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Life Raft Study
provided by West Marine, for
additional information dial (800)BOATING The Traveller's interior beam is only about 20" across. Since the canopy attaches to the center of the top of each hull tube, it is possible for three persons to sit on top of the buoyancy tubes on each side, with one's head bowed toward the center and with one's knees against those on the opposite side. With only two aboard, the Traveller's space seemed cramped but adequate. Three or more would have been pretty horrible. The daggerboard trunk/thwart and the bow dodger take up a lot of interior space that might be used for reclining, although one's legs can be extended underneath both items if seated on the floor. If the person on watch were to sit forward, while the person asleep were to lie aft, it might be possible to rest on board. In general, the Traveller felt too small to spend an appreciable time aboard, and it would benefit by being taller and beamier before we would consider it comfortable at sea. The ORC regulations require 4 sq. ft. of floor area per person, which the MD-2 achieves with its 24 sq. ft. The Traveller has 15.75 sq. ft., so it barely misses the requirement for a four person life raft. CAPSIZE RESISTANCE AND RIGHTING We tried to establish the relative capsize resistance by loading the rafts with all the weight on one side. In the case of the MD-2, two crewmembers sat in the starboard side gunwale, which caused the port side to lift rapidly. It took a short time for the water to drain from the ballast pockets, whereupon a wave hit the raft and it capsized quickly. Observers reported that the pockets appeared to be 1/3 full of water, at most, at the time of capsize, although the raft had been deployed for 30 minutes or so. We were frankly surprised at how easy it was to capsize the raft. The raft floated at about a 135° angle of inclination, supported by the arch tube. One crewman was able to climb aboard the overturned raft, pull the righting strap free of its snaps, and pull the raft over easily. Both crew members boarded without assistance through the doors by means of the webbing ladders. Like all such ladders, they tended to swing under the raft and it took several tries to use the ladder correctly. At night it was felt that the ladders would have been hard to find and use, particularly if the victim were hypothermic. The MD-2 was capsized a second time to check our observations. In this case, the raft was capsized with three persons on board, and it was only necessary to get them on one side of the raft to initiate the capsize. Righting was accomplished by reaching up to the webbing and pulling the raft over while still in the water. When righted, the MD-2 had 40 gallons of water inside after the first capsize, and perhaps 10 gallons after the second capsize. The difference was due to the method of righting. Since we did not stand on the raft during the second righting, there seemed to be less chance of scooping water as it came over. To find out why the MD-2 capsized reasonably easily, we examined the ballast bags while the raft was upright. Even though ballasted with chain, the bags tended to collapse and not hold their "bread box" shape. We are of the opinion that stiff stainless steel wire or the equivalent might be used to force the bags into the shape resulting in the maximum volume. The Traveller was capsized twice with the canopy in place. Since there are no openings athwartships, the two crewmembers had to lean against the inside of canopy, opposite of the drogue. The life boat rolled reluctantly, and the crew ended up lying inside the inflatable canopy. This attitude could have been maintained for some time without discomfort; in fact, the Traveller was arguably more comfortable upside down than right side up. To right the Traveller, the crew simply rolled their bodies in the opposite direction, which caused the boat to resume its upright position. The boat was practically dry when righted, with only a gallon or so left in the hull. This proved to be a much more efficient method of bailing than the pump. We also tried to use the catamaran righting method of using a line on the high side of the boat (in this case the drogue rode) to pull the boat over. This worked well. Crew members in the water could either slide inside the canopy, or right the boat from the outside. If they elected to use the "inside" method, they would avoid the need to re-board the raft over the bow. Most yachtsman's rafts are equipped with a throwing quoit and line to assist in making contact with a person in the water. We threw the MD-2 quoit (the Traveller was not so equipped) using a variety of different techniques, and were able to throw it about 25-40 feet. The weighted rubber ring was effective against the wind as well as downwind.To simulate the recovery of a disabled crew member, one person in the water was pulled aboard