AU610094B2 - Improvements to maring hull - Google Patents

Description

IllI O 1.4 1.6 .1.4 1.6 I I I I I qq COMMONWEALTH OF AUSTRALIA PATENTS ACT 1952-62 COMPLETE SPECIFICATION

(ORIGINAL)

FOR OFFICE USE: Application Number: Lodged: Co rmplete Specification Lodged: Accepted: Published: Rr o ii o a o 0 0 0 Related Art: Class ,I 0 YALUE OF 1ACHED i K t *0~ It tot.. ~fl~00*~ LODGED AT SUB-OFFICE 1 2 N 0V 1987 Adelaide Name of Applicant: o AdtfteSs of Applicant: Actual Inventor: 0o Address for Service: TO BE COMPLETED BY APPLICANT LEONARD JEFFERSON BLEE 66 LESLIE AVENUE, BLAIR ATHOL, STATE OF SOUTH AUSTRALIA, COMMONWEALTH OF AUSTRALIA LEONARD JEFFERSON BLEE Care of R.K. MADDERN ASSOCIATES, 345 King William Street, State of South Australia, Commonwealth of Australia Complete Specification for the invention entitled: "IMPROVEMENTS TO MARING HULL" The following statement is a full description of this invention, including the best method of performing it known to me.

Australian attorney THE COMMISIO-ROFPATENTS ,APP ICAT!ON ACCEPTED AND AMENDMENTS THE COMMISSI OF PATENTS/-a.

This form must be accompanied byeither a provisional sp fe i f Forng.and.tue copy ry.a specification (Form 10 and true copy).

This invention relates to improvements in a marine hull, and is not necessarily limited to a planing hull but the invention is particularly applicable thereto.

BACKGROUND OF THE INVENTION The most commonly used planing hulls for marine purposes have substantially constant dead rises aft of about station 4 or 5, in order to reduce the suction load which can occur with a "hooked" style of hull bottom.

With a constant dead rise however the loading between 0 0 0 10. the surface of the hull bottom ard the water is usually positive for most of the length of the hull (that is, o o 0g there is a kinetic energy imparted to the water due to 0 0 o deflection of the particles of water encountered via the hull bottom surface). The pressure pattern however 0°o 15. is much higher towards the forebody end of the hull o 00 o o 0o .0o than it is towards the aft end, and consequently most of the dynamic forces which are of use to the hull in o o ocean-going conditions occur over a relatively short 0 0 length of the hull, probably not more than 15%. When 0 0 a 0 0 o 00 20. the dynamic forces are relied upon (as in the usual case), oo the loading on the "low" side of the hull when deflected Sby a wave extends over a wider area and the loading on the "high" side extends over a lesser area. It is believed this is one of the limiting features of the standard constant dead rise type of planing hull. If however the loading is more evenly spread over the whole area of the hull, the difference is very much greater and there is a superior righting force.

r (Signature of Declarant) (IMPORTANT Cross out inapplicable words in the above Form.) C. J. THOMPSON, CommorO alth Government Printer n i In our Australian Patent Application 50872/85 entitled "Marine Hull" there is described and claimed a marine hull wherein the shape of the bottom included channels which diverged in a rearward direction, each channel having a downwardly concave portion of such shape that it intercepted and deflected water when the hull was mobile, the water so intercepted and deflected moving firstly upwardly and then rearwardly with respect to the hull imparting a vertical component of kinetic energy o 0 0 1o 0. to that water which was well aft of the normal maximum 0 o o o oooo o o oo o 0 oo00 0 0 oo 0 0 0 o o0 o o 0o0 o o 0 o oo o o a loading area. Experiments with sea-going craft have proved that the theories appear to be correct, and that a hull with such channels is much more stable under rough conditions than a conventional mono-hull type of craft.

15. With most hulls known to the applicant, there is a serious tendency to pound (hydraulically bottom) as the hull leaves one wave and impacts against the next.

Although this pounding effect is worst with hulls the diverging surfaces of which are concave, it is nevertheless a serious disability with hulls having straight deadline shapes (in section) and even with those having convex deadline shapes. Even if the forebody is provided with a large dead rise angle, the pounding can still occur rearwardly of the normal area of maximum loading.

