Hi Ben !
It may well be that the Rebel I flew was an example of bad placement
of the VG's . I believe the builder followed the suppliers recommendations
for placement, but suspect that no proper wind-tunnel tests or analysis
was done to start with - this is likely why some people have great results,
while others are disappointed. If you can install them temporarily, and
don't mind a bunch of real test flying & moving, maybe it'd be worth it.
The positioning is affected by many factors - lighter Rebels with O-235's,
or 912's would need a different location than us O-320 drivers with the
original firewall position, and very forward CofG's ! ;-)
I'd like to hear from Moose drivers who have installed the McKenzie
STOL kit - are there any flying who are on this list ??? One possible reason
the Moose benefitted more from VG's is that it has split flaps & ailerons -
possibly the wing fences also help the aileron effectiveness by taming that
big vortex that comes off the gap.
I DO know that, on the Rebel, Dave Fife's wing tips make a proven,
measurable (over 20%) reduction in takeoff distance, and improve stability -
and that Angus McKenzies STOL kit of leading-edge cuffs & wing fences
greatly improves low speed handling. I can climb at over 800 fpm at 46 mph,
and an unreal attitude !!! That goes up to over 1,500 fpm at 70 mph...
One of the local Super Pitts pilots watched me doing "crash & dashes"
last year - said I was bringing tears to his eyes - one one landing, I swear
the tires didn't even squeak - just spun up to speed, it was so gentle !!
Usually there's nobody around when you get lucky ! ;-) :-)
I do believe that VG's on the bottom of the stab could be helpful in
increasing elevator authority for landing, again, IF they are placed
properly !
As an old glider pilot, I'm very reluctant to add such drag-producing
elements to an airplane - doubly so because they make great snow &
ice catchers ! ;-)
........bobp
-------------------------------orig.-------------------------
On Friday 07 January 2005 05:50 pm,
bransom@dcsol.com wrote:
I do find it curious that VGs helped so much on the Moose and are such a
nothing, or degradation to the Rebel. So, I just emailed PNWAero and asked
what they thought. Jerry (@ PNWAero) said they have done the placement
design work for the Rebel but not tested, and would expect improvements
similar to that of the Moose. If anyone wanted to try it, PNWAero does say
guaranteed, and their kit uses adhesive stick ons until best placement is
determined. I wonder if the past trials of VGs reported here were from
PNWAero VGs, or perhaps limited testing and non-ideal placment of something
else?
-Ben/ 496R
Hi Allen !
I've flown a Rebel with VG's - my advice is don't do it ! The
McKenzie STOL kit (cuff & fences) DOES work - my impression -
<on the Rebel> is the VG's DO NOT !! Just MHO .....
(and YMMD !) :-)
I think VG's can help IF they are placed properly, based on real wind-
tunnel
studies - just slapping them on willy-nilly is a recipe for disaster !
On the Rebel I flew, they destroyed the lateral stability - you couldn't
let go of the stick ! I can fly my Rebel with Fife tips & McKenzie
STOL kit for hours (!) without touching the stick !! The Vg's made for
a sloppy stall, falling off into a spiral dive every time - not possible
to get a
nice,
stable, safe spin out of it ! They also make washing, covering, and
snow removal really difficult !!! I didn't notice any reduction in
stall speed, either....
.........bobp
-------------------------------orig.-------------------------
On Thursday 06 January 2005 06:38 pm,
allen.hewko@dcsol.com wrote:
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