well as while underway.
Still another object of the invention is to provide submerged lifting bodies
for use on various marine vessels that are shaped to result in improved flow to
an integrated propulsor yielding high propulsive efficiency.
SUMMARY OF THE INVENTION
In accordance with an aspect of the present invention, an underwater lifting
body
is provided that meets these objectives. Briefly, off vessel centerline mounted
lifting bodies are disclosed whose shape has been tailored to the flow at its location
to optimize the performance of the body. In cross-section, the lifting body is
parabolic foil shaped and in plan view there is no longitudinal plane of symmetry.
Generally, a three-dimensional low drag underwater lifting body for operation
in a submerged state is provided which has a fore and aft axis and an outer surface
whose shape conforms in plan on one side of the fore and aft axis to a first parabolic
curve whose vertex is located on the fore and aft axis, and on the other side of
the axis to a second different parabolic curve whose vertex is also located on
the fore and aft axis. The parabolic curves together define a leading edge for
the lifting body when viewed in plan. The outer surface of the lifting body also
conforms, in longitudinal cross-sectional planes parallel to the fore and aft axis,
to graduated generally parabolic foil curves having vertices lying on the leading
edge defined by said first and second parabolic curves and which extend aft predetermined
distances, with the thickness of the parabolic foil shaped longitudinal cross-sectional
planes decreasing from the fore and aft axis of the lifting body to the leading
edge of the lifting body.
In another aspect of the invention, the three dimensional low drag underwater
lifting body for operation in a submerged state has a fore and aft axis and an
outer surface whose shape conforms in plan on one side of said axis to a first
parabolic curve whose vertex is located on the fore and aft axis, and on the other
side of said axis to a second different parabolic curve whose vertex is also located
on the fore and aft axis. These parabolic curves together define a leading edge
for the hull when viewed in plan. The lifting body also conforms, in longitudinal
cross-sectional planes parallel to the fore and aft axis, to graduated generally
parabolic foil curves having vertices lying on the leading edge defined by said
first and second parabolic curves and which extend aft predetermined distances,
with the thickness of the parabolic foil shaped longitudinal cross-sectional planes
decreasing from the fore and aft axis of the lifting body to the leading edge of
the lifting body. The lifting body has a bow and a stern and a predetermined length
extending from the bow to the stern; the first parabolic curve increases in width
from said bow to stern with the stern being defined by the segment of a third parabolic
curve transverse to the lifting body's length extending from the widest portion
of the first parabolic curve to said axis.
In yet another aspect of the present invention, a watercraft includes a first
hull having a surface waterline, at least one strut depending from the hull and
a three-dimensional underwater submerged lifting body secured to the strut beneath
the waterline during operation of the watercraft. The lifting body has a fore and
aft axis and an outer surface whose shape conforms in plan on one side of the fore
and aft axis to a first parabolic curve whose vertex is located on the fore and
aft axis, and on the other side of said axis to a second different parabolic curve
whose vertex is also located on the fore and aft axis. The parabolic curves together
defining a leading edge for the hull when viewed in plan. The lifting body also
conforms in longitudinal cross-sectional planes parallel to the fore and aft axis,
to graduated generally parabolic foil curves having vertices lying on the leading
edge defined by said first and second parabolic curves and which extend aft predetermined
distances, with the thickness of the parabolic foil shaped longitudinal cross-sectional
planes decreasing from the fore and aft axis of the lifting body to the leading
edge of the lifting body.
In further aspect of the invention, a watercraft includes a first hull having
a surface waterline, at least one strut depending from the first hull and a three-dimensional
underwater submerged lifting body secured to the strut beneath the waterline during
operation of the watercraft. The lifting body has a fore and aft axis and an outer
surface whose shape conforms in plan on one side of the axis to a first parabolic
curve whose vertex is located on the fore and aft axis, and on the other side of
said axis to a second different parabolic curve whose vertex is also located on
the fore and aft axis. The parabolic curves together define a leading edge for
the hull when viewed in plan. The lifting body also conforms, in longitudinal cross-sectional
planes parallel to the fore and aft axis, to graduated generally parabolic foil
curves having vertices lying on the leading edge defined by the first and second
parabolic curves and which extend aft predetermined distances, with the thickness
of the parabolic foil shaped longitudinal cross-sectional planes decreasing from
the fore and aft axis of the lifting body to the leading edge of the lifting body.
The lifting body also has a bow and a stern and a predetermined length extending
from the bow to the stern. The first parabolic curve increases in width from said
bow to the stern with the stern being defined by a segment of a third parabolic
curve transverse to the lifting body's length and located at the widest portion
of the first parabolic curve.
In accordance with a still further aspect of the invention, a watercraft includes
a first hull having a surface waterline, at least one strut depending from the
first hull and a three-dimensional underwater submerged lifting body secured to
the strut beneath the waterline during operation of the watercraft. The lifting
body has a fore and aft axis and an outer surface whose shape is defined by a leading
edge for the lifting body when viewed in plan and, in longitudinal cross-section
by symmetrical generally parabolic foil curves having vertices lying on the leading
edge of the lifting body and lying in planes parallel to the fore and aft axis.
The lifting body has first and second hull sections on opposite sides of the fore
and aft axis and a midship section between the first and second hull sections and
located to one side of the fore and aft axis. The first and second hull sections
conforming in plan to first and second different parabolic curves whose vertexes
are respectively located on and define a portion of the leading edge; the midship
section having a parabolic foil shape in longitudinal cross-section which is uniform
in planes parallel to the fore and aft axis between the first and second hull sections
across the width thereof. The foil curves of the first and second hull sections
decrease in thickness from the fore and aft axis of the lifting body to the edge thereof.
The lifting bodies of the present invention as described above are asymmetric
about their main fore and aft axis. This permits the lifting bodies to be positioned
relative to the hull of the ship to conform to the hull, to accommodate water flow
characteristics below the hull caused by the hull's shape and to modify the angle
of attack of the lifting body. For example, two lifting bodies can be secured to
opposite sides of the hull so either of their asymmetric sides are adjacent to
the ship's hull so as to present alternative leading edge configurations depending
on the ship's hull shape.
By positioning the lifting bodies outboard of the hull, greater dynamic moment
is created increasing dynamic cont
