Patent Publication Number: US-3879779-A

Title: Portable crossbar for boat use

Description:
Uite States Patent 1 Jewett [451 Apr. 29, 1975 PORTABLE CROSSBAR FOR BOAT USE [22] Filed: Mar. 15, 1974 [211 Appl. No.: 451,563  
  Related US. Application Data [62] Division of Ser. No. 383,379, July 27, 1973, Pat. No.  
 [52] US. Cl 9/1 R [51] Int. Cl. B63c 13/00 [58] Field of Search 9/1 R, 2 R, 2 A, 2 C, 6, 9/6.5,11A,1l R; 115/21, 24.1, 24,5; 416/69-74 [56] References Cited UNITED STATES PATENTS 3,490,085 1/1970 Lewis 3,763,813 10/1973 Holtz 3,777,690 12/1973 Garber 9/1 R Primary Examiner-Duane A. Reger Assistant Examiner.lesus D. Sotelo 5 7 ABSTRACT Novel frontward-rowing crisscrossed boat-spanning angular oars having many unique advantages over usual oars are mounted on a portable crossbar an- L l-11m chored athwart the gunnels of a canoe, dinghy, skiff, or other rowable craft by thin, narrow bars rested lengthwise along the gunnels and bound to them by -waterproof adhesivetape applied to the subjacent faces of the sidewalls of the craft. Streamlined caromtype shields insure against intercontact between oars and boat structure or accessories in case of extremely abnormal or excessive submergence. The blades resemble usual blades in being slabshaped, yet unique buoyancy is achieved by cradling them in terminal portions of especially light-weight, rigid looms, plus use of low-density rigid cellular solid compositions or foams for their bodies; the buoyancy causing them to instantly and automatically rise to any pre-determined degree of above-water emergence when released from immersive rowing force. Also, the blades are instantly replaceable by mere extraction through mouths in their cradles, followed by in-feeding therethrough of blades of selectedly different densities or heights. In addition, the buoyancy of individual blades can be lessened to any desired extent, and their longtime resistance to rowing stresses concomitantly supplemented, simply by in-feeding of elongate, rigid metal bars in horizontal disposition into narrow, vertically disposed, sleeve-like pockets in the blades, through tape-scalable mouths located, e.g., in their upper edges.  
 4 Claims, 37 Drawing Figures FIG. 30.  
 FIG.33.  
 PORTABLE CROSSBAR FOR BOAT USE This is a division of application Ser. No. 383,379, filed 0727-73 now US. Pat. No. 3,857,356.  
  This application relates to a boat mounting for frontward-rowing crisscrossed angular oars having selfsurfacing, self-leveling blades, said mounting comprising a crossbar for affixation athwart the gunnels of a rowboat, canoe, kayak, skiff, or other rowable craft by waterproof adhesive-tape clamping, as well as to said oars and blades themselves, and to novel accessories for them, including streamlined, carom-type shields disposed on said mounting for innocuous preclusion of intercontact between oars and boat structure or accessories, in case of extremely abnormal or excessive submergence.  
  The overall object of the invention is to minimize or eliminate the shortcomings of prior-art oars and their mountings by providing novel oars and novel mountings for them, comprising the following innovations and advantages:  
  i. Frontwardness of rowing via use of said crisscrossed angular oars;  
  ii. Instant mountability and demountability of said oars on any ordinary rowable craft via use of said crossbar and its accessories;  
  iii. Provision for the relatively slight lifting force involved in manipulation of said oars to be exerted in close juxtaposition to the oarsmans chest, rather than with his arms outstretched;  
  iv. Generous spacingapart of the grip portions of the oars at all stages of their front-rear and reverse movement, in place of the conflicting or near-conflicting posture of said portions which characterizes prior-art oars generally;  
  v. Comfortable elevation of said grip portions throughout the return strokes as well as the power strokes of the oars, thereby avoiding the awkwardness incident to the exaggeratedly low posture of prior-art oars during their return strokes;  
  vi. Marked increase in efficiency of conversion of rowing energy by the oars, due to lessened obliquity of their blades at the beginning and end of power strokes of given lengths, as contrasted with the performance of prior-art oars in this regard;  
  vii. Marked decrease in breadth of water-area preemption by the oars, due to greater and more efficient lever use of the between-gunnels boat space, as contrasted with the smaller and far less efficient lever use of such space by prior-art oars;  
  viii. Instant, automatic self-surfacing or self-leveling of the oars to a pre-selected extend of above-water blade protrusion, following any interruption of immersive force upon them during use, as contrasted with the downwardly oblique total or near-total degree of blade submergence which characterizes usual prior-art blades following such interruption;  
  ix. Immediate pre-provision for a desired extent of such protrusion by simple insertion or extraction of weight rods (or weight-plus-stiffener rods) in horizontal disposition through mouths of thin, elongate pockets in the blades, as contrasted with the apparent absence of analogous such means in prior-art blades;  
  x. Unique visibility of the blades when their oars are floating freely at a distance from the boat or shore, due to upwardness of pitch achieved by pre-determined shift of the center of gravity of the oar in the direction of its handle; and  
  xi. Life-preserving utility of the oars due to the unique buoyancy of their blades and light-weight, advantageously hollow looms, particularly when extra large such blades have been installed in the loom cradles, with resultant in-effect reduction of the body density of a person clinging to them to a figure approximating, or even below the density of the water.  
