WeKnow Life Jackets

WeKnow Life Jackets


Lifejackets come as foam-cored as would be typical for infants and children, and as gas-inflated.  These sit comfortably on the body when not activated, are small, and can easily be incorporated with a harness system.  Both types are capable of rotating a face-down incapacitated person in the water, and lifting their head high enough to save them in an unconscious state.  

Inflatable lifejackets come in varying inflated volumes, depending on the type of use.  The inflated volume is expressed as the equivalent upward force the lifejacket is able to exert on the human.  Lowest forces of around 165n for day sailing in good weather mean that the lifejacket is as small as possible.   Larger lifejackets exert typically 190n, whilst the largest systems exert 300n and are made for offshore, ocean sailing.


Inherently Buoyant Life Jackets (Foam Core)

Inherently-buoyant life jackets (foam life jackets) with suitable 'collars' extending around the back of the head are also capable of saving life of an unconscious person, but are always going to be more bulky as their state is fixed.  However, for children, this is more suitable as the activation system is not appropriate due to the need for manual inflation in the case of automatic failure.


CO2 Cylinder-Equipped Inflatable Lifejackets

This system is used in most adult and older child life jackets due to their small size and comfortable fit, allowing the user to freely move, but giving huge buoyancy when in the water.


Activation System

For the vast majority of CO2 activated inflatable lifejackets, the inflation is triggered by one of 4 methods:

1. Manual Inflation.  This is the simplest system, and is initiated by the user pulling sharply on a toggle or handle which is directly connected to the firing pin of the CO2 cartridge inside the lifejacket.  This releases the CO2 into the inflation chambers.  This method is also available for all of the following more complicated systems, to cover for automatic system failure.

2. Automatic Inflation.  Here, the firing pin is activated usually by a strong spring that is normally held back by a special water-soluble paper sheet.  Once the sheet gets wet, and usually within 3 seconds, the spring forces the firing pin to activate the CO2 cartridge.

3. Pro Sensor Automatic.  This gives added user confidence regarding the state of the cartridge by displaying cartridge condition and fill level through a window in the lifejacket.  The user thereby gets confidence that the jacket is indeed ready for use.  Unnoticed leaks and protection against firing an empty cartridge are thereby greatly reduced.

4. Hammar System.  This system uses a different method of determining that you have entered water.  Rather than waiting for water ingress into the lifejacket to activate the cartridge, instead this system uses the air pressure differential created by submerging the lifejacket in water to activate the system.  The system requires that the lifejacket is submerged 10cm or more into water, to create the necessary pressure differential.  In this way, the lifejacket does not rely on the water ingress time, and is not subject to unwanted blanking of the cartridge by the air bladder itself.  This is generally the most expensive system available.




Other Things to Consider

Modern life jackets have more and more extras available.  Here, we can review some of the important ones:

Harness.  This is incorporated throughout the structure of the harness, so that it is also capable of supporting the person's weight if they were lifted by a halyard or helicopter winch.  Thus, the webbing and buckles used are of a much higher strength than would be seen in the non-harness version of the life jacket.  The harness strong points are also used to attached a safety line, which can then secure the person to the boat via hard points in the cockpit, or Jack lines running the length of the boat.

Fit.  Basic life jackets tend to have a  shape that would sit flat if placed on a table.  There have traditionally been the shape of lifejackets.  Examples of this are our SeaGuard 165 and Classic 190.  However, with modern manufacturing techniques, the fit of the life jacket has improved, and companies can form a '3D' shape, which sits perfectly around the neck and back.  these life jackets would not sit flat if placed on a table due to their 3D shape.  Examples of this are our Active 190, and 3Dynamic Professional range.

Buoyancy.  Higher buoyancy life jackets would set the person higher in the water, and provide greater lifting power in extremely rough conditions.  However they would also hinder the persons ability to swim and move in the water.  Lower buoyancies are smaller and lighter on the body, provide greater swimming potential, but make the person less visible in high seas offshore

Hood.  The importance of a deployable hood that is brought over the face and bladders when in the water came to the fore some years ago when the concept of Secondary Drowning was understood.  Suffice to say that water ingress into the airways and lungs whilst in a rough sea greatly reduce the survivability due to a slow 'drowning' process where the lungs become less and less effective.  Recommendations have been made to European Standards and the ISO convention to make hoods mandatory, but they are currently still optional, but recommended.

 Light.  Several companies have installed lights into their lifejackets, or manufacture adhesive lights that are water activated and use the bladders themselves as light boxes to increase visibility of the target in the water, at night.  We Sell such lights, but these must be carefully fitted by the user.  Alternatively we can fit these for you.

PLB/AIS.  As chartplotters with AIS and Man Overboard electronic devices have matured, so the ability to attach a Personal Locator Beacon (PLB) or AIS transmitter has become more and more compelling.  These will activate with the lifejacket and can then send a target to the chart plotter in order to find the person in the water.  Please contact us about these systems