Prepare NOW for Hurricane Earl
31-Aug-2010 NOW is the time to make plans for your boat in advance of Hurricane Earl! Here are some excellent readiness tips from our close friends at Conanicut Marina.
Here's a bit of a longer read that has a ton of good info. Credit for this article goes to Seaworthy Magazine, published by BoatUS.
As a boat owner, the first step in developing a preparation plan is to review your dock contract for language that may require you to take certain steps or to leave the marina when a hurricane threatens. Ask the marina manager what hurricane plan the marina has in place. Planning where your boat will best survive a storm, and what protective steps you need to take when a hurricane threatens, should begin before hurricane season. Marine Insurance claim files have shown that the probability of damage can be reduced considerably by choosing the most storm-worthy location possible and having your plan ready long before a hurricane warning is posted.
The damaging influence of high water, or storm surge, is often underestimated in preparing a boat for a storm. Storm surge raises the water level far above normal high tide, and lifting boats above their docks and pilings. Surge is the result of several factors. Due to low barometric pressure, the ocean surface is drawn upward forming a mound about one foot higher than the surrounding ocean. Large swells generated by the storm reach land first, while storm winds drive water toward the coast. As the storm makes landfall, water levels 10 to 20 feet above normal high tide are possible. Dangerous high tides can reach outward 20 to 50 miles from the storm’s center. Surge makes extra length and positioning of dock lines critical.
A hurricane, of course, brings high winds. Wind speeds of 70 to 130 mph are common, and winds over 200 mph have been recorded. What may be less understood is the force created by such winds. When wind speed doubles, the wind pressure quadruples. To put it in practical terms, when the wind speed increases, the damage it causes increases at a much greater rate. This illustrates the importance of reducing the boat’s windage, which is the amount of area your boat presents to the wind, by removing as much rigging, canvas, and deck gear as possible, and facing the bow toward the greatest exposure.
Waves in the ocean have tremendous energy and can reach mountainous heights. But even in relatively small harbors, bays, and lakes, waves can build to surprising heights. In a hurricane, it is not unusual for steep, breaking waves three to six feet high to pound normally peaceful harbors. Seawalls, barrier beaches, and other structures that normally protect docks and moorings are submerged by the storm surge. This has the effect of greatly extending the “fetch,” or distance, over which the wind can generate waves.
Rainfall of six to 12 inches within 24 hours is normal during a hurricane, with extremes of 24 inches having been recorded. A hurricane that struck Puerto Rico in 1928 is estimated to have dumped over two-and-a-half billion tons of water on the island. Boats that are spared the worst high water and wind still can be sunk by the torrential rain. Unfortunately, the ability of a bilge pump and battery to handle rain accumulation is greatly overestimated. Deck drains and pump discharges located near the waterline can backflow when waves and rain put drains underwater.
Boats ashore should be stored well above the anticipated storm surge, but even when boats are tipped off jack stands and cradles by rising water, the damage they sustain in a storm tends to be less severe than the damage to boats left in the water. Windage is also a consideration. If nothing else, reduce windage as much as possible and make sure your boat has extra jack stands, at least three or four on each side for boats under 30’ and five or six for larger boats. The jack stands must be supported by plywood and chained together. One technique that has proven to be very effective involves strapping boats down to eyes embedded in concrete. All things considered, any attempt to anchor a boat on shore is worth the effort.
Members of the BoatU.S. Cat team estimate that as many as 50% of the boats damaged at fixed docks during hurricanes could have been saved by using better dock lines: lines that were longer, larger, arranged better, and/or protected against chafing. If you decide to leave your boat at a dock, you’ll need to devise a docking plan that is liable to be far different than your normal docking arrangement. By the time preparations are completed, your boat should resemble a spider suspended in the center of a large web. This web will allow the boat to rise on the surge, be bounced around by the storm, and still remain in position. Take a look at your boat slip and its relation to the rest of the harbor. For most boats, you’ll want to arrange the bow toward open water or, lacking that, toward the least protected direction. This reduces windage. The exception is boats with swim platforms, especially swim platforms that are integral to the hull. These boats have been sunk when their platforms were bashed against a bulkhead. If your boat’s swim platform can’t be kept safely away from a bulkhead, secure the boat with its stern toward open water. Next, look for trees, pilings, and dock cleats—anything sturdy—that could be used for securing dock lines. You may want to use other boat owners’ pilings (and vice versa), which calls for a great deal of planning and cooperation with slip neighbors and marina management.
