US3580203A

US3580203A - Sailboat

Info

Publication number: US3580203A
Application number: US773413A
Authority: US
Inventors: Benjamin P Martin
Original assignee: Individual
Current assignee: Individual
Priority date: 1968-11-05
Filing date: 1968-11-05
Publication date: 1971-05-25
Anticipated expiration: 1988-05-25

Abstract

A sailboat including hull having a mast mounted for full 360* rotation thereon and forming the central portion of a sail having the configuration of an air foil and arranged to collapse together with means for adjusting the sail position, the sail being supported so that its aerodynamic center is closely adjacent its axis of rotation and cooperatively arranged with a rotatable centerboard to achieve optimum utilization of the propulsive forces of a wind.

Description

[56] References Cited UNITED STATES PATENTS 685,943 11/1901 Pool 114/128X 1,038,507 9/1912 Crocco et a1. 114/126 2,484,687 10/1949 114/39X 3,381,647 5/1968 Keeler......,................... 114/102 Primary Examiner-Trygve M. Blix Attorney-Paul B. F ihe Benjamin P. Martin 1249 Lime Drive, Sunnyvale, Calif. 94087 [2]] Appl. No. 773,413

Nov. 5, 1968 May 25, 1971 United States Patent [72] Inventor [22] Filed [45] Patented [54] SAILBOAT ABSTRACT: A sailboat including hull having a mast mounted for full 360 rotation thereon and forming the central portion of a sail having the configuration of an air foil and arranged to collapse together with means for adjusting the sail position, the sail being supported so that its aerodynamic center is closely adjacent its axis of rotation and cooperatively arranged 9 9 nmmmna 4 5 1M3h 1 31 36 B m m M m m s m mu .m C C m 5 t .m U h F n H. m 5 5 5 ..1 rt .1.

with a rotatable centerboard to achieve optimum utilization of the propulsive forces of a wind.

Patented May 25, 1971 3,580,203

2 Sheets-Sheet 1 INVI'TN'I'UR. BENJAMIN I? MARTIN lk BY PATENT AGENT Patented May 25, 1971 3,580,203

2 Sheets-Sheet 2 COURSE l COURSE 2 5 t 3 INVENTOR.

BENJAMIN P. MARTIN BY I M Q Y 4 f PATENT AGENT BACKGROUND OF THE INVENTION It is, of course, well known that conventional canvas sails, the mast, and other supporting structure therefor provide relatively inefficient aerodynamic arrangements. For example, the sails, depending upon the character of the wind, form themselves into different curved or cambered shapes of varying efficiency in the conversion of the wind force into the propulsive application of force to a boat. As a consequence, sailors interested in maximum performance frequently carry two or more sets of sails for variant wind conditions. In addition, the conventional mast for supporting the sails creates a great deal of air turbulence as the wind passes thereover and typically losses as high as 18 percent in converting the wind force to a boat propulsive force are experienced. Additional efficiency is lost through twist in the sail and drag on stays and other supports. In view of these obvious problems, some attempts have been made to provide a more efficient sail structure having a rigid aerodynamically efficient configuration, but these too have been troublesome, in the first place, because of the greater sail weight and secondly because of the additional problem of sail control and storage; existent sails cannot be partially reefed for control or tight maneuvering purposes, nor can they be fully reefed for trailering and storage.

SUMMARY OF THE INVENTION In view of the foregoing problems, it is a general objective of the present invention to provide a sailboat including a sail structure of a rigid yet collapsible nature affording the opportunity for maximum aerodynamic efficiency, but, at the same time, permitting ready control for various wind conditions as well as ready erection for use or collapse for storage purposes.

