The boat has a flap (1) forming a part of its V- or spoon-shaped bow and being unfoldable therefrom. This flap is supported by means of projections (9a,9b) arranged on both of its sides on swivel joints (13a,13b) set back into the inside of the boat with respect to the inner wall of the bow. Upon pivoting the flap (1) out of the bow opening (15), the flap is swung away from the bow wall portion with the uncovering of an interspace (2) between the flap and the bow wall portion which latter lies underneath the bow opening (15). The flap outside wall can be urged underneath the surface of the water and can be fixed in its position. The flap (1) is designed as a buoyant member, and when serving as a working or recreational platform, etc., can be folded back into the bow of the boat in such a way that the hydro- and aerodynamic properties as well as the esthetic appearance of the bow are not impaired. The boat according to this invention can thus be utilized, without restriction of its full functional ability, as a rescue boat, salvage boat, pleasure boat, and speedboat. The configuration of the flap (1) acting as a buoyant member makes its use possible without impairing the stability of the boat; in the unfolded condition, this configuration even enhances the capsizing stability of the boat. Furthermore, the design of the boat hull is such that the stern engines, when a curve is traversed, do not leave the water (4), and the boat exhibits a very high capsizing stability.

The invention relates to a boat with a hinged front opening closure portion 
that forms part of a V-shaped or spoon-shaped bow. 
Boats of this type are to be distinguished from those wherein a planar flap 
is arranged by means of a hinge in a planar portion of the boat wall, as, 
for example, in DOS 2,029,165. Those boats have the disadvantage of a 
hydrodynamically unfavorable driving characteristic. 
A boat of the type mentioned above has been known from French Patent 
A-2,511,969. Also in this boat, as in those boats of a different type, 
care is taken to keep the flap, during pivoting, at all times in close 
contact with the wall of the boat. For this purpose, the flap bottom 
section has a recess sealingly engaged by the lower edge of the bow 
opening during the unfolding step. The bow section below the flap opening 
is adapted in its shape to the pivoting motion of the flap about its pivot 
axis, i.e. it is designed as a group of partial circles with the center of 
the circles being on the pivot axis. Therefore, the hull portion located 
below the bow opening can no longer be adapted to optimum flow conditions. 
It is an object of the invention to provide a boat with a bow flap 
exhibiting good driving properties with an opened bow flap as well as in 
case of a closed bow flap.

The boat, illustrated in a lateral view in FIG. 1, has a flap 1 arranged 
symmetrically to the boat center line in its bow shown in FIG. 2; the bow 
has a V or spoon shape in which the apex of the V-S contour is outwardly 
convex and a convex configuration in the longitudinal direction of the 
boat. The hinged flap or bow closure position 1 is shown in FIGS. 3 as 
well as 4 in a position swung outwardly and downwardly from a U-shaped bow 
opening 15 that is open up to the top skirting or rub rail 8a of the boat, 
the outer wall 3 of the flap 1 being partially immersed in the water 4 in 
its open position as shown. 
The outside wall 3 of the flap 1 is likewise curved in a spoon shape and is 
designed so that, in the closed position, its outer shape continues into 
the outer bow wall 7 in an aero- and hydrodynamic fashion. On account of 
this configuration, it acts, when partially immersed in the water 4, as a 
flow-exposable plate with good hydrodynamic properties so that the boat 
can be operated even with a deployed flap 1 partially immersed in the 
water, in which case the flap 1 then lifts the bow. When flap 1 is moved 
to its open position, as shown in FIGS. 3 and 4, the lower portion of flap 
1 adjacent to the water is moved underneath the surface of the water 4 and 
underneath and spaced from the bow wall portion lying below the bottom 
edge of the U-shaped bow opening 15 that is adjacent to the water surface. 
