Kayak with release louvers

A kayak comprising a hull and a deck with one or more louvers provided in said hull at least in a stern section thereof to force water to separate from said hull whereby forming voids which are replaced with air from the water surface or water from the sides as said kayak is displaced thereon. This reduces drag and the kayak benefits from a speed improvement.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to a water vehicle and in particular to a 
kayak having a louvered rockered hull which improves the speed and 
maneuverability of said kayak. 
2. Description of the Prior Art 
Two most important aspects of a kayak are its speed and maneuverability. 
Speed or maneuverability but not both is a common trade-off associated 
with kayaks. Speed is an issue as kayaks are propelled on water by the 
occupant with the use of a paddle. 
In the case of a whitewater kayak; maneuverability is more important than 
speed. For this reason whitewater kayaks have a significantly rockered 
hull. The rockered hull has high profile ends which increase its turning 
ability leading to increased maneuverability. Whitewater kayaks are said 
to have displacement hulls that are very close to planing hulls. 
Nonetheless, fast whitewater kayak are sought after. 
Several aspects affect the forward speed of a kayak: 
the energy required to displace the water at the leading end of the kayak, 
how the molecules travel along the length of the hull, 
how water returns to its original position once the kayak has passed by, 
and 
the amount of wetted surface area. 
Thus energy conservation is important when considering the motion of a 
kayak through water. 
The energy required to displace a water molecule can be significantly 
reduced by increasing the waterline of the kayak. By increasing the length 
of the hull, the displacement of the water molecule to its final position 
can be spread over a greater distance. This modification has to be weighed 
against the resulting increase in the effective wetted surface area of the 
kayak coming from the increase in length. This increase in the waterline 
could slow the kayak down if the induced drag by the wetted surface area 
is disproportional to the increased effectiveness of displacement. 
Another feature of the kayak that affects the motion of water molecules 
past the kayak is the profile of its bow at the moment of entry. A sleeker 
bow is more efficient at moving the molecules to the side, but it also 
increases resistance to sideways movement of the kayak which reduces the 
kayak's turning ability. Similarly a sleeker stern is more efficient in 
guiding the movement of the water molecules as they return to their 
original position, but as above mentioned, it also reduces the kayak's 
turning ability. A rockered bow and stern allows the kayak to turn easier 
but, at the same time, this shortens the effective waterline length of the 
kayak thereby offering a less effective profile for displacing water. 
It would be advantageous to provide whitewater kayaks with speed enhancing 
features. 
SUMMARY OF THE INVENTION 
The present invention deals with the reduction of the drag induced by the 
adhesion of water molecules to the hull of a kayak at its trailing end. 
This reduction in drag is accomplished by providing one or more release 
louvers in the trailing section of a hull. 
It is a feature of the present invention to provide a small louver or a 
plurality thereof which effectively forces the water molecules to separate 
from the hull of a kayak at the lip of the louver. 
According to the present invention there is provided, a kayak comprising a 
deck and a rockered hull, the rockered hull further comprising at least a 
release louver provided under said rockered hull at least in a stern 
portion thereof; to force water to separate from the rockered hull to form 
voids which are filled with either air from the water surface or from 
water from the sides of the kayak as the kayak is displaced thereon.

DETAILED DESCRIPTION OF THE INVENTION 
According to a preferred embodiment of the present invention and as shown 
in FIG. 1, there is shown a kayak provided with a rockered hull 22. A deck 
section 24 is secured on the hull 22. Release louvers 26 and 28 are formed 
in a bow 30 and a stern 32 section of the hull 22, respectively. 
FIG. 2 shows the hull 22 of the kayak 22 with the release louvers 26 and 28 
mounted in the bow 30 and the stern 32 section, respectively. As shown the 
release louvers 28 are curved convexly from the center of the hull. 
FIG. 3 shows the release louvers 28 on the stern section 32 of rockered 
hull 22 to have a substantially flat stepped projection defining a flat 
planning wall 29 and a lip 42, it is important that the lip define an 
abrupt change in the shape of the planning wall 29. 
FIGS. 4a and 4b illustrate the functionality of the release louvers 28 
provided on the rockered hull 22. 
As the kayak 20 passes over the displaced water 34, the displaced water 34 
under and on the side of the hull 22 is forced to raise, as shown at 36, 
to above its original position, as shown at 38, as a cohesive force makes 
it adhere to the skin of the hull, as shown at 40. This adhesion of water 
molecules to the hull 22 is illustrated in FIG. 4a. 
The kayak 20 leaves a water depression behind which must be filled as the 
kayak advances. The release louvers 28 provided on the rockered hull 22 in 
the stern section 32 allow air from the surface or water from the sides to 
fill the void left by the advancing kayak 20, that is traditionally filled 
by rising water molecules from below 36, and forces the water 34 to 
separate cleanly and quickly from the trailing lip 42 of a release louver 
28 as the kayak 20 moves forward. The separation at the lip 42 takes place 
due to the abrupt change in the planning surface 29 at the lip 42 of the 
release louver 28. The separation of water molecules from the hull 22 is 
illustrated in FIG. 4b. The separation of water 34 significantly reduces 
the effect of the adhesion of water molecules to the hull 22, reduces the 
wetted area of the kayak 20 and therefore reduces the drag on the kayak 
20. The kayak 20 then benefits from an enhanced speed. 
Specifically several factors, shown in FIGS. 5a and 5b, must be met in 
order for the release louvers 28 to function effectively: 
each release louver should have a height 44 between 1/8 inch or greater, 
the louvers must be confined to the last 25% of the kayak's total length, 
the bevel radius 46 combined with the radius of flare 48 must be less than 
100% of the total height of the release louver 44. In addition, none of 
the radii should be greater than 50% of the release louver's total height 
44, 
the width 50 of the release louver's should be no more than three times its 
height 44. 
There is no requirement for the number of release louvers 28 used. 
Generally the number and location of the release louvers 28 along the 
stern section 32 of the rockered hull 22 will depend on the following 
factors: the amount of rocker present, the length of the kayak, the weight 
of the kayak 20 and the weight of the occupant, and the top desirable 
speed. Together these factors determine the water level 38 on the kayak on 
a body of water and the location of the release louver as planning is 
achieved. 
Although only release louvers 28 curved convexly from the center of the 
hull 22 are shown in FIG. 2, the overall shape of the release louvers 28 
does not influence the separation of water from the hull. The release 
louvers 28 can be curved convexly from the center of the hull 22, curved 
concavely from the center of the hull 22 or perpendicular to the 
longitudinal axis of the kayak 20 achieving the same effect of reducing 
the wetted area of the kayak 20 and therefore reducing drag. Stability of 
the kayak 20 is affected by the overall shape of the louvers and a kayak 
can have different stability characteristics at different speeds according 
to the shape of the release louver at which water separates at that 
particular speed or range thereof. 
As shown in FIG. 2, release louvers 26 are also provided in the bow section 
30 of the hull 22 of the kayak 20 and these break up water when the kayak 
20 is in motion to create turbulent flow whereby reducing cohesive tension 
on the hull and reducing drag. 
In conclusion, with these louvers, at least in the stern section of the 
hull, drag is diminished thereby making it easier to maneuver the kayak on 
a body of water and to achieve an increase in speed.