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REFLECTOR: Vortex generators and antenna coax





Simon,

> What's your opinion about vortex generators. I think Roberto Salinas has them.

If we knew precisely where and how to put them I'm sure they could improve the
airplane. Is Roberto using the Long Easy kit?  I know there was a kit developed by a
professor.  He used "Long" canard and main wing sections in a wind tunnel to
determine where to put them.  The Velocity airfoils are very different and would
require specific testing.There is the risk that vortex generators miss-placed could
do more harm than good.  Canard alterations could make flare difficult or on the
other hand enable such high Alfa that the main wing could stall first.

Wing section test of vortex generators, fence and tips fail to give the whole
picture.  Wing to wing interaction, wing root turbulence and tip vortices all
function as a whole.  The overall result of even some small changes to one factor
can effect the entire plan form function.

Actual flight test of various devices can be very subjective.  Low speeds are hard
to measure accurately as are oscillations and control responses.

To be on the safe side the "trailer test" that Dan did can be very informative.  The
video tape of the yarn movements at increasing angles of attack give a good picture
at least to be sure the canard is going to stall before the main wing.  This test
still doesn't provide handling information.  Small whole plane model test don't work
very well because of the relative higher density.  Interactions between fuselage,
strake, wing, winglet and canard to wing are dissimilar at different scales.

Tough question and even tougher R&D to be truly objective about.

Antennas:    "The Saga Continues"

The wire conduit at the end of the wing leading edge is too far back.  When you
install the wings the antenna coax runs straight into the end of the center section
spar causing it to make two 90 degree bends.  At least the first of these is
sharp... causing SWR meter readings to go roughly from 2 to 3 in some cases.
The solution is simple.  File out the end of the conduit hole forward at least an
inch.  Then the coax can pass in front of the end of the center spar with minimum
bend.  Follow suite with the rest of the installation by avoiding any "kinks" in the
coax all the way to the back of the radio tray.  If you don't want center to recieve
your transmissions just coil up the excess coax and tie wrap it tight at the ends of
the multiple loops.

Alan

disclaimer:  application of the installation technique outlined in the last sentence
could maybe burn up you output transistors in the long run.

 Dave and Martin?