Little Compass RoseCaribbean Compass   July 2004
 
 
Hurricane Survival
Part One: Prepare for Pop Ups
by Brad Glidden
The time for taking all measures for a ship's safety is while still  able to do so. Nothing is more dangerous for a seaman to be grudging in taking precautions lest they turn out to have been unnecessary. Safety at sea for a thousand years has depended on exactly the opposite philosophy.
- Fleet Admiral Chester Nimitz


"The National Hurricane Center is issuing hurricane warnings for the Windwards,  Leewards, British and US Virgin Islands. At 5 PM Atlantic Standard Time the center of Hurricane Aardvark is located.. Hurricane force winds extend out thirty miles from the center. Tropical storm force winds extend out one hundred miles, mainly north and east of the center. Residents in the warned areas are advised to rush preparations to completion."

Now that we've got your attention. Much as we don't want to admit it, West Indian hurricane season is here. There are people reading this new to the tropics, people who have forgotten the lessons of the last seasons, people who have information to share. Proper seamanship results from the willing cooperation of experienced sailors in our community passing on their body of knowledge, and NOW is the time to start preparing and asking questions. Why now? Well, first:
"Pop up" hurricanes. Unlike August and September, when storms get named soon after they leave Africa, and we have seven days of watching and worrying, July hurricanes tend to develop out of tropical waves just east of the islands. You may have a lot less time to get ready than you think. It is also important to remember that the hurricane forecast is for the center of the storm, and  winds above Tropical Storm force extend out a considerable distance, typically six to 12 hours in advance of the eye. You do not want to be underway, headed for shelter, in 40 knots and rising winds, and you may have a long way to go to find shelter. So.
"Where ya goona go when the hurricane comes on to blow?" If you're cruising through the islands, and you're going to be here through hurricane season, now is the time to answer that question. Look at charts, talk to the locals who seem to know what they are about, pick out one or two good spots and GO THERE NOW! Scope out the area on a calm and peaceful weekend. Take some soundings to check the depth for yourself, and maybe even some samples of the bottom to see whether you're dealing with hard sand, mixed rock, or soupy primordial ooze. Visualize how you're going to get in, and where you're going to go, and then visualize the same situation with 50 other boats crowding in, some at the last minute. Many hurricane holes have local regulations in effect. Talk to the relevant authorities and see what their rules are.
This is also the time to talk to the authorities about public shelters ashore. DO NOT plan on staying on your boat in a hurricane. Yes, I know; it's your boat, your life, your dream, maybe all you have in the world. I live aboard too, and not even under a court order would I (again) stay on board in a storm. It's quite simple. There is no useful work you can do after about 75 knots. All you can do is get hurt, and then, when its time to abandon, find you can't. Hurricane Marilyn destroyed St. Thomas in 1995, flattening 50 percent of the houses and damaging all the rest. She blew down every phone and power pole on the island. In all of that, only nine people died and they were all sailors who went down with their boats. Go ashore, folks, and start over the next day.

Notice that we are discounting the possibility of heading out to sea to avoid the storm. No doubt there will be "experts" in the local bars offering that as an option. Please, Gentle Reader, pass these people by.
It is theoretically possible to leave in advance of a storm, go west or southwest, keep the wind on your port quarter and do a big counter-clockwise loop south of the storm and arrive home 48 hours later. This is the nautical equivalent of playing Russian roulette with three chambers loaded. If you have a big fast powerboat and you can guarantee the engines won't quit, say to sediment stirred up in the tanks, and that the aft-facing doors and hatches won't get stove in, then maybe you can pull this off. Got a really good sea anchor that will keep the vulnerable stern out of the waves if the engines pack it in? A very experienced friend of mine tried this trick in 2000, leaving out of St. Thomas. An unforeseeable minor glitch in his water pump left him dead in the water for three days. Had the storm in question veered a little west, it would have been exciting aboard his boat. In 1999 the 252-foot, 2,000-ton schooner Fantome had the options of seeking shelter in Roatan Island, Honduras, or heading to sea when it was cornered by Hurricane Mitch. The last radio message from her was that she was in 70-mile-an -hour winds and 20-foot seas on the south fringes of the storm. She, and her 31 people, have not been heard from since. She had seven 25-person liferafts aboard, as well as four big life boats. They found pieces of two rafts.

