U.S. patent number 3,763,810 [Application Number 05/237,852] was granted by the patent office on 1973-10-09 for high speed boat with planing hull.
This patent grant is currently assigned to Blade Hulls, Inc.. Invention is credited to Peter R. Payne.
United States Patent |
3,763,810 |
Payne |
October 9, 1973 |
HIGH SPEED BOAT WITH PLANING HULL
Abstract
A boat capable of cutting through rough waves at high speed with
astonishing stability has a hull provided with a flat planing
surface which in plan is the shape of a thin wedge or delta. The
sides of the boat rise upwardly and outwardly with a simple concave
curvature from the two edges leading from a knife edge bow at the
point of the wedge. The slender wedge shape moving through the
water at high speeds develops continuous spray sheets up its sides
which are intercepted by the outwardly curving portions of the hull
sides. Spray rails or deflectors may also be utilized to intercept
the spray sheet, such deflectors being inclined at a small angle to
the bottom of the planing surface. The knife edge bow rises
upwardly and forwardly with a concave curvature from the point of
the wedge and eventually terminates in a forwardly sloped bow
transom. A keel skeg minimizes side slipping. A stern transom,
which rises substantially perpendicular to the trailing edge of the
delta or wedge may have a rearwardly extending bustle secured
thereto for buoyancy and roll stability at low speeds.
Inventors: |
Payne; Peter R. (Silver Spring,
MD) |
Assignee: |
Blade Hulls, Inc. (Rockville,
MD)
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Family
ID: |
22895489 |
Appl.
No.: |
05/237,852 |
Filed: |
March 24, 1972 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
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167737 |
Jul 30, 1971 |
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Current U.S.
Class: |
114/285; 114/291;
D12/300 |
Current CPC
Class: |
B63B
1/04 (20130101); B63B 1/20 (20130101) |
Current International
Class: |
B60V
1/00 (20060101); B63B 1/00 (20060101); B63B
1/20 (20060101); B63B 1/16 (20060101); B63B
1/04 (20060101); B63b 001/18 () |
Field of
Search: |
;114/66.5R,66.5F,66.5P,66.5S |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Buchler; Milton
Assistant Examiner: Frankfort; Charles E.
Parent Case Text
RELATED APPLICATIONS
This application is a continuation-in-part of my prior application
Ser. No. 167,737 filed July 30, 1971, now abandoned in favor of
this application.
Claims
What is claimed is:
1. A boat having a planing hull capable of operating with stability
at high speeds in rough seas comprising:
a. a thin wedge shaped planing surface forming a bottom of the hull
with the apex of the wedge at a bow portion of the hull,
b. a knife edge at a lower portion of the bow of the hull extending
upwardly and forwardly of the apex of the wedge,
c. a forwardly inclined blunt bow transom forming the upper portion
of the bow of the hull above the knife edge,
d. concave sides of the hull extending upwardly and outwardly along
the sides of the wedge shaped planing surface and positioned to
intercept spray sheets thrown up from sides of the planing hull to
assist in stabilizing the boat.
2. A boat having a planing hull as in claim 1 wherein the knife
edge is forwardly inclined in a concave manner and the blunt bow
transom if flat.
3. A boat having a planing hull as in claim 1 wherein said concave
sides are each defined by a smooth simple curve in only one
direction and extend over the entire surface of the sides of the
wedge.
4. A boat having a planing hull as in claim 1 further comprising
turning side slip minimizing means secured to the bottom of the
hull.
5. A boat having a planing hull as in claim 4 wherein the side slip
minimizing means is a keel skeg along a longitudinal axis of the
hull.
6. A boat having a planing hull as in claim 4 wherein the side slip
minimizing means is a fin keel positioned on a longitudinal axis of
the hull.
7. A boat having a planing hull as in claim 1 further comprising
spray sheet deflector means attached to the concave sides of the
hull.
8. A boat having a planing hull as in claim 7 wherein the spray
sheet deflector means are inclined at an angle to the planing
surface.
9. A boat having a planing hull as in claim 8 wherein the spray
sheet deflector means comprise a plurality of separated spaced
deflector sections.
10. A boat having a planing hull as in claim 1 further comprising
propeller torque counteracting means on the hull.
11. A boat having a planing hull as in claim 10 wherein the
propeller torque counteracting means is a trim tab attached to one
side of the bottom rear of the planing surface.
