GB2177353A - Boat keel - Google Patents

Boat keel Download PDF

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Publication number
GB2177353A
GB2177353A GB08616251A GB8616251A GB2177353A GB 2177353 A GB2177353 A GB 2177353A GB 08616251 A GB08616251 A GB 08616251A GB 8616251 A GB8616251 A GB 8616251A GB 2177353 A GB2177353 A GB 2177353A
Authority
GB
United Kingdom
Prior art keywords
foils
boat
hull
keel
downwards
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Granted
Application number
GB08616251A
Other versions
GB8616251D0 (en
GB2177353B (en
Inventor
Basil Cameron Rennie
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Christopher John Rennie
Original Assignee
Christopher John Rennie
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Priority to AUPH138585 priority Critical
Priority to AU59430/86A priority patent/AU575487B2/en
Application filed by Christopher John Rennie filed Critical Christopher John Rennie
Publication of GB8616251D0 publication Critical patent/GB8616251D0/en
Publication of GB2177353A publication Critical patent/GB2177353A/en
Application granted granted Critical
Publication of GB2177353B publication Critical patent/GB2177353B/en
Expired legal-status Critical Current

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Classifications

    • BPERFORMING OPERATIONS; TRANSPORTING
    • B63SHIPS OR OTHER WATERBORNE VESSELS; RELATED EQUIPMENT
    • B63BSHIPS OR OTHER WATERBORNE VESSELS; EQUIPMENT FOR SHIPPING 
    • B63B3/00Hulls characterised by their structure or component parts
    • B63B3/14Hull parts
    • B63B3/38Keels
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B63SHIPS OR OTHER WATERBORNE VESSELS; RELATED EQUIPMENT
    • B63BSHIPS OR OTHER WATERBORNE VESSELS; EQUIPMENT FOR SHIPPING 
    • B63B1/00Hydrodynamic or hydrostatic features of hulls or of hydrofoils
    • B63B1/16Hydrodynamic or hydrostatic features of hulls or of hydrofoils deriving additional lift from hydrodynamic forces
    • B63B1/24Hydrodynamic or hydrostatic features of hulls or of hydrofoils deriving additional lift from hydrodynamic forces of hydrofoil type

Abstract

A boat hull (10) has a keel (11) having a pair of side foils (12) descending from both sides of the hull (10), below the water-line (13), to a junction (14) below the centre line of the hull (10). The side foils (12) may curve convergently downwards to join with a central foil (15). Each foil (12, 15) decreases in width from top to bottom and is of streamlined or aerofoil cross-sectional configuration. Ballast may be fixed at the junction of the foils. The keel (11) imparts a uniform horizontal velocity to the water within the region of the keel (11) when the boat is in motion and thereby lateral force to oppose the lateral force on the boat's sails. In an alternative embodiment, side foils extend convergently downwards to a transverse bottom foil. <IMAGE>

