A multi-hulled boat has at least three hulls, with the outside hulls extending forward beyond the central or inside hull or hulls. The hulls are tapered with a cross-sectional configuration that increases in side front to rear, thus forming a channel or tunnel between adjacent hulls which decreases in cross-sectional size front to rear. Air entering the tunnels is compressed, thus imparting a lifting force to the hulls lifting the hulls partially out of the water to decrease the hydraulic drag on the hulls. The hulls have identical cross-sectional areas at identical transverse planar sections thereof. The bottom of each hull is flat and inclined at an angle with the horizontal. The hull bottoms join the hull sides at a chamfer which increases in size front to rear. Shutters or flaps may be used to partially or fully close off the tunnels between the hulls to control airflow or to trap water-borne material to be collected and recycled.

FIELD OF THE INVENTION 
The present invention generally concerns designs of boat hulls and more 
particularly to multi-hulled boats. 
BACKGROUND OF THE INVENTION 
Boats having several parallel hulls already exist and are well known. For 
instance, boats with two hulls are known as "catamarans." There are also 
three-hulled boats, or "trimarans" wherein the central hull is longer than 
the side hulls, with the side hulls used more as stabilizing floats rather 
than as hulls proper. 
In French Patent No. 2,586,001, there is disclosed a four-hulled boat in 
which the central or inside hulls are shorter in length than the side or 
outside hulls. Such a hull structure helps improve the boat's performance 
by reducing its draft and improving its stability. 
BRIEF DESCRIPTION OF THE INVENTION 
The present invention concerns a boat having at least three parallel hulls 
attached to the underside of the boat bottom, with each central or inside 
hull being shorter in length than the side hulls with the rear walls of 
each hull being coplanar and with the front edge of each inside hull set 
back from the front edge of the side hulls. The purpose of the present 
invention is to provide such a multi-hulled boat with improved or enhanced 
performance characteristics which require less powerful motors to propel 
the boat. 
To accomplish this goal, the cross-sectional of the outside hulls and the 
inside hulls increases continuously from fore to aft, and the side walls 
of each hull are planar and generally vertical. 
An inverted trough is thus formed by the boat bottom and the hull sidewalls 
of adjacent hulls defining an air passage or "tunnel" as described 
hereinbelow. Because the outside hulls are longer than the inside hulls 
and extend forward of the inside hulls at the front of the boat, the 
outside hulls form a type of funnel, forcing the air to rush into the 
tunnels created by the space between adjacent hulls. Because the width of 
the tunnels decreases fore to aft, the air pressure within each tunnel 
increases from fore to aft, providing the boat with a lifting force. When 
the boat is lifted from the water, the submerged volume is reduced, 
allowing the boat to obtain excellent performance while requiring a lower 
power output from the boat's motors. 
Another feature of the present invention is that the bottom of each hull is 
substantially flat and is tilted at an angle of 0.5.degree. to 5.degree. 
with the horizontal. As the boat begins to lift upward with an increase in 
speed, the flat, sloped bottoms of the hulls create an aerodynamic drag 
which produces a dynamic lift. The preferred angle of tilt of the hulled 
bottoms is preferably between 1.degree. and 3.degree.. 
Yet another advantage to the present invention is that the downward-facing 
surface of the boat's bottom which covers the tops of the hulls slopes 
upwardly from rear to front. Preferably, the downward-facing surface of 
the boat bottom is roughly parallel to the bottom surface of the hulls. As 
a result, the height of the tunnel separating adjacent hulls diminishes 
from front to rear which further enhances the phenomenon of air 
compression, once again improving aerodynamic lift. It should be noted 
that the air compression is accomplished with a perfectly laminar airflow 
due to the overall profile of the hulls as described hereinabove. 
