For professional mariners who operate fishing and passenger vessels, the choice is somewhat simplified by the fact that the law requires rafts to be Coast Guard Approved, and even specifies the equipment packs they carry – SOLAS A, SOLAS B or Coastal – depending upon how far from the coast the vessel operates.Glen Justice

Your choice can be limited simply by looking for rafts with Coast Guard approval, which eliminates about half of all available models (for more information, see link below). However, that also includes some of the highest-quality rafts available, which are required for or selected by people such as ocean yacht racers, for whom effectiveness is paramount and cost is no object.

Another strategy is to look for similar quality standards, such as approval by SOLAS, which is an international convention that stands for Safety of Life at Sea (for more information, see link below). Other standards include ISO 9650 and the International Sailing Federation, or ISAF (formerly known as the ORC, or Offshore Racing Council.)

Size is another good place to start. Capacity ratings are based on a floor area of four square feet per person. That's not much, especially for a group of big, wet, probably seasick survivors, though some raft models provide more than the required minimum space.

Consider buying a raft rated for at least 50 percent more people than you might actually have on board. That won't be a problem for vessels with small crews, given that the minimum size Coast Guard-approved raft is four persons and the smallest SOLAS raft is six persons.

Another consideration is weight. While a rugged raft is paramount, it is an open question whether a heavier, more durable fabric – and the attendant higher cost – is an advantage.

A lighter raft that can be readily hand-launched by any member of the crew may be safer than a heavy one that will only deploy when the boat sinks from under it. A lighter raft is easier to right should it inflate upside down or capsize. It affords more options for installation, is easier to remove for repacking, and is less expensive to ship. On the other hand a heavier raft is more stable in the water and probably more durable.

DESIGN CONSIDERATIONS

Quality life rafts come in a variety of designs. They may have a single flotation tube or double independent stacked flotation tubes. They may be square, rectangular or multi-sided. Canopies may be supported by single, double or multiple inflatable arches. Ballast may consist of one or more water pockets of various sizes. Even the weight varies – some six-person rafts weigh far less than 100 pounds while others weight far more than 150 pounds.

In general, the higher-price rafts have double-tube flotation, multi-arch canopy support, inflatable or insulated floors, a boarding ramp and four or five large ballast pockets (or a single large hemispherical pocket). They usually weigh more than 100 pounds.

Rafts may be made of natural rubber, butyl rubber, polyurethane, neoprene or PVC (polyvinylchloride), each of which has advantages and disadvantages. Some manufacturers use two-ply fabrics and others do not.Steven Callahan

Seams on rafts made of rubber and neoprene have to be hand-glued, while polyurethane and PVC seams can be heat welded by machine. Welded seams resist slipping, which can cause slight deformation of the boat over time, though this is less of a problem on rafts because they are not inflated during storage. Some rafts are constructed with both welding and gluing.

Rubber and polyurethane are believed to have the longest useful life – 15 to 20 years if properly maintained – but other materials may be more resistant to abrasion and rotting. Some users also object strongly to the odor of rubber. PVC is popular because it is least expensive and light in weight.

Many raft specialists consider polyurethane to be the best because it has less odor than rubber, is completely impermeable to air, and it resists abrasion, UV light and chemicals. It is used on many of the most expensive, most highly-rated rafts.

BUOYANCY AND BALLAST

Round or multi-sided equilateral shaped rafts are assumed to be slightly more structurally resilient, but square or rectangular shapes better accommodate several bodies packed in side by side, sardine fashion.

Double buoyancy tubes provide more freeboard, better back support and more redundant buoyancy than single-tube design. In any but tropical waters, a double, inflatable, or foam-insulated floor is important for conserving body heat, but this feature is not found in all rafts.