High wings and structural strength

Mxsmanic wrote:
Dylan Smith writes:

Funnily enough, a sturdy metal beam across the fuselage (usually two -
one at the front, where the main spar attaches, and one at the rear).
Windows can still be put in the roof. For a light aircraft 'sturdy'
doesn't mean 'massive'.

It sure is hard to see anything in photos.

Are high-wing designs stronger, weaker, or about the same as low-wing
designs? Do they have cost or safety advantages/disadvantages?

*** On a strut-braced high wing airplane, the wing, the strut, and the
fuselage form a triangle, which is inherently a strong shape. With a
low-wing airplane, the same
loads have to be borne by a spar inside the wing. The lift is trying
to bend the
spar.

Another advantage of high-wing airplanes is that they require less
dihedral, because the fuselage center of gravity is below the wing.

OTOH, the struts are draggy. Don't know if they're more or less
draggy than
the thick wing root that you have to have without them.

- Jerry Kaidor

wrote:

*** On a strut-braced high wing airplane, the wing, the strut, and the
fuselage form a triangle, which is inherently a strong shape. With a
low-wing airplane, the same
loads have to be borne by a spar inside the wing. The lift is trying
to bend the
spar.

Another advantage of high-wing airplanes is that they require less
dihedral, because the fuselage center of gravity is below the wing.

OTOH, the struts are draggy. Don't know if they're more or less
draggy than
the thick wing root that you have to have without them.


The struts are draggier. The strut generates drag, and the
attachment points generate even more; that's called "interference
drag." On a strut-braced low-wing that drag can foul up the boundary
layer pretty good.
The low-wing airplane's strut has to be more massive than the
high winger's because it has to resist buckling. Even then, "jury"
struts are often employed to maintain position of the centre of the
strut to prevent buckling under load. High-wing airplanes like the Cub
and Citabria have those jury struts as well to improve the negative G
figures.
Typical strut-braced low wing airplane:
http://images.google.ca/imgres?imgur...lr%3D%26sa%3DN

Another one:
http://1000aircraftphotos.com/Contributions/3520L-1.jpg

The cantilever wing isn't all that thick. The structure within it is
much heavier.
http://www.aircraftdoorseals.com/ima...ssna%20210.jpg