12. A boat having a planing hull as in claim 1 wherein the included
angle of the apex of the wedge shaped planing surface is between
10.degree. and 30.degree..
13. A boat having a planing hull as in claim 1 wherein the boat is
driven by motive power.
14. A boat as set forth in claim 13 further comprising a bustle
portion secured to and extending aft of said stern transom, said
bustle having a bottom surface stepped up relative to said planing
surface, concave sides having a curvature similar to the curvature
of the sides of the boat along said wedge-shaped planning surface
and a central longitudinally extending notched portion in the
bottom surface to provide clearance for a stern drive extending
through the stern transom.
15. A boat having a planing hull as in claim 13 wherein the motive
power is engine means carried by the hull driving propeller means
under the planing surface.
16. A boat having a planing hull as in claim 1 wherein the boat is
a flying boat and the hull is a portion of a fuselage.
17. A boat having a planing hull as in claim 1 wherein the boat is
a trimaran with a hull as defined in front and a pair of spaced
apart wedge shaped spaced apart hulls aft.
18. A boat having a planing hull as in claim 17 wherein the aft
hull sides are concave on their outer surfaces only.
19. A boat having a planing hull as in claim 1 further comprising a
spray protector extending outward from the bow forwardly of the top
portion of the blunt bow transom.
20. A boat as set forth in claim 1 wherein said wedge shaped
planing surface is defined by a triangular sheet of material having
integral flanges about the periphery which form a receptacle and
further comprising ballast means disposed in said receptacle
forming smooth bottom surface.
21. A boat as set forth in claim 1 having a deck which is wedge
shaped similar to said planing surface but having a larger area.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention is directed to a high speed boat which does
not slam or pound waves but cuts through them to ride smoothly at
high speed even in rough seas.
2. Prior Art
The long established means of water transportation is the
displacement hull which is supported by buoyancy. The speed of such
a craft is limited by the high skin friction caused by large
surface area in contact with the water, the pressure drag due to
waves generated by the hull's passage through the water and the
suction forces on the bottom of the hull tending to pull deeper
into the water as speed increases. The planing hull was developed
in an effort to circumvent these disadvantages and it was found
that certain hull shapes, characterized by "open" water line
planforms at the stern experience a net positive pressure when
underway, so that the hull lifts out of the water with a consequent
reduction in wetted area. The reduction in wetted area, and the
more favorable flow around that part of the boat still in the
water, permits a planing craft to be accelerated through the region
of high pressure drag caused by wave making, provided the boat has
sufficient power. On calm water, a planing hull is very efficient
and speeds approaching 100 m.p.h. are normal for quantity produced
"sport boats" and speeds in the order of 200 m.p.h. are achieved by
racing hydroplanes. Unfortunately, water is rarely smooth, and in
waves such boats are subject to pounding which is physiologically
intolerable and can also break up the hull structure. Thus,
although it is both efficient and simple, the planing craft is not
able to operate at high speed in waves.
Because there is a great need for water craft capable of high
speeds, many alternative vehicle concepts have been developed in
attempts to evade the problem of pounding. Some of these prior art
developments are the surface piercing hydrofoils, fully submerged
hydrofoils, air cushion vehicles, captured air bubble craft, super
critical displacement hulls and submarines. It would be
inappropriate to analyze the characteristics of each of these
vehicles here, but it should be noted that only submarines and
fully submerged hydrofoils have clearly circumvented the pounding
problem while all are much more complicated than a planing boat.
This added complexity manifests itself in greatly increased first
cost, decreased reliability and severe operation limitations of one
kind or another.
The planing craft only planes on a small portion of its bottom at
high speeds. When such a craft encounters a wave, the lifting area
is greatly increased and the craft experiences the upward
acceleration which is the most marked feature of pounding. Because
of the inertia of the water in the wave, the magnitude of this
acceleration is much greater and would be calculated simply from
the increase in wetted area. Thus, the problem which exists is
derived from the fact that most planing craft have planing surfaces
which are much too large. Others have utilized the "deep V" in hull
design in order to reduce pounding. Although it is generally
supposed that a deep V somehow cushions the impact, it actually
reduces the efficiency of the lifting surface and hence, in effect,
constitutes a reduction of the planing surface size for a given
boat size. Unfortunately, the deep V not only does not reduce the
wetted area, but actually increases it thereby leading to higher
skin friction drag.
