US3291091A - Leak-proof centerboard construction for sail boats - Google Patents

Description

Dec. 13, 1966 KOENIG 3,291,091

LEAK-PROOF CENTERBOARD CONSTRUCTION FOR SAIL BOATS Filed Dec. 22, 1,964 2 Sheets-Sheet 1 [/4 T0 Bow .2 /2- mm x J f 4 Dec. 13, 1966 F. L. KOENIG 3,291,091

LEAK-PROOF CENTERBOARD CONSTRUCTION FOR SAIL BOATS Filed Dec. 22, 1964 2 Sheets-Sheet 2 United States Patent 3,291,091 LEAK-PROOF CENTERBOARD CONSTRUCTION FOR SAIL BOATS Francis L. Koenig, 5295 Old Dominion Drive, Arlington, Va. Filed Dec. 22, 1964, Ser. No. 420,277 3 Claims. (Cl. 114-132) This invention pertains to sail boat construction, and especially to an improved centerboard mounting system for small sail boats, which will overcome various problems heretofore encountered in the use of centerboards, lee boards and the like.

The use of retractable centerboards to improve the stability and maneuverability of boats, which centerboards can be raised to allow navigation in shallow water, is almost as old as the art of boat construction itself. In all cases, the board, which is parallel to the vertical plane of the keel or longitudinal center-line of the hull, moves up and down within and beneath a narrow open-bottom enclosure called the trunk, and when a single centerboard is employed, its vertical plane is actually on the centerline of the hull. When two such boards are employed on either side of the hull centerline, each moves in its own trunk, and the boards are usually referred to as lee boards. Two boards may also be used on the centerline, in which case one is forward of the center of hull resistance set up by the sails and the other is aft of this center. Both such boards can be in one long trunk or each may have its own trunk. The trunk may be closed at the top, or it may be open (and above the water line), and some form of pivot for the board is usually provided, allowing the board to be raised and lowered by an attached cable, called the pennant, by manual effort or by a Windlass or winch.

Smaller boats are usually equipped with a dagger type of centerboard, which as the name implies is thrust up and down through the centerboard trunk which is open at the top. Other small boats have pivoting or rolling action centerboards, again operated through an open top trunk with pivoting points or rolling mechanism on the top of theopen centerboard trunk. These devices are either operated by had or through a system of blocks to provide additional operating power. An open top centerboard. trunk has many disadvantages; first, it is crude in appearance since the open top trunk and the operating portions of the centerboard cannot be neatly concealed. Second, the open top trunk with the centerboard protruding through is a dangerous trap for unwary fingers. Third, under certain conditions water is-splashed up through this open centerboard to the discomfort of passengers and crew. Fourth, in the event of a capsize it is almost impossible to bail out the righted hull without first closing the open-top centerboard trunk, which would otherwise allow water to enter the hull as fast as it is bailed out. Fifth, this open topped construction is structurally weak; when lateral pressure is transferred to the centerboard by the sails, only one side of the centerboard trunk reacts, necessitating cumbersome reinforcing members near the open top.

Larger and/or more finished boats have closed top centerboard trunks; this alone answers all of the objections raised above but it requires that the centerboard be pivoted on a bolt or other member referred to as a pivotpin, which is usually located near the forward end of the centerboard trunk, approximately midway between the bottom of the trunk and the top of the trunk cap. The board itself is raised and lowered by a cable attached somewhere aft of the pivot-point, operating upward through a hole in the centerboard cap and connected to a block or Winch. This operating cable is referred to as a pennant. In smaller boats, the pivoting member is somedifilfi l Patented Dec. 13, 1966 times a square shaft which allows the board to be raised or lowered by lever action, with the lever attached to the end or ends of the square pivoting pin that protrudes through the centerboard trunk sides, and having suitable bearing bushings therein.

