Note: Descriptions are shown in the official language in which they were submitted.
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PLI~I~æ CAq~A~ARBN VESS~L
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BACRGROUND OF TaE I~VENTIO~
The present invention relates generally to catamaran-
like vessels in which a superstructure or platform issupported on a pair of hulls, and is particularly directed
to a vessel designed to plane on the watersurface at speed.
Vessels capable of planing on the watersur~ace are able
to reach high speeds in view of the fact that the vessel is
lifted up out of the water to reduce skin Eriction and wave-
making draq. In some boats, leg-type retractable hydrofoils
are employed at the front end of the boat to lift it up out
of the water at speed. Other designs employ ski-like
structures. However, these vessels have hulls which rest in
the water at preplaning speeds and are therefore subject to
relatively hiyh drag at such speed. A wave making "drag
hump" occurs as such vessels start to lift out of the water,
with the bow rising and the stern dropping, and increased
power will be required to achieve planing speeds~
In catamaran-like vessels having twin hulls supporting
a platform or superstructure, it is known to utilize
submerged, buoyant hulls to support the superstructure on
struts above the waterline. Such a structure is described in
my U.S. Patent No. 3,866,557. This structure employs
rectangular shape hulls for supporting the boat platform.
~his produces increased stability. The structure is designed
so that the waterline at rest lies at about the mid-point of
the str~ts, dependent on the boat load. Although not
specifically designed for this purpose, the vessel described
30 in this reference is capable of planing on the lower hulls
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at high speed with sufficient power. However~ this structure is
not particularly efficient for planing purposes, and has to lift a
substantial distance out of the water to plane.
SUMMARY OF TH~ INVENTION
The present invention provides a catama~an vessel,
comprislng: a pair of spaced, parallel elongated pontoons; at
least one strut extending upwardly from each oE the pontoons; each
strut having a streamlined nose region and having a wtdth less
than that of the attached pontoon; a superstructure supported on
said struts for riding above the waterline; and each pontoon
having a lower planing surface for planing on the water surface at
speed and sharp chines at its inner and outer side edges, the
cross-sectional width of ~he pontoon varying along at lea~t part
of its height with the widest point of the cross-section being
below the top of the pontoon, at least a substan~ial part of the
pontoon lying below the waterline when the vessel is at rest in
the water, and the pontoon planing on the water surface wlth
essentially all of the pontoon portions above the chines lyiny
above the water when the vessel travels at speed in the water.
The pontoons provide most of the buoyancy for lifting
the platform or sup~rstructure out of the water. The pontoon
buoyancy is pre~erably designed such that at rest under fully
loaded condltions the water line will lie at or close to the top
of the pontoons, so that most of the strut wlll be out of ~he
water. However, the water line may be slightly above or below
this point, and at high loads part of the struts may also be
submerged.
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Because the pontoons are close to the water surface at
all times, there will be less vertical distance to lift the
vessel out of the water to plane and thus less resistance to
planinq. Preferably, the pontoons have a width about
three times the strut width. The thin surface-piercing
struts will reduce drag at preplaning speeds, and as the
vessel speed increases, the lower planing sur~aces and edge
chines will raise the pontoons out of the water to plane on
the water surface. The long, relatively narrow pontoons,
thin struts, and height of the superstructure above the
pontoons will reduce the vertical acceleration in waves when
planing, increasing boat stability.
The planing surface is preferably generally V-shaped,
and may be asymmetrical. The surface pre~erably has an
inboard and an ~utboard deadrise angle, and the inboard
deadrise angle is preferably greater than the outboard
deadrise angle. The inboard deadrise angle is preferably in
the range from 10 degrees to 90 degrees, while the outboard
deadrise angle preferably lies in the range from 10 degrees
to 25 degrees.
The upper surface of each pontoon may be V-shaped or
rounded, and may be either symmetrical or unsymmetrical
about the line of attachment to the respective strut.
Preferably, the pontoons each have downwardly curved lips at
their outer edges, and may have similar lips at their inner
edges, for improved lift and reduced drag.
Tbe pontoon shapes are designed for reduced wetted
surface area, and thus reduced dragr at low, preplaning
speeds, while increasing efficiency at planing speeds due to
the varying cross-sectional width.
