A boat is said to beturtling or toturn turtle when it is fully inverted.[1][2] The name stems from the appearance of the upside-down boat, similar to thecarapace (top shell) of asea turtle.[3][A][B] The term can be applied to any vessel; turning turtle is less frequent but more dangerous on ships than on smaller boats.[C][4] It is rarer but more hazardous for multihulls than for monohulls, because multihulls are harder to flip in both directions. Measures can be taken to prevent acapsize (where the boat is knocked over on itsbeam-ends but not yet inverted) from becoming a turtle (with bottom up).[5][6][7][8]
When a boat is "turned over completely" it has turned turtle.[1][2][3][9] Some sources treat the term "turtle" as synonymous with "capsize" or "keel over".[4][10] but most others make a distinction.[D] Carrying too much sail or loss of control can lead tobroaching—the boatheels too far to one side, or capsizes.[11] While all turtlings involve a capsize, the converse is untrue. Prevention is the first priority.[6][7][E]
With the exception ofself-righting watercraft, vessels have anangle of vanishing stability (AVS). External forces aside, if they are tilted at an angle less than the AVS, they will pop back upright. If they are tilted at an angle greater than the AVS, they will turn turtle and stay there. In other words, non-self-righting vessels are stable when turtled. Theirprimary stability andsecondary stability are greater than zero, tending to right them, but their tertiary or inverted stability is less than zero, and tends to keep them upside-down.[12]
Capsizing (but not necessarily turtling) is an inherent part ofdinghy sailing, and is considered to be "routine". It is not a question of "if" but a question of "when".[8][13][14]
For those who prefer to avoid the experience, akeelboatmonohull has physics on its side.[13][15] (Seelimit of positive stability.) But evenyachts can capsize and turtle in extraordinary conditions, so design considerations and suitability for particular tasks, locations, weather, duration and situations are essential queries.[13][14][15][16][17][18][19][20] "Such events can overcome skill and experience"; boats need to be appropriate for foreseeable conditions.[14][15][16][17][19][21] It is a fundamental question ofseaworthiness.
Turtling commonly occurs when a boatcapsizes and is not righted or attended to in time, allowing it to roll through the approximately 90 degrees of a capsize through to 180 degrees from upright.[6][7]
Prevention and delay of turtling in dinghies is the highest priority[20]—turtling can be catastrophic in consequences—but it depends on skill, ability and athleticism, which vary greatly.[8][20] AsJohn Rousmaniere wrote: Testing confirms theRoyal Yachting Association's conclusion that "a decisive way to address entrapment is to immediately right the boat by putting weight on thecenterboard",daggerboard, (orbilgeboard in ascow).[6] His 2012 report advises that "US Sailing and other organizations should consider establishing this as doctrine." Thus, reliance on boat handling andseamanship may be misplaced.[6]
A Hobiecatamaran with a masthead float to prevent turtling
Sealingmasts and attaching flotation are effective preventatives for turtling of dinghies, but not widely utilized.[6][7] More certain preventatives for this includes various forms of flotation added to the tip of the mast or top of the mainsail.[F] These include floats (e.g., one that looks like a streamlinedblimp used onHobie 16s)[G][22] or a "sail patch"—a sleeve with built in flotation that fits over the top of the sail, available for example as option on theWayfarer (dinghy) Mark IV.[8][20] Another alternative is to seal the mast, thereby increasing itsbuoyancy.[22]
As an emergency palliative, putting flotation (i.e., a sparelife vest or otherpersonal flotation device), onto the end of the mast straight away after a capsize and without delay, can forestall a turtle. Conversely, climbing onto the side of a knocked down boat can increase the likelihood of turtling, as it moves weight higher over thecenter of gravity, may also increase windage, and thus can effectively drive the mast downward.[7]
Several devices have been patented to prevent turtling.[23][24] Capsizing is particularly troublesome forcatamarans andtrimarans, which are especially hard to right.[6][23]
Righting a turtled dinghy is one of the most difficult maneuvers. Recovery in a monohull requires releasing themain sheet andjib sheet, lowering thespinnaker if it is deployed, standing on the bottom of the boat and levering on the centerboard, or standing on the centerboard (there may be weight and placement restrictions). It is important that other members of the crew not be on top the boat, as this can drastically increase resistance to righting the craft.[7] The use of "righting ropes" materially aids the process. Standing on the centerboard and "piggybacking" of crew members can be highly effective to right a turtled dinghy, as it increases both the weight and leverage being applied. Use of powerboats to aid is problematical, and depending on the technique used—there are several—may or may not succeed.[6] SeeCapsize.[26] Rigging righting lines depends upon proper placement, and critically should be done in advance of the need to use them.[20][27]
MultihullAleph capsizing during America's Cup trials, Plymouth
Inyacht sailing,multihulls are deemed to be more prone to turtling thankeeled monohulls, and there is essentially no way to right them if they overturn. The juxtaposition of the hulls and sail when turtled—it makes them inherently stable when inverted—makes them especially resistant to righting.[6][23] Consequently, some larger multihulls are built with a turtle emergencyescape hatch beneath the hull. Indeed, some locales require such safety hatches.[28] There are, however, those who feel that the likelihood of a capsize of a large multihull is overrated.[29][30] There are others who state that aself-righting multihull is the answer, along with designing in safety and proper operation.[28] A patent has been issued specifically concerning righting of turtled large multihulls.[31] It is intended to avoid the necessity to use divers and special equipment in a recovery.[31]
It is, however, possible (and often successfully) to right a capsized small multihull, e.g., aBeachcat andHobie 16. The process begins with positioning ropes so that the crew can get leverage (acting together is key). RightingBeach catamarans that are turtled can be extremely difficult. Loss of sails, rigging, masts and boats can occur,[26] not to mention sailors.[8] A singled-handed self-rescue can be assisted by filling agarbage bag (called in this context a "righting bag") with water, and throwing it over the rescuer's shoulder.[26] SeeHobie 16 which suggests sitting on the rear of onesponson, which will upturn a turtled Hobie.
