FLAT PLATE / AIRFOIL Cl -Polar and -or Cd Graphs

[Alex Morillo]

Hello
Is possible for anyone to please provide Flat wing Air performance numbers ? like Lift Coefficient.
i need any data or info on the aerodynamics of flat plate -wings .
Thanks Much
Alex

[BillParker]

Mayhaps?:


Computed drag and lift coefficients for NACA 44XX airfoil series ... values with experimental values for flat plate perpendicular to flow ... Extrapolated stall data. Cdmax = 1. Cd = B si. B1 = B2 = C. Cl = A sin ...


http://www3.esc.auckland.ac.nz/EnergyWindWater/Presentations/Presentation%2007%20Joaquim%20Martins.pdf


um... god luck...


bp

[kittyfritters]

If you examine most airfoil CL/CD data sheets you will find that the minimum speed that the test were run was usually something like 42 miles per hour and the minimum chord of the wing section tested was 5 inches. I have never seen any that showed a test speed lower than 28 miles per hours (and that was the Wright Brothers.) In other words, there is no reliable data for the characteristics of airfoils in the speed and size range that our models fly. For small rubber powered models kit designers just pick what should be a reliable one, from past experience, and test a prototype. If it works, fine, if not you build another wing and try it again until you get reasonable performance. That's the one you put in the kit.

If the model is light enough and small enough, such as in the typical, old time R.O.G model, a flat airfoil works fine. Just give the wing enough angle of attack and it flies. I fact, sometimes giving a flat plate wing just a hint of an airfoil gives spectacular performance while applying certain well known airfoils to the wings of small rubber powered models will actually cause them to quit flying. Witness the success of various designs with so called "cracked ribs" in FAC competition,

Basically, with a chord of 4 inches or less, and an air speed of less than 30 miles per hour, if an airfoil looks right, it probably is.

[BillParker]

Thank you Howard.



bp

[Alex Morillo]

Thanks
I am experimenting with joined-wing flat airfoil HLGliders
I cover most wing surfaces with clear tape, to give them a smooth low drag surface. As we know airflows should be mostly Laminar and flows cant
handle -almost no- adverse pressure gradients.
I estimated a 0.1 Cl at low AoA at around 5, 6 mt-sec to produce
about 8 grams of lift.
Alex