  In the drawings, wherein all figures are to be understood as basically diagrammatic 0r schematic, and all expressions such as horizontal, upward, front, rear, etc. as being relative and approximate unless otherwise evident, to be more particularly described later on:  
  FIG. 1 is a rear elevation of the novel crossbar of the invention and associated accessories mounted across the gunnels of a 33-inch beam canoe and pivotally supporting a pair of the novel crisscrossed angular oars of the invention in position of use, with the oarsman facing away from the viewer, i.e., frontwardly;  
 FIG. 2 is a plan view of the oars of FIG. 1;  
  FIG. 3 is a rear elevation detail similar to the central lower portion of FIG. 1 except that the canoe has been replaced by a 48-inch beam rowboat, the oarsmans seat is more elevated, and an auxiliary relatively long, upwardly arched crossbar has been introduced as a support for the crossbar of FIG. 1;  
  FIG. 4 is an exploded side elevation detail depicting the process of adhesive-tape affixation of an elongatebar type clamp along a gunnel of the boat of FIG. 1, to thereby anchor its crossbar in position of use;  
  FIG. 5 is the same as FIG. 4 except that the anchoring has been completed;  
  FIG. 6 is a plan view detail of the parts shown in FIG. 5, plus the application of further adhesive tape crosswise of the clamp bar of FIGS. 5 and 4, and lengthwise of the crossbar, to thereby fix the transverse position of the crossbar relative to the gunnels; FIG. 7 is an end elevation detail showing the contingent functioning of either one of the carom-type arched shields appearing in FIG. 1;  
  FIG. 8 is a left-end perspective detail showing the same functioning from a different viewpoint;  
  FIG. 9 is a perspective detail on enlarged scale of the pivot-end portion and certain adjacent parts of a righthand-operated loom such as that of FIG. 1;  
  FIG. 10 is a side elevation of the oarsman and a central portion of the parts appearing in FIG. 1, except that the pivot-pin block in FIG. 10 is affixed to the upper surface of the crossbar rather than to its under surface;  
  FIG. 11 is a bottom perspective of an end portion of a partially broken-away crossbar such as that of FIG. 9, but with clamp bars such as the one appearing in FIGS. 4-6 affixed to the bottom of a pivot-pin block carried by it;  
  FIG. 12 is the same as FIG. 11 except that the anchoring has been completed;  
  FIG. 13 is a plan view detail of the oars and associated parts appearing in FIG. 1 except that the oars are in a far frontward posture and certain reserve or contingent guide structures have been added on the crossbar;  
  FIG. 14 couples a plan view detail with a side elevation detail of a prior-art structure relevant to a novel pivoting device contemplated for the oars of the invention;  
 FIG. is a plan view detail of said novel pivoting device;  
  FIG. 16 is a side elevation detail of the device of FIG. 15;  
  FIG. 17 is a side elevation detail, largely in crosssection, of a novel pivoting device alternative to that of FIGS. 15-16.  
  FIG. 18 is a plan view detail of the pivoting device of FIG. 17.  
