US1786451A - Oar blade or the like - Google Patents

Description

Dec. 30, 193.0. J. L. RIBARD 1,786,451

OAR BLADE OR THE LIKE Filed June 1, 1928 my W 4770/091 Patented Dec. 38, 1930 UNITED STATES JEAN LOUIS RIBARD, F PARIS, FRANCE OAR BLADE OR THE LIKE Application filed June 1, 1928, Serial No. 282,203, and in France June 10, 1927.

The present invention has for its object 1 an improvement in oar blades or like surfaces which are subjected to the thrust of a fluid,

and the improvement consisting in forming 5 in an oar blade or the like holes having the shape of a truncated cone of which the larger base is placed on the side where the fluid exerts its thrust.

I have discovered that the presence of these apertures, far from diminishing, as might be thought, the total pressure acting upon the surface, has on the contrary, the result of increasing this pressure. It is probable that this effect is due to the fact that the fluid streams, meeting the lateral surface of the truncated cone, are engulfed therein and can no longer flow away except by way of a restricted orifice through which they are wire-drawn. The deviation of the streams towards the edges of the surface, would thus be reduced to a large extent, leading to a reduction of the eddies and losses resulting therefrom.

In the accompanying drawings, Figure 1 represents a front view of an oar blade, Figure 2 a section along the line 22 of Figure l and Figure 3 an analogous section of a modification.

There is formed upon the forward or active wall of the blade a (taking care to keep away from the rather fragile edges) a series of truncated conical holes 6. These holes, ar-

ranged in the form of a quincunx in order to avoid weakening too far the fibres of the wood, have on an average a diameter of one centimetre at the base and of about one millimetre at the apex. The number of these holes must be as large as possible and has no limit other than the strength of the blade to resist fracture.

Tests made with racing oars of which the blade comprised 36 of these holes have shown that there was obtained an extremely clear increase of speed as compared with that obtained with ordinary racing oars.

In the case of oars adapted to be utilized on both faces, it is advisable to give to the holes the shape of two truncated cones c opposed at their smaller bases, as shown in Figure 3.

This arrangement can moreover be utilized even in the case where the wall is not called upon to receive the thrust of the fluid upon one or the other of its faces, the double truncated cone then acting in the manner of a convergent divergent orifice.

The dimensions given above are, of course, not in any way limitative, but may vary according to the particular application. The same applies as regards the shape of the right angle section of the truncated cones.

My invention is applicable to other elements or surfaces which are subjected to the thrust of a fluid.

What I claim is:

An oar blade having longitudinal rows of openings therein, the corresponding openings in relatively adjacent rows being relatively longitudinally offset, and the said openings each having the form of two truncated cones meeting at their smaller ends.

In testimony whereof I have signed my name to this specification.

JEAN LOUIS RIBARD.

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