The centerboard pivot-pin is the basic and uncorrectable weakness of this type of boat. There is no known method of permanently waterproofing the area where the pins project through the sides of the centerboard trunk. The centerboard trunk is narrow, ranging in internal width from A1 of an inch up. Since the pinhole is above the bottom of the boat by one-half of the breadth of the centerboard, it is almost impossible of access. Since the board must fit snug so as to react properly to the thrust of the sails, there is no room on the interior faces of the trunk for gaskets, washers, stuifing boxes or similar devices used on other openings below the water-line. Normal sailboat maintenance requires that centerboards be removed periodically for cleaning, re-painting and for removing growths and debris from the interior surfaces of the centerboard trunk. The pin must be removed from the centerboard trunk to allow the removal of the centerboard. Therefore, even if, through the use of exotic sealants, a boat manages to leave the factory in a fairly watertight condition, this seal is broken the first time the board is removed; and since a thorough technical knowledge of epoxy or other sealans is usually beyond the ken of the average boat owner or servicing mechanic, it is usually returned to the water in a leaking condition. This is because the water-proofing can only be applied to the inboard faces of the trunk, which can be compared to painting the inside of a basement wall to prevent leaks. Water creeps in between the pin and trunk walls, saturating the trunk material and finding'its way through defects in wood or natural openings in fiberglass layers to areas remote from the pin.

When under way and under sail, a strain is applied to the trunk walls by the lever action of the centerboard reacting against the water due to the sail-pressure, which in turn induces movement or flexing of the trunk walls in the area of the pin, further aggravating the tendency to leak.

This invention overcomes all of the disadvantages mentioned above, by the simple procedure of providing for'a fixed sealed pin in the original construction which can be made permanently waterproof because it is never removed. This invention shows two methods of attaching centerboards to fixed pins, one with a pin in the upper half of the trunk and the other with a pin through the trunk just above the inner hull surface. In the case of fiberglass boats, this permanent pin can be cast into the hull construction itself; or, an appropriately located hole can be drilled through the construction after removal from the construction forms, and after insertion of a proper pin, the entire area can be made water-proof through the use of epoxy sealants and additional layers of fiberglass over the protruding ends of the fixed pin. Similar procedures can be used in the case of wood or metal construction. Since the pin never has to be removed, it can be welded into place in the case of metal boats, or, in the case of wooden boats, epoxy or polysulphide sealants can be used at the factory to insure a permanent water-tight installation.

It is accordingly a principal object of the present invention to provide a centerboard (or lee board) construction which overcomes all of the known disadvantages of previous arrangements of this type. Specifically, the invention provides a centerboard system which is adaptable either to open-top trunks or to closed trunks (which often form part of a seat, table or bunk support) and which allows the board to be removed very easily from below,

without any risk of leakage through the pivot pin region, and without any danger of losing the board accidentally as can happen with various prior constructions when the boat is moved backwards while the board is stuck in mud or the like. Even when my new centerboard is in the up position, it cannot be removed unless the pennant is slack, as will appear below, so that its loss by accident is entirely prevented.

Briefly, the above and other objects and advantages of the new construction are attained by an arrangement in which the pivot pin is permanently fixed in the hull of the boat, specifically in the side walls of the trunk, so that removal of the board from the pivot does not entail removal of the pin, and it can be permanently sealed in place in water-tight fashion as an incident of the construction of the hull. The portion of the centerboard which pivotally coacts with the pin is so constructed that the desired pivoting motion is obtained without danger of loss of the board by accident in any conditions of operation, yet without interfering with its ready removal, from below, when this is necessary. Also, the construction ensures that when the board is in its upper or raised position, there are no projections from the underside of the hull, to be broken when the boat is on a marine railway or trailer, or when careened on a beach.

The characteristic features of the invention, and certain preferred ways of practicing it, are described in more detail below, in connection with the specific embodiments illustrated in the accompanying drawings, in which:

FIG. 1 is a vertical section view taken through the centerboard trunk of a typical boat hull, the centerboard being shown in solid lines and in side elevation.

