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

[Chuck Jensen]

Flutter can be in a rudder or structures a lot larger.  This link is to
a site that has video (of various quality) of the Galloping Gurdy Tacoma
bridge. http://www.enm.bris.ac.uk/research/nonlinear/tacoma/tacoma.html.
I would guess the difference between the bridge and a rudder is
frequency of oscillation, though the end result is similar...both will
end up in the drink unless it is stopped.

Chuck   

-----Original Message-----
From: reflector-bounces at tvbf.org [mailto:reflector-bounces at tvbf.org] On
Behalf Of Scott Derrick
Sent: Thursday, November 10, 2005 9:58 AM
To: Velocity Aircraft Owners and Builders list
Subject: Re: REFLECTOR: anyone know the story behind
this-musthavemissedit.....

Having experienced Winglet/Rudder flutter through nobodys fault but my 
own, I can attest to it being violent.  It shakes the entire airframe 
and makes a racket also.

A miss rigged rudder initiates the flutter but once it gets going the 
whole wing is moving. The winglet is almost a blur...

Scott

steve korney wrote:

> Ok... Let me get this straight...Are we talking about Winglet flutter,

> or rudder flutter...???
>
> Best... Steve
>
>
>
> ----Original Message Follows----
> From: "Al Gietzen" <ALVentures at cox.net>
> Reply-To: Velocity Aircraft Owners and Builders list
<reflector at tvbf.org>
> To: "'Velocity Aircraft Owners and Builders list'"
<reflector at tvbf.org>
> Subject: RE: REFLECTOR: anyone know the story behind 
> this-musthavemissedit.....
> Date: Wed, 9 Nov 2005 22:38:12 -0800
>
>
>
>
>
> 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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