WO1994002744A1 - A device to reduce drag over the surface of mast and boom of a sailcraft - Google Patents

A device to reduce drag over the surface of mast and boom of a sailcraft Download PDF

Info

Publication number
WO1994002744A1
WO1994002744A1 PCT/CA1992/000310 CA9200310W WO9402744A1 WO 1994002744 A1 WO1994002744 A1 WO 1994002744A1 CA 9200310 W CA9200310 W CA 9200310W WO 9402744 A1 WO9402744 A1 WO 9402744A1
Authority
WO
WIPO (PCT)
Prior art keywords
tube
rod
wire
mast
boom
Prior art date
Application number
PCT/CA1992/000310
Other languages
French (fr)
Inventor
Willi H. Velke
Original Assignee
Velke Willi H
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
Application filed by Velke Willi H filed Critical Velke Willi H
Publication of WO1994002744A1 publication Critical patent/WO1994002744A1/en

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Classifications

    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15D—FLUID DYNAMICS, i.e. METHODS OR MEANS FOR INFLUENCING THE FLOW OF GASES OR LIQUIDS
    • F15D1/00—Influencing flow of fluids
    • F15D1/10—Influencing flow of fluids around bodies of solid material
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B63—SHIPS OR OTHER WATERBORNE VESSELS; RELATED EQUIPMENT
    • B63B—SHIPS OR OTHER WATERBORNE VESSELS; EQUIPMENT FOR SHIPPING 
    • B63B15/00—Superstructures, deckhouses, wheelhouses or the like; Arrangements or adaptations of masts or spars, e.g. bowsprits

Definitions

  • This invention relates to a mast, and more particularly to a mast of a sailboat, which is equipped with the means to reduce drag across its surface.
  • the mast of a sailboat together with the boom, which is attached to the mast, provides the necessary structure to hold in place the sail which catches the wind and converts its force into the forward motion of the sailboat.
  • the amount of forward velocity a sailboat may achieve depends to a large degree on the strength of the wind and the efficiency of the sail arrangement. Air flow over the sail is affected by the turbulent wake created by the surface of the mast, resulting in a base drag condition which greatly reduces the efficiency of the sail.
  • the combination of wake or low pressure on one side of the mast and the corresponding high pressure on the opposite thereof creates a weight condition which greatly influences the effect of gravity on the mast, which needs to be calculated into the design and construction of a sailboat, especially with respect to the keel.
  • one aspect of the present invention relates to a mast and boom application for a sailboat
  • the scope of the present invention generally embraces all continuous single curvature elongated bodies, such as tubes, rods, cables, wires and the like, which are located adjacent a fluid in relative motion and thereby experiencing significant amounts of base drag.
  • a single curvature elongated body includes in its surface a pattern of surface discontinuities arranged along at least a portion of the surface of such elongated body.
  • the surface discontinuities include discrete, generally spheroidal, concave sub-surfaces extending below the surface of such elongated body.
  • Regular, discretely shaped surface discontinuities have the advantage of dealing uniformly with changing flow patterns and are independent of the angle of attack the flow takes across the surface of such single curvature elongated bodies.
  • the present invention has a broad range of application, and covers a variation of continuous single curvature elongated bodies.
  • the surface is moving and the fluid is generally stationary. Examples of this aspect of the invention includes exterior surfaces of tubular struts and bracings of landing gears and fixed wheel arrangements on small aircraft and on helicopters and the like.
  • fluid passing across a smooth exterior surface of a single curvature elongated body such as a tube, rod or wire, produces turbulent flow creating a low pressure or base drag condition behind such body.
  • the present invention therefore, assists in changing fluid flow behaviour across elongated bodies, such as tubes, rods, wires and the like, thereby significantly reducing the low pressure area or the resulting base drag and increasing overall efficiency.
  • Figure 1 of the drawings depicts a preferred embodiment of the present invention, comprising a portion of a sail arrangement, including part of a mast and boom.
  • Figure 2 of the drawings depicts a section view through the mast or boom, indicated as *S-S' in Figure 1.
  • Figure 3 of the drawings depicts a section view through the mast or boom, indicated as 'S-S' in Figure 1 showing an alternative arrangement.
  • Figure 4 of the drawings depicts a portion of a tube or wire, indicating the direction of relative fluid motion and the location of the corresponding low pressure area.
  • Figure 5 of the drawings depicts a section view through the tube at 'S-S' , as indicated in Figure 4.
  • Figure 6 of the drawings depicts an alternate section view through the tube at 'S-S' as indicated in Figure 4.
  • Figure 7 of the drawings depicts a variety of exterior surface discontinuities.
  • Figure 1 of the drawings shows an elevated view of a portion of a sail (a), including a portion of the mast (b) and the boom (c). Both boom and mast include in their surface a pattern of surface discontinuities (e), designed to affect fluid flow behaviour across such surface areas.
  • Figure 2 of the drawings depicts a view through section line *S-S', through mast or boom, as indicated in Figure 1 of the drawings. This view illustrates the surface discontinuities (e) as depressions in the surface (d) of such mast or boom.
  • Figure 3 of the drawings depicts a view through section line 'S-S', through mast or boom, as indicated in Figure 1 of the drawings, but this time illustrating the surface discontinuities (e) as protrusions in the surface (d) of such mast or boom.
  • Figure 4 of the drawings depicts a more general shape of a portion of a continuous curvature elongated body, suc as a tube, rod or wire, with its surface equipped with a pattern of surface discontinuities (e), and illustrating the direction of relative fluid motion over its surface with arrow (h) and the location of the low pressure area opposite as indicated by arrows (j).
  • Figure 5 of the drawings depicts a section through section line 'S-S' , as indicated in Figure 4, showing an alternative oval shaped circumference of such tube, rod or wire, and including in its surface (d) a pattern of surfac discontinuities (e).
  • FIG. 6 of the drawings shows again another alternative to the shape of the circumference of such tube, rod or wire, as indicated in Figure 4, this time illustrating an uneven shape, and including in its surface (d) a pattern of surface discontinuities (e) .
  • Figure 7 of the drawings depicts a variety of shapes of surface discontinuities, as viewed through section line 'S-S' as indicated in Figure 4 of the drawings.
  • the discontinuities illustrated here show a selection of possible depressions (b), (d), (i) , (j) and (k) , and protrusions (1) and ( ), demonstrating some of the varieties of surface discontinuities able to affect fluid flow behaviour over the surface of a continuous single curvature elongated body.

