![]() At these settings the wings were generating so much lift that it needed minus 17 degrees of down elevator trim to fly level! After much experimentation I finally bit the bullet and modified the wing saddle to minus 1/4 degree (all I could get) and set the top wing at minus 1-1/4-degrees. The bottom wing saddle was set at plus 1/2-degree (manufacturer specs were "zero") and I initially set the top wing at plus 3/4-degrees to get it to stall first for positive stability. My Great Planes Stearman ARF does not use the Clark Y, but its' semi-symetrical wings have somewhat similar charachteristics. Anyone setting the wing(s) with the flat bottom parallel to the airframe's "zero-degree datum" is actually setting them for a plus 2-degree angle of incidence relative to the datum and 7-degrees above the zero lift angle! Some aircraft may work well there but I expect most will not. The Clark Y airfoil stalls at around 13 to 15-degrees at the reynolds number of a typical RC model and has a zero lift angle of minus 5-degrees. Your comments added the most I've read to this thread and you clearly understand the issues well. Any feedback would be helpful as the next step in the building process will be to align the center section of the bottom wing to with the fusealage. I was also hoping to be able to adjust the angle of incidence for the horizontal stab, or maybe just set it at about -1 degree to offset the climb. I was planning on having the bottom wing at a zero angle of incidence and the top wing at about 3 degrees. The other one requires slight down elevator. One of the planes requires slight up elevator for level flight. I never paid much attention to the chord line and had the bottom of the airfoil sit paralell with the horizontal stab. I have designed and built two other models that have a Clark X airfoil. Is the cord line the same as the zero lift angle? If I set the cord line parallel with the thrust line it looks like the airfoil has a negative angle of attack. Compufoil shows shows the cord line for the airfoil. I used Compufoil to generate the airfoil. Increasing the temperature increases lift coefficient slightly where it seems to be better choice in comparison with increment of Jet momentum coefficient due to ease of operation.I am designing/building an electric biplane that has a clark Y airfoil for both wings. The maximum of lift decrement and drag increment occurs around the stall degree. Using the Co-Flow Jet increase the stall degree. The drag and lift coefficients reduces and increases by increasing the jet momentum coefficient, respectively. Results indicate that the enhancement induced by the Co-Flow jet on the compressible flow is less than one in the incompressible flow. A validation is performed for Clark-Y airfoil by comparing the present numerical result and available experimental data in the literature. Clark-Y airfoil has been chosen for this study because of its application in compressible flow, it is the base airfoil for development of new airfoils. The much number of studied flow changes from 0.4 to 0.6. Co-Flow jet is a method of increasing lift to drag ratio and varying the Stall Degree which works via injecting the air from the edge of airfoil and suction from the tail. In this study, the effects of Co-Flow jet and injection temperature on the enhancement of airfoil performance in the compressible flow are investigated numerically.
0 Comments
Leave a Reply. |