Sender: <marv@lancaironline.net> (Marvin Kaye)
To: lml
Date: Mon, 14 Oct 2002 10:48:53 -0400
Message-ID: <redirect-1805145@logan.com>
From: Jim Thomas <mypa12@yahoo.com>
Subject: [LML] Legacy Canopy Hinge/Gas Strut Evaluation
MIME-Version: 1.0
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Valin,

I was very impressed with your graphical analysis of the Legacy canopy
hinge problem and it seems to represent exactly the problem I have
encountered.  The Lancair modification to change the gas strut location
does eliminate the misalignment of the canopy leading edge and the
fuselage, but at the expense of reducing the canopy opening force.  If I
read your post correctly, you feel the problem is with the bending of the
hinge in the closed position and not deformation of the canopy stiffener
itself.  Is that correct?  If so, how will reinforcing the canopy
stiffener solve the problem?

Another Legacy builder corrected his problem by adding an AN washer to the
aft bolt on each hinge between the hinge and the stiffener.  This slightly
changes the angle of the hinge on the stiffener and brings down the
leading edge slightly.  He first used a thick AN washer and found the
canopy and fuselage fit pretty well, but the leading edge of the canopy
stiffener caught on the fuselage joggle when the canopy was opened.  He
then replaced the thick washers with light AN washers and he now gets a
good fit.  He also inverted his gas struts so the barrel was up and the
rod down, claiming a very slight improvement in the mismatch (I cannot
believe this would change anything since the force is the same inverted or
not).

I installed the thick AN washers on my canopy and noted a vast improvement
in the fit.  However, I still had a little mismatch on the right side.  I
then added Lancair modification to the right hinge only and now I have a
perfect fit.  With only one strut modified, I still get pretty good
opening force and my canopy does not come crashing down.  The only problem
I see now is that my installation looks a little funny with one stock
strut and one modified strut.  It should be noted that I only used one
extension block and the original strut end fitting for the modification. 
I did not see the benefit of having the double extension blocks and new
rod end.  

As a follow-up to this issue, I would like to see someone measure the
deformation of the canopy hinge under the various conditions; original
design, modified strut geometry, and AN washers installed.  I think this
might help us come up with the optimum solution to this problem.

Jim Thomas
L2K #166

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