Why twenty-eight-gun sixth rates disappeared from the totals

Why did the Royal Navy's twenty-eight-gun sixth rates disappear so quickly?

Many were rebuilt or rerated with fewer, heavier guns instead of simply being retired.

A change in the fleet table does not necessarily mean that the same number of hulls left service. Twenty-eight-gun ships could receive heavier weapons and be listed under a lower gun count. The example replaces a battery of 12-pounders with fewer 18-pounders. Rearmament therefore helps explain why one rating category shrank even while the navy expanded.