-3i 1 i o 0 o 0 0 0000 o o o 0 00 0 0 0 oooo o o oo .o o oo o ~ooo SOoO o o oo oo oo o o oc oooo o o o or c o o Craft made in accordance with the said Patent Application have proved that pounding is largely reduced but nevertheless it still remains a generally unresolved problem with planing hulls, and it is an object of this invention to provide further improvements whereby the tendency to pound can be substantially reduced, even further than with the hull design identified in the specification of said Australian application.

PRIOR ART 10. In said Australian specification, an attempt was made to reduce pounding and Fig. 8 of that specification identified downwardly convex bottom portions 28 bridging channels, the portions 28 being provided with conduits 26 which allowed air to be drawn into the channels when 15. the hull was in motion. However, the downwardly convex surfaces tended in many instances to become high load surfaces, and the apertures were not as effectual as was at first thought.

Further, in United States Patent Specification 20. 4159691 of Rolland K. Paxton, there was disclosed in Fig. 9 an arrangement whereby a compressor caused a flow of air to a space below the hull bottom, in an attempt to introduce compressed air into the forward ends of tunnels, but this performed an entirely different function from the function which is disclosed by this invention.

BRIEF SUMMARY OF THE INVENTION In this invention a marine hull having a forebody, a transom, and a bottom extending therebetween has walls forming an upwardly extending recess in the bottom, the recess walls extending into the hull and there being at least one aperture in one of those walls, and means are provided for allowing an air flow through the aperture.

In particular, the present invention provides a marine hull having a forebody, a transom, and a bottom extending therebetween, the bottom comprising walls defining an upwardly extending recess therein, said walls extending into l1 the hull, and located between the forebody and transom of the 0 0 0 o o 0 o0oo hull, and the bottom further comprising surfaces defining a 0o plurality of upward-y formed pairs of channels between the forebody and the transom, the channels of each pair diverging 0" 0 o throughout their lengths in a rearward direction, said recess o.1°o walls including a rearwardly facing wall with an air flow 0 00 aperture therein, and further walls within the hull defining a passageway for air flow to the aperture.

0 0oooo If the recess is located between the forebody and the oo o transom, and particularly if it is located rearwardly towards o 0 0. the transom, there will be a relatively low pressure area beneath the hull when the hull is in motion through the o water, and this will induct a flow of air through the 0 0 substantially reducing the suction load on the hull when the hull is moving, so that the negative effects of suction can be very substantially reduced and in some instances almost be eliminated. If a pair of channels diverge rearwardly of the recess, the movement of water through those channels also induces flow of air into the recess. There is in addition, a

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small reduction in the effective wetted surface because of the existence of the bubbles or particles of air. Most importantly of all however the air which is induced into that area will provide a "cushioning" effect which is found to be extremely useful in reducing pounding when the hull is used under adverse conditions. The arrangement appears to be far more effective than that referred to o oo 0 0 00 0 0 000000 oo 000000oooooo o 0 0 0o 0 00 000 00 0 0 0 00 0 0 on 0 0 o0 0 0 00 o 00 o0 o o 0o oo o 00 0 0 0 0 o 0 a 00 a 00 0 0 0 0 0 0 ooo 0 0 o o oooooo o o above and described in my previous Patent application, and is more effective than any other cushioning device known to the applicant.

More specifically, in this invention a marine hull bottom comprises walls defining an upwardly extending recess therein, the walls extending into the hull and located between the forebody and transom of the hull, there being an aperture through a recess wall, said aperture being in the lower portion of that wall and further walls within the hull defining a passageway for 10. air flow to the aperture from within the hull. The further walls can for example be the walls of a compartment which is sealed with respect to the hull and located over the aperture and near or joined to the transom.

15. The invention has a number of advantages over the known prior art:- Air is more effectively introduced to the underside of the hull.

The compartment walls function as a structural member which can assist in supporting the floor of the craft which embodies the hull.

When the hull is at rest, the compartment may be allowed to fill or partly fill with water, artificially increasing the mass of the hull at rest so that it is less sensitive to wave motion and by concentrating the buoyancy to the perimeter of the hull, gives greater stability against roll.

