Air aspiration prevention pan

An air aspiration prevention pan adapted to prevent aerated water from entering the intake of a water jet propulsion unit mounted in the hull of a water craft having low or zero dead rise characteristics or in a hull having sponsons or spaced apart skegs. The air aspiration prevention pan comprises sidewalls extending downwardly from the mounting means in a general V-configuration with the apex of the "V" toward the forward end of the hull. A lip extends outwardly from the bottom of the sidewalls and acts with them to confine and guide the aerated water under the hull so as to prevent a substantial portion of the aerated water from entering the intake of the water jet propulsion unit.

FIELD OF THE INVENTION 
This invention relates to a water jet propelled water craft and, more 
particularly, to an air aspiration prevention pan which is used on hulls 
of low or zero dead rise or on hulls having sponsons or spaced apart 
skegs. 
BACKGROUND OF THE INVENTION 
Water jets are commonly used to propel various types of water craft. There 
are inherent advantages in using water jet propulsion, an important one 
being that the required water operating depth of a water jet propelled 
craft can be minimized. This allows the craft to operate in relatively 
shallow waters or closely to the shore which may be important depending on 
the uses to which the craft may be put. 
Water jets, however, have disadvantages on certain type of vessels. One 
disadvantage of using water jet propulsion is that air may become 
entrapped beneath the boat hull and later enters the intake of the water 
jet. Air entering the water jet propulsion unit results in a loss of 
thrust and efficiency and tends to overspeed the engine. 
This problem is not acute in V-shaped hulls where the presence of aerated 
water at the apex of the "V" is minimal because of the hull shape. As the 
inclination of the "V" decreases, however, it becomes more of a problem 
until when a boat with a flat bottom, sponsons or spaced apart skegs is 
used, the problem becomes of considerable concern. 
SUMMARY OF THE INVENTION 
According to the invention, there is disclosed an air aspiration prevention 
pan adapted for use on the hull of a water jet powered water craft, said 
pan comprising mounting means adapted to mount on the underside and 
rearwardly of said hull, sidewalls extending downwardly from said mounting 
means, a lower lip on the bottom of said sidewalls and extending outwardly 
therefrom, a bottom plate joining the bottom of said sidewalls and 
extending therebetween and an intake opening in said bottom plate, said 
sidewalls and said lower lip acting to confine aerated water under said 
boat hull when under operating conditions and to substantially prevent 
said aerated water from entering said intake opening. 
According to a further aspect of the invention, there is disclosed a water 
craft having a hull of low or zero dead rise configuration, said water 
craft comprising a power source, a water jet propulsion unit operated by 
said power source, a water intake for said water jet propulsion unit, a 
water efflux assembly for said water jet propulsion unit and an air 
aspiration prevention pan mounted on the bottom of said hull and 
rearwardly therein, said air aspiration pan comprising mounting means 
adapted to mount in said hull, sidewalls extending downwardly from said 
mounting means, a lower lip on the bottom of said sidewalls and extending 
outwardly therefrom, and a bottom plate joining the bottom of said 
sidewalls and extending therebetween, said water intake being located in 
said bottom plate, said sidewalls and said lower lip acting to confine 
aerated water under said hull when under operating conditions and to 
substantially prevent said aerated water from entering said intake.

DESCRIPTION OF SPECIFIC EMBODIMENT 
Referring now to the drawings, a conventional V-shaped boat hull 10 with a 
water jet propulsion unit 11 installed therein is shown in FIG. 1. As can 
be seen from this hull design, little or no air become entrapped under 
this hull because of the V-shape. The intake 12 for the water jet 
propulsion unit 11 is located on the bottom of the hull and the air 
entering this intake is of a magnitude that does not present a significant 
loss of power. 
The boat hull 13, however, as illustrated in FIG. 2, is used on utility 
vessels, particularly those vessels known as SEALANDER.TM. work boats. 
These work boats create very little draft and are, therefore, ideal for 
work in shallow water conditions or near the shore. The use of a water jet 
propulsion unit 14 enhances this capability. 
When water craft with hulls similar to that shown in FIG. 2 are operated, 
however, air bubbles or aerated water 15 caused by turbulence, debris, 
waves, etc., become entrained under the hull 13 and enter the intake 12 of 
the water jet propulsion unit 14. This aerated water 15 can cause a loss 
of thrust and efficiency in the water jet propulsion unit 14 and, as well, 
can cause the engine to overspeed. It is, therefore, desirable to reduce 
this problem as far as possible. 
The air aspiration prevention pan of the present invention is generally 
shown at 16. It comprises a mounting flange 17 (FIG. 4A), downwardly 
extending sidewalls 18, 19 and a lower lip 20 which extends outwardly from 
the bottom of the sidewalls 18, 19. Sidewalls 18, 19 are spaced apart at 
the rearward end of the air aspiration prevention pan 16, move forwardly 
generally parallel and then close together to join in an intersection at 
the nose or forward end 21. 
A rearward transom plate 22 joins the sidewalls 18, 19 at the rearward end 
and is adapted to allow the mounting of the water jet propulsion unit 14 
and the engine exhaust 24 (FIG. 2). A bottom plate 23 joins the sidewalls 
18, 19 and has an intake opening 25 located therein (FIG. 4B). 
The sidewalls 18, 19 are designed to extend downwardly from the mounting 
flange 17 a distance sufficient to extend below the lower boundary of the 
aerated water 15. The lower lip 20, on the other hand, is designed to 
extend outwardly a distance from the sidewalls 18, 19 sufficient to keep a 
substantial portion of the aerated water 15 away from the intake opening 
25. 
The air aspiration prevention pan 16 is designed to be inserted into a 
recess or cutout 26 formed in the hull 13 (FIG. 3). The air aspiration 
prevention pan 16 is simply inserted into the cutout 26 with the mounting 
flange 17 resting on the inside of the hull 13. The mounting flange 17 and 
the transom plate 22 are then bolted to the hull 13 and the transom 27, 
respectively, with fasteners 28. After the assembly 16 is mounted to the 
hull 13, the engine (not shown) is mounted to the engine mounts 29 and the 
water jet propulsion unit 14 is mounted to the transom plate 22 and the 
flange of the intake opening 25. 
OPERATION 
Under operation, air which is created by turbulence, mixing, wave action, 
debris, etc. is entrained and passes under the hull 13 until it reaches 
the forward end or nose 21 of the air aspiration prevention pan assembly 
16. A major portion of the aerated water 15 does not extend below the 
lower lip 20 and it therefore passes along the sidewalls 18, 19 as they 
separate from the nose 21. To prevent any "spill over" of the aerated 
water 15, lower lip 20 provides a channel through which the aerated water 
may run thereby preventing it from entering the intake opening 25. 
All of the dimensions of the air aspiration prevention pan may be changed 
depending on the hull configuration and the operating conditions and 
characteristics of the water craft. The air aspiration prevention pan need 
not be an assembly but rather may be mounted as individual pieces as the 
particular craft may require. 
Other modifications may be made to the apparatus without departing from the 
inventive concepts described herein. The description given, therefore, is 
only by way of example and not a limitation to the scope of the 
accompanying claims.