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I'm about to incorporate the flutter modification described by Martin
Hollmann, as modified by Dave Morss.  I'm going to fill the 3 inch wide
"trough" in the fuselage tailcone formed by the joggle between left and
right halves with 13 BID.  I'm posting this because I want to make sure
I have the proper fiber orientation.

Martin's mod includes three BID layers (18" wide, 12" wide and 8"
wide).  This was intended to be an external modification to a finished
airplane, so he wanted a thin layup.  Since I want to put it on the
inside, in the trough, I took the total amount of fiber (18 + 12 + 3 =
33) and figured 13 layers 2.5" wide would be equivalent (13 * 2.5 = 32.5
-- close enough).  I called Martin who said "it should work, but the
analysis wasn't done that way so I can't officially endorse it".
Between his statement that "it should work", Dave Morss' "I did it that
way" and Lance's opinion that "you don't need it anyways" I figure I'm
covered.

The Hollmann documentation states that "the fiberglass should be
oriented at zero degrees to the longitudinal axis of the fuselage" which
to me means the fibers are fore-aft-left-right.  The sketch suggests
that the main axis of the BID is this way, with half the fibers 45
degrees to the longitudinal axis and the other half 45 degrees the other
way.  (i.e. take a standard 45 x 45 BID and line it up nose to tail).
This makes more sense to me since I don't think the fibers would stiffen
torsionally if the actual fibers were fore-aft-left-right.

I'm confused.  Do the fibers go fore-aft-left-right or at 45 degrees to
the aircraft axes?

By the way, I asked Martin about breaking it into two layups, one
forward of and one aft of the baggage bulkhead. (I have a fast build kit
with the bulkhead already installed.)  He said that would be fine.

- Rob Wolf
rwolf99@aol.com

[I used a work e-mail address.  Don't reply there or I won't get
it. rwolf99@aol.com is the proper return address]