TALE OF A TAIL. We've made a near perfect one (tail) for critical measurement of wind direction. We call it Quick 1 because it has

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2 TALE OF A TAIL We've made a near perfect one (tail) for critical measurement of wind direction. We call it Quick 1 because it has a distance constant of 2.5 feet and a damping ratio of 0.6. Overshoot is minimized and oscillation practically damped out. Result: every tail movement has a meaning you can measure... wind direction records are more precise, more accurate and easier to analyze than ever before. T H E O R E T I C A L TAIL Quick 1 was born in theory. Our research staff made a thorough study* to determine what the geometrical and aerodynamic properties of a wind vane must be to obtain a desired distance constant and damping ratio, in this study it was found that damping ratio, f; is proportional to the arm length, rv; the tail planform area, A; the slope of the lift curve of the tail, a; the mass of the tail, Mv; and the mass of the arm, Mb; by the following approximation, where K, and K z are constants:. T rvaa IVi (!) ARM A v = y 2 <Ct + C r ) b T A I L PLANFORM AREA Ct TIP CHORD C r - = ROOT C H O R D b =* S P A N QUARTER CHORD LOW MASS To get a high damping ratio (see (1) above) the tail must be as light as possible. Our problem was to find a light material that was strong enough to be extended in a high aspect-ratio shape. This we finally accomplished by combining two materials: a foam plastic core bonded within an aluminum skin. With this construction we produced a tail for Quick 1 with an aspect ratio of 6. It is so light that the entire vane weighs under five ounces. Yet, it is rugged enough to withstand hurricane winds. For increased strength, the tail is slightly tapered from the root to the tip. This reduces the bending moment and places the load center nearer the supporting arm. OPTIMUM ARM Since both the damping ratio and distance constant are functions of the arm length (See (1) and (2)) this dimension is of great importance. The arm length had to be as long as possible on the tail side of the axis of rotation and as short as possible on the balancing-mass side. Of course, here again we were faced with the limitations of materials and with keeping the mass of the vane to a minimum. After a great deal of engineering and testing we arrived at the optimum arm lengths. The arm itself is constructed of a rugged aluminum alloy and the balancing mass is of stainless steel. These are the basic characteristics which combine to make Quick 1 the optimum tail for sensing micro winds at the earth's surface. And it's rugged... designed, tested and guaranteed to perform to specification in extreme environments with temperatures from 40 to -f 140 F and winds to 90 miles per hour. Quick 1 is thoroughly tested in our own wind tunnel to assure performance to its extraordinary specifications. The results of a typical wind tunnel test of Quick One's dynamic response are shown in following data: It was also found that the distance constant, D, of a vane is a function of the damping ratio and the length of the arm. This function is expressed in the following definition: (2) ry REAL TAIL With this theory in hand, we set out to make a rugged tail with a damping ratio of 0.6 and a distance constant of 2.5 feet. To get this order of performance, it was clear from theory that we needed a tail with very high lift and low mass. HIGH ASPECT RATIO From aerodynamic principles, and from field and wind tunnel studies of many tail foil shapes, it was established that square-like shapes (low aspect ratio) have poorer lift coefficients than tall, narrow shapes (high aspect ratio). In fact, theoretically, the taller and narrower a tail foil is, the higher its lift coefficient. However, this theory is application limited by the materials one can use in tail construction. (We've got a room full of rejected tails to prove it)? 0 (The damping manner: derived Time ratio is derived damping data in the. following In this case the ratio is ) Quick 1 is available now with the Beckman & Whitley WS101 Wind System. Or it can be purchased as standard equipment for the Beckman & Whitley wind systems you are now using. For further information write Meteorological Instrument Applications Department. a subsidiary of TECHNICAL SAN CARLOS, CALIFORNIA high aspect ratio from these f = { 1 -f [7r/ln(X,/X2]2 } OPERATIONS inc. PHONE: CODE 4-15 ^Theoretical Analysis of Wind Vanes; John Corcoran; August, Send for your copy.

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5 The BULLETIN OF THE AMERICAN METEOROLOGICAL SOCIETY is the official organ of the Society, devoted to editorials, survey articles, professional and membership news, announcements, and Society activities. Editing and publishing are under the direction of Kenneth C. Spengler, Executive Secretary. Members are encouraged to send to the Society information which they wish to be considered for publication. Published monthly at Prince and Lemon Streets, Lancaster, Pa Second-class postage paid at Lancaster, Pa. Address all business communications, purchase orders and inquiries regarding the Society to the Executive Secretary, 45 Beacon Street, Boston, Mass technical editor James S. Sandberg news editor E. Ruth Anderson assistant technical Carmela A. Poce editor Front cover photograph: Dr. James Tilton, who as Surgeon General of the Army issued the order on May 2, 1814, initiating official climatological observations in the United States. (Photo courtesy of the National Library of Medicine.) Back cover photograph: First official climatological records in the United States, submitted to the Surgeon General by Dr. Benjamin Waterhouse for Cambridge, Mass., in March (Photo courtesy of the National Library of Medicine.) volume 45, number 5, May 1964 articles early stages of climatology in the United States 268 H. E. Landsberg correspondence a summary on membership structure 277 Arnold Court on membership structure 279 Edwin Kessler on a point of terminology in the optics of the rainbow Chi Epsilon Pi, Meteorology Honor Society an honor society for meteorological students 279 J. E. McDonald and B. M. Herman 280 James J. O'Brien 281 Guy A. Franceschini proposed amendments to the Constitution 275 reviews 282 about our members 286 news and notes 290 news from our chapters 294 at AMS headquarters 298 announcements 299 meetings of the AMS 302 necrology 304 professional directory 306