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Date: Tue, 15 Jan 2013 13:22:08 -0500
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From: "Rob Murawski" <rob@robmurawski.com>
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Subject: RE: [LML] Re: Max Gross 360 LNC2
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With all of this discussion on max gross weights for the Lancair 320/360,
what is the engineering/design decisions that has gone into increasing the
gross weight?  The reason I ask is that, I assume, the factory has done some
type of engineering analysis.  The factory increase in gross weight document
is:

http://www.lancair.com/media/builderupdates/235-320-360/Non-PDF-Docs/WeightI
ncrease320-360.pdf

Here, it states that the new main gear overcenter link must be used
(Standard in kits produced after 10/93), the stall speed will be increased,
and the allowable G limits are reduced to +4.0/-2.0. (Those reduced G limits
aren't normally a problem for me)  The maximum landing weight has not been
changed.

In Mac McClellan's blog
http://macsblog.com/2011/08/when-a-kit-aircraft-is-not-a-kit-aircraft/ he
asserts that all changes to a kit make each one a one-off.  He refers to
Dick (Van's) VanGrunsven's article about the engineering that goes into
setting the RV-10's gross weight:
http://macsblog.com/wp-content/uploads/2011/08/94-99_Handbook_v6.pdf

While Van (nor I) dispute that there are airplanes flying around
(successfully) with higher gross weights, I'm concerned that I do not have
the engineering background to justify any gross weight other than to use
what the factory provides.  Vans asserts that the built-in engineering
margin belongs to the designer and you can't have it.

In particular, does the G loading become so low that I'd have to be
concerned about turbulence breaking my wings off?  I have no idea.

Granted, the 360 has a lot of factory options.  And I agree that no two are
probably alike.  But I feel a little better while building mine that I'm
sticking to something that a real aeronautical engineer designed and
approved.  (That is meant that *I* do not have the aeronautical engineering
skills to make that determination, I can't speak for anyone else)

Thoughts?

I have no idea what mine will weigh when finished.  But I know the
girlfriend likes to pack heavy. Might be time to look for a 4-place...

-Rob  (Lancair 360 MKII, 15% completed)