Why do ships have cicular windows,why not square ones?
In: Physics
Grab a sheet of plastic and put a shear force on the edge (rip it). Now, it either will need a lot of force to rip, or it will just stretch and deform.
Now, put a small cut or a notch in it. Then try to rip it at that cut. It will easily rip.
Corners in the sheets that make up the hull will also be weak for a similar reason. All the shear force is right in the corner. While the steel won’t immediately rip, it will flex more there and gradually weaken.
Already answered, but just to add to the proceedings…
Sharp corners (specifically internal corners) are stress raisers. They’re basically focal points for stress in material’s. Remove the focal point and the material stress is “spread out better”.
To build upon the existing, good answers in this thread, we originally built some jet planes with square windows. [The last surviving example](https://www.bbc.co.uk/news/uk-england-beds-bucks-herts-50585312) of a square windowed De Havilland Comet is now in a museum.
The square windows cause more pressure around the corners than on the flats and ultimately caused planes to crash. When these jet airliners were rolled out in the 50’s, we didn’t know better.
Nowadays, planes have rounded windows without corners to prevent these higher stress areas from causing issues. Boats have been aware of this issue for a long time and have had round windows for longer.
You’ll notice that windows thst undergo different stress profiles on boats and planes sometimes do have “squarer” corners – e.g. [Bridges](https://en.wikipedia.org/wiki/Bridge_(nautical)) on a ship or [the cockpit of a plane](https://en.m
wikipedia.org/wiki/Cockpit). In many cases, we still curve the corners, but in others we simply try to plan for and manage the increased stress this causes.
Particularly in taller boat Bridges – they aren’t going to be subject to harsh waves battering against them, or need to be watertight to several atmospheres of pressure like the windows lower down. The lower levels of stress on the window means it might be easier and cheaper to use a square corner.
Just look up the concept of shear flow. It’s very intuitive if you ignore calculations. Basically, sharp corners get concentrated stress.
It’s so when you change or move the window they can’t fall through the window hole. Also because windows tend to be heavy so they can be rolled away for easier transport.
Try this, you only need paper and scissors. Take two sheets of paper, on one of them, cut out a corner in a rectangle shape (so your sheet looks like a very thick L), and on another, cut out a quarter circle instead. Now try to pull apart the corners that you created by cutting out, like trying to make the part you cut out wider – you will notice it is harder to do with the smooth, curved cut, while the one with the right angle will start tearing at the point of the angle right away.
Corners are sharp, like knives. a ship on the water moves around and bends and you don’t want to push on a sharp edge. So windows and doors are made round
May I present to you the Romans with their new fangled *Teknologie* “The Arch”! Distributing the load it bears across many of its members maintaining compression along the entire structure.
It is known as a [Funicular shape](https://en.wikipedia.org/wiki/Funicular_curve)
>When evaluated from the perspective of an amount of material required to support a given load, the best solid structures are compression-only; with the flexible materials, the same is true for tension-only designs. There is a fundamental symmetry in nature between solid compression-only and flexible tension-only arrangements, noticed by Robert Hooke in 1676: “As hangs the flexible line, so but inverted will stand the rigid arch”, thus the study (and terminology) of arch shapes is inextricably linked to the study of hanging chains, the corresponding curves or polygons are called funicular. Just like the shape of a hanging chain will vary depending on the weights attached to it, the shape of an ideal (compression-only) arch will depend on the distribution of the load.
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