Re: Aeronca 11AC Chief Project FS

On Jun 22, 6:39 pm, "RST Engineering" <j...@[EMAIL PROTECTED]
> 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/certification/continuing/Alert/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