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What is a lock and why should I use it on board?

CROCHETs & HOOKS - POURQUOI INSTALLER un hook ? - Quels sont les avantages ? - conseils - DOIS JE Installer un hook a bord - Karver et les hooks


L’usage courant du mot hook (crochet en français) mot va nous permettre de comprendre facilement sa définition nautique. Pour suspendre un lustre au plafond, vous pouvez utiliser un cordage et une poulie et une fois à la position souhaitée, il suffit d’attacher le cordage. La solution alternative est de lever votre lustre puis de le fixer directement sur un crochet. Il n’y alors plus de tension dans le cordage.

Dans le cas d’un voilier, un hook est un système qui permet de hisser une voile (quel qu’elle soit) à la position souhaitée, de la bloquer avec un système de crochet et éviter ainsi de garder de la tension dans la drisse. Sans tension, il n’est alors plus nécessaire d’attacher le cordage. Sur un voilier on retrouve des hooks principalement sur les voiles d’avant (Trinquette, Code 0, Gennaker, …) mais également sur la Grand Voile et les ris. Plus généralement, on peut considérer qu’il est possible de hooker n’importe quel cordage habituellement sous tension.

Maintenant que tout le monde comprend le principe, attachons-nous à comprendre en quoi est-il intéressant de hooker une voile à bord d’un voilier qu’il soit de course ou de croisière. Point important à intégrer au préalable : contrairement à notre lustre où la tension de drisse est constante, les efforts présents sur la drisse d’un voilier ne sont pas les mêmes au moment de hisser la voile et lors de la navigation lorsque le vent va s’engouffrer dans celle-ci.

Gain weight in the mat : the principle is simple : the more weight you have above the deck, the more weight you will need to add to the keel to maintain the same level of stability. On a 15 m sailboat with 25 meters of mast, you have to compensate 15 kg at the head of the mast by several hundred kilos in the bulb keel ! The less weight there is in the tops, the more stable & faster your sailboat will be. Two concepts as important in racing as in cruising. On a ocean cruising sailboat, you could trade a few kilos in the tops for several hundred liters of beverage (whatever it is) or diesel !  While racing, you use this weight gain by weight gain in the keel to make the boat lighter or faster.

With a lock, the halyard no longer needs to be sized to withstand the significant tensions of the sail when sailing. The halyard has only one function : hoist or lower the sail. Also on our 15-meter sailboat, it is possible to replace your 12 mm dyneema halyard with a simple pure 6 mm braid. If the halyard measured 60 meters, you save 5 kg but also several hundred euros. These figures must be doubled or tripled if you “muffle” your halyard (2-fall hoist to divide the efforts by 2). On some sailboats, the tensions are so great that very large diameter ropes should be used. The lock allows the halyard to be sized only for the weight of the sail. Installing a hook comes at a cost, but you also need to factor in the savings to assess its true cost. The use of a lock makes it possible, for example, to remove the halyard jammer.

Furling lock swivel

Eliminate halyard wear : With a hook, the halyard is no longer in tension and it is therefore the end of the halyards worn or broken by prolonged friction on one or more sheaves or by its jammer.  On long cruises, you no longer have to worry about changing the position of the wear points :  an obvious gain in serenity and real savings.  Anyone who has been through the experience of a broken halyard, the fall and / or loss of a sail and the difficulty of ironing a new halyard will easily understand the value of the hook.