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Physics & Mathematics (AREA)
  • Fluid Mechanics (AREA)
  • General Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Combustion & Propulsion (AREA)
  • Ocean & Marine Engineering (AREA)
  • Toys (AREA)

Abstract

A device which improves fluid flow across the surface of mast and boom of a sailcraft, by including in the surface of such mast and boom, a pattern of discrete surface depressions (e), resulting in the decrease of base drag and the increase of efficiency of the sail arrangement.

Description

A DEVICE TO REDUCE DRAG OVER THE SURFACE OF MAST AND BOOM OF A SAILCRAFT
BACKGROUND OF THE INVENTION. This invention relates to a mast, and more particularly to a mast of a sailboat, which is equipped with the means to reduce drag across its surface.
The mast of a sailboat together with the boom, which is attached to the mast, provides the necessary structure to hold in place the sail which catches the wind and converts its force into the forward motion of the sailboat. The amount of forward velocity a sailboat may achieve, depends to a large degree on the strength of the wind and the efficiency of the sail arrangement. Air flow over the sail is affected by the turbulent wake created by the surface of the mast, resulting in a base drag condition which greatly reduces the efficiency of the sail. Furthermore, the combination of wake or low pressure on one side of the mast and the corresponding high pressure on the opposite thereof, creates a weight condition which greatly influences the effect of gravity on the mast, which needs to be calculated into the design and construction of a sailboat, especially with respect to the keel.
It is a general rule, that a pound of weight or pressure on a mast at a height of 32 feet from the centre of gravity of a boat needs to be countered by at least 30 pounds of weight below the centre of gravity at the keel, in order to maintain proper balance.
As the weight of the keel is considered "dead weight", any reduction of it would be directly expressed in increased boat performance.
It is therefore most desirous to have available a means to reduce the amount of base drag occurring behind mast and boom of a sailboat, thereby increasing its sail efficiency.
SUBSTITUTE SHEET SUMMARY OF THE INVENTION
Although one aspect of the present invention relates to a mast and boom application for a sailboat, the scope of the present invention generally embraces all continuous single curvature elongated bodies, such as tubes, rods, cables, wires and the like, which are located adjacent a fluid in relative motion and thereby experiencing significant amounts of base drag.
In accordance with the present invention, a single curvature elongated body includes in its surface a pattern of surface discontinuities arranged along at least a portion of the surface of such elongated body. Preferably, the surface discontinuities include discrete, generally spheroidal, concave sub-surfaces extending below the surface of such elongated body. Regular, discretely shaped surface discontinuities have the advantage of dealing uniformly with changing flow patterns and are independent of the angle of attack the flow takes across the surface of such single curvature elongated bodies. As already mentioned, the present invention has a broad range of application, and covers a variation of continuous single curvature elongated bodies. In accordance with one aspect of the invention, for example, the surface is moving and the fluid is generally stationary. Examples of this aspect of the invention includes exterior surfaces of tubular struts and bracings of landing gears and fixed wheel arrangements on small aircraft and on helicopters and the like.
In the case of a mast and boom of a sailboat, both the surface and the fluid are in motion.
In another aspect of the invention only the movement of the fluid provides the relative motion between the exterior surface and the fluid. Applications of this type include exterior surfaces of tubular shapes used in the construction of ocean drill platforms, especially for below
SUBSTITUTE SHEET the waterline. Further examples include exterior surfaces of parts of high towers and bridges and the like, using tubular shapes in their construction.