Most importantly can you guarantee the storm's path 24 hours in advance? The National Hurricane Center can't. They offer probabilities, not courses. Most storms follow a west-northwest curve. Some go west, some north. Sebastian in 1995 went southwest direct for Virgin Gorda from way out in the Atlantic, but luckily dissipated just before it got there. Mitch turned southwest and even south when it was in the western Caribbean, ran over Honduras, across Central America almost into the Pacific, turned back north, went to Florida and ended up in Scotland.
If your boat is tucked in a hole or well anchored in a protected harbor, even a direct hit will only produce two hours of hell. At sea in the fringes of a hurricane there will be dozen of hours when something could go terribly wrong.

Another reason to start preparing now is that your deck hardware and anchors might just not be strong enough. Just how much pull does my gear have to withstand?
We've all seen those tables: "for a boat this size use this anchor; for a storm use one size bigger". Your correspondent doesn't know where they get those figures; I got the details below from the American Boat and Yacht Council. ABYC is a group of very serious engineers and architects. Their standards are the standards of the industry and are accepted by Lloyds and the US Coast Guard among others. The data below was extracted from tests done to figure load on cleats, and in giving permission to use it in my book A Cruiser's Guide to Hurricane Survival, ABYC was quite emphatic that is all it is, load on a line on a cleat for a given wind speed. If a skipper is to assume that a load on a cleat is the same load as what's on the other end of the line (like an anchor), then that is the skipper's assumption and not ABYC's. Having said all that, here's the poop:

Design loads for sizing deck hardware
(Boat dimensions are given in feet; Horizontal load on boat is given in pounds)

BOAT DIMENSIONS    HORIZONTAL LOAD ON BOAT

Length Beam    to 15 kts to 30 kts  to 42 kts
  (power) (sail)
10 5  4   40  160  320
15 6  5   60  250  500
20 8  7   90  360  720
25 9  8   125  490  980
30 11  9   175  700  1400
35 13  10   225  900  1800
40 14  11   300  1200 2400
50 16  13   400  1600 3200
60 18  15   500  2000 4000

1) When using this table with the l.o.a. and beam, use whichever gives the highest loads, i.e. 45' x 13' uses 3200 lb.
2) Boats with large superstructures (deckhouses, towers, houseboats, etcetera) should use one category higher than that determined by using the powerboat column.
3) There are a number of assumptions here; that the boat has freedom to oscillate and present its smallest, bow-on profile to the wind; and that there is protection from surge loading from high seas and wave action. Surge will vastly increase the load; this where lots of nylon line to absorb shock and/or a lot of chain to increase weight and the horizontal angle between the rode and the bottom becomes crucial.
There is a simple way to calculate loads above 42 knots. As wind speed doubles, force quadruples; three times the wind speed is nine times the force. Go to the columns for 30 and 42 knots; we will leave calculations for 60, 84 and (God help us) 120 knots as an exercise for the student. An impossibly high number, isn't it? If you are planning - or forced - to ride out a storm at anchor, you must deploy your tackle so you are riding on at least two huge or three really big anchors at all times. An 8,000 pound load spread between three anchors is a realistic goal.

There is a second formula for figuring pull or force. It appeared in older, but not current, editions of Chapman's Piloting Seamanship and Small Boat Handling, and produces numbers consistently lower than the table above. It is, briefly, that pull in pounds is equal to area presented to the wind, times the wind speed squared, divided by 100. Area is beam times height of the highest part of your boat, be it coachroof, dog house or flying bridge, and for sail boats add in the area of the mast(s). While you should be leery of using this for anchor pull, the formula does give a graphic representation of the difference between lying bow to (at anchor) verses broadside (at a dock) to the wind. As an exercise, do the math for your boat and see the startling difference.

All this would imply that a few more REALLY BIG cleats might not be overkill. You may have to attach three anchor lines or five docklines to those forward cleats, and if you only have two, you don't have enough. A serious examination of the through bolts and backing pads on what you have would be a good idea, too.

There is one last task that it is better to do now than when it's blowing 40. You MUST take your roller furling sails off. No ifs, no ands, no buts, no excuses. Modern roller furling gear is wonderful stuff, but it will NOT stay closed up under 12 hours of Tropical Storm force winds. You will not win any popularity contests in your anchorage when (not if) the genoa unfurls in the middle of a storm. So, now is the time to make sure the halyards run free, the blocks and swivels aren't seized, the sail comes down, you can fold it up and find a place for the damn thing below.

Brad Glidden is the author of Cruiser's Guide to Hurricane Survival, available at bookshops and chandleries or from Cruising Guide Publications, www.cruisingguides.com.
 

     
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