by a crewman in the raft. We used a surf rescue technique where the victim faces away from the raft, and the rescuer lifts the victim' by the armpits while falling backwards into the raft. This worked reasonably well , although we were of equal size and not hypothermic. We did not attempt to deflate the MD-2 top tube to lower the freeboard, which is apparently a technique that can be used to make the process easier for rescuers who are of smaller stature. The method for the Traveller is somewhat different: the low bow area is used as a boarding ramp, and the reduced buoyancy there makes for much lower freeboard. This reduced freeboard made recovering the person in the water much easier. The MD-2 was almost entirely dry when initially inflated, and took on water only as wet crew members climbed in and out, and as it was righted after capsize. The high sides of the raft seemed unlikely to allow water in except when struck by breaking waves. The whitecaps that were prevalent during our trails did not cause water to come aboard.Once it had been bailed dry initially, the Traveller remained dry as well . Some water leaked in through the grommets in the dodger where the sailing control lines passed through the fabric. In severe conditions, it is possible that water might leak under the canopy along the top of each buoyancy tube, but we did not notice any during the test. Once again, a bailer with a flat bottom would have been far superior to the dinghy-style piston pump we used. RATE OF DRIFT/MANEUVERABILITY/ABILITY The MD-2's drift rate could have been increased by retrieving the drogue and/or collapsing the ballast pockets with a line under the raft. Otherwise, it was not obvious how to affect its course. While testing the stability of the Tinker, a large container ship was noted approaching the ship channel, and about four miles to seaward. Judging this to be an opportune time to get out of the ship channel, we elected to erect the sailing rig immediately. The Traveller 's sailing rig consists of a three-piece jointed mast, shrouds with adjusters, boom, two sails, and some running rigging. The kit also includes a kick-up rudder and a daggerboard. After striking the canopy, the crew of two were able to assemble the sailing rig in about 10 minutes. With about 20 knots of wind, only the jib was used, and it propelled the boat at 3-4 knots. There was some trouble with the kick-up rudder, but that was remedied and the boat remained under control. Total distance sailed was probably four miles in very rough water. The sailing kit, while effective, consists of numerous small items, the loss of any one of which would have rendered the sailing rig inoperable. For example, the shackles were the loose pin type. The mast sections were not joined with shock cord like tent poles. Because this was also the first time that the rig had been stepped, we would anticipate that tricks could be employed by an experienced crew to make it easier in successive attempts. This is really where the two craft differed the most: the MD-2 is designed to be a stable, practically immobile, survival platform in which the occupants can safely wait for rescue, assuming the rescue agencies have been alerted due to an EPIRB signal or visual sighting. The Traveller provides the option of sailing to a place where a rescue is more likely, or conceivably to land. Several accounts exist of survival in Tinker dinghies where the crew has been able to sail to a higher traffic area and be rescued. Nearly all boaters who travel out of sight of land should have some sort of survival raft in our opinion. The numerous documented cases of vessels sinking, due to known causes or unknown, and the short time that a person can survive without protection makes life rafts a necessary part of offshore survival gear.The craft tested in this test represent two of the best examples of their type: a stable, commodious, unmaneuverable life raft capable of sheltering six occupants; and a multipurpose, maneuverable life boat that can hold five as a dinghy, and 2-3 as a life boat. The Traveller proved that is indeed sailable, and stable, under our test conditions. We have summarized our conclusions by listing the outstanding features and shortcomings of each type of craft tested. Note that these comments are specifically aimed at the craft tested: there are life rafts and dinghies which are far worse than our samples, and which may have additional shortcomings. 1. Life raft contains minimum survival inventory even without
additional gear bag.
LIFE BOAT ADVANTAGES:
Sea Star Capt. Ray Thackeray, Sea Star Yachting Products, Skipper and
"Victim" Vendors:
5 This is primarily an attribute of Switlik rafts which
use polyurethane coated nylon and heat welded seams. Other rafts
employ different fabrics, which may not have the same
properties. Other manufacturer also seal the raft in a vacuum
bag to protect it against the elements. RETURN TO INDEX |