Canting keel
Encyclopedia
A canting keel is a form of sailing ballast
, suspended from a rigid canting strut beneath the boat, which can be swung to windward of a boat under sail, in order to counteract the heeling force of the sail. The canting keel must be able to pivot to either port or starboard, depending on the current tack.
The traditional fin keel, pointing straight down from the boat, provides no righting moment
when the boat is level. The heeling force of the wind on the sails is therefore not counteracted until the boat has heeled over by a certain amount, moving the fixed keel to windward of the centerline. The purpose of the canting keel is to allow the boat to develop righting moment when level, by swinging the keel to windward independent of the boat's angle of heel.
With the canting keel handling the ballast functions, lateral resistance and steering can be managed separately with a foil
(or pair of foils fore and aft
). This allows for much quicker maneuverability than traditional keelboat
s, with about half the weight usually required for ballast.
A version of the technology was invented and patented by CBTF Technology in the 1990s. The canting keel's first use was in the Vendee Globe of 1996-7 which Pete Goss completed in a 50ft, Adrian Thompson-designed yacht named Aqua Quorum. Development of the yacht and the events of the Race are described in detail in Pete's subsequent book Close to the Wind. Subsequent use in major competition was in September 2004, when five boats using the canting keel in the Maxi Yacht Rolex Cup placed ahead of the previously unbeaten world champion Alfa Romeo. Alfa Romeo II, designed by Reichel/Pugh
features a canting keel and fore-and-aft twin foils (CBTF).
A variation of the canting keel is the 3d keel invented by François Lucas in 1998, which allows movement in three directions (side to side, forward and aft, and rotation).
s such as the maxZ86, canting keels are now beginning to appear in smaller boats such as the Open 60, and the VO70 ocean racing classes, and the even smaller Schock 40 and Mini Transat 6.50
. The Schock 40 owned by Tom Schock famously lost its keel and capsized, illustrating the fundamental problem with complicated keel design: without a keel, most boats cannot float upright.
The Volvo Open 70
class boats in the 2006 around-the-world Volvo Ocean Race
are perhaps the most well known boats to use canting keels for ballast. While previous years' boats showed a few percent improvement in speed each race (the race is held every three years) the VO70 class are showing a 30% improvement in speed. The 6.5 ton ballast bulb, hanging over 16 feet (5 meters) below the water and capable of canting up to 40 degrees, produces a tremendous amount of righting moment
(over 130,000 ft·lbf, or 176,000 N·m with the hull level), allowing the boat to reach speeds of over 30 knots.
, one of the first major long term races allowing canting keels, had problems with the keels. One area in particular, the plates sealing the opening through which the keel passes, are prone to leaks. Unlike a centerboard or daggerboard
trunk, the opening for a canting keel must allow significant lateral motion, which requires sliding seals.
The boat movistar
had problems on Leg 4 of the Volvo Ocean Race
, 200 miles off Cape Horn
, during the night on 2 March 2006. It sprung a significant leak when the sliding plates that covered the keel opening fell off in the middle of the night. This was a problem that had occurred earlier. movistars aft keel pivot broke loose and began flooding the boat. They made repairs in Ushuaia on the Beagle Channel. Later on, in Leg 7 the same problem occurred in the north Atlantic. This time the decision was made to abandon ship, and the crew transferred to ABN AMRO TWO. movistar continued to broadcast its position for several days, but an aerial search failed to find the vessel, and it was lost.
In the 2006/2007 VELUX 5 Oceans Race
(a single-handed, round the world race), the Open 60 yacht Hugo Boss
, skippered by Alex Thomson, had to be abandoned in the Southern Ocean
due to the snapping of the hydraulic rams that controlled the keel, which caused the catastrophic failure of the keel. When this failure caused the yacht to nearly capsize, the boat was abandoned; Thomson was rescued by fellow competitor Mike Golding
. On the 25th November 2006, the boat's Sat C transponder stopped transmitting, and the hull has to date not been salvaged.
might have had a canting keel. This would have given Alinghi an advantage over its challenger for the 2007 America's Cup
, unless the challenger, Emirates Team New Zealand, also had a swinging keel. The America's Cup Class Committee, chaired by Ken McAlpine, issued a ruling on 8 May 2007 which stated that canting keels and other movable appendages were specifically prohibited.
Sailing ballast
Ballast is used in sailboats to provide moment to resist the lateral forces on the sail. Insufficiently ballasted boats will tend to tip, or heel, excessively in high winds. Too much heel may result in the boat capsizing. If a sailing vessel should need to voyage without cargo then ballast of...