Generally, this objective is achieved by mounting on a sailboat hull or hulls a substantially rigid sail which may be of rectangular or tapered outline but in cross section has the configuration of an airfoil of maximum aerodynamic efficiency. The sail includes a mast of generally rectangular configuration whose opposite sides form a portion of the airfoil. From the sides of such rectangular mast, a hollow rigid curved structure projects forwardly to form the leading edge portion of the airfoil and a rear foldable structure forms, upon full erection, the rear portion of the airfoil behind the aforementioned mast. In addition to being collapsible or foldable, this rear sail section is preferably mounted on tracks on the mast to enable removal as well as full collapse for purposes of storage and partial collapse of the lower end if desired to minimize boat dimensions for maneuvering near docks or other boats. At its lower extremity, the mast is secured to a base member which can be rotated a full 360 on a substantially vertical axis, thus to enable maximum maneuverability of the boat and to permit a stable sail attitude for all wind and course conditions, thus providing maximum efficiency, and also safety by elimination of the possibility of accidental jibbing. Preferably, the mast is held in an adjusted rotary position by resilient means which permit a certain degree of rotation for accommodation of sudden gusts of wind, and the aerodynamic center of the sail, whereat the propulsive force on the boat may be assumed to act, is displaced but slightly from the sails axis of rotation so that the rotative position of the entire sail will automatically adjust itself to such wind gusts. Because the aerodynamic center may be placed very close to the sails axis of rotation, its longitudinal and lateral displacement will be very small for any and all sail angular positions. Since this center can then be close to the boats center of lateral resistance, the boat is easy to trim with little rudder force for all sail settings, even with the trailing edge forward for reverse sailing of the boat, or for running in a strong wind.

Cooperating with such sail arrangement is a novel form of centerboard which is also pivoted about a central generally upright axis located aft of its hydrodynamic center thus to accommodate itself automatically to various course settings wherefore ultimately the lateral leeway of the sailboat is minimized.

BRIEF DESCRIPTION OF THE DRAWINGS The aforementioned objective of the invention and the manner in which it is achieved, as summarized hereinabove, will be more readily understood by a perusal of the following detailed description of the exemplary sailboat shown in the accompanying drawings wherein:

FIG. 1 is a side-elevational view of a sailboat embodying the present invention, portions of the structure being broken away to illustrate certain inten'or details thereof,

FIG. 2 is an enlarged substantially horizontal fragmentary sectional view taken along line 2-2 of FIG. 1 illustrating additional details of the sail construction,

FIG. 3 is an enlarged fragmentary sectional view taken along line 3-3 of FIG. 1,

FIG. 4 is an enlarged substantially horizontal sectional view taken along line 4-4 of FIG. 1,

FIG. 5 is an enlarged fragmentary sectional view taken along line 5-5 of FIG. 1,

FIG. 6 is another enlarged horizontal sectional view taken along line 6-6 of FIG. 1 illustrating a mechanism for adjusting the rotative position of the sail during the operation,

FIG. 7 is an enlarged fragmentary vertical sectional view taken along line 7-7 of FIG. 6, and

FIG. 8 is a diagrammatic plan view illustrating various operational aspects of a sailboat embodying the invention.

DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENT OF THE INVENTION With initial reference to FIG. 1, a sailboat embodying the invention includes a single hull 10 whose general shape and arrangement is conventional and it will be understood that other hull shapes can be utilized consisting either of single hulls of a different shape or multiple hulls conventionally referred to as catamarans or trimarans. Accordingly, the term hull as used herein refers to either a single hull or multiple hulls.

A centerboard 12 is pivotally suspended from the bottom of the hull 10 on a substantially upright pivot pin 11 located substantially at its transverse center and longitudinally at a predetermined position. More particularly, and for reasons to be described hereinafter, the centerboard 12 is preferably located at a position placing its hydrodynamic center HC of pressure slightly forward of its axis of rotation A, as clearly shown in FIG. 1. A torsion spring 13 resiliently holds the centerboard 12 in its fore and aft position thus to permit limited pivoting. The term centerboard is used broadly so as to encompass daggarboards, keels or other structures of likehydrodynamic purpose.

