Message-ID: <19981023222139.5508.qmail@www02.netaddress.usa.net>
Date: Fri, 23 Oct 1998 22:21:38
From: Dan Schaefer <dfschaefer@usa.net>
To: lancair.list@olsusa.com
Subject: fastener torque, balance, hard points 
Mime-Version: 1.0

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To Bill Gradwohl - It's no laughing matter, Bill - there are no dumb
questions, only dumb answers. Learning new things is one of the 
justifications that allow us to build our airplanes (slightly para-
phrased). According to the regs, we're only doing this for our 
edification and education, etc.,etc., and having a fine airplane at 
the end of the process is, I guess, secondary - yeah, right! Anyway,
get a Standard Aircraft Worker's Manual or the equivalent, (they're
available from places like Aircraft Spruce for around $10). It has a 
great deal more in it than just torque requirements and all of it's 
important to this endeavor. Anyone not in the business, should have 
something like this at their finger-tips at all times. Other books 
that I think are invaluable to most of us ordinary pilgrims who are 
only going to build one , or two airplanes in our lifetimes is Tony 
Bingeles' three (maybe four by now) books. They are filled with a 
wealth of the kind of practical information that will answer many, 
many questions about building an airplane. He covers things like bolt 
torques, plus just about everything else that might come up. What I 
like so much about his books is that Tony explains WHY something 
should be done a certain way in addition to HOW. (No, I don't get 
anything for this, I just think we should use all of the resources 
available to us to build safe - after all, it's our butts in there,
and our friends and family's as well.

One of the quickest ways to render an aircraft un-airworthy, and in 
fact downright dangerous, is to rely on the auto mechanic's 
"armstrong" method of tightening (notice I don't refer to it as 
"torquing") threaded fasteners. The odds are, you'll over-tighten a 
nut, at best stripping it, or much worse, destroying it's design 
strength and setting it to fail when the design load is applied. 
Never use ANY structural fasteners that aren't aircraft grade AN or 
equivalent. They should come from a known source with correct head 
markings per the above manuals. Real AN fasteners are centerless 
ground, threaded after heat treat, provide a minimum tensile strength
of 125,000 psi and are Cadmium plated to very specific standards. 
AN (and equivalent) hardware is designed for this service, it's 
relatively free of stress corrosion and tends to deform when over-stressed rather than completely fail. No "high strength" or 
"hardened" automotive or garden variety hardware store nuts and bolts
should be anywhere near your building site. Thinking you're doing a
good thing, you can pay through the nose for a "premium" bolt at the
racing shop only to have it shatter because it wasn't the correct
alloy or subjected to the correct heat treat process.

One last thing more on this subject: buy a good quality torque wrench 
that covers the ranges you need (those numbers are in the manuals 
mentioned above) and HAVE IT CALIBRATED. You'd be surprised at how 
far off they can be when fresh out of the box. I know that Sacramento 
Sky Ranch did that in the past but you'd have to check with them, or 
go to someone local. It's very sensible insurance.

Have a good flying weekend, Cheers,

Dan Schaefer
N235SP


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