wrote:

Semi-Monocoque is the term, not "complimentary."

Whatever. My professor in graduate school (a Stanford Ph.D.) called it
complimentary, since the stringers and longerons compliment the skin in
that, as I said, they provide strength in a direction that the skin
does not have, which is out of plane stiffness. Since a true Mono
(meaning a single) coque (shell) structure has only a shell for
structure (an egg is a perfect example), any deviation from this is
often called semi-monocoque, even when the skin carries no load, which
is an incorrect way of describing such a structure.


Your average CessBeeMooPip is semi-monocoque in the aft fuselage.

The fuselage skin from the firewall back is the primary structural
member everywhere except at the wing spar attachments, and the landing
gear on Cessnas.


Most of the rest has heavy structural members and the skin is used just to keep
things square.

Dan

Well, I agree that many aircraft are much heavier than they need to be
because the designer couldn't or wouldn't do the calculations and
design that would eliminate excess weight (i.e. the Cirrus airframe,
even though it is supposedly made of modern high strength composite
structure, is actually about 300 lbs heavier than aluminum planes in
its class). Perhaps the longerons and stringers are heavy enough to
take the necessary loads, But the skin serves as the aerodynamic shell,
or Loft as it is called everywhere on the aircraft, and in places where
the skin is in tension, such as the bottom of the wings, the skin is
again a major structural member. In planes that have heavy wing skins,
such as private jets, the wing skin is again a major structural member.
Since the OP was inquiring about wooden aircraft, it is worth
noting that the reason wood still is a wonderful material even though
its tensile strength is much lower than metal (the strongest wood is
Hickory, which has a tensile strength of less than 2000 psi), is
because its weight versus volume is lower, resulting in a thicker
section for the same weight. This means that the thicker section has a
much better buckling load than metal for the same weight. Plywood skin
aircraft carry much more load in the skin (which is the best place to
carry it) due their superior buckling properties.
Aircraft skin, in a properly designed airframe, does much more
than just hold everything square.

Bud