REFLECTOR:Wing/Canard/Fuselage Incidence
Ronnie Brown
reflector@tvbf.org
Sat, 6 Mar 2004 08:15:46 -0500
I found this in the Archives. This is by Alan Shaw:
At cruise I like a Velocity with 1/2" of reflex single pilot. This rig
makes
for a faster cruise and slower landing. Your case may be a little extreme
and
require 1/2 degree less incidence in the canard. A quick fix is to put a
1/32" washer on both outboard top wing bolts...thus decreasing the
difference
between the incidence angle of the canard and main wing. This way you can
test fly the change before you go through the hassle of changing the canard.
Like I said, I like a Velocity that requires full forward trim and full
forward stick by the pilot when solo, wide open at sea level. This will
leave
more elevator authority (flare!) when you are slow and loaded. It should
also
trim fine at the lower indicated airspeeds of cruise at 8,000' and above.
It's a common problem with new Velocities that the new owners fly in this
unusual mode of solo, full throttle, low altitude and then re-rig there A/C
to
"fix" this quirk that really just makes things better on the slow end of the
flight envelope.
With such a powerful canard some people are worried about deep stall. Even
if
you could "make" it deep stall I doubt that you push your canard past
normal
bucking into the violent bucking and rolling etc. that normally precedes the
"big one".
What prevents deep stall is not just as simple as the difference in wing
loading between the two wings but all there differences in characteristics
as
whole. That means incidence angle, aspect ratio, camber, leading edge
radius
and many other lesser factors. In other words, if you decrease the canard
incidence and/or cut it shorter (lower the aspect ratio) then you have
actually increased two factors for deep stall potential. On the other hand
this change has increased you wing loading on the canard and also made it
harder for you to pull the nose up too high. If you are confused so am I.
That's the problem there are so many variables each with different
coefficients of influence over the wing differential we are trying to
maintain while at the same time trying to get as wide a flight envelope as
possible.
The obvious is to keep the CG in front of the center of lift. The problem
here is that the main wing/winglet is comprised of four different airfoils,
incident angles and coefficient's of lift. So where exactly is the center
of
lift?....well the experts don't seem to agree unless they simplify with
rounded off "rules of thumb" that are far from the truth.
That's why the flight test that Dan, myself and especially Jim Patton did
were
so important. When Jim "tickled the dragons tail", as he put it, he found
the Velocity to have far more low speed stability and aft CG capability than
its other "Easy" counter parts. As the head of NASA's GA stall spin R&D
program for almost 20 years Jim has pushed everything out there way past
it's
limits and should know. In his opinion the STD wing Velocity is as good as
it
gets in the compromise between stall prevention and performance. Personally
I
think the STD Velocity will endure the test of time as one of aviation's
more
exceptional designs.
Alan
----- Original Message -----
From: "Pat Shea" <xl340hp@yahoo.com>
To: <reflector@tvbf.org>
Sent: Friday, March 05, 2004 7:32 PM
Subject: Re: REFLECTOR:Wing/Canard/Fuselage Incidence
| Mike,
|
| I suspect you wouldn't want to change the relative
| wing-to-canard incidence (deep stall issues, etc.).
| Increasing the incidence of both, however, should
| cause the nose of the fuselage to be lower in flight.
| In other words, both incidence jigs should still
| center - the fuselage would just need to be in a more
| nose down attitude than before the incidence change.
|
| Of course, the strakes are part of the wing and are
| tied to the fuselage's attitude. Maybe the factory
| could advise you on how much, if any, change is
| reasonable.
|
| Pat
|
| --- mike deeter <iguanamagic@yahoo.com> wrote:
| > Help for advice re: wing incidence
| >
| > I'm sure a bunch of folks have dealt with this
| > issue.
| >
| > My Std Elite RG flies fine but it also seems to fly
| > a
| > bit fuselage-high in cruise. Several people,
| > including one guy w/ an identical Velocity and
| > set of wings (Alan Shaw's), have remarked on it. I
| > think so, too, and since that must be a high-drag
| > attitude I want to explore what (if anything, since
| > it
| > flies fine) to do about it.
| >
| > If it's pertinent, my canard is 1/8" to 1/4" up when
| > I'm flying in cruise with a midrange CG.
| >
| > Questions:
| >
| > 1. I measured the main wings versus the canard using
| > Velocity's incidence jigs and my digital level as a
| > standard and found my canard to be about 0.5 degrees
| > leading edge low as compared to the main wing.
| > Would
| > raising the canard incidence 0.5 degrees have the
| > effect of lowering the nose in cruise?
| >
| > 2. What about shimming the upper, outboard wing
| > bolt?
| > That would seem to raise the angle of incidence of
| > the main wing chord slightly. Would that bring the
| > nose down in cruise? I did measure my main
| > wing/fuselage relationship versus my friend's
| > Velocity
| > and found no appreciable difference. My
| > calculations
| > using geometric relations show a 0.030" shim
| > changing
| > the chord about 0.43 degrees. Significant? Can I
| > get
| > away with just the outboard bolt or must I shim the
| > inboard wing bolt as well?
| >
| > 3. Any other suggestions?
| >
| > Of course, both 1. and 2. would have cosmetic
| > ramifications as well.
| >
| > I'd like to get in touch with Alan Shaw but emails
| > get
| > returned from his old address, wingco@iu.net. Can
| > anyone provide a current email and phone number for
| > Alan?
| >
| > Thanks for any advice.
| >
| > Mike Deeter
| > Velocity Std Elite w/ Franklin/Ivo
| > N2011P
| >
| >
| >
| >
| > =====
| > *******************************************
| > Mike Deeter
| > N2011 Test Pilot
| > iguanamagic@yahoo.com
| > http://iguanamagic.siegesmund.org
| > *******************************************
| >
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