An open space 2 is thus formed, as shown in FIG. 4, between the lower 
portion of flap 1 and the bow wall portion lying below the bow opening 15 
when flap 1 is in the open position. This arrangement acts as a well-known 
water-jet aspirator, because the streaming water on the outside wall 3 of 
the swung out open flap 1, when the boat moves forward in the water, sucks 
air and water if it is present from the inner side of the flap 1 down 
through the open space 2. Air is sucked underneath the boat hull through 
this open space 2 whereby, on the one hand, penetration of water 4 is 
prevented and, on the other hand, the sliding friction of the boat hull is 
reduced. The opened flap 1 furthermore generates additional buoyancy for 
the boat by its configuration as well as by a closed cavity 6 located 
between the flap outside wall 3 and inside wall 5; this cavity is 
illustrated in FIG. 4 in the section through the flap 1. The rub rail 8a 
of the boat is also continued in the flap 1 and serves here as a bumper 
edge 8b and as flap reinforcement. If the flap 1 is utilized as a loading 
ramp and/or landing ramp, as described below, then the bumper edge 8a is 
altered with respect to the configuration shown in FIGS. 2 and 3, in 
correspondence with its purpose of use. 
The flap 1, as can be seen in FIG. 3, has connected thereto, on its inside 
wall 5 on both sides adjacent to the portside and the starboard side of 
the boat respectively one projection 9a and 9b lying in parallel to the 
axis of the boat. Each projection 9a and 9b, respectively, has a transom 
11 oriented toward the bottom 10 of the boat, by way of which the flap 1 
is hingedly supported on respectively one swivel joint 13a and 13b at the 
inside of the boat in the proximity of the bow opening 15 directly above 
the boat bottom 10. The pivoting axis of the flap is set back by a certain 
distance toward the center of the boat with respect to the generally 
vertically inclined bow wall edge 17 and the bottom edge 21 of the 
U-shaped bow opening 15 adjacent to the water surface. Each transom 11 is 
positioned relative to the respective projection 9a, 9b to provide a 
respective downwardly open recess 19a and 19b in projections 9a, 9b, 
respectively, open toward the inside wall 5 of flap 1 between its swivel 
joint 13a and 13b and the connection of the respective projection 9a, 9b 
to the inside wall 5 of flap 1. As shown in FIGS. 2, 3 and 4, the recesses 
19a and 19b are formed so that the lower edge of flap 1 lying adjacent to 
the bottom edge 21 of the U-shaped bow opening 15 when the flap 1 is in 
its closed position, can be moved out of the bow opening 15 and underneath 
the bow wall portion or bow region adjacent to or below the bottom edge 21 
of the bow opening 15, as shown in FIG. 4. The flap 1 is moveable from its 
closed to its open position as shown in the FIGS. 2, 3 and 4, whereby in 
its open position the above mentioned open space 2 is provided between the 
lower edge of flap 1 and the bow wall portion lying below and adjacent to 
the bottom edge 21 of the U-shaped bow opening 15, as shown in FIG. 3. 
During the downward pivoting of the flap 1, the bottom edge 21 of the 
U-shaped bow opening 15 moves into the recesses 19a and 19b. 
At a spacing above the swivel joint 13a and 13b, respectively, the piston 
end of a dual-acting piston-cylinder unit 23a and 23b, i.e. a unit 
exerting tension and pressure, is supported on a bearing 22a and 22b of 
the projection 9a and 9b, respectively. The base 25a or 25b of the 
piston-cylinder unit 23a or 23b is pivotably mounted to the inside of the 
boat at approximately the same level as the piston bearing. 
Electromechanical adjusting devices can likewise be employed in place of 
the piston-cylinder units. 
As described above, the flap 1 has a cavity 6 on the inside in order to 
attain additional buoyancy when the flap 1 is partially urged into the 
water by the piston-cylinder units 23a and 23b; such buoyancy, as 
described below, is of great benefits in diving work, swimming operation, 
or similar activities. Thereby, the bow is likewise urged upwards and 
accordingly can be burdened with additional loads. Buoyancy is so great 
that one to two persons can readily position themselves on the opened flap 
1 without impairing the stability of the boat. The flap 1 is arranged and 
supported in such a way that it can be swung into a position wherein the 
outside of the outer wall 3 of the flap 1 is located almost entirely below 
the waterline and the inside is approximately at the level of the 
waterline. 