Hydrofoils raise the hull of the boat up out of the water so that
high speeds can be obtained but the hydrofoil is limited in rough
sea operations by the distance the hull is raised out of the water.
Thus, with waves above a certain size, the boat will be subjected
to the same severe pounding that ordinary planing craft are
subjected to.
SUMMARY OF THE INVENTION
The present invention provides a high speed boat with a planing
hull which is not subjected to pounding in waves but cuts through
the waves, thereby giving the boat an amazingly steady level ride.
The boat is not only efficient at high speed but has excellent
seaworthiness at low speed due to its low natural frequencies in
roll, and pitch. At high speed, the boat is stabilized by spray
sheets thrown up that contact the hull sides.
The boat is simple and rugged in construction. Preferably, all of
the exterior surfaces of the boat are either planar or provided
with a simple curvature as opposed to other high speed boats all
which include compound curvatures, thus increasing cost and
complexity.
The boat of the invention is provided with a unique bow
configuration which allows the boat to knife through most waves,
thereby reducing the pounding effect, however with extremely large
waves, the lift characteristic of the inclined bow transom enables
the boat to ride over such waves.
The boat of this invention is provided with delta-shaped or thin
wedge-shaped planing surface with the sides of the boat extending
upwardly and outwardly with a concave curvature from the leading
edges of the delta or wedge. Such a configuration substantially
reduces the wetted area giving a reduction in skin friction. It
also produces continuous spray sheets from the sides which contact
the outwardly curving sides to provide both stabilization and lift.
The delta-shaped bottom is normally submerged so that passage
through a wave does not result in an increase in lifting area. The
delta-shaped configuration of the deck results in the aerodynamic
center being located well aft to provide a boat which is almost
impossible to "flip." The concave curvature of the sides of the
boat, allows the boat to bank into far tighter turns than was ever
possible with prior art boats. The same concave curvature of the
sides also leads to a relatively dry cockpit in rough weather since
the spray thrown upwardly is directed outwardly and downwardly
rather than upwardly as is customary with boats having a convex
hull configuration. These spray sheets add to stability in turns.
Deflector rails may be placed on the sides of the hull to intercept
the continuous spray sheets, a keel skeg may be used on the bottom
of the hull to minimize side slip, and trim tabs or other means may
be utilized to counteract propeller torque. While a single wedge
shaped hull is desired in most cases for a powered craft, a number
of separate but connected slim wedge shaped hulls are useful in
other vessels, e. g., a sailing trimaran with one wedge forward and
two wedges aft.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a side elevation of the boat according to the present
invention.
FIG. 2 is a bottom plan view of the boat shown in FIG. 1.
FIG. 3 is a stern view of the boat shown in FIG. 1.
FIG. 4 is a schematic front view of the boat shown in FIG. 1,
illustrating the configuration of the bow transom and the
progressive cross sectional configuration of the boat at selected
points from the bow toward the stern.
FIG. 5 is a longitudinal partial cross sectional view of a modified
boat construction having the overall external configuration similar
to that shown in FIG. 1.
FIG. 6 is a longitudinal partial sectional view of the stern
section of the modified boat construction.
FIG. 7 is a cross sectional view taken along the line 7--7 of FIG.
5.
FIG. 8 is a sectional view taken along the line 8--8 of FIG. 5.
FIG. 9 is a cross sectional view taken along the line 9--9 of FIG.
6.
FIG. 10 is a side elevation of a modification showing a plurality
of deflectors or spray rails on the side of the hull.
FIG. 11 is a detailed sectional view taken along line 11--11 of
FIG. 10 showing a spray rail in section.
FIGS. 12, 13 and 14 are bottom plan, side elevation and sectional
elevation views respectively of a modification of this invention in
the form of a sailing trimaran.
FIGS. 15, 16 and 17 are side elevation and sectional views (2)
respectively of a modification of this invention in the form of a
sea plane.
FIGS. 18, 19 and 20 are side elevation and two sectional views of a
modification of this invention in the form of a larger boat, e.g.,
a large passenger ferry.
FIG. 21 is a graph of the lift drag ratio plotted against the lift
coefficient for various trim angles.
