Airfoil and incidence queston

[birdbrain]

Hello,

Can anyone please tell me if the airfoil section shown below is set at zero degrees, or would zero be when the bottom of the wing is flat. Also, can anyone identify this airfoil and tell me what type of plane it would work well for. I have about 10 of these foam wing panels that are about 7" cord and 15" span and would like to use them for something but am not sure what they would be best suited to.








Thanks in advance for any help.

Birdbrain

[Andy W]

It's zero when the LE and TE are horizontal. Your picture seems to show it having a positive angle of attach (LE is higher than TE).. If the lower surface was horizontal, it would be at an even higher angle.

..a

[birdbrain]

Thanks Andy, that's kind of what I was thinking and I tried to draw a line from the TE to the LE to get an idea.

Thanks,

Birdbrain

[Mike Taylor]

The line you show drawn though the airfoil is the reference line (LE and TE points). The bottom surface is not what you go by, even if it is flat...

[turbojoe]

Check out my thread (http://www.rcgroups.com/forums/showthread.php?t=306019) asking about incidence using the same airfoil. There were a lot of informative responses from the guys.


Joe

[birdbrain]

Thanks everyone, that is what I thought but for some reason it's just hard to convince myself that it will not have neg incidence.


Birdbrain

[Ollie]

Don't confuse an airfoil incidence and angle of attack. Incidence is relative is an airfoil chord line to some reference line of the structure. The angle of attack of an airfoil chord line is relative to the airspeed vector line.

[HELModels]

The line you show drawn though the airfoil is the reference line (LE and TE points). The bottom surface is not what you go by, even if it is flat...

I realize the author's question has been answered satisfactorily, so dont get me wrong.

You can use any reference line you want as long as you relate it to the True Reference Line which is conventionally the line denoted by the LE and TE, also known as the chord line. Why would you use a reference line which is not the convention? Suppose you had some really complex shaped airfoil and could not pinpoint the True Chord Line, but you could accurately locate the TE point and one other point on the top of the thickness. You could still determine the True Incidence Angle.

Early in aerodynamic sciences there was debate about reference lines and not everyone agreed. Knowing that doesnt make me a scientist or an idiot. :p

[vintage1]

Don't confuse an airfoil incidence and angle of attack. Incidence is relative is an airfoil chord line to some reference line of the structure. The angle of attack of an airfoil chord line is relative to the airspeed vector line.

And don't confue 0 degree angle of incidence or even angle of attack with zero lift eiither. Airfoils that are assymetrical can generate lift at apparent negative angles of attack.