  FIG. 19 is an exploded cross-sectional detail of a novel blade of the invention beingfed downwardly onto its cradle;  
  FIG. 20 is an exploded perspective detail-looking downward onthe parts depicted in FIG. 19;  
 - FIG. 21 is the same as FIG. 20 except after completion of the down-feeding of the blade onto its cradle and subsequent spiral-wrap adhesive-taping of the parts;  
  FIG. 22 is a side elevation detail of the right end of the oar of FIG. 1, with the locus of its throat&#34; indicated, said locus corresponding to that of the throat or inner blade end-to-loom connection of a usual oar;  
  FIG. 23 is a side elevation of a usual oar in position of use, except that its blade portion has been replaced by the novel cradle and buoyant blade of the invention, with the locus of its throat being depicted similarly to the locus of the throat in FIG. 22, i.e., as coinciding with the loom connection to the inner end of the blade; FIG. 24 is an exploded plan view detail depicting in its lower part the blade of FIG. 23, in its middle part an elongate closure strip for the blade mouth, and in its upper part a supply of adhesive tape for affixing said closure strip across the top surface of the blade;  
 . FIG. 25 is a group of three identical side elevation diagrams of a cradledblade-such as that of FIGS. 23-24, showing the degree of immersion thereof when unweighted (as in the top diagram), the increased immersion thereof due to insertion of a first stiffener-weight bar into its pocket (as in the middle diagram), and the further increased immersion thereof after insertion of a second stiffener-weight bar (as in the bottom &#39;dia- .gram  
  FIG. 26 is a side elevation detail depicting the oar of FIG. 23 floating freelyapart from the boat, the out-ofwater elevation of its blade end having been predetermined by loading its pivot, or handle, end to thereby shift its center of gravity handleward;  
 FIG. 27 is a side elevation detail showing the oars of both FIGS. 22 and 23 floating freely apart from the boat, with the aforesaid shifting of their centers of gravity sufficiently handleward to causethem to float uprightly, blade end upward, thereby increasing their above-water visibility beyond that depicted in FIG. 26;  
  FIG. 28 is a group of side elevation details depicting the hand and wrist positions of an oarsman feathering oneof the crisscrossed angular oars of the invention;  
 FIG. 29 is a group of side elevation details depicting modification of such oar to permit such style of feather- FIG. 30 is essentially a reproduction of the prior-art FIG. 5 of applicants US. Pat. NO. 3,324,490 showing the horizontally conflicting or near-conflicting handlemovement paths of conventional oars in use;  
  &#39;FIG. 31 is essentially a reproduction of FIG. 4 of app&#39;licants said patent showing the&#39;generously horizontally spaced non-conflicting handle-movement paths of the crisscrossed oars of the invention;  
  FIG. 32 is a side elevation diagram showing the downward-cramping of said conventional oars on the return stroke;  
  FIG. 33 is a side elevation diagram corresponding to FIG. 32 except showing the generous upward spacing for the return stroke in the case of the crisscrossed oars of the invention;  
  FIG. 34 is a plan view diagram depicting the powerstroke length between a 45-degree starting posture of a backward-rowing oar such as that of FIG. 23 and a 45-degree ending posture thereof;  
  FIG. 35 is a plan view diagram depicting the corresponding, but much greater power-stroke length and therefore rowing-energy-conversion superiority of a I frontward-rowing oar such as those of FIG. 1 (they being exactly alike) having the same overall length as the oar of FIG. 34;  
  FIG. 36 illustrates the relatively great breadth of water area pre-empted by a pair of usual oars; and  
 FIG. 37 illustrates the far less breadth of water area,  
 pre-empted by crisscrossed angular oars of the invention having the same individual overall length as that of the oars of FIG. 36; such lessening in breadth being regarded as of major significance in situations such as encountered during canoe trips on narrow rivers, streams, canals and the likein fact, wherever crowded boating conditions are apt to exist.  
