What Went Wrong

A marine sur­veyor ex­plains the land­side stor­age pro­ce­dures that worked and failed dur­ing last year’s deadly hur­ri­canes, and how to pre­pare for fu­ture tem­pests.

Cruising World - - Contents - By­todd Duff

A BVI sur­veyor as­sesses what went wrong and right dur­ing Irma.

On Septem­ber 6, 2017, an un­prece­dented event oc­curred in the British Vir­gin Is­lands when Hur­ri­cane Irma, the strong­est recorded hur­ri­cane to make land­fall in the West­ern Hemi­sphere, passed di­rectly over the is­land chain. Two weeks later, Cat­e­gory 5 Hur­ri­cane Maria passed just south of the is­lands, and the com­bi­na­tion of these two tem­pests pro­duced wide­spread de­struc­tion to many hun­dreds of boats — char­ter yachts and pri­vate ves­sels — stored in these is­lands.

As a re­quire­ment of the var­i­ous in­sur­ers, a num­ber of “hur­ri­cane plans” have been em­ployed in an ef­fort to min­i­mize risk to the ves­sels stored here dur­ing the sum­mer months. As a marine sur­veyor, af­ter the hur­ri­canes I had the op­por­tu­nity to see which prepa­ra­tions al­lowed boats to sur­vive these hur­ri­canes, or in many cases, to note the dam­ages that oc­curred due to fail­ures of the meth­ods used to pre­pare them.

WHAT WORKED, AND WHAT DIDN’T

For decades now, where ves­sels are stored on land, an in­creas­ing num­ber of boats have been “strapped down” with polyester straps to an­chor points on the ground. This method has been used in con­junc­tion with jack stands and cra­dles, and with ves­sels low­ered into “hur­ri­cane pits.” While strap­ping the boats down may have helped, in many cases the polyester straps (which can stretch as much as 5 to 15 per­cent un­der load) al­lowed for sig­nif­i­cant move­ment un­der the tremen­dous pres­sure from the winds, caus­ing the stands to col­lapse. Or, the straps them­selves stretched to the point of fail­ure, tore out their an­chor points on the boats (cleats or bol­lards) or were ripped from the ground.

In other in­stances, where the an­chor points held and the cleats did not fail, the down­wind sides of the boats of­ten sus­tained dam­age from the stands or ad­ja­cent ves­sels be­ing pushed into their hulls. (When the eye­wall of the storm passed, the wind di­rec­tion re­versed, which meant boats went down in both di­rec­tions.) Be­cause these straps stretched so much in the 200-plus mph winds, in some cases, us­ing chains, wire rope or per­haps one of the ul­tra-low-stretch syn­thet­ics, such as Dyneema, would have been far more ef­fec­tive.

How­ever, even some of the ves­sels se­cured with chains and wire suf­fered dam­age. When plac­ing sup­ports and an­chor points, of­ten­times lit­tle at­ten­tion was given to the con­sid­er­able side forces (the idea was to keep boats in po­si­tion solely us­ing down­ward pres­sure). So, re­gard­less of whether polyester strap­ping, wire or chain was used, in­creas­ing the size and num­ber of the an­chor­ing sys­tems and plac­ing them far­ther away from the hulls to help pre­vent side move­ment might have been more ef­fec­tive.

In Tor­tola’s Nanny Cay Ma­rina, quite a few boats were stored in “Lloyd’s-ap­proved cra­dles” — sub­stan­tial bolted-to­gether af­fairs that are widely ac­cepted to be the strong­est type of sys­tem for se­cur­ing boats stored above ground. How­ever, even these heav­ily con­structed cra­dles failed un­der the in­tense

pres­sure of Hur­ri­cane Irma’s pun­ish­ing winds. Again, the syn­thetic strap­ping was likely the cul­prit, al­low­ing too much move­ment and ex­ert­ing tremen­dous pres­sure against the lee­ward sup­ports.

How­ever, in some cases, the cra­dles held, but be­cause the cra­dle sup­port arms can­not al­ways be ad­justed fore and aft to sup­port the hulls cor­rectly at bulk­heads, the hulls of some ves­sels frac­tured from point load­ing of the un­sup­ported hull sec­tions against the un­yield­ing cra­dle sup­ports. It also ap­peared at some yards that tri­pod sup­port stands had not been placed cor­rectly on bulk­heads, caus­ing jack stands or cra­dle arms to be im­paled in the hulls. Straps that failed to im­mo­bi­lize the ves­sels were also, again, a factor.

