REFLECTOR: Vortilions and/or VG's?

[Scott Derrick]

Al's right.

The Vortilon's "main" effect is on the top of the wing, when at a high 
angle of attack..

They are a free enhancement that provides better slow speed stability, 
why throw away a win win solution??? They could make the difference in a 
sticky situation.

Scott

Al Gietzen wrote:

> VGs energize the boundary layer and keep it attached longer and so delay
>
> the onset of stall. I've never heard of them doing anything measurable
>
> to inhibit spanwise flow. Vortilons OTOH were put there specifically to
>
> inhibit spanwise flow and are most active on the lower (high pressure)
>
> wing surface. I don't know how they delay boundary layer separation
>
> except as an incidental benefit of reduced spanwise flow.
>
> IIRC vortilons and VGs pretty much address different issues ... Jim S.
>
> I’ll respectfully disagree on this one. Tuft testing by the guys here 
> in the San Diego EZ-squadron (on both Vari-EZ and Long-EZ) found that 
> the ONLY span-wise flow that showed up was on the upper surface of the 
> wing, under where the flow had separated at high AOA. It would begin 
> inboard near the fuselage, and spread outward (and thicken) as AOA 
> increased.
>
> I also recall reading (I don’t know where) that the reason Rutan added 
> the vortilons was to create vortices OVER the wing at high AOA to 
> provide better aileron authority (presumable because it inhibited 
> span-wise flow near the trailing edge which ‘masked’ the ailerons).
>
> I think it reasonable to extrapolate that behavior to the Velocity wing.
>
> Al
>
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