Wednesday 20 December 2017

Quibans 75: Don't Panic!

This story appeared in most newspapers.  The Sun put it like this:


200 litres every hour!  Clearly letting in water isn't ideal for a ship, but is 200 litres a lot?

How long before it will sink?

Some data here (from the Daily Telegraph) might help:





Some thoughts/answers:
I googled the capacity of a standard bath-tub.  It appears that 120 litres or 150 litres are fairly common capacities.
To put this into perspective: it's letting in about one and a third bath-tubs of water per hour.  That doesn't seem very much!

A length of 920 feet, beam of 230 feet and draught of 36 feet are given in the Daily Telegraph graphic.  I assume that 'beam' means the width of the ship and that the 'draught' is the amount of ship under the waterline.  There is a lot of aircraft carrier above the waterline, but if we find the rough volume of ship underwater (treating it a cuboid) then we would get 920*0.3 * 230*0.3 * 36*0.3, which is about 200,000 cubic metres.  That's 200 million litres.

At 200 litres per hour that is a nice round million hours before the part currently below the waterline to fill with water.  It will take just over 100 years for this to happen.  So if left untreated, if it still exists in a hundred years, if no-one uses a pump, and if the navy runs out of buckets for bailing purposes, then the ship will probably be in trouble early in the 22nd century.


Sources:
https://www.thesun.co.uk/news/5168494/hms-elizabeth-leak-navy-repairs-millions/
http://www.telegraph.co.uk/news/2017/12/18/hms-queen-elizabeth-britains-new-31bn-aircraft-carrier-has-leak/


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