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

[Donald Royer]

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 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.

Don
----- Original Message ----- 
From: Al Gietzen 
To: Velocity Aircraft 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 very 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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