-6- Soo0 00 9 o 00 o o eo 0 0bo 0 000 00 o o 00000 0O0 0 0 00 0 0 0 00 000 o o 0 00 Since the compartment is near the aft end of the hull, the distribution of the volume of water contained therein can be a means for determining the fore and aft trim of the hull.

When transducers are to be mounted in the hull, if they are mounted in that portion of the hull which is beneath the compartment walls, mounting is greatly simplified and there is no need for sealing means which may otherwise prove to be unreliable.

The compartment acts as a structural member of the transom and allows forces developed by an outboard motor to be directly spread over a large portion of the hull, instead of via the transom to the sides and bottom of the hull.

The compartment allows the free passage of air from holes low in the transom to the aperture beneath the hull.

If air is prevented from leaving the top of the compartment, then water is prevented from entering the compartment and the draught of the boat may be usefully reduced when required.

BRIEF DESCRIPTION OF THE DRAWINGS An embodiment is described hereunder in some detail with reference to and is illustrated in the accompanying drawings in which:- Fig. 1 is a side elevation of a hull according to ooo0o 00000 0 0 o 0 00 oo o 2) 0 0 0 0 20.

00000 0 0 this embodiment; Fig. 2 is an end elevation of Fig. 1; Fig. 3 is an underside view of Fig. 1; Fig. 4 is a longitudinal section corresponding to Fig. 1 but showing the compartment arrangement and the recess walls; and Fig. 5 is a section taken on line 5-5 of Fig. 3.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT In the drawings, only single lines are used since o 10. these are all that are required for illustrating the invention.

o, A hull 10 comprises a forebody 11, a transom 12, o o 0° and a bottom 13 extending therebetween.

As in the aforesaid Australian Patent Application 0° No. 50872/85, the bottom 13 is provided with a plurality o 00o 0 0°0 of channels 14 which diverge rearwardly, most of the 15. channels 14 extending from the forebody to the chines oo0 0o0000 15. The channels are not shown in Fig. 4.

At the locality of the section line 5/5, the walls 0 0 °0 17, 18 and 19 extend upwardly into the hull from the 0 0 0 0 bottom 13 and define a recess 20. The wall 17 is a rearwardly facing wall and thz.t wall contains an aperture 21 which is in an area of the hull bottom 13 likely to be a low pressure area in any case, but in being a rearwardly facing wall in the recess 20 it is in an even lower pressure area. The aperture 21 is situated as low as possible to allow a large volume of air to be trapped in the recess above the aperture. If required additional apertures may be situated ingtehe lower forward portions of walls 19 to allow greater air flow. The recess forms the forward end of a V-shaped channel 22 which is similar 1i to the channels 14 in cross-sectir--al shape, and diverges rearwardly to open to the transom 12 as seen best in Fig.

2, allowing a free through flow of water from the channel.

The height of the top of the recess is greater than the topmost portion of channels 22 at their forward ends.

The hull contains compartment walls 25 which surround 00o °0 0 ao o 00 andjeoPery the walls 17, 18 and 19 so that the aperture 21 0oo 10. opens into the compartment 26. This compartment contains a 0 pair of baffles 27 which inhibit for-and-aft water o o 0.o' movement in compartment 26, and also contains walls defining a tank 28. The baffles are also arranged such 8o that water in the rearwardmost compartments is allowed to 0. 15. drain first through holes 42 in the transom. Holes 41 in the transom situated above the waterline allow air into or out of the compartment 26. These holes are opened by valves (not shown) which prevent exit of air when closed.

Alternatively, an upstanding tube 29 contains a valve for controlling air flow into or out of the compartment,but the location of valve 30 is not critical.

A hinged lid 31 in the floor 32 provides access to the tank 28, which is provided also with an inlet conduit 34 (fitted if required with a stop cock S IA4 9

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h.e ound e 21 ns a 1 i i i 1 to in o or 0 o oo 0 0o o 0 0 0 0 0 0 0 0 0 00 0o a 0 0 oo 0 o 0o 0 0 o0 0 0 eo oo0 o 0 o o a 0 so that when the hull is in motion in the water, water is taken from a relatively high pressure area near the forebody 11 and discharged into the tank 28, through the conduit 34 and stop cock 35, the water overflowing at the back into the compartment 26. If desired, a drain plug 37 may also be provided for draining the contents of tank 28. Holes 42 are situated low in the transom and allow the easy movement of water and air into or out of the compartment 26.