Most hur­ri­cane plans are de­signed to sup­port a ves­sel in an av­er­age to strong hur­ri­cane, but vir­tu­ally noth­ing in place in the path of Hur­ri­cane Irma was strong enough be­cause the force of the wind in­creases ex­po­nen­tially as it builds, es­pe­cially when it reaches his­toric pro­por­tions.

Let’s take the ex­am­ple of a 40-foot yacht with a hull that’s 5 feet tall, in­clud­ing the cabin trunk. It presents a sur­face area of 200 square feet (a bit more, ac­tu­ally, if tak­ing into ac­count the mast and rig­ging). The math to de­ter­mine wind force is com­pli­cated, but the side­load cal­cu­la­tor pro­vided on the web­site of the Sound Cedar build­ing com­pany will suit our pur­poses (lum­ber.sound­cedar .com/cal­cu­la­tors/wind­force).

Us­ing this cal­cu­la­tor, in or­der to with­stand a 100 mph wind, the straps and sup­ports for our ves­sel must be ca­pa­ble of with­stand­ing a wind load of 9,250 pounds. This force is eas­ily within the range of what is cur­rently in use at most boat­yards with jack stands, sand screws and polyester straps. But what hap­pens when the wind force jumps to 200 mph? At this speed, the force on the hull is now 37,000 pounds, and in Irma, with recorded gusts as high as 256 mph, the wind force is 60,000 pounds! So it’s no mys­tery why so many boats were knocked down or dis­masted in that cat­a­strophic storm. Still, mak­ing sure that the base for your straps or chains is far enough away from the hull will sig­nif­i­cantly re­duce side-force move­ment. Con­sider your strap­ping an­chor points to be sim­i­lar to a rig’s shroud base: The far­ther out­board the chain­plates are from a mast, the more sub­stan­tial the sup­port.

In re­cent years, hur­ri­cane pits have be­come more pop­u­lar. A ves­sel is low­ered into a pit dug into the ground so that it presents less windage and there­fore less force on the stands or sup­ports. In the Vir­gin Gorda Yacht Har­bour in the BVI, these pits have been in use for more than 20 years, with good suc­cess, but in al­most all cases in Irma, the sup­port stands failed, al­low­ing the ves­sels to fall. Again, im­paled hulls from failed stands caused sub­stan­tial dam­age. In VGYH, these pits were lined with con­crete that caused heavy dam­age to many hulls or keels when the ves­sels fell af­ter be­com­ing dis­lodged from their sup­ports.

In Vuda Point, Fiji, back­hoes are used to dig cus­tom pits for each ves­sel. Then, in­stead of solid stands or block­ing, used truck and car tires are placed around the perime­ter of the boat to sup­port it. With these “soft-sided” pits, even though the straps may stretch, the boats can move with the wind with­out sus­tain­ing dam­age, which has proved to be very suc­cess­ful, es­pe­cially when rigs are left up.

There is a trend in some ar­eas to re­quire that a ves­sel have its mast(s) re­moved in an ef­fort to re­duce windage while in stor­age. I do not, how­ever, think it can be un­equiv­o­cally said that in cases where a ves­sel is left on stands or in cra­dles, the windage of a sail­boat’s mast and rig­ging was the rea­son for the fail­ures of the sup­port sys­tems em­ployed by the var­i­ous boat­yards. Un­doubt­edly, when pre­par­ing

to leave a boat in a hur­ri­ca­neor cy­clone-sus­cep­ti­ble re­gion, re­duc­ing windage is a good idea. But in cases with sup­port struc­tures, whether they be straps and cra­dles or in pits lined with tires, if the sup­port is sub­stan­tial enough, then re­mov­ing the mast(s) might not be nec­es­sary.

How­ever, the mast and its windage should be taken into ac­count when cal­cu­lat­ing the mea­sures needed to en­sure that the ves­sel is prop­erly sup­ported for its stor­age ses­sion.