 Referring to the drawings in detail:  
  In FIGS. 1-13 crossbar 1, supported on gunnels 2 and 3, is fixed in place by clamps 4 and 5 (5 being visible only in FIG. 13), which are anchored tightly to the boat by waterproof, pressure-sensitive adhesive tape 6, which itself is tightly adhered to both the inner and the outer surfaces (unnumbered) of the sidewalls of the boat. To insure against lateral displacement of the crossbar, adhesive tape 7 is tightly applied across the tops of clamps 4 and 5 plus adjacent portions of crossbar 1, as best seen in FIG. 6. Pivoteye poriton 8 of lefthand oar 9 is sleeved on oarlock pin 10, as shown in FIGS. 1, 3 and 13, said pin 10 being snugly secured by upright cylindrical oarlock socket 1 l (depicted by dash lines in FIG. 3 and understood in FIGS. 1 and 13), located at the center of pivot-pin block 12. Left-side counterparts of said members 8-12 will be readily apparent without numbering.  
  Bearing in mind that the assembly of parts in FIG. 1 is symmetrical, and that all numbered parts to the right side of center plane 13 of the boat (said center plane being the vertical plane which includes the geometrical longitudinal axis of the boat) have identical counterparts to the left side thereof, said counterparts are readily identifiable and, unless otherwise appears, will be left unnumbered. Since the right-hand oar thus is identical with left-hand oar 9, as appears in the FIG. 1 at-rest position, it can be seen that each of their looms slopes obliquely upward from its pivoteye portion to a point beyond sad center plane and then, as at angle point 14, turns toward and then continues on until it meets transverse vertical plane 15 (which includes the centers of oarlock pin 10 and its left-side counterpart) pivot-pin block 18 (shown in FIG. 8 optionally united to the upper surface of crossbar 1, instead of the under surface thereof as is pivot-pin block 12 in FIGS. 1, 3  
 and 13) in position to present a rearwardly-upwardly slanting portion 19 which will be glancingly contacted by loom portion 20 whenever the latter, due e.g. to stormy conditions, may, in the course of reciprocating suprajacently across said block during use, happen to descend to such an extremely low elevation as would occasion such contact.  
  In FIG. 9 downwardly-frontwardly curving leaf guide 21 is affixed to crossbar l in close proximity to and beneath reinforcing sleeve 22 of loom portion 23, to glancingly guide said sleeve 22 upwardly, in manner analogous to that of said portion 19 of shield 17, and thereby insure against any chance of downward contacting of gunnel 3 (FIGS. 1, 3 and 13) by the righthand oar. (An optional variation of the positioning of said guide 21 is shown in FIG. 13.)  
  A still further form of analogous guide is exemplified by surface 24 in FIGS. 1, 3 and 13 (25 in FIG. 9), whose purpose is to insure against the highly unlikely yet conceivable contingency of hooking interengagement between outer portions of the looms and end portions of the crossbar.  
  Details of blades 26 and blade cradles 27, formed by terminal portions of the looms themselves, will be set out below.  
  Since the center-to-center distance between the oarlock pins in FIG. 1 is 36 inches, FIGS. 11-12 have been addressed to the situation where the crossbar needs to be mounted on a boat having a 36-inch beam, in which case the presence of pivot-pin block 12 on the crossbar would preclude use of separate clamps such as 4 and 5 (FIGS. 4-6) for affixing the crossbar to the boat in precisely symmetrical relation thereto. Hence, corresponding clamps 28 and 29 are integrated to the bottom of the overlying pivot-pin block 12, thereby permitting tape-clamping of their outward portions to the gunnels in the same manner as depicted in FIGS. 4-6 and 13.  
  FIG. 14 represents applicants recollection of an oarlock on a l-Ians Klepper Corporation boat displayed at a Boat Show at the DC. Armory in Washington, DC, on February 23, 1972, which applicant did not then and has not since seen or heard described. In said figure, vertical oarlock socket 30 is pivotally mounted between bracket 31 and loom 32 so as to permit simultaneous rotative reciprocation of the loom 32 about vertical pivot pin 33, and up-down rotative reciprocation thereof about horizontal pivot pins 34 and 35.  
  While the structure of FIGS. -16 embody this same general principle, they apply to the terminal portion of a crisscrossed angular oar of the invention rather than to a conventional oar, and do not require the offsetting expedient shown in FIG. 14. In other words, said structures expand the width of the oar symmetrically rather than to one side only, besides permitting unlimited dimensioning and strength of the parts plus shifting of the oars center of gravity handleward, such shifting being essential to achievement of the unique upright-floating visibility of lost oars which is discussed below. Thus, oar end portion 36 is bifurcated to flank opposite faces 37 and 38 of pivot-pin block 39 and thereby provide for horizontal rotative movement about vertical pivot pin 40 either separately or concomitantly with up-down reciprocation about horizontal pivot pins 41 and 42, during use.  
