EXPLANATION OF APPENDIX 2

When the first edition of this book was written an attempt was made to include, in Appendix 2, all the known, reliable wind tunnel test results on aerofoils at model aircraft values of Reynolds number. There were not many such results and they were not easily found in the aeronautical literature. Some other useful material, notably from Lnenicka and Horeni in Czechoslovakia and from Dr Gates’ Group in Italy, came to the author*s attention too late for inclusion. In this edition, the old measurements, still not easily accessible to the ordinary reader, are retained and still provide useful information. To them have been added, with permission, some of the charts produced by Jaroslav Lncnicka. Although these have been published in Czechoslovakia, they are not widely known elsewhere.

Much more tunnel testing has been done since 1978 and it is no longer possible to assemble all into a single appendix of reasonable length. The Delft, Cranfleld and Notre Dame studies have been mentioned briefly in Chapter 9, and those seeking to know more will have to search the literature emanating from these institutions. The list of references at the end of this chapter will be a useful starting point. Most model fliers know already of the Stuttgart wind tunnel and the results from there published by Dr Althaus, in the series Profilpolaren fur den Modellflug. No serious aeromodeller should be without these volumes. The charts arc easily understandable by anyone who has read this book, and the brief text in German, describing the wind tunnel and the methods used in measurement, is not of fundamental importance from the modeller’s viewpoint With Dr Althaus’s permission, four test results on two Eppler and two Selig aerofoils carried out in 1986 are included in the Appendix.

During the years 1986—89 the team of Selig, Donovan and Fraser at Princeton University carried out a series of wind tunnel tests at model values of Re. The results were published in 1989 in a single volume, Soartech 8, Airfoils at Low Speeds. (See full details in the References listed below.) This represents by far the most extensive and valuable body of work on model wing profiles so far accomplished and for the serious model aircraft designer, like the Althaus volumes, it is indispensable.

The Princeton wind tunnel, described in the volume, was most carefully calibrated. Over sixty distinct profiles were tested but in many cases more than one test piece was used, for comparison. Where it seemed appropriate tuibulators were tried in different positions. More than 130 charts and associated tabulated figures were produced.

Of particular importance is the fact that all the test wings were made for the Princeton group by practising model aircraft builders, rather than by specialist wind tunnel craftsmen. Some of the profiles submitted were favourites of the modellers who made them, others, including the new SD series, were made to order. Every model wing tested was submitted to close scrutiny and departures from perfect accuracy were noted and published with the measured figures. Those using the results may therefore be confident that, with ordinary workshop equipment and sufficient attention to detail, it is possible to achieve results in a real wing which are similar to those from the Princeton tests.

Michael Selig, after leaving Princeton, became Professor in the Department of Aeronautical and Astronautical Engineering at the University of Illinois, Urbana. In 1993 a new pro­gramme of research and wind tunnel testing was announced, calling as before on ordinary modellers to make the required test wing sections. Results, when published, will be of great interest and importance.

The cautionary remarks made elsewhere in this chapter still apply.