Sender: <marv@lancaironline.net> (Marvin Kaye)
To: lml
Date: Wed, 21 Aug 2002 09:14:03 -0400
Message-ID: <redirect-1701592@logan.com>
From: "Greg Nelson" <gnelson@gt.rr.com>
Subject: [LML] Re: delaminations of aileron counterweight web LNC2
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Scott:

>> I meant the stiffening web on the outside of the aileron -- so water does
not collect there either?  Ans.  As of yesterday, yes.

>> Make sure to check the hinges for wear.  Res.  I've thoroughly checked
everything and find no further evidence of damage.  Thanks.

Scott, I have serious concern for your personal safety in flying any
airplane at very high speeds wherein counterweights are not held rigidly.
To wit:

>> PS - I have no counterweight webs installed on mine.  400 hours, Teflon
spaghetti/SS welding rod hinge pins, both rigged to fly slightly high.

You are the engineer and I am not scientific in the least so please let here
me express my ignorance without unnecessarily harsh criticism.

It seems to me that you are courting mishap by not rigidly tying the
counterweights to the ailerons because, at the onset of flutter, you will
have two independent weights (i.e., the counterweights and separately the
ailerons) thrashing around each exciting the other but in terribly
complicated ever worsening waves.  This is so because both weights are equal
but their periods are quite different- one perhaps two to three times the
length of the other.  All of this would happen in just a second or less
leaving no realistic reaction or recovery time- and no acceptable
alternatives.

Consider this.  The two equal weights held rigidly at 100% mass balance are,
well... balanced.  Those same weights anchored on a hinge point at an angle
of 90 degrees to each other are equivalent to no balancing whatsoever
because the weight that would theoretically position on the centerline will
not influence motion in either the up or down directions.  These same two
weights at a 45 degree angle will be only 50% mass balanced.  The
counterweights are located on the end of the curved lower leading edge
(bottom skin) of the ailerons which, though stiff, obviously flexes quite
determinedly (as evidenced by the five web delaminations that my plane just
incurred).  Whenever this flexing occurs, that stiff curved surface acts as
a spring to store energy that is moving up and subsequently to throw it back
down again with about equal force- thus exacerbating the flutter condition.
The only way to prevent this spring-like force is to stop the flexing
altogether which requires webs to tightly tie the two masses with their
separate pendulum periods together so there is absolute 100% mass balancing.

What do you think?  Do I pass?    Greg Nelson