SUMMING UP

Hav­ing wit­nessed and sur­vived the un­prece­dented 2017 Caribbean hur­ri­cane sea­son, it’s clear to me that no sin­gle method of prepa­ra­tion could be ab­so­lutely guar­an­teed to pre­vent dam­age to a yacht stored on land. But there are lessons for own­ers pon­der­ing the op­tions for leav­ing their ves­sels in boat­yards sus­cep­ti­ble to trop­i­cal sys­tems.

1) Re­duc­ing windage is vi­tal, so of course, re­mov­ing all sails and can­vas is a given. Tak­ing the next step, by re­mov­ing the mast or low­er­ing the ves­sel into a pit, or even just re­mov­ing the boom and can­vas frame­works, helps re­duce wind loads.

From my ob­ser­va­tions, I don’t be­lieve that the windage from a stand­ing rig was the cul­prit in the fail­ures of sup­port sys­tems in the var­i­ous boat­yards. If the sup­port sys­tem is strong enough, masts can stay in boats.

2) Un­yield­ing stands or sup­ports are of no use if the ves­sel is im­prop­erly blocked or if the strap­ping sup­ports al­low for sub­stan­tial stretch, and it is vi­tally im­por­tant to make sure that the an­chor points for your straps, chains or wires are spread far enough apart that they are ef­fec­tive in pre­vent­ing side­ways move­ment.

3) Em­ploy­ing “soft” hur­ri­cane pits with tires in the perime­ter might be the most ef­fec­tive man­ner of sup­port­ing a ves­sel dur­ing a hur­ri­cane, es­pe­cially if its mast re­mains up. But keep in mind the is­sue of po­ten­tial storm surge in your area. A ves­sel in a pit will be more likely to float away than one firmly blocked a few feet higher should the boat­yard be flooded.

4) If a ves­sel is to be strapped down, suf­fi­cient low-stretch strap­ping must be present to al­low for a safety mar­gin to en­com­pass the high­est amount of wind force that a hull and rig might en­counter (two 10,000-pound straps on each side of a 50-foot boat is not enough, and four on one side might still be in­suf­fi­cient in 200-plus mph hur­ri­cane winds).

Ask your boat­yard to run the wind-force cal­cu­la­tions for your par­tic­u­lar ves­sel to en­sure an ad­e­quate safety mar­gin is al­lowed for.

5) When sup­port­ing your ves­sel — by jack stands, a cra­dle or truck tires — be sure to place the sup­ports at bulk­heads or other strong points of your hull. Tap around the bot­tom of your hull with a phe­no­lic ham­mer to find these strong points. Be sure to check the in­te­rior to make sure you are not go­ing to be point load­ing an area that might not be able to with­stand tremen­dous pres­sure. Small par­tial bulk­heads or fur­ni­ture might “sound” solid, but are not ca­pa­ble of with­stand­ing high struc­tural loads.

6) No mat­ter what prepa­ra­tions you make, un­der­stand that even the best ef­forts might not be enough to pre­vent a to­tal loss of a ves­sel. Make sure you carry suf­fi­cient in­sur­ance, that your in­surer is in agree­ment with your storm plan and, as a fi­nal mea­sure, take any per­sonal me­men­tos or spe­cial pos­ses­sions off the boat and store them some­where safe. Mem­o­ries last for­ever, but your boat might not.

Fre­quent CW con­trib­u­tor Todd Duff is a Sams-ac­cred­ited marine sur­veyor based in the BVI and is also a cruis­ing writer and author of the new sailing ad­ven­ture novel Kid­napped from the Caribbean, avail­able from Ama­zon and other book­sell­ers.

When a seem­ingly se­cured, strapped-down sail­boat still suc­cumbs to the power of the wind, in­suf­fi­cient strap­ping may be the cul­prit. In this photo, note the parted strap off the bow. Chains, wire rope or Dyneema may have saved this yacht from catas­tro­phe.

From Top: In ex­treme cases like the hur­ri­canes that sav­aged the Vir­gin Is­lands last fall, even a mas­sive Lloyd’s-ap­proved cra­dle may be no match for the con­di­tions. Some ves­sels nes­tled in hur­ri­cane pits suf­fered sub­stan­tial dam­age due to the un­yield­ing na­ture of the pit’s walls. The in­cred­i­ble power of Hur­ri­cane Irma’s winds caused this hull to breach when forced down on its stand.

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