To facilitate the manufacturing of the hulls and give the hulls good shock 
absorption characteristics in water, the bottom of each hull is connected 
to each lateral or side wall of each hull by means of a flat, 
partially-tilted surface, forming a chamfer. The angle of this chamfer 
decreases continuously from back to front in conjunction with the the tilt 
of the hull bottom until the chamfer is totally horizontal at the front 
part of the hull. Consequently, the height of the chamfer determines the 
slope of the bottom of each hull. 
The backs of each hull all lay in a single plane perpendicular to the 
boat's axis and the hulls are all identically sized and shaped, and thus 
all have identical cross-sections at identical points along their lengths 
to the front of the shortest hulls. This feature makes construction of the 
boat easier because all hulls are identical from the back to the front of 
the shortest hulls. The outside hulls, which are longer than the shorter 
inside hulls, have streamlined extensions built at the front to enable the 
outside hulls to extend forward beyond the ends of the inside hulls. 
Each tunnel between adjacent hulls may be equipped with a flap or shutter 
hinged horizontally at its fore-edge under the boat bottom between 
adjacent hulls, roughly at the mid-length of the boat, each shutter having 
a control means, such as a hydraulic jack to adjust, if need be, the 
airflow through the tunnels and, thereby, the tilt of the boat. 
This type of boat which may have, for example, four hulls or more, has 
advantages because of the lift capability it features, which enables the 
use of a smaller engine to drive the boat than if the hulls did not lift 
out of the water while the boat is under way. Furthermore, it should be 
noted that it is an advantage to increase the number of low-powered 
engines used by placing one such engine in each hull, thereby providing an 
extra margin of safety because in the case of the failure of one engine, 
the boat can sail on using the other engines. The engines can be 
conventional propeller-driving type engines or surface propulsive engines 
of the hydrojet type. In accordance with the usable volume within the boat 
hulls and the lightness of the construction, the boat can be made 
unsinkable by filling each hull with expanded thermoplastic material such 
as polystyrene rated, for example, at 30 kilograms per cubic meter. 
Such a boat can be used either for leisure or for more commercial purposes 
such as transporting passengers or as ferries for carrying cars and 
freight. In any case, the boat is lifted from the water as it reaches the 
speed of about 15 knots and the submerged surface area is greatly reduced 
because the length of the water line is reduced by two-thirds while the 
boat is cruising. 
It is also possible to consider other uses for this type of boat, such as 
helping in the battle against pollution by collecting trash floating on 
the water utilizing the tunnels between the different hulls to pick up 
floating waste due to the flaps hinged along the aft edge of the hulls and 
to store the waste in settling or collecting bins at the back of the boat. 
The invention will be more easily understood upon a consideration of the 
accompanying drawings. The drawings herein show the boat in a 
configuration intended for leisure use, but is not intended to limit the 
scope of the invention.

As shown in the drawings, and referring to FIGS. 2 and 3, a boat 1 of the 
present invention has four hulls in two sets of two identical hulls each, 
namely, two outside hulls 2 and two inside hulls 3. The backs 9 of each 
outside hull 2 and each central hull 3 are coplanar in a plane 
perpendicular to the fore-and-aft axis of the boat. 
As shown in the drawings, each outside hull 2 and inside hull 3 has a 
generally triangular shape as viewed from a horizontal plane above the 
hulls with the width of each hull increasing continuously from front to 
rear. Furthermore, as shown particularly in FIG. 3, side walls 4 of each 
hull 2, 3 are substantially vertical and planar or flat. 
As best seen in FIG. 4, hulls 2, 3 are identical in shape, size and 
construction. Preferably 2, 3 are assembled to boat 1 with rear walls 9 
aligned in a single plane perpendicular to the fore-and-aft axis of boat 
1. Thus, the cross-sectional shapes and areas of all hulls will be 
identical when measured at identical points along the hulls' lengths. 
In accordance with yet another feature of the present invention, and as 
shown in FIGS. 1 and 2, bottom 5 of each hull is substantially flat and 
sloped upward from rear to front at an angle between 0.5.degree. and 
5.degree., preferably at an angle between 1.degree. and 3.degree. as 
measured from the horizontal. 