The sail structure, itself, includes an elongated mast 14 which, as illustrated best in FIGS. 2 and 6, is essentially rectangular in cross section and is removably received within a corresponding rectangular socket 16 in a rotary base member or turntable 18 supported for its rotation about a substantially vertical axis in suitable bearings 17 located immediately above the bottom of the hull 10 and also at the top, or deck thereof. As will appear hereinafter, the sides of the mast 14 form the central portion of an airfoil.

At spaced intervals along the mast length, a plurality of generally semielliptical ribs 20 are secured rigidly to project forwardly therefrom and carry conjointly on their perimeters a smooth covering or skin 22 which can constitute a curved sheet of aluminum, plastic, fiberglass, or any other material capable of being readily formed into a smooth curved extension of the mast sides, thus to provide the leading edge 24 of the mentioned airfoil. Preferably, the material is liquid impervious and all exterior joints are sealed so that the entire leading edge portion 24 of the airfoil sail, together with the hollow mast 14, constitutes a hollow buoyant chamber to prevent complete overturning of the boat, and as an additional safety feature, in the unlikely event of boat destruction, the entire sail can, in case of such an emergency, function as a life raft. Preferably, as shown clearly in FIG. 2, the spaced ribs 20 are each formed with one or more apertures, which may be hermetically sealed by light membranes 2] so as to minimize their weight while, at the same time, retaining the requisite strength characteristics and providing individual watertight compartments.

The main portion of the sail which extends rearwardly from the mast 14 and forms the rear or trailing edge portion 26 of the airfoil is foldably and removably mounted to the mast 14 and for this purpose, a pair of

tracks

28, 30 extend upwardly in parallelism along the entire rear surface-of the mast adjacent opposite sides thereof. Both

tracks

28, 30 are generally C- shaped in cross section and are arranged to slidably and rotatively receive therewithin

aft rib slides

32, 34 secured at the forwardly projecting comer extremities of an apertured rib 40 whose overall outline takes the general form of the requisite trailing edge portion 26 of the airfoil. Accordingly, the two

slides

32, 34 at the forward comers of the rib 40 can be placed within the parallel C-

shaped tracks

28, 30 at their lower extremities and then 'moved upwardly to adjust the position of an individual rib 40 longitudinally of the mast 14. Furthermore, the individual rib 40 can be pivoted or folded about the axis defined by the line extending between the two

slides

32, 34 in the

tracks

28, 30. Although the entire rib 40 can be moved longitudinally of the mast l4 and can be folded, as described, its transverse planar disposition is always maintained relative to the mounting mast.

A plurality of the ribs 40 of like configuration are slidably received in the

tracks

28, 30 on the mast l4 and conjointly support on their perimeters flexible sail skin 42 which may constitute conventional, light, sailcloth or thin plastic film. More particularly, as best shown in FIG. 3, the inner surface of the sail skin 42 has stitched thereto, at spaced parallel intervals, sections of rope 44 that are, in turn, slidably inserted within C-shaped guides 46 fastened to the edges of the ribs 40. The forward extremities of the two rope sections 44 are releasably secured by small clamps 47. The precise disposition of the rope sections 44 are such that if the ribs 40 extend rearwardly from the mast 14 in perpendicular relation thereto and thus inparallelism to each other, as shown in FIG. I, the sail skin 42 is supported in a taut smooth configuration forming a rearward extension of the sides of the mast and thus defining the trailing edge portion 26 of the airfoil. Thus, although the sail skin 42 is flexible, its support is such that a substantially rigid airfoil section of optimum wrinkle-free shape is achieved so that in aerodynamic terms, a maximum lift to drag ratio is provided wherefore the overall efficiency of the sail is optimized.

While the same character of rib 40 can be utilized at all sailsupporting positions,

ribs

52, 54 of trusslike configuration are preferably employed to support the sail skin 42 at its upper and lower extremities. More particularly, these

ribs

52, 54, which are of substantially identical natures are formed by open tubular sections joined by bolts at their extremities and by a bolted crossbar 51 and angular braces 53 at an intermediate position (see FIG. The sail skin 42 is looped at its upper and lower ends so as to be slidably received over the tubular sections, as shown best in FIG. 5, before the bolted connections are made. In this fashion, the sail skin 42 is fixed to the

ribs

52, 54 until replacement is required. It will, of course, be understood that ribs such as the above-mentioned tubular sections of the

trusslike ribs

52, 54 can be used as alternatives to the ribs 40 at the intermediate positions, if desired.