, suspended from a rigid canting strut beneath the boat, which can be swung to windward of a boat under sail, in order to counteract the heeling force of the sail. The canting keel must be able to pivot to either port or starboard, depending on the current tack.
Purpose and history
The traditional yacht keel performs four functions:- the development of lateral water force to resist lateral aerodynamic force from sails and superstructure,
- the physical housing of ballast load as low as possible,
- roll-damping to resist energy inputs from waves and disturbed water, and
- a contribution to directional stability.
The traditional fin keel, pointing straight down from the boat, provides no righting moment
Moment (physics)
In physics, the term moment can refer to many different concepts:*Moment of force is the tendency of a force to twist or rotate an object; see the article torque for details. This is an important, basic concept in engineering and physics. A moment is valued mathematically as the product of the...
when the boat is level. The heeling force of the wind on the sails is therefore not counteracted until the boat has heeled over by a certain amount, moving the fixed keel to windward of the centerline. The purpose of the canting keel is to allow the boat to develop righting moment when level, by swinging the keel to windward independent of the boat's angle of heel.
With the canting keel handling the ballast functions, lateral resistance and steering can be managed separately with a foil
Foil (fluid mechanics)
A foil is a solid object with a shape such that when placed in a moving fluid at a suitable angle of attack the lift is substantially larger than the drag...
(or pair of foils fore and aft
Glossary of nautical terms
This is a glossary of nautical terms; some remain current, many date from the 17th-19th century. See also Wiktionary's nautical terms, :Category:Nautical terms, and Nautical metaphors in English.- A :...
). This allows for much quicker maneuverability than traditional keelboat
Keelboat
Keelboat has two distinct meanings related to two different types of boats: one a riverine cargo-capable working boat, and the other a classification for small- to mid-sized recreational sailing yachts.-Historical keel-boats:...
s, with about half the weight usually required for ballast.
A version of the technology was invented and patented by CBTF Technology in the 1990s. The canting keel's first use was in the Vendee Globe of 1996-7 which Pete Goss completed in a 50ft, Adrian Thompson-designed yacht named Aqua Quorum. Development of the yacht and the events of the Race are described in detail in Pete's subsequent book Close to the Wind. Subsequent use in major competition was in September 2004, when five boats using the canting keel in the Maxi Yacht Rolex Cup placed ahead of the previously unbeaten world champion Alfa Romeo. Alfa Romeo II, designed by Reichel/Pugh
Reichel/Pugh
Reichel/Pugh is a yacht design company based in San Diego, California, USA. It is led by John Reichel and Jim Pugh.Since the late 1990s, Reichel/Pugh-designed yachts have successfully competed in many major races, including the America's Cup...
features a canting keel and fore-and-aft twin foils (CBTF).
A variation of the canting keel is the 3d keel invented by François Lucas in 1998, which allows movement in three directions (side to side, forward and aft, and rotation).
Current use
Originally used in large maxi yachtMaxi yacht
A maxi yacht usually refers to a racing sailboat of at least in length. It is also a Swedish brand of smaller sailing yachts.-Origin:The term maxi originated with the International Offshore Rule rating system, which in the 1970s and 1980s measured offshore racing yachts and applied a...
s such as the maxZ86, canting keels are now beginning to appear in smaller boats such as the Open 60, and the VO70 ocean racing classes, and the even smaller Schock 40 and Mini Transat 6.50
Mini Transat 6.50
Mini Transat 6.50 also known as Transat 650 is a solo transatlantic yacht race that starts in France and ends in Brasil covering over 4000 miles with a stop in the Madeira or the Canary Islands. The yachts are very small with respect to the race, and are sanctioned by the organization...
. The Schock 40 owned by Tom Schock famously lost its keel and capsized, illustrating the fundamental problem with complicated keel design: without a keel, most boats cannot float upright.
The Volvo Open 70
Volvo Open 70
The Volvo Open 70 is the current class of racing yachts designed for the Volvo Ocean Race. It was first used in the 2005-2006 race and use a Canting keel which is capable of canting transversely up to an angle of 40 degrees.According to the VO70 rule, the yachts can be made...
class boats in the 2006 around-the-world Volvo Ocean Race
Volvo Ocean Race
The Volvo Ocean Race is a yacht race around the world, held every three years. It is named after its current owner, Volvo...
are perhaps the most well known boats to use canting keels for ballast. While previous years' boats showed a few percent improvement in speed each race (the race is held every three years) the VO70 class are showing a 30% improvement in speed. The 6.5 ton ballast bulb, hanging over 16 feet (5 meters) below the water and capable of canting up to 40 degrees, produces a tremendous amount of righting moment
Moment (physics)
In physics, the term moment can refer to many different concepts:*Moment of force is the tendency of a force to twist or rotate an object; see the article torque for details. This is an important, basic concept in engineering and physics. A moment is valued mathematically as the product of the...
