Unexpected behaviour - rebuild vs new build

[wlbjork]

1900 start, custom fleet build, no tech variance

Opened my CA counter-raider for a rebuild after developing Steam Turbines, Testing Tank for Hull Form and Oil Fired Boilers (among other techs), and found I could increase speed by 2kn with a major rebuild of the engines and left with 200t free (too much to push speed to 23kn).



"Excellent," I thought, "but 10 months at 1,400 is probably not much less than a new build and I can probably get another knot or two with the extra weight reductions in play."



It appears that:

The increase in speed requires additional armour to the value of 300t per knot of speed, which seems somewhat excessive considering I'm switching from VTEs to more efficient Steam Turbines (less volume and less space required for same power output)

Testing Tank appears to apply to rebuilds (unexpected behaviour - the testing tank is to allow the hull to be redesigned to optimise it's efficiency, something that is difficult to do with a ship already in existence!)

Finally, I don't see any effect from the Improved Turret design tech - I'd expect a 1t reduction per turret (to 106t/110t) for another 14t saving.

[attemptingsuccess]

I'd guess that the new-build ship is longer and narrower due to the increase in speed, whereas the rebuild doesn't get longer since its using the same hull form, longer ships with more machinery would likely need more armor

[wlbjork]

I can understand maybe a little more armour - but that 538t extra displacement (assuming short tons) is the equivalent of 2,189 cubic feet of pure iron.

Obviously, the armour in question is not pure iron, but some form of steel-like alloy - but nonetheless, iron will still be the largest element within the alloy so let's assume it's something over 2,000 cubic feet of armour (again, assuming short tons).

[wlbjork]

I can understand maybe a little more armour - but that 538t extra displacement (assuming short tons) is the equivalent of 2,189 cubic feet of pure iron.

Obviously, the armour in question is not pure iron, but some form of steel-like alloy - but nonetheless, iron will still be the largest element within the alloy so let's assume it's something over 2,000 cubic feet of armour (again, assuming short tons).