Message-ID: <3B051751.FFE468F8@regandesigns.com>
Date: Fri, 18 May 2001 07:36:33 -0500
From: Brent Regan <Brent@regandesigns.com>
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To: Lancair List <lancair.list@olsusa.com>
Subject: Re: LNC4-P Presure Bulkhead Installation
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Reply-To: lancair.list@olsusa.com

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When the IV-P cabin pressurizes it tries to turn into a sphere. The corners
that poke out of the sphere are moving in towards the center, pealing off
the bid in the process. This is why "Chicken Blocks" are needed around the
firewall and aft bulkhead.

The current system of lay-ups and bolts was pressure tested AND life cycle
tested (remember Aloha Airlines?). Unless you plan to do the same, don't
F*&$ with it.

To install the nut plates on my plane I cut slots on the inside (not holes
from the back) so that I could install them from the side. If the section of
the bulkhead support is a right triangle, I cut the slot in the apex that
points to the centerline rather than the hypotenuse. This way I could sand a
flat pad and remove all the foam before bonding. To install I the nut plate
I made a tongue depressor shaped aluminum plate with a hole in the tip that
the nutplate's back pressed into so that  I could control the Hysoled plate
as I slid it into the slot. I sprayed some bolts with silicone and screwed
them into the nutplates to align them with the previously drilled holes. I
could then remove the tool and jam a couple of tongue depressors behind the
nutplate to hold it. Foam, flox and 2 bid closed the holes.

I pressure tested my fuselage to 7.5 PSI prior to first flight. I know of
three pressure bulkheads that failed at 6.5 PSI due to insufficient bonding
to the core.

Regards
Brent Regan

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