In general, fluid passing across a smooth exterior surface of a single curvature elongated body, such as a tube, rod or wire, produces turbulent flow creating a low pressure or base drag condition behind such body.
The present invention therefore, assists in changing fluid flow behaviour across elongated bodies, such as tubes, rods, wires and the like, thereby significantly reducing the low pressure area or the resulting base drag and increasing overall efficiency.
BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 of the drawings depicts a preferred embodiment of the present invention, comprising a portion of a sail arrangement, including part of a mast and boom.
Figure 2 of the drawings depicts a section view through the mast or boom, indicated as *S-S' in Figure 1. Figure 3 of the drawings depicts a section view through the mast or boom, indicated as 'S-S' in Figure 1 showing an alternative arrangement.
Figure 4 of the drawings depicts a portion of a tube or wire, indicating the direction of relative fluid motion and the location of the corresponding low pressure area. Figure 5 of the drawings depicts a section view through the tube at 'S-S' , as indicated in Figure 4.
Figure 6 of the drawings depicts an alternate section view through the tube at 'S-S' as indicated in Figure 4. Figure 7 of the drawings depicts a variety of exterior surface discontinuities.
DETAILED DESCRIPTION OF THE DRAWINGS
For the purpose of understanding the principle of the present invention, reference will now be made to the embodiment illustrated in the drawings, and specific
SUBSTITUTE SHEET language will be used to describe the same. It will nevertheless be understood that no limitations of the scop of the invention is hereby intended, such alterations and further modifications in the illustrated device, and such further applications of the principles of the invention as illustrated therein being contemplated as would normally occur to one skilled in the art to which the invention relates.
Figure 1 of the drawings shows an elevated view of a portion of a sail (a), including a portion of the mast (b) and the boom (c). Both boom and mast include in their surface a pattern of surface discontinuities (e), designed to affect fluid flow behaviour across such surface areas. Figure 2 of the drawings depicts a view through section line *S-S', through mast or boom, as indicated in Figure 1 of the drawings. This view illustrates the surface discontinuities (e) as depressions in the surface (d) of such mast or boom.
Figure 3 of the drawings depicts a view through section line 'S-S', through mast or boom, as indicated in Figure 1 of the drawings, but this time illustrating the surface discontinuities (e) as protrusions in the surface (d) of such mast or boom.
Figure 4 of the drawings depicts a more general shape of a portion of a continuous curvature elongated body, suc as a tube, rod or wire, with its surface equipped with a pattern of surface discontinuities (e), and illustrating the direction of relative fluid motion over its surface with arrow (h) and the location of the low pressure area opposite as indicated by arrows (j).
Figure 5 of the drawings depicts a section through section line 'S-S' , as indicated in Figure 4, showing an alternative oval shaped circumference of such tube, rod or wire, and including in its surface (d) a pattern of surfac discontinuities (e).
SUBSTITUTE SHEET Figure 6 of the drawings shows again another alternative to the shape of the circumference of such tube, rod or wire, as indicated in Figure 4, this time illustrating an uneven shape, and including in its surface (d) a pattern of surface discontinuities (e) .
Figure 7 of the drawings depicts a variety of shapes of surface discontinuities, as viewed through section line 'S-S' as indicated in Figure 4 of the drawings. The discontinuities illustrated here show a selection of possible depressions (b), (d), (i) , (j) and (k) , and protrusions (1) and ( ), demonstrating some of the varieties of surface discontinuities able to affect fluid flow behaviour over the surface of a continuous single curvature elongated body.
SUBSTITUTE SHEET