  In FIGS. 17-18 the parts correspond to those appearing in FIG. 9 except that welding metal used in their visible. The spacing leeway between the nut 48 and the top of the pivot-eye piece 45, plus that between the front and rear bottom boundaries 49 and 50 of the eye, permits up-down reciprocation without need for horizontal pivot pins, i.e., via said leeway under the nut 48 at the top, and slight slippage of said boundaries 49 and 50 across the pivot-pin block 51 at the bottom. And the horizontal reciprocation about pivot pin 52 is similar to that depicted in FIG. 16.  
  In FIGS. 19-21 inverted peripheral trough 53 in the rigid foam (e.g., expanded polystyrene having a bulk density of, say, about 3 points per cu. ft.) ofv the blade 26 may be formed by in-place foaming in a complementarily configurated mold, or by searing with a complementarily dimensioned, heated round rod to appropriately convert the surface polymer into a tough, rigid skin, or, if desired, by purely mechanical means.  
  Because of the form-fit between the sides of the trough 53 and the converging upper surface of the tubular-loom cradle 27 on and against which it snugly rests, no displacement will normally occur during use, unless by water-induced upward floating of the blade. And this is insured against by water-proof, pressuresensitive adhesive-taping such as indicated in FIG. 21.  
  The significance of FIGS. 22 and 23 and the loci 54 of the throats appearing in them has already been pointed out, except for the matter of optimum extent of blade immersion. It has long been appreciated that substantial submergence of the upper edge of the blade during use tends to produce twists and twirls (Brit. 15,375 of 1913) so that an above-water posture of the entire length of said edge is desirable (U.S. Pat. No. 2,367,222, FIG. 8). But there has not been complete unanimity as to the optimum extent of such posture. Thus, page 127 of Aquatics Handbook by M.- A. Gabrielsen et al., Prentice-Hall, Inc., 1960, states: About two-thirds or three-fourths of the blade should enter the water; page 97 of Boating from Bow to Stern by .l. P. Kenealy, Dodd, Mead &amp; Co., 1966, advises that the blades should dip three-quarters submerged in the water; and page 54 of an article on How to Handle a Rowboat by F. Clark (Boating Journal, April-May, 1966, pages 50-55) advises: Dont dig in too deeply; seven-eighths of blade in water is enough. Of course, these statements were made in contemplation of usual oars and blades, not of the crisscrossed oars of the invention. Consequently, in view of the extremely light weight of the latter, it is not seen why above-water protrusion of more than one-eighth, one-fourth or onethird of their faces would be undesirable, unless on account of resultantly increased air or wind pressure during stroking or feathering, or why deeper immersion, if desired, might&#39;not be practiced, with extra-large slabshaped blades, to thereby achieve more powerful and therefore faster rowing.  
  In such case, the novel self-leveling action of a blade of the invention can readily be provided for by the expedient illustrated in FIGS. 24 and 25. In said figures, upwardly open mouth 55 of narrow, elongate pocket 56 of upright-in-use blade 26 seated in cradle 27 is disposed for reception of one or more weight, or stiffenerplus-weight, bars 57 into the pocket 56, so that it will rest lengthwise on the bottom 58 thereof. Of course, a shorter pocket and differently shaped weights could be used, but it is preferred to employ elongate weights (either singly or in multiples) comprising considerable vertical dimension, so as to thereby supplement the inherent rigidity of the blade and its skin and/or other facing against undue flexure in use. Such rigidity per se can be made very substantial merely by applying the sear treatment of the flat surfaces of the blade in manner such as mentioned in connection with FIGS. 19-21 above, or by in-place foam-molding methods well known to workers in that art. By way of illustration, it may be remarked that if the blade be inches in length and 1 inch wide (at the water level) a bar weighing one-half pound will produce about 1 inch of submergence, since the volume of displaced water will be 15 cu. in. and therefore have a weight of about one-half pound.  
  Sealing of the mouth 55 of the pocket 56 is accom plished by affixing closure element 59 with waterproof adhesive tape 60 applied across its top and down along each subjacent side surface of the blade.  