DETAILED DESCRIPTION OF THE INVENTION
A powered boat 10 having high speed planing capability in rough
seas, is provided with a delta-shaped planing surface 12 with the
apex 14 disposed adjacent the bow and the base line 16 disposed
adjacent the stern. The delta or thin wedge shaped planing surface
need not be formed of straight sides as good results are also
obtained if the long sides of the delta or wedge are slightly
convex or concave. The bottom of the planing surface also need not
be perfectly flat but may vary to some concavity.
The bow of the boat immediately adjacent the planing surface is
formed as a concave knife edge 18 which extends upwardly and
forwardly from the planing surface 12 and terminates in a bow
transom 20 which is flat and angled at approximately 45.degree.
relative to the planing surface 12. The sharper the knife edge, the
less spray will be thrown up at this edge.
The sides of the boat 22 and 24 extend upwardly and outwardly from
the edges or chines 26 and 28 respectively of the long sides of the
delta-shaped planing surface 12. The concave configuration of the
sides 22 and 24 is conveniently a simple curvature and the sides
terminate at the upper edge in gunwales 30 and 32. As an example of
a simple curvature a cubic curve can be used. Such a cubic curve
could be y = a.sub.0 + a.sub.1 .sup.. z + a.sub.3 .sup.. z.sup.3
where y is a lateral dimension, z is height above the planing
surface and a.sub.0, a.sub.1 and a.sub. 3 are constants. A spray
rail 33 is along each gunwale. A transom 34 extends upwardly
relative to the planing surface 12 and is joined thereto along the
base line 16 of the delta-shaped configuration.
A bustle 36 may be secured to the transom 34 to provide additional
roll stability, especially at lower speeds, when the boat is not
planing. Sides 38 and 40 of the bustle have a slightly different
curvature than the sides of the boat but could be a continuous
extension of the sides 22 and 24 of the boat. The bustle 36 is
provided with a channel 42 extending from the boat transom 34 to
the bustle transom 44 to provide the necessary clearance for the
drive train between the engine 35 inside the boat and the propeller
37. On opposite sides of the channel the bottom of the bustle has
two angular surfaces 46 and 48 which are stepped relative to the
planing surface 12 so they are not in contact with the water while
the boat is planing. The gunwales 50 and 52 of the bustle are shown
in a stepped manner relative to the gunwales 30 and 32 on the main
hull but the gunwales on the bustle could be a straight
continuation of the gunwales on the boat hull.
The decking and interior configuration of the boat may vary
considerably. In the embodiment shown in FIGS. 1 - 4 inclusive, the
decking 54 is provided with a convex curvature between the gunwales
and is continuous relative to the boat per se and the bustle. The
forward portion of the decking 54 extends outwardly over the blunt
bow transom 20 a short distance and functions as a spray deflector.
That is, when the blunt bow transom 20 strikes a wave and causes
spray, the spray will not fly back into the passenger's face as it
will be deflected by deflector 55. This deflector will also
incidentally provide some lift from this spray deflection. A
forward cockpit 56 is provided for the driver with a suitable wind
screen 58. An aft cockpit 60 is provided for the passengers and
rearwardly of the passengers, is the engine hatch 62 which is flush
with the decking 54 in the closed position. In the preferred
embodiment, the plan configuration of the decking will be
delta-shaped similar to the planing surface but of greater area
thereby locating the aerodynamic center well aft to prevent
flipping of the boat at high speeds.
FIG. 4 clearly shows the flat bow transom 20 and the various cross
sectional configurations A, B, C and D taken along the lines A--A,
B--B, C--C and D--D respectively in FIG. 1. FIG. 4 also shows the
concave curvature of the sides 22 and 24 as they rise from the
progressively widening delta-shaped planing hull 12.
The boat hull, according to the present invention, may be
constructed from any suitable material such as plywood, fiberglass
or metal and the size of the boat may vary considerably from a
small runabout to a large ocean line type vessel since the
principles of construction are valid for all sizes. By utilizing
the concave sides having only a simple curvature, it is extremely
economical and easy to construct the boat. In view of the wave
cutting characteristics of the boat in rough water, it is
unnecessary to provide an extremely heavy, strong internal frame,
since pounding is minimal.
