
The Fairey Rotodyne, the vertical takeoff and landing airliner time forgot - rbanffy
https://arstechnica.com/cars/2020/02/the-fairey-rotodyne-the-vertical-take-off-and-landing-airliner-time-forgot/
======
bediger4000
This is a great picture, if you're a structural engineer. If you look at the
body panels aft of the landing gear, you see wrinkles in the skin, from lower
left to upper right. Under the wing, you can see wrinkles from lower right to
upper left. That means the skin has buckled in shear. This is known in the
airplane trade as "diagonal tension". If you are careful, you can save a lot
of weight by making the web of a deepish beam so thin that it buckles under
limit load. You have to put in compression members to keep the flanges of the
beam from collapsing vertically. In the case of the Rotodyne's body, that
would probably be the periodic frames or rings.

I believe this technique was first used on the DC-3 wing spar.

Anyway, this means that the helicopter-rotor is pulling the Rotodyne up,
causing the body to sag down on both sides of the wing. Either the Rotodyne is
heavily loaded (crash-test dummies or something) or it's accelerating
vertically. The depth of wrinkles would make me wonder if they skin is too
thin, or ask if this was some kind of limit load flight test.

One of the other pictures in this article's slideshow is of the Rotodyne's
interior, showing an alternative technique of lightening a beam's web: putting
flanged holes in the web of the body frames. Sometimes you can't do thin webs
for other reasons, maybe secondary loads like wiring or control surface
cabling. You just cut holes and use some kind of ram to draw out flanges on
the side of them.

