Incidence

If you have a flat bottomed airfoil or similar air foil to the Clark Y, would you need less negative stab incidence relative to the wing chord line than say if the wing was symmetrical or near symmetrical?

Reply to
Paul Sutphen
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In general the answer is "yes", but that depends on the type of aircraft you are talking about.

Many airfoils like the Clark Y have a zero lift angle of incidence that is negative relative to the chord line, therefore if you place their chord line at zero incidence relative to the tailplane you indeed have a setup where the actual angle of incidence is a degree or two - the amount depends of course on the angle of zero lift for that particular wing airfoil. So if you wanted to achieve a setup where the wing sits at an effective incidence of say 2 degrees, the relative angles of the chord lines would be different depending on the wing's airfoil. A symmetrical wing airfoil would sit with its chord line at 2 degrees, airfoils with varying degrees of camber would sit at varying angles below that.

Basically, you decide/determine what angle of incidence you want to have, look at the wing's angle of zero lift, and set up the wing chord line so that:

Wing incidence (measured at chord line) = (Desired incidence angle) + (Angle of zero lift)

i.e. if the zero lift angle for the wing's wirfoil is -2 degrees, and you want three degrees of incidence:

Wing incidence (measured at chord line) = 3 degrees + (-2 degrees)

= 1 degree

On top of that, you need to consider downwash as it can affect the effective angle of incidence of the stab relative to the wing.

Andy Lennon's book (title is ?? Designing Radio Controlled Model Aircraft ?? or similar. I own one but it's at home..) covers all that and more at a level of both simplicity and depth that is easily absorbed and understood. I like it.

Mike D.

Reply to
M Dennett

yes.

Reply to
The Natural Philosopher

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