What is the minimum diameter of a bell or gong on a vessel of 20m or more in length?

The minimum diameter of a bell or gong on a vessel of 20 meters or more in length is 200 mm. This specification is part of the International Regulations for Preventing Collisions at Sea (COLREGs) that outline the sound signaling devices required for vessels of different sizes.

The use of sound signals is essential for ensuring safety in navigation, especially in conditions of restricted visibility. For vessels that are 20 meters or longer, a bell or gong serves as an audible signal to indicate their presence to other vessels nearby. The diameter of 200 mm has been established to ensure that the sound produced is adequate for being heard at a sufficient distance, which is crucial for maintaining safe distances and preventing collisions at sea.

This size requirement reflects a balance between being loud enough to be effective in alerting other vessels while still being manageable for the crew to maintain and operate.