The bottom 5 of each hull is connected to the corresponding sides 4 by a 
flat, partially tilted hull surface 6 forming a chamfer. The height or 
size of chamfer 6 decreases continuously from back to front as a result of 
the tilt of each hull bottom 5. This shape results in easy-to-build 
low-cost hulls that can be made of low density metal or metal alloys such 
as aluminum alloy. 
As seen in FIG. 4, the hulls are assembled conventionally, using transverse 
braces 7 to impart lateral rigidity and stability to hull walls 4. 
The fact that the cross-sections of outside hulls 2 and inside hulls 3 are 
identical along the entire lengths of the hulls extending to the front 
edges 10 of the shortest hulls facilitates manufacturing and allows 
manufacturing to be standardized, as the two outside hulls 2 are the same 
in shape as inside hulls 3 except for streamlined extensions 11 attached 
at the front of each side hull 2. 
Hulls 2 and 3 are attached one to the other to boat bottom 8 lower surface. 
In a preferred embodiment, bottom 8 is pitched upward from rear to front. 
This pitched feature, as well as the increasing cross-sectional area of 
the hulls front to back contributes to reducing the size of the air 
passage between adjacent hulls which enhances the lift phenomenon. 
As seen in FIGS. 2 and 3, a tunnel 12 is formed between each pair of 
adjacent hulls, each said tunnel 12 being defined by a pair of opposed 
hull sides walls 4 and bottom 8. As best seen in FIG. 4, each tunnel 12 
has a larger cross-sectional area at its entry 13 than at its exit 14. As 
best seen in FIG. 2, the tilt of bottom 8 also decreases the 
cross-sectional area of each tunnel 12 along the tunnel length from front 
to rear. The narrowing of each tunnel 12 along the path of airflow there 
through compresses the air within the tunnels, causing the lift effect 
described earlier. 
As further shown in FIGS. 2, 3 and 4, adjacent hulls 2, 3 or 3, 3 are 
spaced the same distance apart. All tunnels 12 are thus substantially 
identically sized and shaped to present substantially identical flow paths 
for air passing therethrough. 
Referring now to FIG. 4, the numeral 15 indicates generally a shutter or 
flap positioned approximately midway between entrance 13 and exit 14 of 
tunnel 12. It is contemplated that one such shutter 15 may be placed 
within each such tunnel 12. Adjusting controls (not herein specifically 
shown) are provided to adjust the angle of shutter 15 and, consequently, 
the extent to which shutter 15 covers or closes off tunnel 12. Shutter 15 
may be variously used to trap or collect trash or debris within tunnel 12, 
or to affect or control the degree to which hulls 2, 3 are lifted above 
water line 16 while boat 1 is under way. 
The boat shown in the accompanying drawings has a superstructure 
corresponding to that of a yacht, but could also have other 
superstructures as well as, for example, if the boat were designed to 
collect trash on the water. In that case, it would be necessary to place 
shutters in the tunnels to trap waste and direct it to settling tanks 
which could also be located at the back of the boat. 
As shown herein, the present invention demonstrates improvements to 
existing boat construction techniques by offering a boat with a simple 
design, high performance driven by low-powered motors which results in 
savings both in terms of manufacturing costs as well as use and 
maintenance. 
The foregoing has described a specific embodiment of the present invention, 
it is not intended that the invention be limited only to the example 
herein described and shown. The present invention could also apply to a 
variety of different boat configurations and the description is not 
intended to limit the spirit and scope of the invention described and 
claimed herein. 
For example, the number of hulls can be different so long as the inside 
hulls are shorter than the outside hulls to preserve the funnel system 
which directs air to the tunnels between the hulls. In addition, the 
tunnels could be closed off at their openings by attached shutters while 
still remaining within the boundaries of the invention described herein.