Why Hood's armor belt was not F3 protection

Hood cannot be considered as well protected as the F3 design. Her armor belt was long and comparatively shallow, whereas F3 belonged to a design line explicitly described as fully armored. Tiger provides another comparison because denser subdivision helps explain her displacement and resilience relative to Renown and Repulse. Two ships can both list a 12-inch belt while protecting very different areas and placing different internal structures behind it. Belt thickness alone cannot establish equivalent protection or settle whether a design is a fast battleship or a battlecruiser. Protected area, internal armor, and subdivision must be read with the headline thickness. A hypothetical 15-inch-gunned Tiger is judged decisively stronger than Renown or Repulse in a fight.