Air Draught Detector
'Air Draught' is the height of a ship above water. Many ships have masts or superstructure that can be temporarily lowered to reduce their air draught when required.
The Manchester Ship Canal is crossed by a dozen fixed high level bridges. Some of these were originally equipped with a means of alerting over-height ships approaching them. This consisted of a cable stretched between two masts, connected so that a ship which snagged it would lift some weights and perhaps ring a bell.
Here, Arklow Cape passes between the abandoned masts below Warburton Bridge; you can just see the pulleys at the top of each mast but the cable is long gone.
Air Draught Detector
'Air Draught' is the height of a ship above water. Many ships have masts or superstructure that can be temporarily lowered to reduce their air draught when required.
The Manchester Ship Canal is crossed by a dozen fixed high level bridges. Some of these were originally equipped with a means of alerting over-height ships approaching them. This consisted of a cable stretched between two masts, connected so that a ship which snagged it would lift some weights and perhaps ring a bell.
Here, Arklow Cape passes between the abandoned masts below Warburton Bridge; you can just see the pulleys at the top of each mast but the cable is long gone.