spoiler hinge moments

[lincoln]

Anyone have an easy but valid way to calculate forces on a spoiler? I saw a simple summary someplace by Mark Drela for things like ailerons, but not for spoilers.

[HugePanic]

a first calculation could be this one:

(assuming cw = 1)

F = 0.5 * 1 * roh * A * v^2

[lincoln]

cw? Not sure I recall what that is. Are you just saying the dynamic pressure evenly distributed over the spoiler surface??? Is that accurate?

[MarkusN]

cw? Not sure I recall what that is. Are you just saying the dynamic pressure evenly distributed over the spoiler surface??? Is that accurate?Cw is Cd (German nomenclature). As a first approximation that's certainly in the ballpark. I'd assume the center of pressure to be a bit farther off the hinge line, though, but then again full dynamic pressure over all the area is probably not present either.

[HugePanic]

Cw is Cd (German nomenclature)...

sorry, my mistake! :)

[Neil Stainton]

Does anyone know what torque is required to strip the gears of an HS85 servo? I did this opening my Super AVA's spoiler at speed at a competition last weekend. I was at about 800 ft (240m) with a minute to go and I put the nose down first, and THEN opened the spoiler. Bad idea. I would guess the forward speed when I opened the spoiler would have been no more than 60 mph (88fps, 27m/s). I can measure the spoiler size if anyone is interested...

Neil.

[Jurgen Heilig]

Does anyone know what torque is required to strip the gears of an HS85 servo? ...

Hi Neil,

no matter what the spoiler forces are, you would assume that the servo gears should withstand the torque of the motor. Well, the easy solution would be an HS-85MG. ;)

:) Jürgen