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BRIEF DESCRIP'rION OF TIIE: DR~WI~S
The present invention will be better understood from
the following detailed description of some preferred
embodiments of the invention, taken in conjunction with the
accompanying drawings, in which like re~erence numerals
re~er to like parts, and in which:
Figure 1 is a side elevation view of a typical small
boat incorporating the planing catamaran structure;
Figure 2 is a sectional view taken on the line 2-2 oE
Figure l;
Figure 3 is a front end view of the boat of Figure l;
Figure 4 is a front end view showing an alternative
pontoon and strut arrangement;
Figure 5 is a sectional view similar to Figure 2,
showing a dual strut configuration;
Figure 6 is a side elevation view showing a stepped
pontoon;
Figure 7 is an underside view of the pontoon of Figure
6;
Figure 8 is an enlarged sectional view taken on the
line 8-8 of Figure l;
Figure 9 is a similar sectional view showing an
inclined strut and an alternative pontoon shape;
; Figure 10 is a similae sectional view showing another
alternative pontoon shape and an extendible hydrofoil;
Figure 11 is an underside view of the structure of
Figure 10: and
: Figures 12 to 15 are sectional views similar to Figure
8 showing fu~ther altern~tive pontoon configurations.
DESoRIPTION O~ T~E P~EF~RRED E~BODI~E~TS
Figures 1 to 3 and 8 of the drawings show a catamaran~
like vessel 10 according to a first embodiment of the
present invention. The vessel 10 shown in the drawings i5 a
small power driven pleasure boat. However, this invention
can be applied to any size boat from several feet long to
100 feet or more having relatively high speed, such as
pleasure boats, commercial boats or military boats~ and can
also be applied to sailboats.
The vessel 10 basically comprises a pair of spaced,
parallel elongated pontoons or hulls 12 each having at least
one strut 14 extending upwardly from it, and a
superstructure or platform 16 supported on the struts.
Although only one strut is shown extending along the length
of each pontoon in the embodiment of Figures 1 to 3, two or
more struts 50 may be used as shown in the modification of
Figure 5.
As shown in Figure 3, the pontoons 12 are submerged
below the waterline 18 when the vessel is at rest in the
water while the superstructure 16 is raised up out of ~he
water. The pontoons are buoyant members oE a suitable
liyhtweight material such as metal, wood, plastics or
fiberglass, ~r combinations of these materials, and they may
be hollow as shown or filled with a suitable buoyant
material such as foam.
As shown in Figures 2 and 3, the struts 14 are thinner
than the pontoons and have straamlined nose regions 20, for
reduced drag when travelling through the water at low
speeds. They are preferably hollow and constructed of
similar material to the pontoons, Preerably, the pontoons
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have a maximum thickness about three times that af the
struts. The pontoons preferably extend at least to the
length of the superstructure. The pontoon buoyancy is
designed such that at rest under normal or fully loaded
vessel conditions, the water level 18 lies at or close to
the top of the pontoons, as shown in Figure 3. Thus the
majority or all of the buoyancy for lifting the vessel out
of the water is provided by the pontoons. The water level 18
may be above or below the level shown in Figure 3, dependent
on the pontoon buoyancy and the boat load. Under very light
loads up to half of the pontoon volume may be out of the
water. Under full or high loads, part of the struts may
also be submerged. The buoyancy of the submerged parts of
the pontoons and struts will be equal to the total boat
weight in air.
The pontoons themselves are shaped to plane on the
water surface at high speed. A suitable planing shape is
shown in Figure 8. As shown in Figure 8, each pontoon has
sharp chines 22 at its inboard and outboard edges 24, 26,
respecti~ely and has a cross-sectional width which varies
along its height, with the widest portion of the pon~oon
being spaced below the po~nt of attachment to the strut and
below the upper surface 28 of the pontoon. The lower surface
3D of the pontoon comprises a planing surface, and is
preferably V-shaped and asymmetrical as shown in Figure 8. A
V-shape is generally the most efficient planing surface
shape. In the embodiment shawn in Figure 8, the upper
~urface of the pontoon is an inverted V-shape. The upper
surface may be symmetrical as shownl or unsymmetrical.
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As can be seen in Figure 8, the planing surface 30 of
the pontoon has inboard and outboard deadrise angles 32, 34,
respectlvely, which are preferably different, with the
inboard deadrise angle preferably being greater than the
outboard deadrise angle. The asymmetry and different
deadrise angles improve the turning or banking ability of
the boat and also allow it to turn faster. In the embodiment
shown in Figure 8 the outboard deadrise angle is of the
order of 15 degrees while the inboard deadrise angle is of
the order of 28 degrees. ~owever, the outboard deadrise
angle may be anywhere in the range 10 to 25 degrees while
the inboard deadrise angle may lie between 10 degrees to 90
degrees. Figures 9 to 15 show some alternative pontoon
configurations, which will be described in more detail
below.
