REFLECTOR: Canard incidence

[Al Gietzen]

Subject: Re: REFLECTOR: Canard incidence

 

Al,

 

FWIW, I have the Alan's wings and canard on my XL. The standard incidence
gauges seem to have rigged the plane properly. My point here is that the
additional camber *might* not be the culprit. 

 

However, if your canard is longer than the standard (build your own)
dimension, that seems like it could cause a rigging problem. Have you heard
from anyone with a your specific set-up: 173 wings, standard fuselage,
longer canard (approx 162" sans tips)? I'd

be curious to know if the standard incidence gauges worked for them.

 

Pat

 

I have standard wings, standard fuselage, and a canard that is 8” longer and
has more camber.  A couple of others have responded that had the same
problem with canard incidence on the SE, and Scott Swing confirmed that it
was an issue.  Apparently others have had the problem with XL.  There may be
enough variation in airfoils and incidence gauges that the results are not
consistent. 

 

For example; the leading edge profile of one of my wings was/is different
than the other. Noting this during installation, I found that the right wing
had lots of filler over a ridge of epoxy on the leading edge, apparently
where the excess is extracted from the mold.  Instead of this being removed,
as on the left wing, it had been covered by about ¼” of filler and smoothed
over – changing the shape. This gave it a lower leading edge (point of
tangency to vertical).  I worked that off as well as I could without
damaging the underlying triax, but it still has a different profile and
lower leading edge.

 

I determined where the leading edge actually was, then got actual incidence
angles from Mark Machado at Velocity, and attempted to get the wing chords
the same on both sides.  Now that it is flying, and finding that the right
wing incidence is too high, I realize aligning the wing chords was not
necessarily correct.  The lower leading edge results in more camber – and
more lift.  I’ve had to decrease the right wing incidence, and increase left
wing incidence. So with the parts and gauges I was working with, I didn’t
know what I had until the plane flew.

 

Long boring story, but the same principles apply to canard incidence.  The
Shaw canard and factory incidence gauge aren’t a match; so you find out when
you fly. I have shimmed and modified to get about 1 degree less incidence,
and we’ll see how that works next time we fly.

 

Al

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