US2363668A

US2363668A - Otter board

Info

Publication number: US2363668A
Application number: US446320A
Authority: US
Inventors: Groen Donald Julius
Original assignee: Individual
Current assignee: Individual
Priority date: 1941-07-01
Filing date: 1942-06-08
Publication date: 1944-11-28
Anticipated expiration: 1961-11-28

Description

D. J. GROEN Nov. 28; 1944.

OTTERBOARD Filed June 8, 1942 3 Sheets-Sheet l f..].1 UNITED 1 STATES PATENT Patented Nov. 28, 1944 OFFICE orTEnBoAnD r Donald Julius Groen, Surbiton, England Application June 8, 1942, 'SerialNo.446,320

In Great Britain July 1, 1941 I 4Claims. (01.114435) This invention relates to improvements in otterboards and is particularly concerned with I such devices for use in marine mine sweeping.

operations. An otterboard is used in side sweeping to extend a cable outwardly from the side of a ship and means are provided such as a float to prevent the cable from sinking. The tendency for the otterboard to move away from the side is due to the angle at which it is set to'the direction of travel but this angle of incidence creates a drag which retards forward movement and if 1 this angle is decreased to reduce'the dragthe force urging the board away from the ship is also reduced. It may be mentioned that on the magnitude of that force depends the length of cable which may be used as well as the position at which the board will ride with respect to the ship towing it, and hence the area which may be swept. I

Now, an object of the present invention is to provide a more eflicient otterboard which rides at a desirably small angle of incidence so that there is reduced drag and yetgives an increased forcetending to move it away from the ship, so

used therewith, or the board will ride at a more favourable position. I

According to the present invention, the otterboard, which is preferably of streamline, aerofoil, curved or similar form in section seen in plan, has an overall height which is greater than its length. I I To cause the board to ride at the desired small angle of incidence, the towing cable may be branched into, or attached to, three, four or more cables or chains which are secured to the board 1 on one side thereof, either directly or through members projecting from the board, at points.

near the edges thereof, for example, at three points triangularly arranged, in the four corners of a rectangular board, or otherwise as may be 1 convenient.

- Further to ensure that the otterboard will ride upright as desired, the lower end thereof may be weighted. I

The oneend of the otterboard maybe longer than the other providing always that the height be greater and. preferably substantially greater than the length but it is further preferred that creased towards the top and bottom either by curving r inclining either the leading or the trailingedge or by a combination of these possibilities.

Figure 3 is a plan view looking down on Figure 1. i a l I Figures 4, 5 and 6 are views similar to Figures 1 to 3 of the same form of otterboard but having different means for the attachment of ,the towthat either longer or more robust cables may be 2.

ing cable. 7 v

Figure 7 is a side elevation of a modified form of otterboard, and

FigureB isa plan view of the otterboard of Figure7. v Referring now to the said drawings throughout which like parts bear like reference: numerals and with particular reference to Figures l to 3, the otterboard I, seen in elevation, has the shape of an elongated rectangular parallelogram,

whilst in section as may be seen from Figure 3 it is of aerofoil or streamline shape. The exact construction of the board is not material to the present invention as it may be made of wood, or wood and metal, or entirely of metal. The trailing or narrow edge is conveniently reinforced or protected by a metal or rerlay or reinforcement 2 which extends down onboth sides. This edge is" also protected by the provision of two or more projections 3 which serve as feet when the board the board be symmetrically shaped on opposite sides of a line bisecting its major axis. In the latter casethe length of the board may be deis not in use and is standing ona ship's deck or other surface. The lower, portion. of the board is desirably similarly protected by a me tallic overlay or reinforcement 4 which may also be arranged to give additional weight to that end of the board. The reinforcement 4 may be arranged to carry an additional weightingportion 5 arranged forwardly of the major axis so that most weight is in the region of the forward lower corner of the board. e

On the one side of the board which is the substantially fiat side in the form of board, illustrated, there is provided near each corner of the board a projecting element 6 which is conveniently given a streamline form as may be seen in Figure 1 which element has an aperture near its outer end within which is arranged a ring 1 to which may be connected a length of chain or cable 8 in any convenient manner, for example, by means of a holding device 9. The four chains or cables 8 are all connected to a ring In to which the towing cable (not shown) may be attached either directly or through the medium of a short length of chain ll conveniently by means of a clamping device [2. The lengths of the chains or cables 8 may all be substan- \tially the same although desirably the two chains or cables. nearer the forward rounded edge are slightlyshorter than the two chains or cables curves along the portion 23 t0 the apex and is similarly curved along the portion 24 to the base. The rear edge 25 is parallel to the corresponding portion of the front edge 22 and continues as

