The Protection Of A Hurricane Hole

By Bob Adriance
Illustrations By ©2016 Mirto Art Studio

If a hurricane is on the way, preparation is key. Sometimes your boat may be better off riding out the storm in a protected anchorage.

Hurricane anchoring figure 1 illustration Tandem anchors work well when the wind is primarily from one direction.

When Jim Bloom heard that Hurricane Wilma was likely to be coming ashore near his house in North Palm Beach, Florida, he began making plans to move his 42-foot catamaran sailboat to a hurricane hole, a well-protected area just off the Intracoastal Waterway. He'd done this twice before, in Hurricane Francis and Hurricane Jeanne, and his boat had survived both of those storms without damage.

The decision to move his boat to a hurricane hole wasn't one that he made lightly. Bloom's private dock had been fine for riding out everyday weather, but he had doubts that the aging pilings could survive a hurricane. And he couldn't rely on any of the nearby marinas to haul his boat before a storm; they'd be too busy with their own boats. Fortunately for him, he knew of an area just off the Intracoastal Waterway that was 12 feet deep and had good holding in mud for his anchors. Another plus: It wasn't likely to be crowded with other boats.

Techniques: On Open Water

Anchoring in a hurricane involves much more than throwing out the boat's usual working anchor and hoping for the best. Jim used two storm anchors, a 65-pound CQR and a 33-pound Bruce, deployed in tandem on the same rode with 30 feet of chain from the Bruce to the CQR and 120 feet to the bridle (see Fig. 1). The advantage to this technique, which is documented in U.S. Navy tests, is that it allows the trailing anchor to bury itself in the furrow created by the lead anchor. The result, according to the Navy test, is that using anchors in tandem yields a 30-percent improvement over the sum of their individual holding powers.

A friend of Bloom's anchored his 40-foot monohull sailboat nearby using a more traditional technique: two large anchors set 90 degrees apart off the bow. Using two anchors increases holding power and also reduces a boat's tendency to sail back and forth (sometimes called "kiting"), which is a typical consequence in high winds when a boat rides on just one anchor. Some experts recommend setting the anchors at 45 degrees, although I know of no data supporting a wider or narrower angle. Note, however, that setting the anchors too close together — at an angle of less than 45 degrees — increases the chances of the anchors fouling if the boat drags. The heavier anchor should be set toward the direction of the highest anticipated winds (see Fig. 2). Both boats rode out the storm successfully with only slight damage, just a few scrapes to the monohull.

Closer To Shore

Another hurricane-hole strategy is to use a combination of anchors and lines to shore to secure the boat. BoatUS member Marilyn Mower and a friend moved her 44-foot ketch to a mangrove south of Miami before Hurricane Andrew (see Fig. 3). Using a spool of line that had been purchased earlier for just such an emergency, they ran eight 5/8-inch nylon lines to sturdy trees on shore and used three anchors: a 60-pound Danforth, a 37-pound Fortress for the bow, and a 45-pound Bruce set off the boat's stern. Each anchor line had 10 feet of additional slack to allow for tidal surge. Mower's boat, in addition to most of the other boats in the mangrove, survived the monster storm without damage.

Before The Storm

Be sure to visit potential hurricane holes before you need to use them. Features to look for include good holding, surrounding hills to block wind, and little wind funneling between those hills. Don't choose a place surrounded by low, flat terrain that offers no wind protection and that will flood in a surge. And should your boat drag, you don't want your hurricane hole surrounded by docks, pilings, or any other shoreside structures.

Practice setting the anchors a time or two before hurricane warnings are posted. No matter where you decide your boat will be safest, all the rules of storm anchoring apply. The more scope the better, bearing in mind that other boats may be close by. Note that scope will be greatly reduced by any tidal surge. Chain is always preferable to nylon, but if an all-chain rode is used, nylon line — at least a third the length of the chain — should be used as a snubber to absorb shock. The weight of the chain between the anchor and the stem, coupled with the elasticity of the nylon snubber, increase the ability to absorb shock loads. Steel cable has also been found to dig into certain bottoms, such as mud, better, relieving some stress on the anchor. However, many boats aren't equipped for this.

Chafe protection is a subject unto itself. In years past, the recommendation has been to use garden hose to reduce chafe. However, an anchor line, when it slides back and forth across a chock or bow roller, can generate enough heat to melt nylon fibers. The nylon fails from the inside out. Impermeable chafe protection, such as a water hose, can increase the chances of a line failing by preventing rain and spray from cooling the heated fibers. A better solution is to use water-permeable protection, such as woven polyester or a product such as Chafe-Pro. Note also that tests have found that new nylon line is far stronger than older line, whose fibers typically have less lubricity to reduce yarn-on-yarn friction.

Other preparation includes charging batteries for bilge pumps, securing dorade vents and other means of water ingress, and freeing scuppers of debris. Finally, any boat, whether it's in a slip, tied down ashore, or in a hurricane hole, must be completely stripped to reduce windage; the wheel or tiller must be locked down on the centerline. Valuables and ship's papers should be taken home for safekeeping. And a little luck doesn't hurt, either. 

Bob Adriance is the former editor of Seaworthy, the BoatUS Marine Insurance damage-avoidance newsletter.

— Published: May 2016


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