(over 130,000 ft·lbf, or 176,000 N·m with the hull level), allowing the boat to reach speeds of over 30 knots.
Problems
The current canting keel technology is far from perfect. At least three of the seven boats in the 2006 Volvo Ocean RaceVolvo Ocean Race
The Volvo Ocean Race is a yacht race around the world, held every three years. It is named after its current owner, Volvo...
, one of the first major long term races allowing canting keels, had problems with the keels. One area in particular, the plates sealing the opening through which the keel passes, are prone to leaks. Unlike a centerboard or daggerboard
Daggerboard
A daggerboard is a retractable centreboard used by various sailing craft. While other types of centreboard may pivot to retract, a daggerboard slides in a casing. The shape of the daggerboard converts the forward motion into a windward lift, countering the leeward push of the...
trunk, the opening for a canting keel must allow significant lateral motion, which requires sliding seals.
The boat movistar
Movistar
Movistar is a major Spanish mobile phone operator owned by Telefónica Móviles. It operates in Spain and in many Latin American countries. It is the largest carrier in Spain with 22 million customers and 41.58% of market share. Its principal competitor in Latin America is America Movil...
had problems on Leg 4 of the Volvo Ocean Race
Volvo Ocean Race
The Volvo Ocean Race is a yacht race around the world, held every three years. It is named after its current owner, Volvo...
, 200 miles off Cape Horn
Cape Horn
Cape Horn is the southernmost headland of the Tierra del Fuego archipelago of southern Chile, and is located on the small Hornos Island...
, during the night on 2 March 2006. It sprung a significant leak when the sliding plates that covered the keel opening fell off in the middle of the night. This was a problem that had occurred earlier. movistars aft keel pivot broke loose and began flooding the boat. They made repairs in Ushuaia on the Beagle Channel. Later on, in Leg 7 the same problem occurred in the north Atlantic. This time the decision was made to abandon ship, and the crew transferred to ABN AMRO TWO. movistar continued to broadcast its position for several days, but an aerial search failed to find the vessel, and it was lost.
In the 2006/2007 VELUX 5 Oceans Race
VELUX 5 Oceans Race
The VELUX 5 OCEANS Race is a round-the-world single-handed yacht race, sailed in stages, managed by Clipper Ventures Plc since 2000. Its current name comes from its main sponsor, VELUX, a Danish company. Originally known as the BOC Challenge, for the title sponsor BOC Gases, the first edition was...
(a single-handed, round the world race), the Open 60 yacht Hugo Boss
Hugo Boss
Hugo Ferdinand Boss was the founder of clothing company Hugo Boss.-Early life:Boss was born in Metzingen, Germany. After completing his apprenticeship and one year of employment, he founded his own company in Metzingen in 1923.-Support of Nazism:Boss joined the Nazi Party in 1931, two years before...
, skippered by Alex Thomson, had to be abandoned in the Southern Ocean
Southern Ocean
The Southern Ocean comprises the southernmost waters of the World Ocean, generally taken to be south of 60°S latitude and encircling Antarctica. It is usually regarded as the fourth-largest of the five principal oceanic divisions...
due to the snapping of the hydraulic rams that controlled the keel, which caused the catastrophic failure of the keel. When this failure caused the yacht to nearly capsize, the boat was abandoned; Thomson was rescued by fellow competitor Mike Golding
Mike Golding
Mike Golding is an English yachtsman. He is one of the few yachtsmen to have raced round the world non stop in both directions...
. On the 25th November 2006, the boat's Sat C transponder stopped transmitting, and the hull has to date not been salvaged.
America's Cup
There were rumors that the 2007 International America's Cup Class yacht AlinghiAlinghi
Alinghi is the syndicate set up by Ernesto Bertarelli, racing under the colors of the Société Nautique de Genève, to challenge for the America's Cup. Bertarelli had raced several smaller yachts named Alinghi previously, but 2003 was his first attempt at the America's Cup...
might have had a canting keel. This would have given Alinghi an advantage over its challenger for the 2007 America's Cup
2007 America's Cup
The 2007 America's Cup was the thirty-second challenge for the America's Cup and was won by Alinghi in the 7th race. The Cup is the most famous and most prestigious regatta and Match Race in the sport of sailing....
, unless the challenger, Emirates Team New Zealand, also had a swinging keel. The America's Cup Class Committee, chaired by Ken McAlpine, issued a ruling on 8 May 2007 which stated that canting keels and other movable appendages were specifically prohibited.