Remove the lengthening of the halyard. You will agree, the fabrics used for our sails are more and more technical (3DL, titanium, laminated racing :  save weight (see first advantage) and avoid fabric deformation to obtain stability of the shape of the sail and thus improve performance.  If you have invested in a technical sail you should understand that using a halyard that is too elastic will seriously reduce the benefits of your investment!  The use of a good quality dyneema halyard is therefore compulsory.  Better still, the use of a hook will avoid any deformation of the profile of the sail.  This is an advantage highly sought after by sailors but it is far from being negligible on a cruising sailboat and even more so on heavy weather sails which usually work very poorly (complex implementation, not enough tension, halyard elastic,…)

Decrease halyard compression in the mast. It becomes more technical and not being an engineer, my explanation may be simplistic. If we imagine an average tension of 5 tons in the sail, this tension will necessarily apply to the mast but the direction of the forces will not be the same with or without a hook.  A classic binding with a halyard compresses the mast more and tires it more.  Thus, a mast originally designed for use with hooks will usually be subjected to less effort and it is therefore possible to use a less reinforced section, therefore lighter which brings us once again to our first advantage :  weight gain.


Tension from bottom : Since there is now a fixed point at the top, the only way to add tension to the sail is to be from the bottom.

This is an important point to think about when changing to adapt your fittings.  If we take the example of a code 0, we usually fix the armor point to the bow then we hoist the sail with the halyard that we block with a jammer (installed on the mast or the piano).  With a lock, you first hoist the sail to the lock point before taking the tension back through the weave point.

If you are using a furler, you will need to add a termination allowing the use of a hoist to have sufficient strength. It is usual to position the jammer that will block the tack point rope as close to the bow as possible to avoid the rope elasticity issues that we have sought to eliminate from the equation. Clamps that can be operated from the cockpit (such as our KJ clamps) are perfect to complete the setup.

Let’s say that the main constraint of a hook is that its installation cannot be improvised. The forces applied to the mast are different, the sizing of the ropes must be adapted, the fittings and its position are also different. We advise you to carry out this modification with a professional.

Maintenance & reliability : Locks don’t always get a good press, but that’s a very wrong judgment. Reliability has been there for many years and recent systems are very far from the mainsail locks of your Hobby Cat which regularly blocked. On the other hand, these are systems that require maintenance. Nothing very restrictive, but it is not imaginable to leave a lock “in its own juice” as we would do with a winch. You don’t need to hire a professional. Maintenance mainly consists of checking the state of wear and cleanliness of the parts.


If you are a racer and more particularly offshore racers, hooks are undoubtedly products that will help you improve performance. Chances are you already have them equipped unless your class’s gauge rules prohibit them. On an Imoca participating in the Vendée Globe, all the sails are hooked.

For occasional boaters, the financial and technical constraints are out of balance with the advantages. Nothing prevents having fun of course but it is quite rare to find hooks on a cruising sailboat that practices coastal navigation.

On the other hand, the hooks are particularly recommended on sailboats and almost essential on multihulls whose workloads can be very heavy. For these sailboats, the hooks are above all a guarantee of safety. All frequent travelers have had problems with halyards or reefing bumps that break in the middle of their trip. The hooks definitively solve this problem and significantly extend the life of the sails.



Soucieux de fournir de l’accastillage qui apporte plus de performance et/ou de confort et de sécurité, vous trouverez dans notre gamme de nombreux hooks. Sans rentrer dans les détails techniques, voici un tour d’horizon de nos solutions.

• Pour la Grand Voile :

Chariot de têtière de GV hooké disponible sur les gammes KMS40, 60, 80 et customs

Croc de ris KHR à installer sur la bôme

Pour les voiles d’avant (génois,gennaker,code 0,spi,…)

Hook de drisse interne au mat KMH

Hook de drisse externe KHL

– Hook de drisse externe avec émerillon KFH : il s’agit d’un hook et d’un émerillon dans un même produit dédié aux voiles utilisant un emmagasineur. C’est le modèle qui est le plus utilisé aujourd’hui sur les voiliers de course au large (Ultim, Imoca, Multi 50, MOD70, Class40, ..)

Bloqueur de cordage haute charge KJ

– Un bloqueur n’est pas un hook mais nos bloqueurs KJ a 3 mâchoires sont si efficaces qu’ils apportent certains bénéfices des hooks tel que le fait d’éviter le glissement du cordage.


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