Note: Descriptions are shown in the official language in which they were submitted.
FIELD OF T.HE INVENTION
his invention relates to a water jet propelled water
cxaft and, more particularly, to an air aspiration prevention
pan which is used on hulls of low or zero dead rlse 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 uslng 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 o~ 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 comprisi.ng mounting
m~ans 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 ~o 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 ~et 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
~ 2 --
c~ rlsing mounting means adapted to mount in s~ld hull,
sidewalls extendlng downwardly from said mounting means, a
lower lip on the bottom of said sidewalls and e~tending
outwardly therefrom, and a bottom plate joining the bot-tom
of said sidewalls and extending therebetween, said wa-ter
intake being located in said bottom plate, said sidewalls
and said lower lip acting to confine aerated wa-ter under
said hull when under operating conditions and to substantially
prevent said aerated water from entering said intake.
DESCRIPTION OF THE DRAWINGS
In drawings, which illustrate an embodiment of the
inventlon,
..
Figure 1 depicts a V-shaped boat hull with a water jet
propulsion unit mounted therein;
Figure 2 is a cross-sectional view of the boat hull used
with the present invention;
Figure 3 depicts the jet pan cutout in the boat hull;
Figure 4A depicts the air aspiration prevention pan of the
present invention before installation; and
Figure 4B depicts the intake opening i.n the air aspiration
prevention pan.
J~ ;r` ~PE(~ ,.,v, ~
Referring now to the drawings, a conventional V-shaped
boat hull 10 with a water jet propulsion unit 11 installed
-ther~in is shown in Figure 1. As can be seen from this hull
design, little or no air can 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 105S Of power.
The boat hull 13, however, as illustrated in Figure 2,
is used on utility vessels, particularly those vessels known
as SEALANDERT 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
Figure 2 are operated, however, air bubbles or aerated water
15 caused by turbulance, 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.
4 --
The air aspiration prevention pan of the present
.invention is generally shown at 16. It comprises a mounting
flange 17 (Figure 4A), downwardly e~tending sidewalls 18, 19
and a lower lip 20 which extends outwardly from the bot-tom
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 toyether 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
(Figure 2). A bottom plate 23 joins the sidewalls 18, 19
and has an intake opening 25 located therein (Figure 4s).
The sidewalls 18, 19 are designed to extend downwardly
~rom the mounting flange 17 a distance sufficient to e~tend
below the lower boundary of the aera-ted water 15. The lower
lip 20, on the other hand, is designed to e~tend 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
(Figure 3). The air aspiration prevention pan 16 is sirnply
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.
OPERATI ON
Under operation, air which is created by turbulance,
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 chanyed depending on the hull configuration and the
operating conditions and characteris-tics 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.
