NMI and the Icelandic government found that the best normal water-ballast pockets were triangular in section and usually weighted to promote quick filling. Many ballast pockets still failed and, "Of the six rafts put into the water, only those on which sea anchors remained operational did not capsize," the study said. The last test showed, "the sea anchor was a powerful stabilizing force and could prevent the life raft from capsizing even when the ballast pockets were destroyed."
Not just any sea anchor, however. Most are dogs. The improved sea anchor is a tapered sleeve, at least twice as long as the mouth is wide and the tail a third the mouth's diameter. The mouth should be stiff and open to promote quick filling. If it's made of porous mesh it doesn't need a swivel, but a swivel never hurts. Flat panels of cloth forming parachute-type sea anchors, and cones, will spin, so they require swivels. Even so, they can foul themselves with their bridles if they tumble forward in breaking waves.
Steven Callahan
NMI found that mesh or laces sewn around the sea anchor bridle prevented sea anchors from fouling themselves. A new option is the series drogue, which is a string of smaller cones that reduce shock loads by evening out the sea anchor's pull over numerous waves aft. In any case, our sea-anchor rode, swivels, and attachment point on the raft had better be tough because the snatch loads in even moderate conditions can be eight or nine times the anchor's steady pull.
BALLAST BAGS
Numerous raft styles with varying water-ballast schemes have survived upright in blows exceeding 80 knot winds and 30-foot waves. One heavily-ballasted Givens raft resisted wind gusts to 170 knots and 35-foot seas when survivors were forced under water numerous times and the tubes began to separate. Who knows if other rafts could survive such conditions at all, but if force equals mass times acceleration (or deceleration), then the mass of boat or raft must increase the loads it experiences when at sea. So it is no surprise that the most heavily-ballasted rafts must be the most heavily built.
This concept was supported by tests. "Over-large ballast pockets can place a great strain on the raft structure leading to a need to strengthen it, with a consequent increase in weight and cost. Also, an already uncomfortable motion is made much worse on a raft carrying too much ballast," According to Testing of Liferafts by E.J. Foreman of BMT. Proponents of heavily-ballasted rafts continue to debate this view. I only know that riding a life raft of any kind is hellish in a gale, all have suffered failures and being capsized is only one of numerous worries for survivors, not in itself necessarily critical. The records for distance and time afloat go to much more lightly ballasted rafts. All types, including the Givens, have been knocked down to 90 degrees in waves of only 15-feet. As on the mother craft, sailors should always plan to have the sea turn their life upside down at some point.
A REAL DRAG
It is moderating? Most of a long survival voyage is spent drifting slowly in moderate weather, and boats more often come to grief for reasons other than horrendous weather. In any case, our EPIRB hasn't brought help, so why not get the hell out of here?
Now our big ballast bags are a real drag and we wish the canopy would open up more. Cut the ballast off? Why have it to begin with, then? And what about the next blow? Tie the bags up? Okay, best we can do.
It certainly would be nice to have a completely different kind of raft now, what the French call a "Dynamic" raft, meaning the thing sails. When I lost my boat in 1982, had I been able to beam reach, I could have shortened my drift from 1,800 miles to 450; had I been able to sail even dead downwind but increase speed to a moderate 2.5 knots, I would have been afloat 25 days rather than 76; had I been able to do both I would have sailed to safety in a mere six or seven days.