10. In many boats, use is made of transducers, earthing plates for radios and the like, and by having for example a transducer 38 in the hull bottom, the problems of sealing are removed, the transducer 38 being connected by a cable 39 to an echo sounder 40 routed via a tube with the upper opening above the waterline (shown only 15. diagrammatically in Fig. 4).

When the hull is at rest with the water, water flows freely into compartment 26 through the apertures 21 and 42, and, if the drain plug 37 is open, the tank 28 will 20. also contain water. When however the hull is in motion, the water in the tank 28 is continually replenished with fresh water, such that the tank 28 makes a good live bait tank. Further, the compartment 26 will empty of water via apertures 21 and 42 and allow air to reach aperture 21.

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e 34 With this arrangement, the effective mass of the o 00 0 0 0 0 00 0 o 00 S0 0 000 0 0 o oo 0 00 0 o 0o oo 0 o 00 craft is reduced when the craft is in motion but increased when the compartment 26 and tank 28 are filled with water, that is, when the vessel is at rest. If the valve 30 is closed when the compartment 26 is empty, the air can be trapped within the compartment and the effective draft of the vessel can be substantially reduced.

Reference is made to Fig. 6 when using power units other than an outboard, increased weight must generally be carried as in the case of a stern drive or inboard 10. motor, thus needing more buoyancy, and these units would be mounted as shown in Fig. 6, in the same general position as compartment 26. To cope with these requirements, the compartment 26 can be eliminated and the airflow to aperture 21 in recess 20 can be delivered via a pipe 43 following the path of the stem and the keelson. As well as providing the air flow required, the pipe also acts as a structural member to strengthen the forward portion of the hull. This arrangement is shown in Fig. 6.

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Claims (9)

1. A marine hull having a forebody, a transom, and a bottom extending therebetween, the bottom comprising walls defining an upwardly extending recess therein, said walls extending into the hull, and located between the forebody and transom of the hull, and the bottom further comprising surfaces defining a plurality of upwardly formed pairs of channels between the forebody and the transom, the channels of each pair diverging throughout their lengths in a rearward direction, .i0 said recess walls including a rearwardly facing wall with an air flow aperture therein, and further walls within the hull defining a passageway ior air flow to the aperture.

2. A marine hull according to claim 1 wherein said I aperture is in the lower part of said rearwardly facing wall such that a volume of air may be trapped in the upwardly extending recess above the horizontal level of said aperture.

3. A marine hull according to claim 1 or claim 2 wherein said channels open to the transom.

4. A marine hull according to any one of c' ims 1 to 3, wherein said further walls are located within the hull near its transom, and are sealed with respect to the hull, thereby further defining a compartment located over said aperture, the location of said aperture and said air flow passageway being such that, when the hull moves through water, water if in the compartment drains through the -12- aperture and thereafter air flows through the aperture and discharges beneath the hull near the transom end thereof.

A marine hull according to claim 4 wherein an upper or rearward portion of said compartment comprises an air inlet opening, and valve means associated with the opening to control air flow into the compartment.

6. A marine hull according to claim 4 further comprising a tank within the hull, an opening in the tank to allow water flow between the tank and the compartment, and a conduit extending from such a location in the hull to the tank as to conduct water into the tank when the hull moves through the water.

7. A marine hull according to claim 6 wherein the tank is wholly contained within the hull and the water conducted through the conduit into the tank overflows from the tank and drains through the aperture or transom when the hull moves through the water.

8. A marine hull according to claim 1 further comprising walls defining a pipe overlying'the stem and keelson, opening at one end near the bow of the boat and at the other end to said aperture.

9. A marine hull substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings. DATED this 11th day of February 1991. LEONARD JEFFERSON BLEE By his Patent Attorneys R K MADDERN ASSOCIATES -13-