offshore safety - page 6
4.6 Personal safety equipment
Lifejackets and buoyancy aids provide buoyancy using air, foam, or combining foam and air. Inflatable air jackets are becoming the norm, though regulations in some countries now require the carriage of full foam lifejackets, and it is left to the skipper to decide whether inflatable jackets are also carried. Inflatable jackets are comfortable to wear and worn more often, but require regular checks.
When to wear?
The decision to wear a lifejackets is often based on the weather conditions and experience of the crew and the roles they perform. A widely adopted rule aboard larger boats is: "wear a lifejacket unless you are sure you don't need to".
Generally, lifejackets should be worn:
When you want to wear one.
By non-swimmers when on deck.
When the skipper deems it necessary.
When abandoning ship.
If there is a reef in the sail.
In reduced visibility or confused sea states.
When performing high risk jobs such as bow.
A lifejacket should be available for every crew member. Specialist lifejackets are available for infants and children.
Life Jackets are rated in the following Buoyancy Rating Categories:
275 N - 150 N - 100 N - 50 N.
This means that a 150 N life Jacket provides 150 N for floating force. If a rock on the bottom of the ocean weighed 14 kg on a sunken scale, then a 150 N rated life jacket would hold it afloat - barely. A 15 kg rock with a 150 N life jacket would have neutral buoyancy.
The average male weighing about 91 kg (200 lbs) requires about 4kg (10 lbs) of buoyancy. The math here is done using the person's body makeup of 80% water (neutral buoyancy) and 15% fat (positive buoyancy). 4 kg converts to 40 newtons. Thus, the 150 Newtons is plenty for the average person and considered the minimum for an adult in off-shore conditions.
Safety lines tethers
Harnesses. A deck harness and safety line connects the wearer to strong points around the boat. Harnesses are often integral to a lifejacket and reduce the likelihood of you being lost overboard. There is a history of sailors who have been clipped on, falling out of their harness when they hit the water because they are not fitted tightly. The best practice for using a safety line is to clip on to strong points set well inboard, and use as short a safety line as practical. Safety lines with a mid-line clip provide greater flexibility. Harnesses have saved many lives, but they are generally not designed for towing people in the water of for lifting people. They are there to prevent you from falling overboard.
Harness with safety line
Jackstays and strong points. Safety lines are clipped to strong points in the cockpit, near the steering position, companionway, and to jackstays running fore and aft along the decks to provide a seamless path around the boat. Jackstays can be of wire, spectra or webbing tape.