Weighty mat­ter about the QE2

The Herald - - OPINION -

IN your re­port (“Pride of the Clyde”, The Her­ald, De­cem­ber 1) it is stated that the QE2 has “70,327 tonnes weight”. This is wrong.

It is true that records show the QE2 as hav­ing a gross ton­nage which ranged from 65,863 to 70,327 dur­ing her seago­ing ca­reer but, in mar­itime cir­cles, gross ton­nage is not a mea­sure of weight. It is, rather, a mea­sure of in­ter­nal vol­ume which orig­i­nally equated 100 cu­bic feet to one ton. Since 1969, gross ton­nage has been a pure num­ber de­rived from a for­mula based on the log­a­rithm of the in­ter­nal vol­ume in cu­bic me­tres.

The weight of a ship is rep­re­sented by its dis­place­ment from Archimedes’ Prin­ci­ple : “a float­ing body dis­places its own weight of fluid”. In the case of the QE2, the dis­place­ment dur­ing the tri­als of De­cem­ber 1968 was 49,444 tons (Im­pe­rial tons of 2240 pounds each) at a mean draught of 29ft 8ins.

At the full load draught of 32ft, the dis­place­ment would be about 54,000 tons. You can see the ex­tent of the ex­ag­ger­a­tion of the weight, which con­cerns me.

For a num­ber of his­tor­i­cal rea­sons a ship’s gross ton­nage, which may re­main con­stant for many years, is well pub­li­cised and pub­licly avail­able while dis­place­ment, which varies from day to day as fuel, stores, pas­sen­gers and/or cargo come and go, is nei­ther pub­li­cised nor pub­licly avail­able – ex­cept for naval ships

I did not have the plea­sure of sail­ing on the QE2 but the ar­ti­cle did re­mind me of a Satur­day visit to Clydebank, 50 years ago, ar­ranged by Glas­gow Univer­sity En­gi­neers So­ci­ety, to see and tour the ship shortly be­fore her de­par­ture for tri­als. I still re­mem­ber be­ing im­pressed by the depth of the pile on the car­pets.

David L Smith,

4 Aber­corn Road,

New­ton Mearns,

Glas­gow.

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