S!
If you look in ANC-18, the standard for design of aerostructures in wood, there isn't much data. But they do say that for fully reversed loading (R=-1) in douglas fir, the fatigue limit is around 30% of the ultimate strength.
Modern aluminium alloys have a fatigue limit about the same, but the older aluminium alloys used on WWII fighter aircraft, although almost as good were very prone to stress corrosion cracking. I think the main argument against wooden aircraft is not so much strength or lightness, but that they are prone to moisture absorption and so require hangars to be stored.
W.
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03-16-2010, 12:22 AM
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