HumanPoweredDesigner
Well-Known Member
Have you built a variety of airfoils for your RC wings and found that some are more likely than others to get flow bubbles?
I'm just wondering why the Clark Y is not used more on human powered vehicles, with its very low drag. The only explanation I can think of is it has a lower coefficient of lift, and higher drag at the coefficient of lift that some hpa's operate at.
I was looking at Cl vs Cd graphs for various airfoils, between Re = 200,000 and 1,000,000, and for the hpa airfoils, the slope changed in a monotone (non wavy) way. The Clark Y graph had some waves in it, and I read that waves in a Cl vs Cd graph are hits of separation bubbles, since the programs don't show the bubbles as well as they should.
So I'm wondering if anyone has flown any DAE or FX MP section on their RC planes and compared them to Clark Y serious airfoils. Or do you just put zig zag tape on the highest point of the airfoil and call it a day?
Someone else also told me that flow bubbles rarely happen below half Cl max. Is that true? I'm making a fixed rotor, so I have a lot of control over AoA. I don't need the whole range like an airplane would use.
I'm just wondering why the Clark Y is not used more on human powered vehicles, with its very low drag. The only explanation I can think of is it has a lower coefficient of lift, and higher drag at the coefficient of lift that some hpa's operate at.
I was looking at Cl vs Cd graphs for various airfoils, between Re = 200,000 and 1,000,000, and for the hpa airfoils, the slope changed in a monotone (non wavy) way. The Clark Y graph had some waves in it, and I read that waves in a Cl vs Cd graph are hits of separation bubbles, since the programs don't show the bubbles as well as they should.
So I'm wondering if anyone has flown any DAE or FX MP section on their RC planes and compared them to Clark Y serious airfoils. Or do you just put zig zag tape on the highest point of the airfoil and call it a day?
Someone else also told me that flow bubbles rarely happen below half Cl max. Is that true? I'm making a fixed rotor, so I have a lot of control over AoA. I don't need the whole range like an airplane would use.
