REFLECTOR: Winglet concave surface

[Al Gietzen]

Hi, Don;

 

I have Alan Shaw wings and outer surface of my winglets are definitely
concave. Most of the curvature is in the rudder rather than in the fixed
portion of the winglet, but it is most definitely there. 

I find that there is some curvature (concave) in the outer surface of the
rudder - near the bottom probably a bit more than 1/16" gap under a straight
edge on the rudder.  The winglet surface itself is flat in front of the
rudder.  It is possible that in the process of sanding for finishing the
rudder may have been reduced just a bit.

 

I ordered my wings without the mounted control surfaces,and when I cut out
and mounted my rudders I was careful to keep the outer surfaces the same way
that they were before the cut was made. 

Mine were cut out, but not mounted.

 

Interesting - I was just perusing the article in the Oct Sport Aviation
about Steve Wright's 'Stagger EZ', and it mentions that he removed the
toe-in on the winglet (pg. 80, 3rd column).  Hum-m-m, reduced drag; but . .
. 

 

Al

 

----- Original Message ----- 

From: Al Gietzen <mailto:ALVentures at cox.net>  

To: Velocity Aircraft <mailto:reflector at tvbf.org>  Owners and Builders list

Sent: 11/9/2005 11:36:53 PM 

Subject: RE: REFLECTOR: anyone know the story behind
this-musthavemissedit.....

 

 

 

Looking at the outside shape of the winglet and rudder, one will notice a
slight cuff (concave shape).  Builders sometimes mistakenly believe the
concave area should be filled in with micro in order to make a straight
surface along the winglet and rudder outside line.  Wrong.  The cuff is part
of the "wing" shape and is designed in this fashion for a purpose - and that
is, to allow the winglet to create lift in a horizontal direction towards
the fuselage.  The winglet forces mimic that of a person pushing the winglet
from the outside towards the fuselage.  This "loads" the winglet and adds to
stability.  It also creates a design that does not support flutter.  It is
v! ery important that builders who build from the basic kit make absolutely
sure that the toe-in of the winglets are built according to the construction
manual.  Straight winglets and the absence of a slight concave line on the
outside of the winglet invite flutter.  This is what happened with Brendan
and the first "Brazil" set of wings.  The toe-in was reduced by a fraction
of an inch and the shape of the outside of the winglet did not feature a
concave feature.  It was just enough to begin winglet flutter, which once
started - could not be stopped once the rudder cables broke.

SB

 

Scott;

 

I put a straight edge on my Alan Shaw winglets, and find that the outside is
flat, no "slight concave line". I certainly don't want to be inviting
flutter.  I assume they have the correct 'toe-in' for a positive AOA; but
have no way of knowing.  How concerned should I be? I suppose a rudder
shimmed just slightly outward from flat would constitute slight concavity.  

 

Any cases of flutter with wings built by Alan?

 

Al

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