FIG. 2 is a vertical sectional view taken along line 22 of FIG. 1.

FIG. 3 is an enlarged detail side view of the pivot region of FIG. 1, with the pivot pin itself shown in section.

FIG. 4 is a view looking toward the bottom of the pivot pin block of FIG. 4.

FIG. 5 is a view similar to FIG. 1 of a modified construction of the parts.

FIG. 6 is a vertical sectional view taken along line 6-6 of FIG. 5.

FIG. 7 is an enlarged section, looking in the same direction as FIG. 5, of a modification thereof.

For purposes of illustration, I have chosen to show the invention as applied to a hull of glass fiber construction, but it will be understood that it is equally applicable to other materials as well. The centerboard itself, in the case of a glass fiber hull, would normally be of such material, but this is not an essential requirement. Depending upon the size of the vessel and other factors, the centerboard may be of solid construction (wood, or plate or cast metal), or it may be largely hollow, and in that case loaded with metal shot, lead or the like as is familiar to those skilled in boat construction.

In FIG. 1, a portion of the bottom of the hull is indicated by numeral 10, and upstanding therefrom, in the interior of the hull, is the usual centerboard trunk 12, here shown as having a closed top except for an opening at 14 to allow passage of the centerboard pennant 16 as from a winch 18 to the upper edge of the centenboard 20. At the bottoms of the side walls 22 and 24 of the trunk 12, a fixed pivot pin 26 is provided, the same being integrally cast in place, preferably during the construction of the hull, as by being embedded in the glass fiber and resin material of the trunk walls, and/ or closed off by overlayed resin-impregnated layers as at numeral 27 before curing, or otherwise passed in a permanent, water-tight manner through holes formed at the bottom of the trunks side walls preferably at the level of the inner surface of the bottom of'the hull, as best shown in FIG. 2. This placement of the pivot pin, which is preferably of brass, stainless steel or other in-corrodible metal, allows the major stress due to the weight of the centerboard to be carried by the hull bottom itself, rather than by the side walls of the trunk.

As indicated by dotted lines in FIG. 1, the centerboard can be dropped the maximum amount corresponding to degrees from its upper or full line position, by paying out the pennant 16; in practice, it would be dropped to some intermediate angle depending upon sailing conditions and the judgment of the user. To permit this pivoting action, the forward upper corner of the board is rounded as at 28 on a circular are centered on the axis of pin 26, and if the board is a close lengthwise fit within the trunk, the rearward edge is rounder or chamfered as at 30 about the same axis. The height of the board is preferably equal to or slightly less than the clear height of the trunk, so that no part of the board projects beneath the bottom of the hull when the board is raised.

The connection between the board 20 and the pivot pin 26 is by means of a removable pivot block 32, best shown in FIGS. 3 and 4. This block fits within a rectangular notch or mortise in the lower edge of the board, the notch being just sulficiently longer than the block to allow it to be tipped downward out of the notch when its fastening screws 34 have been removed. The lower edge of the block 32 is flush with the bottom of the board 20 (and hence with the bottom of the hull) so that there are no downward projections to be struck or to interfere with the proper support of the hull on a carrier or the like, or when the boat is beached or is grounded. The block 32 may be made of wood, marine bronze, stainless steel or the like, but I prefer to employ Delrin (an acetal resin) which simplifies the manufacture of the blocks in quantity.

It will be observed, in FIG. 3, that the rearward edge of the block 32 has a rearwardly-opening semicylindrical slot or groove 36, sized to fit snugly about the fixed pivot pin 26. Actually, the slot 36 is not truly semicircular, but has a semicylindrical bottom of pin radius, being recessed into the body of the block to a greater depth than the radius of the pin, the mouth of the slot being inclined downwardly at an angle of about 10 degrees, as indicated in FIG. 3, to assure seating of .the pin against the bearing block by gravity. Moreover, the upper rear corner of the block 32 is rounded about the pin axis, as at 38, so that the block can be swung downwardly about the pin, as indicated at arrow A in FIG. 3, when screws 34 are removed, to allow the block to be rotated on the pin until it can be slid out lengthwise from the notch or recess in the centerboard. To permit this rotary motion, the lower rear corner of the block 32 is chamfered at an angle of about 24 degrees (indicated at 40) to avoid binding against the after end of the notch.

