Groundhog Thread Part Deux - P-39 Fantasy and Fetish - The Never Ending Story (Mods take no responsibility for head against wall injuries sustained) (6 Viewers)

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I love the Safety Plane. Why use riveted panels when you could use screws?
That might be the first plane I ever tried to research on Wiki. I had to know if it was real or not.
Screws are a.) heavier (steel vs aluminum), and b.) usually 'overkill' re; Shank dia/shear stress allowable relative to the skin, c.) labor intensive to install, d.) more chance of 'backing out' due to vibration and flex of ribs and skin. A typical 'screw' installation is a nutplate which is ridiculously overweight re; AN bucked rivet.

95% of sheet metal installations over rib/bulkhead are structural shear panels designed to help absorb and transfer loads and should be 'permanent'.
 
Screws are a.) heavier (steel vs aluminum), and b.) usually 'overkill' re; Shank dia/shear stress allowable relative to the skin, c.) labor intensive to install, d.) more chance of 'backing out' due to vibration and flex of ribs and skin.
And:
e.) subject to dissimilar metals corrosion over time or in a marine environment.

re; Shank dia/shear stress allowable relative to the skin
To those of us who aren't engineers:
An aluminum rivet in an aluminum skin will have similar resistance to distortion, and when stressed to the point of flexing, will "share" the stress, each yielding a tiny amount and minimizing the concentration of stress at any one point. A steel screw in an aluminum skin has almost no "give", forcing the aluminum to do all the yielding and increasing the risk of failure. One failed fastener point tends to put heavier loads on adjoining points, leading to a "zipper" type failure.
 
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