FIGS. 5 - 9 inclusive show a specific embodiment of the boat
wherein a metalic skin, such as aluminum, is used for the hull. The
boat shown in FIGS. 5 - 9 is substantially identical in
configuration to the boat shown in FIGS. 1 - 4 and differs only in
detailed construction features which are primarily internal of the
boat. The only superficial difference is best shown in FIGS. 6 and
9 and involves only the shape of the tunnel in the bustle which
provides the necessary clearance for the drive train. In this
embodiment, the tunnel is curved to facilitate the construction
using metal sheets as opposed to the rectangular tunnel shown in
FIGS. 1 - 4.
FIG. 5 shows two internal bow plates 70 and 72. Each of the bow
plates 70 and 72 is provided with a concave curvature which extends
upwardly and forwardly from the bottom of the boat which is defined
by a delta-shaped plate 74. The bow plates 70 and 72 have flanged
edges 76 and 78 for attaching the sides of the boat thereto. The
bottom edge of the plate 70 has a flange 80 for securement to the
plate 74 and the three edges of the delta-shaped plate 74 are bent
downwardly to form similar attaching flanges 82. The bow plate 72
is substantially narrower throughout than the bow plate 70 as best
shown in FIG. 7. The inner and outer side walls of the hull 84 and
86 are secured to the bow plates 70 and 72. The outer wall 86 stops
at the bow plate 72 and separate knife edge component 89 is
attached by fastenings 91 shown in FIG. 7.
The bow transom 90 extends upwardly from the bow plate 72 at
substantially a 45.degree. angle relative to the bottom 74 and has
flanged edges 92. An inner bow transom 94 extends parallel to the
bow transom 90 but extends only downwardly as far as the innermost
bow plate 70 to which it is secured. Both bow transoms 90 and 94
are secured to a deck plate 96 and the outer skin 86 of the boat
along their flanged edges. In all instances the various members may
be secured to each other by any suitable means, such as riveting or
welding.
The decking 100, FIGS. 7 and 8, is provided with a flange 102 for
attachment to the upper edge of the outer skin 86. The joint of
flange 102 is encapsulated in rubber or the like 103 to form robust
spray rails which also serves to protect the hull against impact,
e. g., with the dock. The decking is provided with a step at 104
for receiving any internal cross structure such as the bow hatch,
engine hatch, or the like so that these structural members will be
flush with the decking 100. The inner edge of the decking 100 is
secured to the inner skin or wall 84 of the hull.
In FIG. 6 the transom has an inner wall 110 and an outer wall 112,
which may be of integral one-piece construction joined by an upper
cross member 114. The bottom edges of the transom are separated by
and secured to a crossbar 116 and the inner wall of the transom 110
is secured to the downwardly turned flange 82 of the bottom plate
74.
The bustle 120 has bottom and side member 122 with a semicircular
curvature at 124 to define the tunnel which provides the necessary
clearance for the drive train. The member 122 also has a flat
bottom portion 126 which extends outwardly at a small angle
relative to the horizontal and an upwardly and outwardly curved
side portion 128 of a concave curvature which is a continuation of
the curved sides of the boat. The bustle also has a cross member
130 with an upwardly and outwardly turned flange 132. A decking
member 134 with a configuration similar to the decking member 100
is secured to the flange 132 and the edge of the side 128. A
gunwale 136 is formed as a continuous line along the entire length
of the boat and is encapsulated in a resilient material as
described above. A bustle transom has an inner wall 140 and an
outer wall 142, which extend upwardly at an angle parallel to the
main boat transom.
As seen from the previous detailed discussion of the various
components, a double walled boat hull is provided. The entire
chamber defined by the dual wall structure may be filled with any
suitable buoyant cellular material such as polystyrene foam or the
like to provide buoyancy of flotation tanks. The various members of
the boat hull are defined chambers of watertight construction. An
epoxy concrete 150 or other suitable material completely fills the
depression defined by the flanges 82 on the delta-shaped base plate
74. This epoxy concrete which has considerable weight per unit
volume provides a sealing means for the various seams and also
provides the correct degree of ballast necessary to provide the
boat with roll stability when in a displacement mode. Numerous
other materials may be used as ballast and separate sealing means
may be used to seal the seams. Also, the ballast may be located
above the delta-shaped planing surface within the boat.
As stated previously, the bustle is not an absolutely essential
feature to the present boat construction but if used, does provide
additional roll stability at low speeds. The voids in the bustle
structure may also be filled with a foam material similar to that
shown in FIGS. 5, 7 and 8.