It is obvious that the rounding at 38 can be obviated if there is a slight clearance between the top of .the centerboard and the underside of the top of the trunk 12, as indicated at 42 in FIG. 1, so that the board can be raised slightly when the upper left corner of the block strikes the top of the recess from which it is being withdrawn.

The centerboard operation will be clear from what has already been said. When the board is lowered by paying out pennant 16, and the boat is under way, the board can tilt rearwardly in case the bottom or other obstruction is encountered, but it cannot in any case drop free of the trunk, because the pivot pin is surrounded by the board and pivot block 32 acting in concert. This secure fastening is retained when the board is raised to its upper position also. When it is necessary to remove the centerboard, this is easily done from beneath the boat, by raising the centerboard and withdrawing the fastening screws 34 (which may be stainless'steel screws of the selftapping type for glass fiber constructions, or wood screws for wooden boards or machine screws for metal boards) to allow the block 32 to be tipped down and slid out of its recess. Even now, however, the centerboard will not fall out, as the fixed pivot pin will continue to support it. The board is now rotated downward out of the trunk to an angle such that it may be moved toward the stern of the boat (to the left in FIG. 1) so as to clear the pivot pin and thence be lowered free of the boat, and the pennant disconnected. Replacement @merely requires the reversal of these operations, which is far different than the two-man operation heretofore necessary wherein one man must be in the hull directing the vertical and horizontal moveme it of the board by a second hand, in order to align board and trunk holes for pin insertion.

It will be observed that the block 32 can be produced in different thicknesses to accommodate boards of the same variations, and in fact can be extruded or machined in extended lengths with the profile shown in FIG. 3 and then cut or sawed to size to minimize the inventory of parts. In a typical size, for a centerboard of thickness, the block 32 may be recessed into the board of an inch, and may be about 2 inches long. In such a typical case, a pin diameter of /8" is adequate. It is to be noted that the screws 34 do not support the weight of the centerboard, but merely secure the block 32 in place; the Weight of the board when down is transferred to the bearing block at surface 43 and entirely carried by the pin 26 which, as noted, is effectively an integral part of the centerboard trunk or the hull. It will also be noted that the material of block 32 is always strained in compression, regardless of the angle assumed by the centerboard.

A modified form of the invention is shown in FIGS. 5 and 6, and in which form the fixed or integral pivotal pin is still a feature, although the removable pivot block has been eliminated. Like parts are designated by the same numerals as before, but the centerboard 20 is now formed with a right-angled slot 4-4, having a portion 46 which (when the board is raised, as shown in solid lines) is vertical, and a portion 48 which is horizontal and extends forwardly from the portion 46. At its forward end, this horizontal slot portion 48 is terminated by a half-cylindrical bearing 5d of tough plastic cemented or mechanically attached to the material of the centerboard. As before, the pivot pin 26 is sealed integrally and immovably in the material forming the walls of the centerboard trunk. Layers 27 again designate an applied form of waterproofing permanently applied to the area during the construction of the hull.

In this modification, the length of the centerboard 20' is chosen sufficiently shorter than the length of the trunk space, to allow a space 52 so that, if the board is purposely moved to the forward end of the space, the board can drop free of pin 26 via slot portion 46. To prevent this from happening during sailing, the pennant 16 is connected to the board at such a point that its tension, induced by the weight of the board, pulls the board toward the stern (or to the left, as shown in FIG. 5). Even if the board 20' should be partly lowered (as shown in dash lines), and the boat should be backed while the board is touching bottom, the board could not move forward relative to pin 26 (to allow the pin to reach the vertical slot portion 46), because the lip 54 would be engaged behind the pin. The centerboard, when partially lowered, cannot ride up the inclined plane formed by slot portion 48, and become detached, because the centerboard cap or top acts as a stop for the radial end of the board 28. However, when removal of the board is desired, it is held in its upper position, as shown, from beneath the boat, there being sufficient slack in the pennant to allow the board to he slid forward, the slot portion 46 ultimately allowing the board to drop away from the pivot pin. To allow space for the pennant to move forward with the centerboard during this operation, a housing at may be formed atop the trunk, shaped as shown to provide space allowing the ennant to move to the forwardmost position indicated at 63.

