The RNLI continues to develop lifesaving equipment of all kinds, to meet new demands as new techniques and materials become available. Tust as with the Severn and Trent class lifeboats often no commercial product suits the exacting needs of lifeboat crews and the Institution has to break new ground to find the right answer. A new lifejacket for the crews of all-weather lifeboats was a case in point:What does a lifejacket need to do? The boats and equipment used by lifeboat crews may have changed almost beyond recognition over the years, but the essential task which they carry out remains the same.

As a result the basic requirements for some items of equipment also remain the same, even though technological advances may result in a totally different product.

One example is the lifejacket, which must fulfill the same functions today as it did when the first was designed back in the 1850s.

It must: enable crew members to go into the water on a split second's decision, and immediately provide enough buoyancy (floating power) to support them and another person, restrict movement as little as possible and not interfere with other protective clothing, either in the boat or in the water, be comfortable - or crews would not be willing to wear it at all times be quick and simple to put on be hard wearing When different pieces of equipment are used together, it is vital that their designs are kept in step. In 1971 the RNLI introduced a new lifeboat design which had an enclosed wheelhouse, unlike the mainly open boats usedpreviously. Although this obviously offered greater protection and shelter, lifeboat crews found that their current, closed-cell foam lifejackets were very bulky and too hot to wear.

Nothing which met all the requirements of lifeboat crews was available on the open market, so the RNLI decided to develop a new lifejacket which crew members would be happy to wear all the time.

Sizing up the problem The major problem with the existing lifejacket was its bulk, and to solve this a new approach was needed. The lifejackets used by crews in the past had all been made from bulky materials which had inherent buoyancy - cork, kapok and closed-cell foam.

The new lifejacket has no bulky, buoyant material and is therefore not inherently buoyant but it is light and comfortable to wear. However, the moment the person wearing it enters the water it inflates automatically to provide the bulk, and therefore buoyancy, needed to support them.

Following considerable preliminary work in-house, the RNLI enlisted the help of the commercial lifejacket designers and manufacturers Crewsaver. Together they set up a small working group with representatives from the RNLI, Crewsaver, Musto (specialists in foul weather clothing) and The Institute of Aviation Medicine (responsible for technical and scientific testing of the lifejacket).

They came up with a design in which three layers of polyurethane-coated nylon fabric were joined to make two 'stoles' (inflatable bags) laid on top of each other.

The stoles and a cover are securely fixed to a safety harness.

The stole nearest to the body inflates automatically when a crew member hits the water. The water causes a paper ring to break, allowing a strong spring to force a plunger against the lifejacket's operating head. This then pierces a small carbon dioxide canister with a needle and the gas escapes to inflate the stole. The lifejacket begins to inflate within five seconds of hitting the water.

The outer stole, furthest from the body, can also be inflated to provide extra buoyancy if required. It too has a gas bottle, but the release of gas is triggered manually by pulling a small toggle.

Testing times The new lifejacket has been carefully designed to ensure it meets the requirements of the RNLI, British standard BS3595 and European CEN standards. Tests included monitoring the lifejacket's buoyancy at different temperatures and over different periods of time, and checking how long it takes for the lifejacket to inflate.Once the basic design had been finalised, 12 prototype jackets were made and tested by crews at two lifeboat stations. Following their comments, minor modifications were made and 50 new prototypes were issued to four lifeboat stations for a three month in-service trial. At the end of the trial crews filled in questionnaires and the lifejackets were returned for inspection. Once again, slight modifications were made, including changing the fabric used to cover the stoles and introducing a different method to attach the lifeline.

1850s CORK JL S crews still had to row their lifeboat out to sea, lightness and flexibility were vital to a successful lifejacket design in the last century.

The RNLI tested the buoyancy, flexibility, weight, durability and resistance to water of a range of materials: • air - light and easy to stow, but punctured easily • horse hair and rushes - light and buoyant, but neither waterproof nor durable • woods such as baobab and balsa - light and buoyant, but hard to obtain and expensive to buy.

The final design used narrow strips of cork fitted together so that the lifejacket moved with the crew member's body. It was bulky and hard to stow, but provided good buoyancy, was very hard wearing and, importantly, was popular with the lifeboat crews who used it.1908 KAPOK jT .t the start of this century a new material, kapok, was introduced. A fine, cotton-like material, kapok is mainly used nowadays to stuff cushions and soft toys.

But as THE LIFEBOAT noted in 1929, kapok also had properties which made it the ideal material for lifejackets: 'It looks very like cotton, but its follicles, which are really tubes closed at the ends - like hair and rushes - have a natural oil which makes them entirely non-absorbent of water, while the air contained in these tubes and between the follicles themselves give a very high buoyancy . . . per pound (weight) of lifejacket, the supporting force of kapok is 3.5 times that of cork.' Although there were some problems developing the kapok design - at first many crews announced that they'd rather drown than wear the new jackets - the brown canvas-covered kapok jacket remained in use until the late 1960s.1970 CLOSED CELL FORM At the end of the 1960s the RNLI decided to replace the kapok lifejacket.

Early design models failed because brass eyelets on the jacket's cover reacted with the salt water and reduced the effectiveness of the fabric.

Modifications were made, and in 1970 the closed cell foam lifejacket made by Beaufort was introduced.

The lifejacket consists of a rubberised bladder (bag) containing buoyant closed cell foam. This is contained within a hard-wearing orange nylon cover which is removable. The inherent buoyancy provided by the foam in the bladder is sufficient to support a crew member, and an oral inflation of the bladder provides the extra buoyancy needed to support another person.

Although the Beaufort lifejacket is easier to work in and more supportive than kapok, it is still fairly bulky.

Now, in line with changes to lifeboat design, the RNLI is looking for a new lifejacket which provides the buoyancy needed, but is also light and comfortable to wear.

A lifeboatman wearing the current closed cell foam design This material was originally compiled by the Design Council in collaboration with the RNLI. It was distributed as a poster with DESIGNING, the Design Council's magazine for secondary schools.

The Design Council publishes a wide range of resources to support design education, including magazines, books, video and slide packs..