Referring back to Figures 1 to 3, it can be seen that
the forward region of each pontoon is also streamlined, and
curves into a point or near-horizontal line at the bow 36,
which is located somewhere between the mid-plane and upper
surface of the pontoon, and may even be located above the
upper surace of the pontoon in a water-ski like
~onfiguration. This may improve the planing characteristics
of the pontoons, and the general streamli~ing will reduce
drag at preplaning speeds. The rear portion of the pontoon
also tapers, and is preferably cut off before it tapers to a
point, as shown in Figures 1 and 2.
Figure 2 shows optional trim plates 38 or inboard trim
foil 40 which may be placed near the transom of each pontoon
to control the trim and help stabilize the boat in pitch.
The trim plates may be needed for some larger boats where
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the trim angle needs to be controlled to get over the so-
called "drag hump" as the vessel starts to plane, or may be
used in any size boat simply to control the planing angle.
One trim plate is attached to the rear end of each face of
the V-shaped planing surface. The trim foil can be used in a
similar fashion, but would also provide greater pitch
stability for extended operation at speeds below the "drag
hump n,
The struts 14 are preferably tapered at both their
front and rear ends, as shown in Figure 2, to reduce drag in
low speed travel. The taper on one side of the strut may be
different from that on the other side at the rear or aft
end, if this should prove more convenient in manufacture.
The rear portion of each strut may be cut off before it
tapers to a point, as shown in Figure 2. In the embodiment
shown in Figure 2, the struts are generally vertical and are
attached along the center line of the upper surface of the
pontoon. However, they may be attached off-center to the
pontoons, as described in more detail below and shown in
Figures 4, 10 and 15.
Any suitable superstructure 16 may be provided Eor the
ves~el, depending on its intended use. In the embodiment
shown in Figures 1 to 3, the vessel is a small, motor-driven
pleasure craft~ The super~tructure is located at about one
pontoon height above the water surface when the vessel is at
restl as shown in Figure 3. The upper and lower surfaces of
the superstructure near the bow preferably taper to a
horizontal line at the bow 52, as indicated in Figure 1,
which lies between 10 percent and 100 percent o~ the
distance between the bottom and top surface of the
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superstructure, and preferably between 40 and 100 percent.
In the preferre~ embodiment the bow line 52 is located at
about 65 percent of the distance above the bottom of the
superstructure. The upper surface of the cross structure
may taper downward near the stern, as shown in Figure 1.
The superstructure shown in Figure 3 has a V-shaped
formation 54 under its center which tapers to a point at the
bow, extends along the full length of the superstructure,
and is cut off at the stern~ ~he V-shaped formation is
preferably centered at or around the centerline o~ the
superstructure. The forward end of the formation 54
preferably ~erges into the underside of the cuperstructure
at or near the bow, while the aft end terminates in the
vicinity of the stern of the superstructure, and is
preferably untapered and cut off. The side edges of the V-
formation preferably terminate about one strut thickness
inboard of each strut. The V-formation at the bow will help
to reduce wave impact loads on the cross structure in heavy
seas, and also provides an increased, lowered area at the
stern for mounting of an outboard motor.
More than one longitudinal V-formation 54 may be
provided in alternative embodiments. In Figure 4, a modified
version is shown in which V-formations 55 on each side of
the structure are used to secure ~he upper end of the struts
to the undersurface of the superstructure. Inboard engines
may be located in each of the V-formations. In addition to
the reduction of wave impact loads on the cross structure,
this version also provides mounting points for two outboard
motors at the stern, and also reduces stresses in the struts
; 30 by spreading out the strut loads over a larger area of the
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cross structure. The enlarged V-formation at the stern also
provides an increased mounting area which may be useful in
larger scale boats for mounting relatively large engines.
One or more additional ~-formations could be placed between
the struts.
