How effective would a Type XXI U-boat with anechoic tiles be in the Second World War?
Short answerPotentially useful if perfectly installed, but unreliable adhesion could make the boat noisier and harder to maintain rather than stealthier.
NotesThe answer focuses on the practical weakness of early anechoic-tile technology rather than assuming a simple stealth upgrade. German Type XXI experiments showed that adhesive quality and maintenance mattered as much as the acoustic idea. A properly attached coating could reduce detection, but missing tiles left an uneven hull surface. Partly detached pieces could flap or disturb the flow and create noise of their own. The system is therefore an advantage only when production and upkeep keep the tiles securely on the boat.