Even some large multihulls can be righted at sea—it is a long shot—provided that the skipper is well prepared, knows what they are doing, and has appropriate devices, tools, skills, a workable plan, cooperative waves, weather and wind, and some luck.[28][29]
In December 2008, the high speed experimentalsailing hydrofoiltrimaranHydroptère set a world speed record, thenpitchpoled while going over 60 knots. The turtled yacht had to be towed back to port for being turned right side up.[35]
In the 2011Chicago Yacht Club Race to Mackinac, the high performance monohullsportsyachtWingNuts, a Kiwi 35, turtled in an extreme storm, killing the captain and one crew member. Later inquiry determined the boat—specifically its high performance extremely wide low displacementhull[21][25][36]—was unfit for the location, weather, and the lengthy multiday race format, and urged race officials to change ratings and revoke privileges for similar boats to enter the race.[14][16][17][25][I] The waves were not all that unusual, although the wind was. The boat may have buried one of itshiking wings into a wave, causing it to 'trip', and had the other lifted by the wind.[36] It is rare but not unheard of for keelboats to turtle and remain upside down, particularly if its keel is intact. However, this boat's unique hull form, which made it very fast, also rendered it more stable upside down than right side up. This was a recipe for the disaster.[21][36] This loss was occasioned despite a competent and experienced crew which was as well equipped and prepared as thought to be necessary.[14][16][17][21][36]WingNuts met then current offshore stability standards, which failed to adequately take into account the dynamic effect of the "radical" winged hull.[14][16][25][36][J]
On 13 June 2012, in the trials leading to theAmerica's Cup,Oracle Team USA on anAC45 spectacularly capsized the boat, and it was righted with minimal damage ("there's a little rip there") ten minutes later. SkipperRussell Coutts dismissed it as "a learning experience". This was an epilogue to earlier similar incidents by other teams in Australia.[37][38]
^A related nautical turtlemetaphor is the termTurtleback Deck or "deck, turtle nautical: A term applied to a weather deck that is rounded over from the shell of the ship so that it has a shape similar to the back of a turtle. Used on ships of thewhaleback type and on the forward weather deck oftorpedo boats.""World War II Naval Dictionary".USS Abbot (DD-629). Archived fromthe original on 12 December 2013. Retrieved19 February 2014.
^In larger vessels a capsize almost inevitably leads to a sinking. "To turn upside down, and usually, to sink. There is no vessel so large that the largest ocean wave, taken broadside, cannot capsize.""Naval Slang Dictionary"(PDF). p. 6. Archived fromthe original(PDF) on 2 November 2013. Retrieved19 February 2014.
^"A seaman laboring under an undue sense of security becomes at once worth hardly half his salt." –Joseph Conrad.Conrad, Joseph (1921).The Mirror of the Sea. Doubleday, Page. p. 18. cited in Rousmaniere at p. 19.
^Intended for "rough weather or novice racers"."Hartley Wayfarer Mark IV". Retrieved13 November 2013. Distances, obstacles and the likelihood of rescue are other factors that should be considered in deciding whether to prepare for the worst. AsFranz Kafka,Larry McMurtry inLonesome Dove, andHuey Lewis and the News have written: "It is better to have it and not need it, than need it and not have it."
Veteran Chicago-Mac racers have encountered similar conditions during previous races and understand that coping with severe weather is part of the challenge. Skippers must prepare their boats, train their crew, maintain a watchful eye for approaching storms and "the dearest friend (and most menacing foe) of all sailors—the wind.
^"On paper, WingNuts met all stability requirements for the Chicago-Mac race. The race required that all boats have an Offshore Racing Rule (ORR) handicap measurement certificate, a document that includes two measures of stability: Limit of Positive Stability (LPS) and the Stability Index (SI). However, after the accident, the US Sailing panel found that the ORR formulas did not adequately penalize the Kiwi 35's extreme flare, the difference between the waterline beam and the maximum beam. When the panel eliminated a fixed lower limit for the "capsize increment"—one of the factors used in the calculating stability index—WingNuts' index of 100.7 plummeted to 74.4. No other boat in the race had the same drastic reduction in its stability index when the same math was applied. In addition, the panel noted that the Right Arm Curve (GZ Curve)—a graphic representation of the boat's stability—revealed WingNuts to be just as stable inverted as it was right side up, sharply reducing any chance of recovery from a full capsize.""PS Analysis: The 2011 WingNuts Capsize Practical Sailor".Practical Sailor. April 2012. Retrieved6 December 2013.
^Pardey, Lin (2008).Storm Tactics Handbook, 3rd Ed., Modern methods of heaving-to for survival in extreme conditions. Arcata, California: Pardey Books. p. 97.ISBN978-1-92921-447-1.
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