"With a barbette ship (Tiger) the framing that you have to chop out, and rebuild is much less; and if you can gut the barbette cylinder and fit the Terrier launcher revolver magazine inside it, you get an armored magazine as well as a reduced top-weight problem that allows you to fit a huge 983 3 D radar and the Type 83 Yellow Rivers for missile guidance.  "

That is done to prevent flex and bend in the hull. (hogging) which goes for steel ships just as much as it does for wooden ones. You don't want the hull to have too much weight (I refer to this as its understood in gravitation, acceleration and INERTIA) in some segments and not enough in others to induce massive changes in force loading over the length of the ship. This is true for any LONG object in a fluid medium (aircraft for example) so I understand the principle as it causes unnecessary BEND and TWIST. 

 

In this Swiftsure/Tiger case we look at the heavy radars and the lightweight missile launchers and we apply ballast load correction, segment by segmnent. We cut down superstructure where needed and use masts where we install the radar instead of towers and add steel ballast load where we need it, to make up for the lost turret gun house mass in those sections where we remove it.

 

Shipwrights became very good at this (witness the rebuilds of Tennessee, Maryland, and West Virginia), possibly the most fantastic rebuilds in history for the IMPROVEMENT of a ship class type.  The British also became outstanding at this (though no-one ever credits their remodeling of the Type 12s into the Broadbeam Leanders as the CLASSIC example of a hull rework). The critics prefer to remember the Type 22/23 debacles that followed.. 

 

The US SCL and SCB carrier rebuilds show  where you have to be careful when you do a segmented section rebuild. The Essexes were already well desugned so the angled flight decks which were float tank tested on scale models to check calculations were easily fitted. Not so were the Midways.  The Midways were almost ruined because the Brooklyn Navy Yard nitwits put too massive a flight deck on a badly modified Iowa hull originally, and didn't do their buoyancy calculations properly. The carriers were NOSE heavy in aircraft trim parlance. Compounding the problem with a HUGE angled flight deck and deck edge lifts in the rebuilds, drove that poor ship (Midway) almost five feet deeper into the water, made her stern heavy, and made her continuously WET. By godfrey, though, they solved that bow heavy problem!

 

The Princetons also show what bad design loading means. Hogged out and actual death traps while in service, they never should have seen service in a peacetime Navy. Its a miracle we only lost one of them to a bombing.. In that case there was too much end loading with the flight deck overhangs over bow and stern. They bent and twisted in the middle.

 

Just TIDAL gravitatiom forces can ruin ships; never mind slamming them into waves. (Arleigh Burkes)