GB2381514A

GB2381514A - Device for controlling the flow of water to a marine propeller

Info

Publication number: GB2381514A
Application number: GB0126049A
Authority: GB
Inventors: Roderick Douglas Pike
Original assignee: Individual
Current assignee: Individual
Priority date: 2001-10-31
Filing date: 2001-10-31
Publication date: 2003-05-07
Also published as: GB0126049D0

Abstract

A vessel is provided with a movable hinged flap 3 which can be raised or lowered to control the flow of water to a marine propeller 1, to allow the propeller to operate in either a fully submerged or a surface piercing mode. The flap may extend the planing surfaces of the hull 6 when in its lowered position and may either be incorporated into the hull structure of the vessel or provided as a bolt-on attachment. The flap may be incorporated into a semi-tunnel propeller channel in the bottom surface of the hull and may be used to open ventilation channels 9 that allow air or exhaust gases to an upper portion of the propeller. The flap may be used in combination with a two speed gearbox in the transmission to allow the propeller speed to be matched to its loading.

Description

A DEVICE FOR CONTROLLING THE FLOW OF WATER TO MARINE PROPELLERS 1. Surface-piercing propellers are widely used on modern fast marine craft. The increased efficiency comes because only the bottom blades of the propeller are in the water, which removes the drag and flow disturbance created by the appendages such as the proper ?- shaft and its supports in front of the propeller. At slow speeds, a surface-piercing propeller is fully submerged and it only changes into surface piercing mode as speed rises and the water flow emanating from below the transom of the boat, or a Step below the hull lowers the level of the water flow. This occurs when the boat comes onto the plari and the lowered level of the water flow means that only the bottom blades of the propeller are in the water. The transiticn from fully immersed propeller to surface piecing propeller is dictated by the speed of the boat and apart from this it is not ender the cer@rol of the person driving the boat. This applies to propellers attached to a fixed shaft.

2. An alternative type of surface piercing propeller system is mounted or a . iaft that ca be raised or lowered under the control of the driver of the boat. This gives the driver some control over when the propeller converts into the surface piercing mode but it h still dictated to a certain extent by the How of water emanating from the transom. This type of system generally uses an apparatus attached to the transom of the boat with a shaft having a universal joint carrying. he propeller, with hydraulic coiHol varying th vertical angle of the propeller shaft.

3. The invention claimed here is based on a propeller (1) mounted on a lixed shaft (2 ! Instead of using the speed of the boat to control the flow of water to tne propeller, a

hinged flap (3) in front of the propeller is proposed to control the water JJO\". Ths 1a'J i-. hinged (4) at a point flush or nearly flush with the bottom of the transom) 5) or the bo'JOIn of the boat (6). depending on the type of installation. The hinge pivot lies par.. ll1el to the bottom of the boat and the hinge is forward of the propeller, The angular movement of the flap about this hinge point is controlled by an hydraulic ram (7) or otrer device so@ hat the aft end of the flap can be raised or lowered in relation to the fxed wpel er.

4. With the plate hinged or lifted upwards, the water flow covers the whole of"he

propeller which can then operate in the fully submerged mode, wtth all of the propelk :' blades in the flow of water from under the boat. With the plate lowered--o t. iat it i.'- parallel or nearly parallel with the propeller shaft, the flow of waster embraces only the lower blades of the propeller, so the propeller can operate in the surface-oiercing mode.

5. The main advantages of this system compared with current surface propulsion ys' : e"rs is that the driver of the boat can dictate the speed of the craft when the transition from fully submerged to surface piercing operation takes place. This will allow smoother and more controllable operation of the boat, particularly at transition speeds between 10 arc 30 knots, without compromising the high-speed performance. It will also allow better performance in rough seas where the flow of water to the propeller when it is in surface piercing mode will be much more controlled.

6. The operation of raising and lowering the plate can be under the control of the driver of the boat through hydraulic or other fonns of control. Alternatively it can operate automatically with the height of the plate being adjusted in relation to the speed or some other parameters of the craft. It could te advantageous to introduce a variable speed gearbox into the transmission system of the craft in order to cope with the different loadings on the propeller in fully submerged and in surface piercing modes.

7. The advantages of this flow control late are found in the ability of tht dliver to control the timing of the transition fron fully submerged to surface piercing mode and in the plate forming an extension of the hull planing surfaces when it is in t. 1e lowered position which increases the planing efficiency of the hull. There can also be advantages for this system in rough seas when the water flow to an existing surface piercing propeller system can very considerably in relation to the propeller as the boat pitches in waves. With the flow control plate ending close in front of the propeller, the water now to the propeller is much more closely controlled and consistent.