  In FIG. 26 oar 61 corresponds to a usual oar except for its novel blade cradle 27 and blade 26, and the fact that its center of gravity has been located sufficiently handleward for its tip 62 to be elevated entirely above the water level, thereby giving it improved visibility as compared with tips of floatable conventional oars when lost in the water. Preferably the elevation of the tip 62 will be such that an above-water vertical distance equal to at least one-half, five-fourths, twice or more the maximum thickness of the blade will underlie said elevation. Of course, as said handleward shifting of the center of gravity is increased, the counter-clockwise rotation of the blade will speed up until it reaches the optimum posture shown in FIG. 27.  
  Due to necessary (for strength) weight of the pivotcontacting portion 63 of the angular oar 9 in said figure, the free-floating posture of such oar and its tip 62a will generally be as depicted therein.  
  In applying said test, the tip of the oar is taken to be the point on the blade end farthest from the pivot, or handle, end.  
  In FIG. 28, A represents the posture 64 of oarsmans hand and wrist at the end of a power stroke with one of the novel oars 9 of the invention, B said posture during lifting and feathering of the oar, and C said posture at the conclusion thereof; while D represents said posture following frontward manipulation of the oar preparatory to a new power stroke, E said posture during lowering and de-feathering of the oar, and F said posture at the beginning of the new power stroke.  
  The optional structuring shown in FIG. 29 adapts the novel crisscrossed oars of the invention to feathering in the manner depicted by FIG. 28. Thus, an inner splice the lower wall 72 of this recess, and is blocked by it against rotational movement during the .F to A power stroke. At the end of the latter, however, the oarsman applies an outward force to said bladeward section 67, as indicated by the horizontal arrow in the top portion of FIG. 29 and, having thereby released the tooth from said engagement, feathers the bladeward section into the posture indicated by the dash lines at the lower right bottom of said top portion. Next, when the D position is reached, he feeds the tooth back into said recess 69 and thereupon rotates it into reengagement with said wall 72, for the start of a new power stroke -all as depicted by the arrows and dash lines in FIG. 29.  
  Endward displacement of the s lideable bladeward section 67 is precluded by the lug 73 on the splice tube 65, said lug being positioned to engage the left end 74 of the horizontal opening 75 in the bladeward section 67, in the event of excessive outward movement thereof during use.  
  The above explained significance of diagrammatic FIGS. 30-33 in respect to abundance of the available space for uncramped and comfortably elevated hand movements during manipulation of the crisscrossed oars of the invention, i.e., as contrasted with the restricted and cramped hand-movement space in the case of usual oars, is repeated here.  
  The overall length of each of the oars in FIGS. 34-37 is 5% feet. No numeralizing of their parts appears needed, in view of the general description already made of them hereinabove.  
  FIGS. 34 and 35 each shows an oar in position of use with its blade at a frontward 45-degree-angle strokestarting posture, as well as the same blade in a 45- degree-angle stroke-ending posture; the oar of FIG. 34 being a conventional (lever-of-the-first-kind) oar, while that of FIG. 35 is a crisscross angular (lever-ofthe-third-kind) oar of the invention. By leverof-thethird-kind, as used herein, is meant any lever wherein the locus of the effort is between the locus of the load and the locus of the fulcrum, as, e.g., in the case of a broom or a canoe paddle, the blade-pushed water being considered as the load for purposes of the lexicography of this application, even though some analysts (believed to be in the minority) have preferred to characterize the boat (via its oarlock socket or thole pin) as the load, and the blade-pushed water as the fulcrum; which, itmay be noted, would make an ordinary oar, as a matter of semantics, a lever of the second kind (analogous to a wheelbarrow) rather than a lever of the first kind as denominated herein. It is notable that the stroke length S in FIG. 34 is only 5% feet, while that in FIG. 35 is 7% feet (about 50 per cent greater).  
  FIGS. 36 and 37 each shows a pair of the same oars as respectively shown in FIGS. 34-35, but pivoted on the gunnels of a 36-inch-beam boat; the breadth of water area pre-emption P&#34; by the conventional pair (FIG. 36) being I 1 feet, as contrasted with the mere 8 feet of such pre-emption by the crisscrossed angular oars of the invention (FIG. 37).  