Description

SPECIFICATION An improved boat keel BACKGROUND OF THE INVENTION (1) Field of the Invention This invention relates to an improved boat keel.
(2) Prior Art The keel or centre-board of a sailing boat is in some respects analogous to the wing of an aeroplane; whereas the wing generates lift by its forward motion, the keel generates lateral force to resist the opposing lateral force on.
the boat's sails.
A typical keel, however, is considerably less efficient than a typical wing. The efficiency of an aeroplane wing is measured by the lift/drag ratio, typically of the order of 20 to 50; but the efficiency of a conventional boat keel is of the order of about 5. The inefficiency of the keel is not due to skin friction or to form drag, but to induced drag which results in large-scale movement of the water, skin friction and form drag resulting mainly in different degrees of turbulence. With an aircraft, the induced drag may be reduced by designing for a larger aspect ratio by increasing the wingspan, but with a sailing boat the analogous remedy, of making the keel deeper, is not generally available as it would aggravate the heeling problem in light craft, it would make shallow waters inaccessible and, in the case of a formula racing boat, it would attract penalties.
SUMMARY OF THE PRESENT INVENTION The present invention has been devised with the general object of providing a boat keel which is particularly efficient in operation.
Accordingly, the invention resides broadly in a boat keel including a pair of side foils converging symmetrically downwards from corresponding positions at opposite sides of the boat hull and co-joined below the centre-line of the hull. The side foils are preferably of streamlined or aerofoil cross-sectional configuration. Preferably one ar more intermediate foils extend down from the hull bottom to the side foils or to their junction.
Other preferred features of the invention will become apparent from the following description.
BRIEF DESCRIPTION OF THE DRA WINGS Various embodiments of the invention are shown, by way of illustrative example only, in the accompanying drawings, wherein: Figure 1 is a side elevational view of a sailing boat with a keel according to one embodiment of the invention, Figure 2 is a front elevational view of the boat shown in Fig. 1; Figure 3 is a perspective view of the boat from below, Figure 4 is a sectional view, to larger scale, taken along any of the lines 4-4 in Fig. 2, and Figures 5 and 6 are midship sections of boat hulls with keels according to further embodiments of the invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring initially to Figs. 1 to 4 inclusive of the drawings, a sailing boat hull 10 of generally conventional lines except for the configuration of its keel 11. This keel comprises two side foils 12 descending from both sides of the hull 10, from corresponding positions somewhat below its waterline 13, to curve convergently downwards to join at a junction 14 with the bottom of a central foil 15 extending downwardly from the bottom centreline of the hull. Each of the side foils 12 and the central foil 15 decreases somewhat in width from top to bottom and, as shown in Fig. 4, is of streamlined cross-sectional configuration.
The keel assembly, then, although of no undue depth whether the boat is upright or heeled, has a very considerable effective length without the disadvantages of likelihood of fouling a jetty or river bank when moored.
These considerations define an "available region" below the boat's water line within which the whole of the keel should be contained. It is believed that the keel according to the invention will be very effective in imparting to the whole of the water within the "available region" a suitable uniform horizontal velocity when the boat is in motion.
The boundary of the "available region" will be a discontinuity of velocity, or vortex sheet coming from the tapered trailing edges of the side foils 12. The central foil 15 structurally reinforces the keel assembly and should not increase induced drag or generate a vortex sheet at its trailing edge.
The boat shown in midship section in Fig. 5 is of shallow draught river-boat type. From corresponding locations at both sides of its hull 20, somewhat below the water line 21, side foils 22 extend convergently downwards and are connected by a transverse bottom foil section 23, two intermediate and laterally spaced foils 24 extend from the hull bottom to be rigidly connected to this bottom section 23.
The embodiment of Fig. 6 is applicable to a deep-sea boat, the hull 30 of which has a keel comprising two side foils 31 which are substantially straight, and which are convergent downwards to a junction at 32, where the ballast is fixed, no central or intermediate foils being included in this embodiment.
Keels according to the invention will be found to be very effective in achieving the objects for which they have been devised. It will, of course, be understood that many modifications of constructional detail and design, which will be readily apparent to persons skilled in the art, may be made within the scope and ambit of the invention defined in the appended claims.

Claims (1)

1. A boat keel including a pair of side foils converging symmetrically downwards from corresponding positions at opposite sides of the boat hull and co-joined below the centreline of the hull.
2. A boat hull as claimed in claim 1 wherein: the side foils are of streamlined or aerofoil cross-sectional configuration.
3. A boat hull as claimed in claim 1 or claim 2 wherein: one or more intermediate foils extend down from the hull bottom to the side foils or to their junction.
4. A boat hull as claimed in any one of claims 1 to 3 wherein: the side foils decrease in width from top to bottom.
5. A boat hull as claimed in any one of claims 1 to 4 wherein: the side foils curve convergently downwards to the junction.
6. A boat hull as claimed in any one of claims 1 to 5 wherein: the side foils extend convergently downwards and are connected by a transverse substantially horizontal bottom foil section.
7. A boat hull as claimed in claim 6 wherein: two or more intermediate and laterally spaced foils extend from the hull bottom and are rigidly connected to the bottom foil section.
8. A boat hull as claimed in claim 1 wherein: ballast is fixed to the junction of the side foils.
9. A boat hull substantially as hereinbefore described with reference to Figs. 1 to 4, or Fig. 5, or Fig. 6 of the accompanying drawings.
CLAIMS Amendments to the claims have been filed, and have the following effect: Claims 1 and 2 above have been deleted or textually amended.
New or textually amended claims have been filed as follows:
1. A boat keel including a pair of side foils converging symmetrically downwards from corresponding positions at opposite sides of the boat keel and co-joined below the centre line of the hull, said side foils being of streamlined or aerofoil cross-sectional configuration.
Claims 3-9 above have been re-numbered as 2-8 and their appendancies corrected.
GB08616251A 1985-07-09 1986-07-03 An improved boat keel Expired GB2177353B (en)

Priority Applications (2)

Application Number Priority Date Filing Date Title
AUPH138585 1985-07-09
AU59430/86A AU575487B2 (en) 1985-07-09 1986-06-27 An improved boat keel

Publications (3)

Publication Number Publication Date
GB8616251D0 GB8616251D0 (en) 1986-08-13
GB2177353A true GB2177353A (en) 1987-01-21
GB2177353B GB2177353B (en) 1988-10-05

Family

ID=25632379

Family Applications (1)

Application Number Title Priority Date Filing Date
GB08616251A Expired GB2177353B (en) 1985-07-09 1986-07-03 An improved boat keel