The outside bottom 35 of the boat has an angular transition 36 to the outer 
sidewall 37 of the boat, as shown in FIGS. 1, 5 and 8, and has a rounded 
transition 39 in its stern portion. The angular transition 36 passes over 
into the round transition 39 with an interruption 41 located approximately 
in the center of the length of the boat. Depending on requirements to be 
met by the boat, the interruption 41 can be arranged at a spacing of 
two-thirds of the entire boat length as seen from the bow of the boat. 
The boat profile as well as, in particular, the rounded and angular 
transitions 36 and 39, respectively, are illustrated in FIG. 5. Since the 
boat profile extends symmetrically with respect to the center line 40, the 
illustration in each case shows merely one-half of the profile in order to 
avoid confusion in the drawing. The profiles with an angular transition 36 
are shown on the right-hand side in FIG. 5, and the round transitions are 
illustrated on the left-hand side. Letters A through G denote the 
locations of the profiles as indicated in the lateral view of the boat in 
FIG. 1. 
As can furthermore be seen from FIG. 5, the center of gravity of the boat 
lies at a very deep level, contributing toward the safety against 
capsizing as mentioned hereinbelow. 
The above-described arrangement of the angular and rounded transitions 36 
and 39 has proven itself well, in particular, when a boat 46 equipped with 
two stern engines 45a and 45b is operated to describe curves 44 on the 
water, as illustrated in FIGS. 6 and 7. By virtue of the angular 
transition 36, the water underneath the bottom 35 of the boat is channeled 
in parallel to the longitudinal axis of the boat. When a curve 44 is 
traversed, the boat 46 tilts toward the center of the curve, as shown in 
FIG. 7. Thereby, the water 4, as indicated by two schematic flow lines 47a 
and 47b, is conducted in the portion of the boat 46 on the bow side up to 
the interruption 41 in parallel to the axis of the boat toward the stern 
and, immediately downstream of the interruption 41, is bent away toward 
the outside underneath the boat 46. The interruptions 41, in 
contradistinction to the actual configuration as derivable from FIGS. 1 
and 5, are drawn in FIG. 6 to project laterally for a better 
identification. On account of the design of the outside bottom 35 of the 
boat with an angular and round transition 36 and 39, respectively, as well 
as owing to the interruption 41, water 4 is conducted upwards to the 
propeller 48a of the stern engine 45a, which is lifted upwards on the left 
when a right-hand curve is traversed, whereupon this stern engine remains 
fully immersed in the water and can continue to transmit its full thrust 
power to the water. Due to the round transition 39, the boat slightly 
yields in a gliding fashion with its stern in the curve 44 whereby its 
curve radius is considerably reduced. With this design of the boat hull, 
an extremely accurate targeting of a desired approach location in a 
waterway is made possible, in order to then perform at this location, with 
the ramp 1 being extended, for example salvaging operations, taking on of 
swimmers, placing of divers, as well as driving into the proximity of a 
beach or a shore in order to disembark easily. 
For the unfolding of the flap 1, the piston-cylinder units 23a and 23b are 
set to thrust by means of a control valve, not shown, whereby the flap 
section 1 is moved out of the bow toward the surface of the water. The 
flap 1 can be continuously adjusted by way of the piston-cylinder units 
23a and 23b and can thereby be fixed in any angular position. The lowest 
pivoting point of the flap 1 is attained when the bumper edge 8b, as the 
upper flap edge, is just above the waterline. In this condition, the outer 
wall 3 of the flap is almost completely immersed in the water 4. Since the 
flap outer wall 3 is curved in the manner of a spoon, and its two sides 
are closed off by the projections 9a and 9b, the flap 1 urged into the 
water 4 acts as a buoyant body, alone due to its external configuration, 
and lifts the bow of the boat. If water 4 were to pass to the inside of 
the flap 1 on account of waves, or if the flap is loaded down with too 
great a weight, then the flap still acts as a buoyant body due to its 
cavity 6. On account of the rigid connection of the flap 1 with the 
remainder of the boat by way of the piston-cylinder units 23a and 23b, 
tipping is impossible even in case of an extremely high weight load on the 
flap 1. The buoyancy of the bow is additionally enhanced by lateral 
buoyant bodies 29a and 29b, as can be seen in FIGS. 2 and 3. These buoyant 
bodies 29a and 29b can include, as the topside, a door that can be swung 
out; also, the accessory equipment for the piston-cylinder units 23a and 
23b can be accommodated therein. 