In order to minimize side slip when turning, the boat is provided
with suitable side slip prevention means such as a keel skeg 152 as
shown in FIGS. 1 - 3 or a fin keel 154 on the bottom of the planing
surface as shown in FIG. 10.
When the boat is planing with the forefoot of its bow above the
waterline, a turn can cause side slip. This side slip can cause the
chine to drop and "dig in" resulting in unpleasant lateral
deceleration. The use of side slip prevention means in the form of
a keel skeg or fin keel on the bottom of the planing surface serves
to minimize side slip.
The torque from the propeller causes the thin wedge shaped hull of
this boat to tend to list to one side. This is compensated by
torque counteracting means which in a preferred embodiment can be a
simple trim tab 156 on one side of the aft end of the planing
surface of the hull as shown in FIGS. 1 - 3. This trim tab could be
adjustable, but this is not necessary. Moreover, other means of
counteracting torque can be used to provide a rolling moment equal
and opposite to the propeller torque moment. Additionally, such
torque opposing means could incorporate the engine cooling water
inlet in the trim tab.
As an example of this invention, an 18 foot marine plywood boat
built in accordance with the principles disclosed above knifed
through 3 and 4 foot waves of the Chesapeake Bay at speeds between
35 and 50 miles per hour with the boat carrying three people having
approximate gross weight of 2,200 pounds. The power was transmitted
to a cupped prop at approximately 4,400 r.p.m. by a Mercruiser 140
h. p. engine. On the straightaway and in turns the ride was
exceptionally stable even when small craft warnings and high seas
forced other boats to harbor. Boats built in 22 foot length with
aluminum hulls have cleanly parted waves of 4 - 5 feet high and
wave lengths of 20 - 40 feet at speeds near 50 miles per hour with
no pounding as compared with the best of conventional hulls which
have to drop speed to keep control. The boats have consistently
crossed the Chesapeake Bay in winds of 20 - 40 knots and are
outstandingly safe in rough weather at all speeds of operation.
When the boat gets underway the hull lifts progressively and
rapidly to move from a displacement mode to a planing mode. When
initially accelerating, the bow raises but then trims in a few
seconds to provide a smooth ride. The knife edge bow cuts through
some waves and passes over some. When underway, the planing bottom
of the hull functions as a planing surface. Spray sheets spray up
from each side edge of the hull aft of the knife edge bow and these
aid in supporting and stabilizing the boat. Because the hull is
"super critical," i. e., it has a resonant frequency less than the
frequency of encounter of waves, acceleration of the boat in rough
seas makes the ride even smoother.
As shown in FIGS. 10 and 11 the side surfaces 22 and 24 of the boat
may be provided with a plurality of deflectors or spray rails 158,
158' and 158". These are to take advantage of the spray sheets and
increase the lift to drag ratio. As a slender wedge such as the
hull of this boat moves through the water at high speeds, spray
sheets develop up and along the sides. The spray sheet will go
upwardly and outwardly from the bow of the boat and from the side
edges, and the spray angle may vary along the length of the hull.
The water in the spray sheet has kinetic energy which is utilized
as the spray sheet hits the curve of the hull; in other words, the
spray sheet momentum is reacted as a lift force on the boat by
deflecting it back downward. While the outer curved surfaces of the
sides 22 and 24 of the hull can and do accomplish this, an
additional effect can be obtained by utilizing deflectors or
inclined spray rails 158, 158' and 158" as shown in FIG. 10. The
spray rails are inclined at an angle to the normal inclination of
the boat while planing so that the pressure drag is partially
offset by a forwardly acting component of the resulting force.
Summarizing, the boat of this invention utilizes a fully submerged
planing surface with a thin wedge shape so that lift area is not
increased when it passes through the wave, nor is the boat
decelerated by a bluff bow shape. Propelling such a thin wedge
shape through the water results in the development of lateral spray
sheets, the momentum flux in which is comparable to the total lift
on the bottom. The sides of the boat deflect these spray sheets
outward, substantially recovering this momentum flux; or if
desired, deflectors can be utilized to deflect the spray sheet
outward and downward, thus recovering even more lift. If the boat
banks, then the spray sheet on the low side becomes thicker and its
additional momentum provides the necessary "roll stiffness." The
same is true in side slip, except that the spray sheet on the side
to which it is slipping becomes thicker adding force to oppose the
side slip. A most dramatic example of the power in these spray
sheets is obtained when the boat is trimmed with the bow very high,
then jumped sideways drift off a wake. Upon reimpact with the
water, it starts to trip in the direction of motion; at the same
time the spray sheet rises up the side and pushes it back again.
