Until early 2009, the construction of lifeboat hulls was outsourced to Green Marine, so when the company was put up for sale, the RNLI had a difficult decision to make.
Green Marine was the only manufacturer in the UK able to produce, to the RNLI's exacting standards, the technologically advanced composite hulls required for our lifeboats. Loss of this capability would have had catastrophic consequences for our Tamar class, Atlantic 85 and other future lifeboat construction.It therefore became imperative to acquire the lifeboat hull construction capability from Green Marine in order to safeguard the supply of high quality hulls for the future development of the institution's lifeboat fleet.
In April 2009, the RNLI took on the lifeboat hull facility under the name SAR Composites Ltd, so the supply of lifeboat hulls is assured.
The construction of hulls for use by the RNLI requires specialist boatbuilding and laminating skills. Our lifeboats have to operate in the very worst conditions and cope with large amounts of wear and tear, while also remaining dependable and fit for the job of saving lives at sea for a minimum of 25 years.
The use of advanced composite materials gives the best combination of robustness and light weight to enable a lifeboat to do its job. The specialist materials used are able to withstand the enormous stresses that an RNLI all-weather lifeboat must undergo in her lifesaving work. The hulls are so strong that if the boat was upside down you could park a loaded articulated truck on each side of the hull bottom!
The composites used are laminates or pre-pregs. They are pre-impregnated with the resin that binds the material together and harden to give the hull its strength. The cloth is supplied on rolls and cut to shape, then carefully applied onto the surface of the mould. Several cloths are laid on top of the first to build up the required thickness.
Different areas of an RNLI lifeboat will use different types of fabric, typically glass fibre or carbon fibre with an epoxy resin system, and different types of varying weights are used to provide strength and stiffness in the right areas.
Since April 2009 the hulls for Tamar lifeboats have been built at the RNLI’s dedicated boatbuilding facility in Lymington. Manufacture of the glass and carbon fibre composite hulls requires specialist skills and large processing ovens are needed to cure the resins.
The lifeboat hull is made in two longitudinal sections and the pre-impregnated fabric is laid into the moulds by hand.
The hull bottom is constructed from solid glass fibre laminate, which is 10mm thick, but the upper part of a Tamar hull is of a sandwich construction that comprises an inner and outer 3mm skin of glass fibre laminate around a thick core (108mm) of high-density foam. This makes panels that are very strong and stiff, yet lightweight. Then, carbon fibre-reinforced top-hat stiffeners are used on the inside of the hull to stiffen it and stop it twisting.
In other parts of the lifeboat there is a single skin made from multiple layers of cloth, with several reinforcing stiffeners attached to the inside.
SAR Composites Ltd Waterloo Road Lymington Hampshire SO41 9DB
UK telephone: 01590 646760
Fax: 01590 646761
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