Why are portholes round?

Plodd

"The constant up-and-down motion of a ship puts considerable stress on the ship's skin, or outer covering. If portholes were designed with angles, this stress would tend to concentrate at those points and perhaps crack the skin. With round portholes such stress is evenly distributed around the holes, making it less likely for such cracks to occur." http://www.bitesizecanada.org/cause_11.htm Sep 05 10, 1:15 AM

Baloo55th

Portholes can actually prevent cracks from spreading too far. If they were square cornered, as Plodd points out, the stresses would not stop - and the square corners might well be the starting point for cracks. A well designed ship once had a nice neat square cornered lift shaft installed. Result: disaster. (Source: 'Structures', J.E. Gordon) In fact, a crack in metal can often be stopped by drilling a nice round hole at the tip (or just past the crack so long as you're sure which way it is going). By this, you're creating a mini-porthole. Sep 05 10, 7:46 AM