The trailing edge portion 26 of the airfoil sail is held in its described operative erected disposition by a pair of simple foldable braces 48, 50, one of which, as shown in FIG. 4, is connected to the upper trusslike rib 52 pivotally joined to the

tracks

28, 30 at the top of the mast 14 like the ribs 40, and the other of which is similarly connected to the lower rib 54, pivoted to the

tracks

28, 30 on the mast 14 adjacent its lower end. A releasable pin 55 is used to hold the forward pivoted end of the top rib 52 in position. Preferably, each of the braces 48, 50 includes a

tubular section

56, 58 which is pivotally joined to the

rib

52, 54 at its one end and is pivotally joined to the other section of the brace in the form of a

channel member

60, 62 at its opposite extremity. In turn, the remote extremity of the

channel brace section

60, 62 is pivotally joined to the mast by a pin or hinge 64, 66 fixedly carried on the mast by a

suitable bracket

68, 70. Each of the hinge pins 64, 66 can be withdrawn, thus to release the brace connection to the mast l4 and the entire sail structure can then be removed from its support on the mast by the simple longitudinal sliding of the

slides

32, 34 on the intermediate ribs 40, and each

rib

52, 54 to the lower open end of the described tracks 28, 30. When the braces 48, 50 are connected to the mast 14 and are pivoted to their extended dispositions, as illustrated, the upper and

lower ribs

52, 54 are both constrained to remain in perpendicular relationship to the mast, thus to hold the sail skin 42 tautly therebetween with all the ribs 40 held at their proper positions by means of the above-described attachment to the sail skin, resulting in a tight, wrinkle-free sail. Because of the sail skin connection between the upper and

lower ribs

52, 54 and the intermediate ribs 40 thereof, all are maintained in parallel relationship and, in effect, a substantially rigid sail structure is provided. Because of the rather short span between the ribs 40 and

ribs

52, 54 the sail skin 42, itself, can be of rather light material and, yet, will not tear or generally deform even under extremely heavy wind conditions.

The braces 48, 50 are preferably maintained in their extended rectilinear dispositions, as'shown in FIG. 1, by means of a simple slidable latch 72, 74 carried by the

tubular sections

56, 58 and arranged to engage the

channel sections

60, 62 adjacent their pivotal juncture. Manual release of the latches 72, 74 from both the top and bottom braces 48, 50 then permits the

trusses

52, 54 to be folded inwardly toward the mast 14. Since the ribs 40 are, through their slideable attachment, suspended by the sail skin, upon folding of the end ribs, the intermediate ribs 40 are caused to fold inwardly about their slide pivots, thus to provide what is, in effect, a complete collapse or reefing of the sail. While partial reefing of the described sail is normally not necessary for reasons to be discussed hereinafter, a mere release of the latch 74 from the lower brace 50 will enable a portion of the sail to be collapsed to provide such a partial reefing if it is desired.

As previously mentioned, the lower end of the rectangular mast 14 is received within a corresponding rectangular socket 16 in a rotary base member 18 which is not only rotatively mounted on the hull 10 but is capable of rotation through an entire 360 since complete rotation of the sail is not interfered with by any stays, halyards or controlling sheets. Preferably, the exterior of the rotary member 18 is provided with a groove much in the fashion of a large pulley, as clearly illustrated in FIGS. 6 and 7 and an endless belt passes around this grooved rotary member and a control pulley 82 located preferably towards the aft end of the hull 10 for a single-hull boat as shown, but may be placed in the most convenient location for control. The latter pulley 82, in turn, mounts an operating crank 84, actuation of which will effect rotation of the rotary member and the sail therewith in either direction and, as mentioned, through a full 360, if desired.