curved portions

26, 21 which match the curvature of the corresponding portions 23, 24 of the front edge but in opposite sense. The forward rounded portion of the board is protected by a metal reinforcement 28 whilst the rearward portion is similarly protected by a metal reinforcement 29. The lower part of theboard is weighted by a weight 3|] which is shaped to conform to v the configuration of the board and an extra tom edges. In this way, the otterboard will always tend to ride with its rounded edge foremost in an upright position when, as may be clearly seen from Figure 1 of the drawings,-its height preferably exceeds its length. The ratio of the height to the length may vary over wide limits but desirably the ratio is of the order of 2.3:1-to 5:1.

In Figures 4, 5 and 6, is illustrated an otterboard identical with that illustrated in Figures 1 1 to 3 but having different means for connectthrough the limbs of a bifurcated connecting ele-' ment i! to which the towingcable (not shown) may be attached. In this case also thelengths weight3| is provided i a forward position at on the plane side of the board and the branched ends of the towing cable may be attach-ed directly to the rings 32 or indirectly attached responding to the cables or chains 8 androds of the rods ti l are substantially the same, al- I though the. front pair are preferably shorter apart from detail variations in length so that the eyes in the ends thereof will stack to be engaged by the bolt I6 as may be seen in Figure-5 and to position the connecting element l1 nearer to the front edge than the rear edge at a point 1 substantially equidistantly spaced from top and bottom edges. When not in use, the connecting element I! may be removed .when the rods, I4 may be collapsed to lie against the board.

Whilst in both of the foregoing examples the towing cable is indirectly connected to the board, in the one case through chains or cables 8 and projecting element 6 and in the. other case through rods M, the towing cable itself may be branched and directly. attached to the board or to rings'attached thereto. The points of connection are conveniently situated as far as possible from one another but the invention is not limited to. four connection points since there may be three points of connection triangularly arranged as is later described with reference to" a modified form of otterboard shown in Fig ures '7 and 8, or there may be more than four connection points say five in number, v as may be most convenient having regard to the size of the board or the particular connection employed.

' The otterboard shown in Figures 7 and 8 may be of similar general construction to the otterboards already described but isdifferentiatedin- [4 already described, the arrangement in any case desirably being such that the point of divergence of the branched ends of the towing cable or of the auxiliary attachment means-is situated forwardly along a line which bisects the major axis of the board. As in the previous example, the reinforcement 29 is provided with feet 3.

It will be appreciated from the foregoing examples that the boardis desirably of symmetrical shape on opposite sides but its shapes are not limited to the examples above given since the forward edge may incline away from the mid point or be curved away from that point whilst the rear edge may be straight throughout its length or vice versa and although, such anarrangement is preferred it is not essential since in some cases the length of the board may be determined by the respective lengths of the cable branches or the indirect attachment means and the arrangement is such that the board is arranged to ride, at a minimum practical angle of,

incidence; I v i ,7

By causing the otterboard to ride at a lesser angle of incidence than is now customary, the drag set up by the device is reduced, but this does not reduce the forcetending to move the device away from the ship since, due to the fact that its height exceeds its length and its preferred horizontal sectional shape that .force is increased or in other words the board has. a greaterlift. As th drag is reduced andthe said force isin: creased, the otterboard may ride at a more favourable position in relation to the ship towing it, a longer towingcable maybeused' so. that during mine sweeping operations a wider-field. may be swept, a more robust cable may be used, 'the towing operation carried outwitha lesser expenditureof energy, or a combinationaof these possibilities to achieve greater'efiiciencyi- 1. An otterboard'of aerofoil section which has an overall height whichis greater than itslength; at least three projecting 'elementsof streameline form on one side ofsaid board, to the ends of which. elements are connectedthe endsofzele ments connected to a towing cable, means for weighting the lower portion of the board and additional weighting means for weighting the lower forward portion of the board.

2. An otterboard of aerofoil section which has an overall height which is greater than its length,

at leastthree projecting elements of streamline form on one side of said board, chains connected to the ends of said elements, means for connecting the free ends of-said chains and for connecting them to a towing cable, and means for weighting the lower portion of the board.

3. An otterboard of aerofoil section which has an overall height which is greater than its average length which is of diminishing extent in both directions away from the middle of the board,

connecting means leading from at least three points on the one side of said board, a towing connector common to all said connecting means,

to which elements are attached to receive the connection of a towing cable, anda plurality of weighting means at the lower portion of the board, with, one of said weighting means wholly forward of the major axis of the board.

DONALD JULIUS GROEN,