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Keeping green water out of the chain locker



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What is the issue?
Whilst 'going to weather' or enduring severe conditions, a vessel can take in a large quantity of green water through the smallest aperture. The vast majority of a vessels seals are gravity-based covers but in very rough conditions these are easily overwhelmed as water is practically injected in. That is the face of the wave lays over the aperture and then the following body and its energy press upon this to literally inject water in through the smallest crack.

Why address this?
Getting any water below is far from ideal, especially so in round hulled vessels where it tends to slosh about as the vessel rolls about.

How to address this?
Make up a set of secure bungs that can be tightly wedged into every vent aboard and label them so they can be easily positioned.

This vulnerability was noted in the 'Fastnet 79' (link to download as zipped PDF of the special incident report External link) disaster that cost the lives of 15 sailors. One of the earliest inquiries into the disaster was published jointly by the RYA and the Royal Ocean Racing Club (available as a PDF External link) pointed to a number of other significant water entry points, beyond the companionway, and that this issue was a lesson already learned...
A questionnaire following the 1956 Channel Race gale revealed that the majority had serious problems caused by water entering the boat through cockpit lockers, hatches, ventilators and similar openings not normally under water... That report stated that those findings were passed to designers and builders without comment. Some of those lessons were either not properly learnt or appear to have been forgotten.


One of the most difficult apertures to plug is the chain hole. Waves frequently break over this area on the foredeck which, if it drains back into the vessel, makes it one of the most critical to plug. Worse water that overfills from the anchor locker also tends to wash back silt that has accumulated there - often rich in organic material and smelly. A complete seal with a tight fitting plug that fits around the chain can be made up as illustrated below.

Chain hole plug
Photo: Tony Gibson

The plug can be used as two halves and then pressed into place. Alternatively, the two pieces can be bonded together into the chain with epoxy, making it an integrated and permanent end piece to the chain. This offers the best water seal.

With thanks to:
Michael Harpur, Yacht Obsession.
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