Why an 80-gun two-decker makes an adaptable battle line

What would the ideal ship of the line look like?

A two-decked 80-gun ship offers the best broad balance of power, numbers, handling, and maintainability across periods.

The ideal choice depends on period and navy, but an 80-gun two-decker offers the greatest general versatility. Its rating might shift between first, second, and third rate as standards changed, yet it would remain a credible line-of-battle ship. Two decks give a useful length-to-beam ratio without the maintenance and handling burden of a three-decker. It also preserves enough economy to field a proper squadron rather than concentrating resources in a few exceptional ships.