  Referring again to the crossbar of FIGS. 1-13, its novel tape-fastening makes it readily eligible for use (optionally with obvious variations) as a thwart-type support for any desired objects including, e.g., seating of passengers.  
  Particularly appropriate illustrations of suitable pressure-sensitive adhesive tapes for said fastening are exemplified, e.g., by Scotch (3M Company) Industrial Tape Nos. 890 or 870.  
  Should a particular tape happen to prove waterpermeable to more than a negligible extent, it could of course be protected by a thin overlay of rubber-type tape such as the tapes commonly available in hardware stores under the designation electrical tapes.  
  It may be remarked that preliminary application of a relatively thick double-stick tape to the top of the gunnels of a boat, before placing the clamp bars of FIGS. 4-6 on them, is an optional expedient.  
  When the crossbar of FIGS. l-l3 is used for the purposes directly contemplated in those figures, the affixation of the pivot-pin block may be by any desired means, e.g., gluing with waterproof epoxy-type glues and/or bolting. I  
  When the pin blocks are affixed to the upper surface of the crossbar, as in FIG. 12, and given suitable height, the crossbar becomes useful as a mounting for lever-ofthe-first-kind oars which may comprise oarlock sockets such e.g. as the one shown in FIG. 14, without difficulty arising from intercontact with the crossbar during the return stroke. In such case, the cramped-space inconveniences depicted in FIGS. 30-33 will be obviated. And in addition, lengthening of the crossbar will make available any desired outrigger loci for placement of the pivots of such oars.  
  As regards the tubular looms of the figures, the ends of course are closed against entry of water, as e.g. by rubber stoppers or rubber furniture tips of appropriate diameter.  
  The aluminum alloy known as 606l-T6WWT, in 1- inch CD. or /s-inch OD. and 0.065-inch wall thickness has been found satisfactory, particularly when its angles have been imparted by cold-bending so as to preserve the temper of the tubing.  
  Resistance to sea water is enhanced by anodizing; but alternatively, alloys of comparable strength and rigidity, together with extremely high inherent resistance to sea water, are understood to be presently available.  
  Said 6061 alloy is excellently suitable for the cradlesegment end of the oars of the invention, by virtue of its toughness and ruggedness, when such segment is used for pushing the craft from shore or for making pushing contact with the bottom of a stream or lake.  
  A unique advantage of making the subject oars exactly alike is that it enables a person seated oppositely to the oarsman to take over the rowing from him, without any shifting of position by either. Also, should any overstressing occur during use of the oars, i.e., such as would give rise to incipient distortion, mere switching of the oars would readily correct it via the wellknown phenomenon of work-hardening.  
  Blade-space, as used herein and in the appended claims, means the space enclosed within an imaginary flexible film wrapped tightly around all portions of the entire blade, inclusive of its cradle.  
  Should collapsibility of the subject oars be desired, that of course may be accomplished by segmentation in accordance with techniques well known in the art; or an internal splice tube analogous to tube 65 in FIG. 29 but caged in place, e.g., by bends in the segments of the loom to be joinable, may be employed, with such segments inter-united, e.g., by longitudinal laps of waterproof adhesive tape, such laps optionally being reenforced by circumferential laps in turn applied to them.  
 Strengthening tubular inserts can, of course, be used&#34; as desired, in any portions of the looms, e.g., within a portion such as the loom portion 23 appearing in FIG. 9.  
  In connection with the optional hollowness of the tubular looms, it will be noted that internal enforcement with rigid foam is available, as well as external re-enforcement with, e.g., fiberglass-resin compositions in accordance with U.S. Pat. No. 3,561,760 (col. 2).  
 As for hollow blades of the prior art, it may be remarked that if they spring a leak their buoyancy is gone; whereas with expanded polystyrene or polyurethane, e.g., abrasion or gouging of the same causes no such trouble, owing not only to the almost total water-impermeability thereof, but also to the relative simplicity of repairing the blade in such case.  