Lines should also be a larger diameter to resist chafe and excessive stretching. On most boats, you should use 1/2” line for boats up to 25’; 5/8” line for boats 25’ to 34’; and 3/4” to 1” lines for larger boats. Chafe protectors must be on any portion of the line that could be chafed by chocks, pulpits, pilings, etc. To secure lines to hard-to-reach outer pilings, put the eye on the piling so that lines can be adjusted from the boat. For other lines, put the eye on the boat to allow for final adjustment from the dock.
If you plan to weather the storm at a fixed dock, you nod to consider that dock's mobility. Because they rise with the surge, floating docks allow boats to be secured more readily than boats at fixed docks. There’s no need to run lines to distant pilings because the boats and docks rise in tandem. Floating docks only offer protection from the surge, however, if the pilings are tall enough to accommodate the surge. In almost every major hurricane, there have been instances where the surge has lifted floating docks up and over pilings. When that happens, the docks and boats, still tied together, are usually washed ashore in battered clumps. If you plan to leave your boat at a floating dock, it’s critical that you measure the height of the pilings—will they remain above the predicted storm surge? Pilings that are only six or seven feet above the normal high tide probably won’t be safe.
Mooring in a sheltered location can also be an alternative to exposed harbors and/or crowded marinas. A boat on a mooring can swing to face the wind, which reduces windage, and it can’t be slammed into a dock unless the mooring or anchor drags. The first question, then, is: Will your mooring hold? As a result of numerous moorings being dragged during recent hurricanes and northeasters, however, this may not be the safest option. Studies have found that when the angle of pull increases to 25˚, a mooring’s holding power begins to weaken precipitously. So in shallow harbors, where a scope of 3:1 can be had with, say, 20’- 30’ of chain, the advantage of scope is all but eliminated in a storm by a combination of a large tidal surge and the high, pumping motion of waves. Finally, when was the last time your mooring’s chain was inspected? Chain that is marginal in the spring will not be sufficiently strong at summer’s end to stand up to a hurricane. A harbormaster should know how long your chain has been in use and whether its condition could be iffy. If you have any doubts about your mooring, it's probably best to avoid this option.
A trailer is, or should be, a ticket to take your boat inland to a more sheltered location away from the tidal surge. But your boat won’t get far on a neglected trailer that has two flat tires and rusted wheel bearings. Inspect your trailer regularly to make sure it will be operable when it’s needed. If you take your boat home, you may want to leave it, and not your car, in the garage. A boat is lighter and more vulnerable to high winds than a car. If this isn’t practical, put the boat and trailer where they will get the best protection from wind, falling branches, etc. Let some air out of the trailer tires and block the wheels. You can increase the weight of lighter outboard boats by leaving the drain plug in and using a garden hose to add water. (Rain will add a lot more water later.) This has the added advantage of giving you emergency water (non-drinking) if the main water supply gets knocked out by the hurricane. Place wood blocks between the trailer’s frame and springs to support the added weight. On a boat with a stern drive, remove the drain plug so that the engine won’t be damaged by flooding. Secure the trailer to trees or with anchors or augers. Strip all loose gear and canvas tops, and then lash the boat to the trailer.
One of the most dangerous mistakes a skipper can make is to stay aboard his or her boat during a hurricane. Several accounts indicate that there is little, if anything, a skipper can do to save a boat when winds are blowing over 100 mph, tides are surging, and visibility is only a few feet. What can happen? Consider the case of a 68-year-old skipper in Charleston, who together with his grown nephew, took their trawler up the Wando River to ride out Hurricane Hugo in what they thought would be a "sheltered" hurricane hole. He reported that the boat seemed to be doing fairly well initially, but later that night the wind picked up to over 100 mph and 15’ seas sent the boat crashing completely over. The two men were trapped briefly in a pocket of air underwater when another wave rolled the boat back upright. They then scrambled onto the deck and were eventually rescued, but not before almost drowning and being overcome by exposure. Another skipper who stayed aboard his motorsailer at a marina during Gloria had to jump overboard and swim through breaking waves, drifting boats, and debris after another boat broke free and rammed its mast (the boat was on its beam ends) through his boat’s pilothouse window. Again, he was lucky to reach shore alive. Two Miami men who stayed aboard a Sportfishing boat during Hurricane Andrew were not so lucky. They both drowned while trying to escape their battered and sinking boat. When a hurricane is approaching, you should certainly do everything you can to protect your boat: Secure extra lines, set out anchors, add chafe protection, strip the boat above and below decks, etc. Do whatever it takes, and then head inland. Your boat can be replaced; you can’t.
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