From: RWolf99@aol.com
Message-ID: <a1.d72e05c.274ea9af@aol.com>
Date: Thu, 23 Nov 2000 12:11:11 EST
Subject: Modification Philosophy
To: lancair.list@olsusa.com
Reply-To: lancair.list@olsusa.com
Mime-Version: 1.0

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Ted and Curtis have raised interesting points.  I think Ted was driving at 
"Think carefully before making modifications because there may be other 
effects you haven't foreseen".  An example would be deleting the header tank 
and running straight off the wing tanks.  If you didn't foresee the 
subsequent requirement to change from 1/4 inch fuel lines to 3/8 inch you 
could set yourself up for a problem.  This is a trivial example of the basic 
point.

I think Curtis was driving at "The factory has told us to manufacture this 
part in a particular way but this other way seems easier".  Maybe blind 
rivets in pushrods isn't the best example but there are many times where the 
factory approach is less desirable -- maybe you have a tool that most of us 
don't have which makes the job easier, or maybe you don't have that expensive 
tool that the factory has, or maybe you're more skilled at some manufacturing 
technique and prefer to use that one over what the factory described, or 
maybe you're stuck doing it by yourself and the four-handed approach won't 
work.  So you do it a different way.

So their discussion was a little bit of "apples vs oranges" but they each 
raised good issues.

Since you asked for my two cents (didn't you?), I think both approaches have 
merit and risks.  The forward hinge canopy most of us use on LNC2s is the 
result of a builder-developed upgrade, for example.  So are the torque tube 
canopy latch and the main gear shock absorbers (both kinds).  All of these 
positive changes required a fair amount of engineering, but if you can do it, 
more power to you, and please let us know what you've done so we can copy it 
if we want to.  (It's a shame we builders are so secretive about our 
innovations, ain't it?)  But like Ted says, you might be biting off more than 
you think.

Concerning alternate manufacturing techniques, I think we're fooling 
ourselves if we say the factory and the FAA know all.  However, there are 
standard practices that have proven themselves over time to be airworthy, and 
the FAA goes to great pains to get the word out.  Having said that, there are 
many manufacturing techniques that don't make sense in our garages because we 
don't have the hundred-thousand-dollar tool or we don't build a jig because 
we're only doing it once.  Or maybe it just seems awkward to do it that way.  
And Curtis rightfully said "I have a problem doing it that way, how about 
this other way of getting it done?"

I'm fortunate to have the engineering training that allows me to say "I 
understand this substitution and it's okay" in certain limited areas.  But I 
think I know my limitations and often ask for advice in the other areas.  
That's why this forum, and the telephones at the factory, and the EAA 
chapters and their Tech Counselors are so valuable.  Don't be bashful.

- Rob Wolf
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