Country Status (1)

Country Link
GB (1) GB2177353B (en)

Cited By (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE4344740A1 (en) * 1993-12-24 1995-06-29 Guenter J Dipl Ing Peters Split keel with jet effect for yachts
WO1999065764A1 (en) * 1998-06-17 1999-12-23 Bolen Robert D Stabilizing element for use on mobile devices
WO2001060690A1 (en) * 2000-02-18 2001-08-23 Steve Daniel Burns Hydrodynamic device
WO2003086851A1 (en) * 2002-04-11 2003-10-23 Don Andrew Smith A stabiliser device
GB2408487A (en) * 2004-12-20 2005-06-01 Jonathan Sebastian Howes Waterborne vessel with a loop keel
WO2005061319A1 (en) * 2003-12-23 2005-07-07 Macnaghten, James Waterborne vessel with loop keel
WO2006135971A1 (en) * 2005-06-21 2006-12-28 Konstrukt Design Pty Ltd An element for a watercraft
WO2009100479A1 (en) * 2008-02-11 2009-08-20 Courtney James Potter Surfboard fin
FR2929236A1 (en) * 2008-03-28 2009-10-02 Marc Marcel Ellegeest Single-piece keel for sailboat, has lateral and central supports fixed under sail boat hull to serve as low draught keel, where fixed or movable center-boards and lateral supports are buoyant
WO2013071329A1 (en) * 2011-11-14 2013-05-23 3Dfins Pty Ltd Watercraft fin

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB972196A (en) * 1961-06-27 1964-10-07 John Wightman Ecroyd Improvements relating to water-craft
US4077077A (en) * 1977-01-13 1978-03-07 Harper Alex M Stabilizer keel

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB972196A (en) * 1961-06-27 1964-10-07 John Wightman Ecroyd Improvements relating to water-craft
US4077077A (en) * 1977-01-13 1978-03-07 Harper Alex M Stabilizer keel

Cited By (19)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE4344740A1 (en) * 1993-12-24 1995-06-29 Guenter J Dipl Ing Peters Split keel with jet effect for yachts
WO1995018036A1 (en) * 1993-12-24 1995-07-06 Peters Guenter J Slotted keel with jet action
DE19522035A1 (en) * 1993-12-24 1996-12-19 Guenter J Dipl Ing Peters Keel construction for yacht
WO1999065764A1 (en) * 1998-06-17 1999-12-23 Bolen Robert D Stabilizing element for use on mobile devices
US6217402B1 (en) 1998-06-17 2001-04-17 Robert Bolen Stabilizing element for use on mobile devices
US6379204B2 (en) 1998-06-17 2002-04-30 Robert Bolen Stabilizing element for use on mobile devices
AU757137B2 (en) * 1998-06-17 2003-02-06 Robert D. Bolen Stabilizing element for use on mobile devices
WO2001060690A1 (en) * 2000-02-18 2001-08-23 Steve Daniel Burns Hydrodynamic device
US6739925B2 (en) 2000-02-18 2004-05-25 Steve Daniel Burns Hydrodynamic device
WO2003086851A1 (en) * 2002-04-11 2003-10-23 Don Andrew Smith A stabiliser device
US7192323B2 (en) 2002-04-11 2007-03-20 Smithkins Holding Ptyltd Acn. Stabilizer device
WO2005061319A1 (en) * 2003-12-23 2005-07-07 Macnaghten, James Waterborne vessel with loop keel
US7841285B2 (en) 2003-12-23 2010-11-30 Jonathan Sebastian Howes Waterborne vessel with loop keel
GB2408487A (en) * 2004-12-20 2005-06-01 Jonathan Sebastian Howes Waterborne vessel with a loop keel
GB2408487B (en) * 2004-12-20 2006-03-15 Jonathan Sebastian Howes Waterborne vessel with keel
WO2006135971A1 (en) * 2005-06-21 2006-12-28 Konstrukt Design Pty Ltd An element for a watercraft
WO2009100479A1 (en) * 2008-02-11 2009-08-20 Courtney James Potter Surfboard fin
FR2929236A1 (en) * 2008-03-28 2009-10-02 Marc Marcel Ellegeest Single-piece keel for sailboat, has lateral and central supports fixed under sail boat hull to serve as low draught keel, where fixed or movable center-boards and lateral supports are buoyant
WO2013071329A1 (en) * 2011-11-14 2013-05-23 3Dfins Pty Ltd Watercraft fin

Also Published As

Publication number Publication date
GB2177353B (en) 1988-10-05
GB8616251D0 (en) 1986-08-13

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Legal Events

Date Code Title Description
PCNP Patent ceased through non-payment of renewal fee

Effective date: 19920703