8. The proposed flow control plate, which can be of a length to suit the application, ca ; l have a slot down its centre with connecting cross members so that it can pass either side of the propeller shaft to focus the surface water flow at the propeller hub Alternatively. the plate can be shaped with a longitudinal recess into which the propelkr shaft can be accommodated with the main part of the plate forming the flow control surfaces and the centre part extending over the propeller shaft. Another option in the application ofth : device is to have the propeller shaft enclosed within a vertical fin (8 in fis 4 & 5). sc the flow control plate can fit closely down each side of the fi n. The bottom cfth. s fin can be

an extension of the bottom of the boat ; 0 that it forms a part oflhe planirg surfaces of the , ; t., rfaces (f the hull when the flow control plate is in both the raised and lowered position Thc fow control plate can be flat or curved in both the transverse and fore and aft directions to suit the application.

9. This flow control plate can be used when the propeller is mounted behind the transom (fig 3), when the propeller is mounted @nder the hull (fig 1), or when the propeller is located in the semi-tunnels (figs 2.4 & 5) when are frequently used to accommodate t'T. e propellers on many planing craft. In all these applications it may be ecesar' o introduce air or exhaust gases into the ; pace above the plate to help c car the water fro-T. this space and to ensure that the top blades of the propeller are operating in air when the flow control pate is lowered. This can be done by means of openings iï the hull which allow air or exhaust gases (9) to be drawn down and these openings can be opened manually or in conjunction with the movement of the plate.

10. A fourth embodiment of this flow control plate concept can be in the form of separate unit that can be bolted or otherwise attached to the transom (10) of the craft (fig 3). Here a bracket (I I) would support the propeller and shaft and the flow centrol plate would be hinged at or close to the bottom of the ransom. With the flow control plate raised. the water emerging from the transom would flow over the whole of the propeller but wit'.,) the flap lowered. the propeller would operate in the surface piercing mod. with only the

bottom blades of the propeller immersed. This bolt-on unit would simplify installation for the boat builder.

! I. In a preferred application of this concept, the propeller would operate in a semi-tunnel created in the planing surfaces of the hill at the stem (figs 2,4 & 5). This type of semitunnel is already in wide use on planing craft hulls. The plate would be hinged at its forward end at the forward point of the semi-tunnel, below the bottom ot the propeller shaft at the point where it emerges fron the hull. The propeller shaft would be contained within a vertical fin (8) extending from the forward end of the fin to a point close behind the propeller. In its raised position the slate would be flush or nearly flush with the tor of the semi-tunnel, allowing a full flow of water to the propeller so that it could operate in the fully submerged mode.

12. When the flow control plate is lowered, it would fill the semi-tunnel opening each side of the vertical fin, effectively blanking the tunnel off and forming an extension to the hull planing surfaces. In this position, only the bottom blades of the propeller wou d protrude below the flow control plate and the bottom of the hull (fig 5) so that the propeller would be operating in the surface piercing mode. When the pla. e is lowered, it could automatically open an air or exhaust vent to allow air or gases into the space above the plate so that the top blades of the propeller could be ventilated. With the plate in the lowered position, it would be parallel with the propeller shaft and its rear er. d would close to the front of the propeller so that the water flow from under the hull is only directed at the lower blades of the propeller.

Claims

CLAIMS 1. A hinged flap under the centred of the driver or operating automatically that can control the flow of water to a marine propeller to allow the propeller to operate either in the fully submerged 01 surface piercing mode.
2. A hinged flap as in Claim 1 that will extend the planing surfaces of the hull when it is in the lowered position as weB as controlling the water flow to the propeller.

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3. A hinged flap as in Claim 1 that can be incorporated into the hull structure of a craft or which can be part of a twit-on propulsion attachment to Ine transom of the craft
4. A hinged flap as in Claim 1 that can be used to open ventilation channels that allow air or exhaust gases tc the upper portion of the propeller in order to ventilate it when it is operating in the surface piercing mode.
5. A hinged flap as in Claim 1 that can be incorporated into a semi-tunnel propelier channel in the bottom surfaces of the hull of a craft in order to allow the propeller to operate alternately in the fully submerged or surface piercing mode.
6. A hinged flap as in Claim I used in combination with a 2 speed gearbox in the transmission to allow the propeller speed to be matched to its loading.