Preferably, means are provided to releasably retard rotation of the rotary member 18 and the sail thereon and, as illustrated in FIGS. 6 and 7 such means takes the form of a pivoted member 86 arranged at one end to engage the top of the retary member 18 and connected at its opposite extremity to a control line 88 which passes rearwardly through a conventional jam cleat 90. If the sailor wishes to rotate the sail, he releases the jam cleat 90 which, in turn, removes the frictional retardation and permits the sailor, by appropriate turning of the crank 84, to rotate the sail to any desired position optimized in accordance with the wind direction and the desired direction of sailboat advance. Also, because of the sail's slight weathercocking ability, the wind can be used to rotate the sail nearly into position, with only final adjustment caused by the sailor. If desired, the line 88, itself, can be of resilient material or a spring 89 can be used to enable a manual variation of the frictional retarding force depending upon the particular wind conditions encountered. Optionally, the belt, 80, may be made of resilient material to allow return of the sail to its prior attitude after being rotatably displaced by a gust. In this type of installation the clutch-type mechanism, 86 or other appropriate means of maintaining an angular position, would operate against pulley 82.

Under normal forward sailing conditions along Course 1, close-hauled under wind conditions as indicated diagrammatically by Wind 1 in FIG. 8, the aerodynamic center of the sail, indicated at AC is slightly aft of its axis of rotation and the hydrodynamic center HC of lateral resistance of the centerboard 12. As a consequence, depending upon the setting of the amount of frictional retardation on the rotary member 18, the sail disposition will normally be maintained as shown in full lines and indicated by Sail 1, but, in the event an exceptionally strong gust of wind is encountered, the entire sail can rotate slightly against the retarding force to ship" the excessive wind gust and thus preclude tipping or knock-down of the boat.

It should be expressly observed that the aerodynamic center AC is but slightly displaced from the sails axis of rotation and therefore, with proper design, also will be close to the boats center of lateral resistance HC for all sail positions so that maximum efiiciency results from the coaction of the wind forces on the sail and the reactive water forces on the centerboard. More particularly, since the centerboard 12 is resiliently pivoted aft of its hydrodynamic center of pressure I-IC, a reverse weathercocking is provided which means that the centerboard can pivot about its axis so as to develop a lateral hydrodynamic force to balance the aerodynamic force on the sail and at the same time assure, by the angular adjustment, a maximum lift to drag ratio. Leeway of the hull is effectively eliminated and the rudder 92 can be maintained in general course alignment.

In view of the described efficient sail offering high ratio of lift to drag and therefore a small side or tipping force and the resultant automatic safety precaution against tipping or knock-down of the sailboat, the total sail area of the described structure can be made greater than that of a conventional sail. By way of example, a 12 foot catamaran normally having a total sail area of no more than 60 sq. ft. as a safety precaution, can, with the present invention, have a total sail area as great as 100 sq. ft. without danger. Thus, not only is efficiency increased providing greater speed with equivalent sail area, but the sail area can be increased so the total applicable force and consequent speed are further increased.

Because of the noted absence of stays and halyards as well as control sheets of a conventional nature, the sail can, of course, be positioned essentially at right angles to the hull for running before the wind. If the following wind is excessive so as to cause the bow of the boat to sail under, that is, to penetrate downwardly into the water, the sail can be rotated further forwardly to the precise dotted line disposition (Wind 2, Course 2, Sail 2 conditions in FIG. 8) or beyond until the trailing edge is all the way forward, if desired, thus to provide a controlled impedance to the wind force which is very simply achieved without the necessity for reefing in the conventional manner.

Additionally, it should be pointed out that because of the full 360 rotation of the sail, and the very small translation of the aerodynamic center as it is turned, it can be positioned to create rearward motion of the sailboat, as indicated in FIG. 8, (Course 3, Wind 3, Sail 3) as well as normal maneuvering and, by way of example, a sailboat having the described sail thereon can, in practice, be backed away from a dock or shore or rocks to be avoided and then sailed forward, which constitutes an obvious additional safety feature, particularly during operation not providing space for coming about. Furthermore, because the sail position is positively controlled,

and is always in a stable attitude with respect to airflow, no accidental jibbing will occur, even if the boat is sailed in a course nearly circular in shape, which is easily accomplished.