Inboard or outboard engines, or sails may be used for
power. In the embodiment shown in Figures 1 to 3, a single
outboard motor 56 driving a propeller is shown attached to
the superstructure transom. More than one motor may be
a~tached to the transom. An inboard motor may be located in
the superstructure, in a longitudinal ~ region below the
superstructure, in a pontoon, or in a region where the strut
joins the pontoon which has been locally enlarged. This
latter alternative is illustrated by bulge portion 57 in
Figure 14. Any suitable drive train may be used to transmit
power from SUCh an inboard motor to a thruster~
The superstructure shown in Figure 1 is provided with
suitable seats 58, a forward windshield 60, and a cargo
compartment (not shown). ~owever, alternative boat
platform designs may be used, dependent on the slze and
intended use of the vessel.
The txansom o~ the superstructure pre~erably lies in
the region of, or forward of the tra~som of the struts,
while the transom of the struts preferably lies in the
region of, or forward of the transom of the pontoons.
When the vessel shown in Figures 1 to 3 is at rest or
~; travelliny at low speeds, the pontoons will be submerged
with the wa~er line 18 in the vicinity of the top o~ the
pontoons, depending on the boat load. Thus, the water line
18 may in practice ~e slightly above or below the level
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shown in Figure 3r and may even be well below the top of the
pontoons under very light load conditions. The wave motion
will be reduced because most of the mass of the vessel is
raised up out of the water and away from impact, and al50
because the pontoons are designed to have relatively small
water plane areas and damp out mo~ion slnce their maximum
beam typically lies below the water surface. When travelling
at low/ preplaning speedsl drag will be low due to the thin,
streamlined struts and completely or mostly submerged
pontoons.
As the speed is increased, the planing surfaces and
chines of the struts will lift the vessel out of the water
until it starts to plane~ Since the pontoons are not
submerged very far below the water surface prior to planing,
the amount of lift required to raise the vessel completely
out of the water is redu~ed or minimized. The planing water
line 61 is shown in Figure 1. The wave making "drag hump" as
the vessel starts to plane is reduced due to the narrow
width or beam of the pontoons and the pontoon shape. Once
the vessel is planing on the water surface, it will be able
to reach higher speeds due to reduction in the wave making
drag. The planing catamaran vessel will be more stable due
to the reduction in vertical acceleration when planing as a
result of the long, narrow pontoons which provide the
planing surfaces, the thin struts, and the height of the
superstructure above the pontoons~
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Figures 9 to 15 show some alternative pontoon shapes
having planing surfaces which may be attached to struts 14
of a vessel as shown in Figures 1 to 3 or 4. In Figure 9,
pontoon 62 has a planing surface 64 identical to that shown
in Figure 8 while the upper surface 66 is rounded or oval
rather than angular. Strut 14 attaches to the center of the
upper surface 66. In Figure 9, strut 14 is shown canted
inwardly. Although in the preferred embodiments of the
invention the struts are generally vertical, they may
optlonally be canted in, canted out, or curved~ The cant may
be determined by the desired width of the passenger platform
or superstructure relative to the pontoon ~pacing. In Figure
3, the superstructure width is the same as the distance
between the outer surfaces of the struts, while in Figure 4
the superstructure is wider than the strut spacing.
In Figures 10 and 11, pontoon 70 is of an asymmetrical
shape and has a flat inboard face 72, outwardly angled
planing surface 74, and outboard chine 76 separates planing
surface 74 from upper surface 78. The strut 14 in this
embodiment is attached asymmetrically. This version of the
pontoon is also shown in the vessel of Figure 4. An
optional, cantilevered hydrofoil 80 is pivotally attached
via shaft 82 to each of the pontoons 70, and cants inward
and downward of the pontoon. The hydrofoils can be retracted
as indicated in Figure 11 by being rotated rearwardly to a
position flush with a part of the lower surface of the
pontoon~ Hydrofoils such as this may be used optionally with
any of the pontoon structures shown in the drawings to
provide auxiliary lift. They do not lift the boat out of the
water as in a normal hydrofoil boat, but simply increase the
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efficiency in some cases~ Optional hydrofoils 80 are
illustrated in dotted outline attached to the pontoons in
Figures 3 and 4. ~ydrofoils may be desired, for example, in
heavier, larger boats to improve lift.
Where hydrofoils are used, they are preferably placed
on each side of the boat near to the center of gravity. One
or more hydrofoils may be attached to each pontoon. Where
more than one hydrofoil i5 placed on each side, their net
area should lie near to the center of gravity. In Figure 4,
the hydrofoils ~0 are more or less horizontal and span the
gap between the pontoons. The particular hydrofoil used will
depend on the particular application, and will only normally
be necessary in relatively large boats requiring some
auxiliary lift.
