reply to post by Grayarea
Yes i belive that the window thing came directly from subsequent lab studies of the failures of the two aircraft.
To the "Its just another cover story by TPTB" crowd, not so at all.
the loss of these two aircraft was a shock to the british aeronuatics comunity, and to air travel in general.
When subjected to turbulance at altitude the skin failed and the plane broke up, simple as that, no need for devils triangle and the like.
At a time when the industry was just really beginning to take hold, these two crashes had chilling effect. Air travel had to be viewed as safe if it
was going to compete with rail and ship for long distances.
British engineers looked long and hard into the possible causes of the planes breaking up.
They took fuselages into the pressure chamber, then they took them into a pressure chamber that was chilled.
They cycled the fuselages through a number of take off to landing cycles at altitude, and they had failures.
Through exhaustive engineering they tracked the problem down to one main thing, an aluminum alloy that was not suitable to the task.
In some aluminum alloys, mechanical properties vary greately with temp.,
They get less ductile as they get colder.
This lead to stress cracks forming from rivet holes and the afore mentioned square corners on windows.
As the aircraft went through cycles of heating and cooling the skin also developed cracks.
These accidents lead to changes in the way aircraft are built, they learned more about how al alloys perform.
The process of changing physical properties with changing temp, is utilized today in the industry in "refigerator" rivets, or self tempering
The high quality rivets used on aircraft skins are made from an alloy whos pysicacal properties change greatly with temperature, but this time in
reverse, they become less ductile as they warm up.
The rivets are kept chilled till use, and at this chilled temp they are very workable allowing for the heads to dished over without cracking.
But once they start to warm up they alloying elements move around into their preferred positions there by stregthening the rivet.