Thus, in summary, a more efiicient sailboat is provided, one which is also capable of accepting greater wind forces without sacrificing safety, and, in fact, has much greater inherent safetythan that provided by a conventional sail arrangement and is much more maneuverable than any sailboat of a conventional variety.

It will be apparent that many modifications and/or alterations can be made in the structure as described without departing from the spirit of the invention, and the foregoing description of one embodiment is accordingly to be considered as purely exemplary and not in a limiting sense.

What I claim is:

1. A sailboat which comprises a hull, and

a sail including a mast mounted on said hull and projecting upwardly therefrom, and having lateral sides arranged to form the opposite sides of the central portion of an airfoil,

means mounted on the forward side of said mast to form the leading edge portion of the airfoil, and

means mounted on the rearward side of the mast to form the trailin g edge portion of the airfoil.

2. A sailboat according to claim 1 which comprises a centerboard rotatably mounted below said hull at a position slightly aft of its hydrodynamic center.

3. A sailboat according to claim 2 which comprises means for resiliently maintaining said centerboard in longitudinal alignment with said hull.

4. A sailboat according to claim 1 wherein said mast has a generally open rectangular cross section.

5. A sailboat according to claim 1 wherein said means forming said leading edge portion forms a hollow liquid impervious chamber of a buoyant nature.

6. A sailboat according to claim 1 wherein said mast forms a liquid impervious chamber of a buoyant nature.

7. A sailboat according to claim 1 wherein said means forming the trailing edge portion of the airfoil is removably attached to said mast.

8. A sailboat according to claim I wherein said means forming the trailing edge portion of the airfoil is collapsible on said mast.

9. A sailboat according to claim 1 wherein said means forming the trailing edge portion of the airfoil includes a plurality of ribs slidably and rotatably joined to said mast and sail skin secured to the rib perimeters to form a substantially rigid but collapsible extension of the lateral sides of said mast.

10. A sailboat according to claim 9 wherein said means forming the trailing edge portion includes a pair of releasable braces connected between said mast and the uppermost and lowermost ribs to hold said ribs in substantially perpendicular relation to the longitudinal axis of said mast.

11. A sailboat according to claim 1 which comprises means mounting said mast on said hull for 360 rotation.

12. A sailboat according to claim 11 which comprises manually operable means for rotating said mast mounting means.

13. A sailboat according to claim 11 which comprises means resiliently retarding rotation of said mast.

14. A sail which comprises a mast adapted for mounting on a hull to project upwardly therefrom and having lateral sides arranged to form the opposite sides of the central portion of an airfoil,

means mounted on the forward side of said mast to form the leading edge of the airfoil, and

means mounted on the rearward side of the mast to form the trailing edge portion of the airfoil.

15. A sail according to claim 14 wherein at least one of said means is collapsible.

Claims

1. A sailboat which comprises a hull, and a sail including a mast mounted on said hull and projecting upwardly therefrom, and having lateral sides arranged to form the opposite sides of the central portion of an airfoil, means mounted on the forward side of said mast to form the leading edge portion of the airfoil, and means mounted on the rearward side of the mast to form the trailing edge portion of the airfoil.

8. A sailboat according to claim 1 wherein said means forming the trailing edge portion of the airfoil is collapsible on said mast.

11. A sailboat according to claim 1 which comprises means mounting said mast on said hull for 360* rotation.

14. A sail which comprises a mast adapted for mounting on a hull to project upwardly therefrom and having lateral sides arranged to form the opposite sides of the central portion of an airfoil, means mounted on the forward side of said mast to form the leading edge of the airfoil, and means mounted on the rearward side of the mast to form the trailing edge portion of the airfoil.