[0001] This invention is a solution to a usual problem in the field of navigation: how to
reduce water resistance and at the same time how to navigate stably at high speeds
both in calm and rough waters.
BACKGROUND OF THE INVENTION.
[0002] Attempts have been made to solve this problem, but for different reasons none of
them has been a real solution as they lack stability or describe a structure which
considerably reduces the effect to be achieved.
[0003] The Argentine patent number 213.661 discloses submerged floats which have the shape
of an ellipsoid-of-revolution. However, it fails to mention stabilizing means such
as the ones mentioned in this invention.
[0004] The Japanese patent application Kokai 52-31486 includes submerged floats; however,
it does not disclose their shape, and includes perpendicular levelling means between
two floats (at the rear end of said floats) joined to them, as well as a horizontal
and vertical rudder system, also positioned between the two floats (at the front end
of said floats) and joined to them. Both this levelling system and the rudder system,
increase the navigation surface because of their features, and because their shape
is incompatible with the design characteristics required to reduce shape resistance,
they cause a significant increase in driving resistance.
[0005] The EP-A-0080308 includes removable semisubmerged floats, fixed both at their front
and rear ends to partially submerged columns which are perpendicular to the water
surface.
[0006] The submerged ends of said columns include pairs of quarters which function as stabilizing
means. As indicated in the previous specifications, this vessel has been designed
for low speeds and to be at rest. This is apparent because the columns which are located
near the ends of the floats dramatically reduce the shape effect achieved by said
floats; at the same time these columns produce wave resistance, increase driving resistance
and require a solid structure to drive the float removing means.
[0007] Now that the background has been reviewed, it will be noted that no appropriate stabilizing
means have been found that can be combined with the floats supporting a vessel, and
that said vessel cannot navigate stably in either rough or calm waters.
SUMMARY OF THE INVENTION
[0008] According to a preferred embodiment of this invention, there is provided a vessel
or boat whose hull or useful volume (1) is above the surface of the water, and whose
submerged part (2) and semi-submerged part (3) comprises anti-rolling floats (2,3),
basically oblong, the axis of which is parallel to the longitudinal axis of the whole
set, supporting columns which are a series of ellipses, and at least two, designed
in such a way that they minimize the driving resistance, increase righting moment
and make manoeuverability and stability easier.
DESCRIPTION OF THE INVENTION
[0009] A vessel according to the present invention, as basically designed, offers a plurality
of advantages compared to conventional vessels, as it reduces wave formation resistance
significantly; reduces driving resistance; makes it possible to use propelling power
better; saves fuel; makes transport at higher speeds possible; has a limited draught
and a greater breath; achieves optimum balance between surface resistance and shape
resistance in order to achieve the least driving resistance and the maximum stability
and manoeuverability; solves stability problems as it produces righting moment (response
to the vessel rolling) with a minimum of undulating movement; it does not use energy
to produce "gliding effect" as the vessel buoyancy is basically is static instead
of dynamic; and moreover it can transport heavy loads.
[0010] The performance of a vessel using this invention under variable conditions of speed
and in both rough and calm waters will now be analysed.
There are basically three kinds of resistances that use propelling power, that is:
surface resistance, shape resistance and wave formation resistance. At relatively
low speeds (between 0 and 1.5 according to a unitless standard related to Froude number),
friction forces comprising between 80 % and 85% of total resistance are more commonly
observed. At relatively high speeds without gliding (from 1.5 to 3), friction forces
comprise 50% of the total resistance, and said resistance (from 1.5) increases much
more rapidly than at low speeds, especially because of wave formation.
[0011] As a reference for relative speeds, it can be said that a cargo boat sails at 0.8;
a warship at 2.0; and an off-shore power boat at 7.0 or more. As practically the entire
anti-rolling floats (2,3) are submerged (80% - 100% of their volume), and considering
the way they are arranged - as described in the Argentine patent number 213.661, the
only patent in which the shape of the floats is totally used - flow is almost perfect
and complete, the air/water contact surface is much smaller than in conventional vessels
and boats because of the floats, and the corresponding resistances are much lower,
which consequently makes it possible to use propelling power better, especially at
high speeds.
[0012] In order to achieve the required level of stability in calm waters, the floats may
be equipped with stabilizers, both in the bow and in the stern. Said stabilizers may
be controlled by any known means, e.g. manually or by hydraulic drives or drives controlled
by microprocessors, and offset both pitch and roll of the vessel.
[0013] At high speeds and as the waters become rough, the stabilizers are not enough to
achieve the desired level of stability of the boat. This invention makes the best
out of the floats' shape in order to minimize shape resistance as well as wave formation
resistance, and however increase stability gradually as the boat requires it.