In Figure 12 an alternative pontoon shape 90 is shown
which has a rounded, oval upper surface 91, inboard and
outboard chines 92, 94, and a symmetrical, V~shaped planing
surface 96. Concave lips 98, 100 extend along the inboard
and outboard edges of each pontoon. These lips will provide
2~ improved lift and therefore reduced spray when lifting out
of the water, and will red~ce dragO Lips may be provided on
the inboard and outboard edges of any of the pontoon shapes
shown in Figures 8 to 15. A lip may be pro~ided at the
outboard edge only, but another lip is preferably also
provided at the inboard edge for improved performance, as
shown in Figure 12. The lips terminate at a downward angle
between zero and 90 degrees to the horizontal. In other
words, they may extend at any angle from horizontal to
vertical from the edge of the pontoon. In Figure 12, the
downward angle is close to vertical but an angle of between
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10 to 15 degrees to the horizontal may be optimum for small
boat designs. Any size lip may be used according to the
particular boat design, but in a particular embodlment of
the invention comprising a small, trailer size pleasure boat
lips of approximately 3% of the maximum pontoon width were
used .
The pontoon shape 110 shown in E'igure 13 consists of a~
upper, rounded surface 112, inboard and outboard edges or
chines 114, 116, and a planing surface comprising a central
flat portion 118 and inboard and outboard inclined portions
120, 122 separated from the central portion by edges 124,
126. I,ips or ridges 128, 130 may be located at edges 124 and
126, respectively, as shown.
In Figure 14 an alternative pontoon 140 is shown which
is of generally trapezoid shape havin~ a flat bottom planing
surtace 142, and inclined inner and outer faces 144, 146. In
Figure 15 the pontoon 150 is of a shape similar to that
shown in Figure 10 but the upper surEace 152 is rounded
rather than angular. An outer edge lip 154 is shown at the
outboard chine 156, and additional lips 158 may be provided
across the planing surface 160 as shown~
~he actual pontoon shape selected will be dependent on
the overall boat design and application, the relative costs
of the various shapes and the structural materials usedO
All tbe shapes shown will be feasible. A preferred small
boat shape will consist of a V-shaped planing surace with a
rounded upper surface to minimize the we~ted surface area at
low, preplaning speeds. This type of shape is shown in
Figure 9. An unsymmetrical shape is preferred since this
wlll improve turning ability. However, in some boats this
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may not be necessary and the symmetrical versions may prove
~ore convenient in such designs.
Figures 6 and 7 of the drawings show an optional
modification to the pontoon undersurface which ~ay help to
reduce drag. In the modification shown, steps 170 are
provided on the planing surfaces, and openings 172 are
provided to allow air to be pumped along suitable internal
passageways 174 into the region behind the steps.
In one specific example of a small, trailer sized
pleasure boat as shown in Figures 1 to 3 of the drawings
above, the struts 14 were vertical, had streamlined noses,
and tapered near the stern to a cut off of around 70% of
their maximum width. The pontoons had a width of about 3
times the strut width, tapered at the bow to a point located
about 65% of the height above the keel, and had outboard and
inboard deadrise angles of about 15 degrees and 27.5
degrees, respectively. The pontoons had lips at their outer
and inner edges, and had upper surfaces which were inverted
vees inclined at about 45 degrees to the horizontal. The
cross structure was located about one pontoon height above
the water level at rest, had a width the same as the
distance between the outer surfaces of the struts, and had a
slngle V-formation below its center tapering to a point at
the bowr cut of at the stern, and terminating at its sides
at about one strut thickness inboard of each strut. The
uppee and lower surfaces of the cross structure near the bow
tapered to a horizontal line at the bow located about 65% of
the tructure height above the bottom of the structure. The
~ransom of the structure was located about 15% of the boat
length forward of the strut and pontoon sterns. The cross
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structure had a retractable windshield angled up and forward
about 15 degrees from the veetical. However, these specific
dimensions are given by way of example only of one possible
design out of many alternative vessel designs which are
possible.
Although some preferred embodlments of the invention
have been described above by way of example only, it will be
understood by those ~killed in the field that modifications
may be made to the disclosed embodiments without departing
from the scope of the invention, which is defined by the
appended claims.
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