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Date: Wed, 23 Sep 1998 06:16:43 -0400
To: lancair.list@olsusa.com
From: John Cooper <heyduke@digital.net>
Subject: Rollover support in the 320/360
In-Reply-To: <001401bde621$d3e8cac0$6a35ebc6@jimmy.solect.com>
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>>
James--

>I looked at several aircraft, and most noticably Orin Riddel's (sp?, from
>the >factory) has a very odd shape.  The doc's recommend a uniform 3 inch
>width, and yet most I have seen taper towards the longerons.  Has anyone
>seen, or >could recommend reasons for the irregular shape?
>
  Those of us who are tall had to recline the seat-back several inches
behind the rollover. This left the bottom of the structure hanging down in
mid air, ready to gouge into our shoulders. In my case, I tapered the
bottom of the rollover somewhat so it would clear my shoulder, and blended
it into the side of the fuselage.

>A second question:  the manual indicates that the longeron's, once
>installed, should have the innermost spruce laminate running the complete
>length of the wood, i.e. no trimming.  However, the manual says nothing
>with respect to finishing the piece, should it me layered with a 2 bid
>layup? bonded to the honeycomb?  suggestions also welcome...
>

The longerons are STRUCTURAL! Do not trim them in whatsoever - they need
all the cross-sectional area possible since they are what is supporting
your engine hanging out there in front. I know enough about statics to be
dangerous, and when I ran the numbers I got real scared. Based on my
simplified calculations, I figgured the longerons should snap in tension
directly above the main spars at about 10Gs, assuming that they had no
holes in them.

Therefore I did not install the NACA ducts in the side of the fuselage in
this area, neither did I drill any holes for the canopy mounts in my
longerons. I also beefed up my longerons with unidirectional carbon fiber
in the critical area.  Yeah, I know that mixing carbon and glass is not
recommended, but I figure the worst that can happen is the carbon debonds
from the regular glass and I will be no worse off than I was before... At
least I won't be worring about the front half of my plane breaking off on a
hard landing <G>.

But I digress...yes, you attach the longerons to the fuselage with 2 bid.

--John, L-235