![]() ![]() ![]() The Wrights used a very unusual set of balances to make their measurements. ![]() The wind tunnel data is contained in Appendix II. McFarland (ed.), The Papers of Wilbur and Orville Wright, Volume One 1899-1905, McGraw-Hill Book Company, 1953. Application to a complete aircraft requires consideration of the aerodynamic effects of parts of the aircraft other than just the wings.ġ – Marvin W. Keep in mind that this data is for the wing models tested. Most of this data has no direct applicability to our models. See the notes for each source for specifics. Most measured in steps of a few degrees, so maximum values could be off by a bit if they occurred between angles at which measurements were made. Some were recorded in numerical form, while others were in graphical form and required measurement and conversion. Each set required conversion from the source format into a standard format. Definitions of terms and units varied from one to another. The measurements were made at different times and places using different kinds of equipment and measuring processes. It tells you how rapidly the lift coefficient increases with increasing attack angle. This is usually a couple degrees higher than the attack angle at which the maximum L/D occurs.Ĭl slope – is the slope of the lift coefficient with respect to the attack angle. Lift and drag coefficients are for foot-pound-second units.Ī max PF – the attack angle at which the maximum PF occurs. It determines the minimum power required to fly and the minimum sinking speed without power. It is the square root of the ratio of the cube of the lift coefficient to the square of the drag coefficient. Max PF – the maximum value of the Power Factor, sometimes called the Sink Factor. (This is not a measure of efficiency, as it usually has a value much greater than 1.)Ī max L/D – the attack angle at which the maximum L/D occurs. Max L/D – the maximum lift to drag ratio. This corresponds to a negative attack angle. For positively cambered airfoils, the wing will be tipped down in front several degrees to produce zero lift. This is the angle of the chord to the oncoming air stream that corresponds to zero lift. Thickness – The maximum thickness of the airfoil expressed as a percent of the chord. Reynolds – The Reynolds Number, estimated as the product of the wing chord in feet, times the airspeed in feet per second times 6,369.Īspect Ratio – The ratio of the wing span to its average chord. Aspect ratio has a strong effect on aerodynamic properties of wings. Location – the location of the maximum camber point along the chord, expressed as a percent of the chord. Max Camber – the maximum separation between the chord line and the mean thickness curve, the height of the highest point on the arc, expressed as a percent of the chord. You can click on this link Small Airfoil Data to download the original Open Office file. You can copy, save and print the picture, or double click to enlarge. This table contains the results of that collecting. Over the years I have gathered what I could find. There is very little wind tunnel data to guide us in the selection and use of airfoils for our little models. Most full scale aircraft have thick airfoil sections. Our airfoils are usually thin arcs or flat plates. There is a vast quantity of aerodynamic data published, but most of it is for full scale aircraft with Reynolds Numbers in the millions.Īerodynamic properties also depend on the shape of the airfoil cross section. The Cloud Tramp, with a wing chord of 3″ and a flight speed of around 10 feet per second, has a Reynolds Number of about 16,000. The 6,369 assumes certain values of air density and viscosity that are taken as standard. For our purposes, Reynolds Number is the product of wing chord, in feet, times the airspeed, in feet per second, times 6,369. Aerodynamic scale is quantified as the Reynolds Number. Aerodynamic scale of airfoils is dependent on the wing chord and the air speed. There are several aerodynamic regimes with different phenomena, such as viscosity, inertia, turbulence or compressability, predominating in each. The values of these coefficients vary with aerodynamic scale. The data may be presented in tables or in graphs. Lift to drag ratio and power factor are calculated at each angle. Lift coefficient, drag coefficient and moment coefficient are measured over a range of attack angles. The aerodynamic properties of airfoils are measured in wind tunnels. ![]()
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