To facilitate this motion of the board, the pennant may, as shown in FIG. 7, be secured at the bottom of a notch in the upper edge of the board 20'', angled rearwardly as at 56 to allow this sliding motion, and having its other margin preferably curved (and optionally grooved as at 58) to guide the pennant during ordinary raising and lowering operations. As suggested by the dash lines at 64- in FIG. 7, the pennant may also be passed 'reely through a hole in the top of the board if the board is hollow in this region, and secured to the lower edge of the board by swaging in a tapered hole or by other convenient fastening means. It will be noted that, as before, the forward and upper corner of the board 22 is rounded at 28, which permits the downward swing of the board only as long as the pin is at the closed end of slot portion 48.

While I have described my invention in considerable detail and in connection with a variety of embodiments, so as to enable those skilled in the art to understand and to practice the same, I do not wish the invention to be limited to the details thus given, except as may be required by the scope of the appended claims.

What is claimed is:

I. A centerboard construction for boats, including a pivot pin fixedly sealed in an open-bottom centerboard trunk, said pin being disposed athwart said trunk near its connection with the hull of the boat and forward of the lengthwise center of said trunk; said centerboard being arcuate at its forward corner with an arc center at the pin axis; said pin passing within a downwardly open recess in the lower edge of said centerboard and substantially in contact with one vertical wall of said recess; an edge-notched bearing block substantially filling said recess with the margins of its edge notch substantially encompassing said pin about its region away from said wall of said recess, and fastener means for removably securing said bearing block in said recess, and for thereby securing the centerboard to the pivot pin and to the boat.

2. A centerboard construction for boats, in accordance with claim 1, in which said fastener means comprises at least one screw passing vertically through said bearing block and into the material of said centerboard.

3. A. centerboard construction for boats, in accordance with claim l, in which said bearing block is chamfered at its lower corner adjacent its edge notch, to facilitate swinging removal thereof.

References Cited by the Examiner UNITED STATES PATENTS 11/1867 Corbett 1l4l32 2/1884 Center 1l4132

Claims (1)

1. A CENTERBOARD CONSTRUCTION FOR BOATS, INCLUDING A PIVOT PIN FIXEDLY SEALED IN AN OPEN-BOTTOM CENTERBOARD TRUNK, SAID PIN BEING DISPOSED ATHWART SAID TRUNK NEAR ITS CONNECTION WITH THE HULL OF THE BOAT AND FORWARD OF THE LENGTH WISE CENTER OF SAID TRUNK; SAID CENTERBOARD BEING ARCUATE AT ITS FORWARD CORNER WITH AN ARC CENTER AT THE PIN AXIS; SAID PIN PASSING WITHIN A DOWNWARDLY OPEN RECESS IN THE LOWER EDGE OF SAID CENTERBOARD AND SUBSTANTIALLY IN CONTACT WITH ONE VERTICAL WALL OF SAID RECESS; AN EDGE-NOTCHED BEARING BLOCK SUBSTANTIALLY FILLING SAID RECESS WITH THE MARGINS OF ITS EDGE NOTCH SUBSTANTIALLY ENCOMPASSING SAID PIN ABOUT ITS REGION AWAY FROM SAID WALL OF SAID RECESS, AND FASTENER MEANS FOR REMOVABLY SECURING SAID BEARING BLOCK IN SAID RECESS, AND FOR THERE-

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