[0014] The conformation of each antirolling float (2,3) according to an ellispsoid of revolution,
is an excellent condition to make the best of propelling power, as it has been proved
that the higher the ratio between the major and the minor axis, or in other words,
the more oblong the float, the higher the speed the boat can reach.
[0015] It is known that the body that has the smallest surface area for a certain volume
is a sphere. This is the case of a bubble. So as to know what shape a bubble would
adopt when affected by a field of external and uniform forces, we can compare a bubble
to the electron cloud of a hydrogen atom. When this cloud is under the effect of a
field of force that can deform it in a given direction, for example a uniform external
electrical field, said cloud will deform, and give way to an induced electrical dipole.
The shape this cloud will adopt in space is an ellipsoid of revolution.
[0016] Apart from the above mentioned, when a body moves in fluid, it produces an undulating
disturbance. If a particle is placed under the effect of the first whirl of said disturbance,
its path equation is sine or cosine.
[0017] When said particle defines a semiwave, the points reached during the corresponding
path, for example corresponding to the sine, coincide with one of the points given
by the equation of a semiellipse. If instead of taking a particle, a group of particles
is selected, so that the plane they are contained in is normal with respect to the
direction of the forces of the field, and the centre of symmetry coincides with the
intersection of said plane with the path direction, we will obtain the equation corresponding
to an ellipsoid of revolution in space.
[0018] According to the above-mentioned, we conclude that for our case in particular, the
best shape of a body having a given volume, and that moves in water at regular speed
and that produces the least disturbance is an ellipsoid of revolution.
[0019] Moreover, if we cut this ellipsoid of revolution with a horizontal plane, so that
it contains the main axis of the ellipsoid, we can see that the fluid drains not only
in the lower part, but also in all of the top part. This means that the fluid flows
all around the body. In order to provide the boat with an adequate righting moment,
the antirolling floats (2,3) are not totally ellipsoids of revolution, as they would
be in the boat described in the Argentine patent 213.661. If we cut the antirolling
float (2,3) according to a plane normal to its longitudinal axis, the latter will
be shaped as shown in Fig. 3, and if we cut the float at any horizontal plane we will
find an elliptical shape, which means shapes similar to an ellipse and not exclusively
a geometrical ellipse, which preferably will keep the radius ratio both in its propelling
section and its anti-rolling section. When the vessel rocks (Figs. 5 and 6), the floating
plane changes and grows larger, and consequently the moment of inertia opposing the
rolling increases too. In the same way, the submerged volume increases as much as
V' (Fig. 6) so that this extra volume produces a push at a distance L from the centre
of the vessel, generating a moment opposing the movement. The exact shape and dimensions
of the unsubmerged region (2) of the antirolling float (2,3) will depend on the antirolling
characteristics the vessel may require; the response can be either slow or sudden,
and the section which is horizontal to the longitudinal axis of the unsubmerged volume
(3) will be ovoid or ellipsoidal.
[0020] After designing the floats in this way and after selecting the measures of the axes
of the ellipses that generate the former, it is possible to reduce driving resistance
and undulating movements. In fact, if we call the larger semiaxis of the generating
ellipse "R" and if we call the semiaxis of the same ellipse "r", the quotient R/r
will determine in each case a value having a corresponding speed for which said driving
resistance and undulating movement are slight.
[0021] Given a supporting volume "T", there will be a large number of ratios between "R"
and "r", and an optimum speed "V" will correspond to each of them. If the quotient
R/r increases, so will "V". Therefore, if "T" is kept constant, "V" will be increased
by only increasing "R" with respect to "r" for the same number of floats; or given
a "R" determined by the length of a vessel, the optimum speed will be successfully
increased if the number of floats is increased for the same volume. If the floats
are longer, or if the number of floats is increased, their external surface will be
increased too, which will lead to more contact with water, and therefore, a decrease
in speed. If motive power is always constant, speed will reach a maximum value for
each volume "T", and then will decrease if the surface is larger. Said maximum speed
will be useful to determine the number of and the size of floats for a volume "T"
which will support a given weight, for which the motive power required will be the
least. Therefore, it is possible that once the cargo and speed are fixed, a vessel
according to this invention will use less motive power for said cargo at that given
speed.
[0022] The antirolling float (2,3) used in this invention can be designed without taking
into account the shape restrictions that a conventional hull or the previous models
have; in this way the undulating movement generated by the part of the float that
is in contact with the air-water surface can be minimized; it is possible to provide
the necessary righting moment and achieve lateral resistance for a better manoeuverability
of the vessel. The floats can be totally hollow and/or divided into watertight compartments,
which is advantageous in case of accident or damage. Said compartments can be made
by means of cross-sectional supports. Also, they can be divided into compartments
where loads or fuel can be stored, or else they can be used to place the propelling
engines. They can be provided with propellers, directional rudders, rolling stabilizers,
etc.
