REFLECTOR:Vortex Generators on XL

[Jim Sower]

The short answer is no.  There will be a decrease in cruise speed (they do after all
undeniably have drag) but my best information is that it's not detectable with the
naked eye.  I observed none on my plane.  All of my VG info comes from Jim Price who
in addition to impressive academic credentials in Aero Engineering holds a world
altitude record (35000'+ in a NA O-320 Long-EZ).  He encouraged me to change mine from
wedge shaped to rectangular, and to move them from the 25% chord line to 20%.  I did
so just for the hell of it - it seemed a couple of truly trivial changes, but the
little buggers only cost two cents each - and was surprised at the amount of
improvement that seemed way out of proportion to what I actually changed.
That's how it works for me ... Jim S.

John Dibble wrote:

> Do vg's affect cruise speed?
>
> John
>
> Chuck Jensen wrote:
>
> >Jack,
> >
> >Everything I do is trial and error.....though I did use the patterns
> >provided by Velocity.  They are installed on both the canard and wing (and
> >both sides, naturally).  I don't remember the exact count but buy a 100
> >(they're cheap) and use the extra for replacements.  To paint them, after
> >scuffing the bottom on sandpaper, I just stuck them on packing tape and gave
> >a few light coats of enamel for UV protection.
> >
> >Do us a favor.  Before you install, do a few altitude stalls and see if you
> >can nail a number.  After installation, repeat and see what difference, if
> >any, you note.  Maybe you already have a hard number for touchdown IAS that
> >you can reference---that would make a before/after comparison even simpler.
> >Most seem to think it reduces touchdown by 5 to 7 kts.
> >
> >Chuck Jensen
> >
> >
> >
>
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--
Jim Sower
Crossville, TN; Chapter 5
Long-EZ N83RT, Velocity N4095T