Dan ...

I maintain on an inspection basis a few 11ACs. I have yet to see one with
that AD spar cracking problem. It was reported a few times to Ok City under
their wonderful "tell us about your problems" program and (I'm wild ass
guessing here) some wet behind the ears history major puke that couldn't
tell a cotter pin from a diaper pin picked up on it and made it an AD. It
is, as far as I can tell, not a "tendency" but an abberation that a few of
the Airnockers have suffered. Not a widespread problem.

On the other hand, a few years ago, I inspected airplane after airplane with
cracked spars. Upon investigation, I found that I had a cracked inspection
mirror {;-)


Jim

--
"It is the mark of an educated mind to be able to entertain a thought
without accepting it."
--Aristotle


wrote in message
...
On Jun 22, 6:39 pm, "RST Engineering" wrote:
An 11AC with a possible
busted spar isn't a bargain at giveaway prices, much less the asking
price.

I would expect to replace those spars anyway. The AD 2000-25-02R1
addresses the tendency of Aeronca spars to crack through the rib nail
holes as the wood dries out and shrinks across the grain while the
metal ribs try to prevent it, splitting the spars along the grain. The
plywood doublers at the spar attach points cause local stiffness that
forces the wood at the top of the spar at the ends of the doublers to
suffer compression fractures which extend down through the spar. The
plywood doubles at the spar butts cover cracks through the spar
itself, and perhaps those doublers are contributing to stress cracking
in the same way as the metal ribs.
See this:
http://www.tc.gc.ca/civilaviation/ce...rt/2001-05.htm
Re-sparring isn't cheap, and those aluminum ribs are often
corroded, too. American Champion sells brand-new all-metal wings with
or without the fabric. They aren't cheap, either.

Dan