Ocean Racing Magazine - #5 - October & November 2007 - (Page 68)

LAB The mystery of THE CANTING KEEL ©I. Abery The canting keel is now a must on ocean racing monohulls. It is about time that we took a look at how it works present in yacht racing, and ensures the structural elements are working thus avoiding some of the nightmares skippers have endured in the past. Energy The hydraulic pump ensures that oil pressure is maintained where required. The power of this unit powered by the battery pack will depend on the required specifications concerning the time to cant and the force applied by the rams. As an example, a hydraulic system for a 60’ IMOCA usually has a power supply of around 3 to 4 kW, which is enough to cant a keel by 40° in less than 30 seconds and to generate a force of 30 tonnes. A power supply offering 1.5 kW will be enough for a thirty foot boat, while at the opposite end, 30 kW were necessary to cant the 20 tonne keel of the giant Mari Cha IV, whose ram (the largest ever made by Cariboni) delivered a force in excess of 300 tonnes… A canting keel rotates around an axis at the bottom of the hull. To move it, you have to push or pull at the top of the keel, which is inside the boat. As so much effort is required, usually hydraulics are involved on ocean racing yachts. The overall installation is fairly complicated. In order to make it easier to understand, we offer you a general presentation of the arrangement for a 60-foot IMOCA boat. The brain A typical installation includes one or two hydraulic rams, a control and regulation unit located close to the rams, a hydraulic pump, an electronic control box and one or two control panels. The control and regulation unit near the rams has several key functions in terms of the accuracy and working of the system. This is the core of the hydraulic system. It has four main functions: 1/Distribution of oil to the rams to carry out port or starboard swing, 2/Keeping the keel in position, 3/Ensuring the hydraulic pressure to avoid any vibrations in some points of sail («floating») and 4/Sudden release of pressure on the rams if the keel blade is overloaded. This unit brings together the expertise of the hydraulic engineer. In fact, too much rigidity (through the absence of a safety valve) can lead to the keel blade breaking off, if too much pressure is applied too quickly or without control. It’s a bit like what a car would be like without shock absorbers. On the other hand, a lack of hydraulic pressure will lead to vibrations in the structure leading to the phenomenon known as floating. This technical approach, which is common in industry is even more The automaton The electrical control box is fitted with a mini programmable robotic system enabling some functions to be automatic during a change of tack in order to relieve the skipper. Such as: automatic canting of the keel in an extreme position with stop if overloaded, auto- Ocean Racing - october 2007

Table of Contents for the Digital Edition of Ocean Racing Magazine - #5 - October & November 2007

Edito
Contents
What they said
News
Portfolio
America's Cup - One Cup or two?
Jules Verne Trophy - Cammas, down to 48 days ?
Personality - Missing Fosset
Mini - Thirty years of innovations
Transat Jacques Vabre
Portrait - Lemonchois, quietly and discreetly
Barcelona World Race - Duos around the world
TP 52 - Where the stars shine
Figaro - Desjoyeaux not so alone
Trial - Sun Fast 3200
Tactics - Why the New Zealanders lost the America’s Cup
Fasnet Race
Lab
Portrait - Andrew Pindar
Fifty years ago - The Admiral’s Cup - offshore racing
Equipment
New products
Opinion

Ocean Racing Magazine - #5 - October & November 2007

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