Claims

I claim:
1. A device which improves fluid flow behaviour over the surface of a continuous, single curvature elongated body, such as a tube, rod or wire, positioned adjacent a fluid, moving relative thereto, with such device consisting of a pattern of surface discontinuities, arranged over at least a portion of the surface of the elongated body, thereby forming a distinct pattern of designed surface and sub¬ surface regions with certain sheering qualities, effective in reducing, without inducing off-setting surface friction, low pressure and base drag normally existing behind such elongated body, opposite the direction of relative fluid motion.
2. A tube, rod or wire according to claim 1, which is of a predetermined length.
3. A tube, rod or wire according to claim 1, wherein the circumference of such tube, rod or wire is round.
4. A tube, rod or wire according to claim-1, wherein the circumference of such tube, rod or wire is oval.
5. A tube, rod or wire according to claim 1, wherein the circumference of such tube, rod or wire is of uneven shape.
6. A tube, rod or wire according to claim 2, wherein the length of such tube, rod or wire is of a tapered configuration.
7. A surface according to claim 1, wherein said surface discontinuities consist of discrete depressions, extending below the surface, creating a sub-surface region with certain sheering qualities.
8. A surface according to claim 1, wherein said surface discontinuities consist of protrusions, extending above the surface, creating a sub-surface region with certain sheering qualities.
9. A surface according to claim 7, wherein said depressions are trough-like, and arranged in a generally 90° angle to the expected direction of fluid flow.
SUBSTITUTE SHEET
10. A surface according to claim 8, wherein said protrusions are ridge-like, and arranged in a generally 90c angle to the expected direction of fluid flow.
11. A surface according to claim 8, wherein said protrusions are inter-connected or in communication with each other.
SUBSTITUTE SHEET
PCT/CA1992/000310 1991-07-18 1992-07-16 A device to reduce drag over the surface of mast and boom of a sailcraft WO1994002744A1 (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
CA2047405 1991-07-18

Publications (1)

Publication Number Publication Date
WO1994002744A1 true WO1994002744A1 (en) 1994-02-03

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Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1994022274A1 (en) * 1993-03-23 1994-09-29 Joseph Francis Hayes Acoustic reflector
WO1999034237A1 (en) * 1997-12-23 1999-07-08 Schlumberger Holdings Limited Fairings for cables
GB2362938A (en) * 2000-06-01 2001-12-05 Imperial College Reduction of vortex shedding and drag
WO2002044015A1 (en) * 2000-11-29 2002-06-06 Westerngeco, L.L.C. Dimpled marine seismic cables
WO2014001514A1 (en) * 2012-06-28 2014-01-03 Danmarks Tekniske Universitet A construction and a tension element comprising a cable and one or more strakes

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB730121A (en) * 1953-05-15 1955-05-18 Vivian Cleland Dewar Gray Improvements in bodies adapted to have relative motion with respect to a fluid
GB1440330A (en) * 1973-09-26 1976-06-23 Couch B C Masts for wind propelled craft or vehicle
FR2301715A1 (en) * 1975-02-18 1976-09-17 Tno CYLINDRIQ BODY
DE3110513A1 (en) * 1981-03-18 1982-10-07 geb. Kint Maria 8752 Daxberg Stein Mast, preferably mast for sailing boats
WO1991001247A1 (en) * 1989-07-25 1991-02-07 Hans Willi Velke Fluid dynamic surfaces

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB730121A (en) * 1953-05-15 1955-05-18 Vivian Cleland Dewar Gray Improvements in bodies adapted to have relative motion with respect to a fluid
GB1440330A (en) * 1973-09-26 1976-06-23 Couch B C Masts for wind propelled craft or vehicle
FR2301715A1 (en) * 1975-02-18 1976-09-17 Tno CYLINDRIQ BODY
DE3110513A1 (en) * 1981-03-18 1982-10-07 geb. Kint Maria 8752 Daxberg Stein Mast, preferably mast for sailing boats
WO1991001247A1 (en) * 1989-07-25 1991-02-07 Hans Willi Velke Fluid dynamic surfaces

Cited By (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1994022274A1 (en) * 1993-03-23 1994-09-29 Joseph Francis Hayes Acoustic reflector
US5764782A (en) * 1993-03-23 1998-06-09 Hayes; Joseph Francis Acoustic reflector
WO1999034237A1 (en) * 1997-12-23 1999-07-08 Schlumberger Holdings Limited Fairings for cables
GB2362938A (en) * 2000-06-01 2001-12-05 Imperial College Reduction of vortex shedding and drag
US6908063B2 (en) 2000-06-01 2005-06-21 Imperial College Of Science, Technology And Medicine Vortex shedding and drag force reduction
WO2002044015A1 (en) * 2000-11-29 2002-06-06 Westerngeco, L.L.C. Dimpled marine seismic cables
WO2014001514A1 (en) * 2012-06-28 2014-01-03 Danmarks Tekniske Universitet A construction and a tension element comprising a cable and one or more strakes
CN104411888A (en) * 2012-06-28 2015-03-11 丹麦技术大学 A construction and a tension element comprising a cable and one or more strakes
US9476171B2 (en) 2012-06-28 2016-10-25 Danmarks Tekniske Universitet Construction and a tension element comprising a cable and one or more strakes

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