The resultant wiggle takes a very short space of time.
While the foregoing description is applied to a powered planing
boat, the theory of operation and the shape of the hull are not so
limited. For example, the invention can be applied to a sailing
trimaran as shown in FIGS. 12, 13 and 14. In this case the hull 170
is formed of three slim wedges 172, 174, 176 with the slim wedge
172 forward and the other wedge sections 174, 176 aft. The bow
configuration still includes the knife edge 178 and the outwardly
flaring concave sides such as side 180; these sides flare outwardly
of each of the wedge shaped sections, except for the inboard sides
of the aft wedge sections. Trim tabs 182 may be used to trim the
boat in pitch and roll, and flaring side deflectors 184 may also be
provided. Of course, the boat has the conventional rudder 186 and
control 188 and may have optional footwells 190 in each of the
aftmost wedge sections. This embodiment of a trimaran could be
powered.
FIGS. 15, 16 and 17 show application of the principles of this
invention to the body of a flying boat, i. e., a seaplane. The
plane fuselage 190 is constructed with the bottom in accordance
with the principles of this invention including a thin wedge shaped
planing surface 192 with a knife edge 194 at the bow thereof and
outwardly curving sides 196. The plane may have retractable wing
tip floats 198 and a retractable fairing 199.
The principles of operation of the FIGS. 12 - 14 and FIGS. 15 - 17
embodiments are the same as the principles for the other described
embodiments.
FIGS. 18 - 20 show a further embodiment of the invention as applied
to a larger ship, in this case an 85 foot long passenger ferry. The
principles of the invention are the same. That is, the boat has a
thin wedge shaped planing bottom 200 with a sharp knife edge
concave bow portion 202 and above it, a blunt inclined bow portion
204. Concave sides 206 and 208 extend upwardly and outwardly from
the sides of the bottom to gunwales 210 and 212. In this case the
bustle 214 is behind a step 216 at the end of the planing surface
or wedge shaped bottom. A propeller drive 218 is below the planing
surface, not behind it. Propeller shafts 220 are connected to the
propellers from each of three diesel engines 222, 224, 226. A keel
skeg and fairing 228 are provided for each shaft and steering is by
means of one or more rudders 230. The space above the gunwales can
conveniently have rows of seats 230 for passengers with a control
cabin 232 on top. This 85 foot long, 200 passenger ferry cruises at
40 knots and has ninety tons gross weight. It is powered by three
1450 horsepower diesels.
FIG. 21 is a plot of the lift drag ratio, an indication of the
efficiency of the hull against the lift coefficient. The lift
coefficient is a non-dimensional coefficient equal to the pressure
supporting the boat over the dynamic pressure in the water. In the
equation .DELTA. equals the total weight, q.sub.0 equals the
dynamic pressure of the water which in turn is one-half times .rho.
times v.sup.2 where .rho. equals the mass density of water (about 2
slugs per cubic foot) and v equals the velocity of the boat in feet
per second. .theta. is the wedge angle (one-half the included angle
of the apex of the wedge) and x is the length of the planing
surface in feet. The trim angle is the angle of trim in the water.
Both the trim angle and the wedge angle are expressed in radians.
The wedge angle, the curve of the side and the height of the
gunwales can vary depending upon the condition the boat is designed
for. However, with the criteria applicant has disclosed, these
choices would be apparent to skilled boat designers. As can be seen
from FIG. 21 the preferred included angle of the wedge apex is
between about 10.degree. and 30.degree. for most applications.
While the invention has been particularly shown and described with
reference to preferred embodiments thereof, it will be understood
by those in the art that various changes in form and details may be
made therein without departing from the spirit and scope of the
invention. For example, although the plan form of the planing
surface has been described as a delta or thin wedge, its sides need
not be straight in plan as they can be concave or convex. Also the
sides of the boat can curve inward near the planing surface before
curving upwardly and outwardly.
* * * * *