The Application of Photogrammetry in the Study of the Effects of Sailboard Fin Flexibility

Abstract

In recent years, the reduction of aero- or hydrodynamic drag on fins and finite wings by passive means has been a popular research topic. Among many drag reduction devices being investigated, the flexible tip is of particular interest to non-aerospace application. In the wind-surfing industry, slender fins with flexible tips have shown high performance recently. The development of sailboard fins, however, has been on a trial-and-error basis and the physics behind the improved performance has not been fully understood, although some suggest that the flexible tip helps to reduce the induced drag. At Exeter University a series of comparative studies has thus been carried out in order to help fully understand the effects of tip flexibility on performance. This paper presents the experiments which were aimed at observing and measuring the bending deflection and twist of the fins of various degrees of reinforcement due to fluid dynamic forces. Fin deformation was measured by means of photogrammetry which is a low-cost non-interfering technique suited for steady displacement measurement.

Keywords

photogrammetry sailboard fin flexibility drag reduction bending deflection twist fluid dynamic forces fin deformation

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References

Swales

P. D.

Wright

A. J.

McGregor

R. C.

Rothblum

R. S.

The mechanisms of ventilation inception of surface piercing foils. J. Mech. Engng Sci., 1974, 16(1), 18]–24.

Burkett

C. W.

Reductions in induced drag by the use of aft swept wing tips. Aeronaut. J., December 1989, 93(930), 400–405.

Dam

C. P.

Vijgen

P. M. H. W.

Holmes

B. J.

Windtunnel investigation on the effect of the crescent planform shape on drag. AIAA–90–0300, 1990.

Lam

Maull

D. J.

Induced drag of a crescent wing planform. J. Aircraft, 1993, 30(5), 594–602.

Broers

C. A. M.

Chiu

T. W.

Pourzanjani

M. M. A.

Buckingham

D. J.

Effects of fin geometry and surface finish on sailboard performance and manoeuvrability. In Manoeuvring and control of marine craft (Ed. Wilson

P. A.

), 1992, pp. 275–289 (Computational Mechanics Publications).

Chiu

T. W.

Bersselaar

Broers

C. A. M.

Buckingham

D. J.

Pourzanjani

M. M. A.

The effects of tip flexibility on the performance of a blade-type windsurfer fin. In Manoeuvring and control of marine craft (Ed. Wilson

P. A.

), 1992, pp. 261–273 (Computational Mechanics Publications).

Hallert

Deformation measurements by photogrammetric methods. Photogrammetric Engng, 1954, 20, 836–842.

Moffitt

F. H.

Mikhail

E. M.

Photogrammetry, 3rd edition, 1980 (Harper and Row, New York).

Wolf

P. R.

Elements of photogrammetry, 2nd edition, 1983 (McGraw-Hill, New York).

10.

Tucker

Ambiguities in stereopsis. Nature, 1989, 337, 605.

11.

Wilson

J. H.

Three's company for stereo viewing. Nature, 1989, 339, 433.

12.

Gere

J. M.

Timoshenko

S. P.

Mechanics of materials, 3rd SI edition, 1991 (Chapman and Hall, London).

13.

Anderson

J. D.

Fundamentals of aerodynamics, 2nd edition, 1991 (McGraw-Hill International, New York).