  Production of the tough, rigid skin contemplated for the water-engaging surfaces of the blade, as spoken of elsewhere herein, can be carried out by methods pointed out on page 169 of the Journal of Cellular Plastics, Vol. 6, No. 4 (July-Aug, 1970), in the course of an article entitled A New Generation of Structural Foam Polymers&#34; by R. L. Grieve et al. (Upjohn Co. Research Labs, North Haven, Conn.), wherein it is stated that The applications of integral skin foam molding for structual and decorative parts are unlimited And on page 167 (in the course of the same article) the statement appears that The integral skin foam process leads naturally to the concept of very stiff (high modulus) ingegrated parts. The outer surface and the reinforcing configuration may be achieved in a single molding, with stiffness of course enhanced by ribbing wherever possible.  
  The wide variety of cellular solids eligible for use in the bodies of the blades-particularly when internal structures embedded via pre-molding or pre-foaming processes are to be provided, e.g., structures such as the pockets in FIGS. 24-25 and the peripheral recesses of FIGS. 9 and l9-2l-will become evident on inspection of The Survey of Foamed Plastics appearing on pages 294-296 of The Modern Plastics Encyclopedia for 1965 which accompanied the issue of Modern Plastics (published by McGraw-l-Iill, Inc.) for Sept., 1964, as well, of course, as in the highly revealing U.S. patent literature on the subject.  
  Supplementing the introductory statement of advantages of the invention appearing hereinabove, it may be remarked that by relieving oarsmen of having to keep looking over their shoulders to see where they are going, the new oars are uniquely suited to general use by all persons preferring rowing to motor power, whether for exercise, quietness, economy, ecology, or otherwise, and even more so to special use by all persons employing rowboats for such purposes as sneak approaches in hunting, fishing, exploring, and picturetaking; tender service over shallow, swampy, obstruction-ridden waters; activities potentially involving rescue or other emergency operations; rental to noveltyseekers at amusement part or playground lakes and ponds; and physical therapy at recreation, convalescent and rehabilitation centers. Also, in reduced sizes on small, easily maneuverable boats, the new oars open up an unlimited range of water sports, games, contests, and group exercises hitherto automatically ruled out by risks of collision and other mishaps inherent in the centuries-old backward-facing rowing done with usual oars, but eliminated by the frontward-facing rowing done with the new oars.  
 What is claimed is:  
  1. An assembly for supplying a removable support bar for objects carried by a rowboat, canoe, kayak, skiff or like craft, said assembly comprising:  
 A said support bar having symmetrically spacedapart, flat under surfaces for placement athwart the gunnels of such craft,  
 2. In combination:  
 A boat having a pair of gunnels,  
 A crossbar resting athwart said gunnels, and  
 A pair of elongate rigid clamp bars having upwardly recessed bottom surfaces and being respectively contoured for lengthwise placement along said gunnels with said upwardly recessed surfaces in overlying contact with portions of said crossbar at loci directly suprajacent to said gunnels,  
 Frontward and rearward portions of each said clamp bar being secured on said gunnels by strips of fastening tape, one endward portion of each such strip being adhesively attached to an outer wall surface of said boat subjacently to a said clamp bar, and the oppositely endward portion of such strip being adhesively attached to an inner wall surface of said boat subjacently to the same clamp bar,  
 Said crossbar thereby serving as a potential support for objects carried by said boat.  
 3. The combination of claim 2, wherein:  
 Each of said pair of rigid clamp bars is integral with said crossbar.  
 4. The combination of claim 2, wherein:  
 Said fastening tape comprises pressure-sensitive adhesive.  
  UNITED STATES PATENT ewiee QE&#39;HMQAT i C&#39;EQH PATENT NO. 3 879 779 DATED April 29 19 7S r vE 0 (5) Harold A Jewett it is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:  
 Col. 1]., line 6, after &#34;craft,&#34; insert:  
  &#34;A pair of flat, elongate rigid clamp bars, each of said clamp bars having endward portions defining a recess in its under surface,  
  Said recess being dimensioned for invertedly seating crosswise of and removably on said support bar concomitantly with seating of said endward portions removably on and lengthwise along the gunnels of such craft,  
  A supply of waterproof, pressure-sensitive adhesive tape for binding said terminal portions tightly to said gunnels by adhering said tape both thereto and to outer and inner subjacent surfaces of the respective side walls of the craft.  
 Signed and sealed this 15th day of July 1975.,  
 (SEAL) Attest 2 C. MARSHALL DANN Commissioner of Patents and Trademarks RUTH C u MASON Attesting Officer