Since the inner wall 5 of the swung-down flap 1 is located directly above 
the water level and, additionally, the flap 1 proper acts as a buoyant 
member, the swung-out flap 1, as already hinted at above, can be utilized 
as a platform for entering and leaving the water during diving and 
rescuing operations as well as other work performed on the water; also, 
this flap 1 can be utilized as a swimming platform. Rescuing of injured 
persons swimming in the water 4 and also salvage of flotsam floating in 
the water 4 can be accomplished in a simple way, since the injured person 
as well as the cargo can be readily pulled into the boat over the flap 
edge 8b. 
The flap 1 can also be utilized as a landing ramp in case the boat is 
driven to the riverbank and the flap 1 is unfolded toward the bank. On 
account of the dual-acting piston-cylinder units 23a and 23b, the flap 1 
remains fixed in the once-set angular position, no matter how the boat is 
moved by waves or varying loads. 
In addition to or in place of the flap 1 in the bow, a flap can also be 
mounted at the stern or in one of the boat sidewalls. In case a flap is 
mounted in the sidewalls on the left-hand and right-hand sides, it can be 
utilized, in the deployed condition, as a working platform as well as a 
stabilizing outrigger. However, with flaps arranged in the lateral boat 
walls, the boat can be driven either not at all or only extremely slowly. 
A flap arranged at the stern requires a special structure of the boat 
driving mechanism. Outboard motors can then be installed only 
conditionally. Only one flap in the boat sidewall or at the stern would 
constitute a less advantageous embodiment of the invention. 
One of the advantages of the boat according to this invention resides in 
that its flap 1, serving as a working or recreational platform, can be 
folded back into the bow wall in such a way that its hydro- and 
aero-dynamic properties as well as its esthetic appearance are not 
impaired. The boat according to this invention thus can be utilized, 
without any restriction of its full functional ability, as a rescue boat, 
a salvage boat, a pleasure boat, and a speedboat. An additional advantage 
is to be seen in the configuration of the flap, acting as a buoyant 
member, the use of which is possible independently of stability problems 
of the boat; such configuration even increases, in the swung-out 
condition, the capsizing stability of the boat. The outer wall of the flap 
is designed so that, with the flap urged into the water and the boat going 
forward, the bow is pressed in the upward direction. On account of the 
open space 2 between the lower edge of the bow opening and the lower edge 
of the flap 1, this latter edge is displaced toward the front in the 
driving direction so that the water flowing along at this location evokes 
a suction effect with respect to the open space 2. Thereby, on the one 
hand, water cannot penetrate into the boat through the interspace open 
space 2; any water that may have entered would be removed by suction; and, 
on the other hand, air taken in by the suction effect is sucked underneath 
the boat hull whereby the water friction of the latter is reduced. On 
account of the structure of the flap according to this invention with the 
open space 2, as compared, for example, with the arrangement of a bow flap 
disclosed in French Patent 2,511,969, a significantly simpler structure 
that is safe in its operation is furthermore obtained since, for example, 
small contaminants, such as sand and dirt, cannot impair the closing and 
sealing step. Furthermore, the configuration of the boat hull as derivable 
from FIGS. 1 and 5, is designed so that capsizing of the boat is almost 
impossible.