[0023] In another embodiment, the anti-rolling floats (2,3) can be provided with supports
so as to minimize resistance. Therefore, the supports of the floats that are not external
can be oblong, or else a series of curves of elliptical shape, but the side walls
are separated forming an angle which is smaller than that of the external floats,
or a slight angle. In this way, a new embodiment of the antirolling float divides
it into two sections: the inside antirolling section and the distal closed. Said examples
are neither limiting nor protected exclusively by the scope of this specification.
DESCRIPTION OF THE DRAWINGS
[0024]
Fig. 1 shows a front view of the vessel;
Fig. 2 shows a side, schematic view in elevation of the same vessel shown in Fig.
1;
Figs. 3 and 4 correspond to a longitudinal section and a cross-section of a generic
antirolling float, according to a preferred embodiment of the invention; and
Figs. 5 and 6 show the effect of the floats when the vessel rocks, in relation to
the changes in the floating area of the float and the submerged volume.
[0025] In all the drawings, same numerals correspond to the same or equivalent parts of,
according to the examples chosen for this explanation of the vessel object of the
invention.
[0026] As it can be seen in Fig. 1, the vessel illustrated is provided with a superior set
corresponding to the hull (1) and at least two floats (2) which are connected to the
hull by antirolling means (3). The antirolling means (3) are oblong inverted frusto-conical
bodies whose bases are fixed to the lower part of the hull (1) and whose frusta are
joined respectively to the upper parts of the floats (2), preferably so that each
float (2) and associated antirolling means (3) forms a single anti-rolling float body
(2,3).
[0027] The front end (7) and the rear end (6) of each said antirolling means (3) comprise
tapered ends defining sharp edges (8 and 9) of hydrodynamic profile for a better displacement.
The total volume of the floats (2) is such that it supports the hull (1) and its cargo,
above the surface of the water.
[0028] Figs. 3 and 4 show a longitudinal section and a cross-section of an antirolling float
body (2,3) which is formed by a lower revolution body (2) with a top longitudinal
opening (a-a) from whose opposing ends two upwardly diverging walls (12 and 13) extend.
At their upper ends, the walls (12 and 13) bend inwardly towards one another over
horizontal sections (10 and 11), which are useful to join said body to the hull (1),
and furthermore the structure of the truncated-conical section they define is an antirolling
means.
[0029] Having described this vessel and the examples, modifications and improvements will
occur to those skilled in the art, all of which must be considered within the scope
of this letter patent; this scope is limited only by the claims that follow.
1. A vessel whose hull (1) or other useful volume is above the surface of the water in
use and is provided with float means (2,3) joined to said hull (1), characterized
in that said float means (2,3) comprise at least two oblong float bodies (2) arranged
in parallel fashion to the longitudinal axis of the vessel, and antirolling means
(3) in an upper part of said float means (2,3).
2. A vessel according to claim 1, characterized in that each antirolling means (3) comprises
an oblong body having a longer base connected to the hull and a shorter base connected
to the floating body (2).
3. A vessel according to claim 1, characterized in that each antirolling means (3) comprises
an inverted frusto-conical body whose base is joined to the hull and whose frustum
is joined to the float body (2).
4. A vessel according to claim 1, characterized in that the antirolling means (3) serve
as joining means between the float bodies (2) and the hull (1).
5. A vessel according to claim 1, characterized in that fore and aft ends of the antirolling
means (3) form an air dynamic edge for water displacement.
6. A vessel according to claim 2, characterized in that when the float body (2) is cut
by a horizontal plane an elliptical area is defined.
7. A vessel according to claim 1, characterized in that the float volume that is submerged
is about 80 - 100% of its total volume.
8. A vessel according to claim 1, characterized in that the radius ratio between ellipsoids
of revolution of the float propelling section and elliptical forms of the antirolling
means is the same.
9. A vessel according to claim 1, characterized in that ends of the propelling section
of the antirolling float means form a hydrodynamic edge for water displacement.
10. A vessel according to claim 1, characterized in that the float means (2,3) comprise
watertight compartments.
11. A vessel according to claim 1, characterized in that it comprises means that modify
the waterline and fix it at the hull of said vessel.
12. A vessel according to claim 1, characterized in that the antirolling means (3) comprise
stabilizing means.
13. A vessel according to claim 1, characterized in that it comprises means for filling
and emptying the float means (2,3).