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Aeronca 11AC Chief Project FS
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 |
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