Karver KJ Jammer

We are constantly reporting on the latest innovations in the marine industry which offer weight savings whilst, at the same time, increasing safety factors. The result: lighter, faster, safer and more exciting sailing.

Images credit: Karver Systems 
French hardware manufacturer, Karver has been active in the French offshore sailing scene (IMOCA and offshore multihull) since its inception in 2004. Their reputation is based on developing a range of innovative products that combine ergonomics, efficiency and lightweight. One of these is the: Karver KJ Jammer.

What is a Jammer

For a full definition of a jammer vs a clutch, see our previous blog here. Interestingly, despite its name, the Karver KJ jammer could be argued to span the two definitions, being releasable under (low) load together with the reliability of a high load jammer.

KArver KJ Jammer


The Karver KJ Jammer

Traditionally, clutches and jammers clamp the rope using just two jaws and matching rope diameter to the distance between these two jaws is critical to ensure good performance. The innovative development in the Karver KJ Jammer is the use of three jaws, providing 360 degree grip surface on the rope, together with its conical body shape, which gives extremely secure and reliable rope holding.





The Karver KJ Jammer comes in four sizes KJ10, KJ15, KJ25 and KJ50 with Safe Working Loads (SWL) ranging from 1 – 5 tonnes and for use with ropes from 5 to 20mm. 






Additional Features / Benefits


Lightweight – innovative design and the use of ultramodern materials gives the unit a very high strength to weight ration


Full Remote operation - Both the locking and unlocking mechanisms are in-line with the load on the rope and can be operated remotely by trip lines. This has some significant advantages and allow the position of the jammer to be optimized to reduce compression loads. For example, they are often used for tack lines on asymmetric spinnakers where they are mounted on the bow and operated from the cockpit.


They are also great for reefing lines and can be mounted inside the boom which removes the need for highly loaded lines back to the cockpit. This in-line operating mechanism also means the jammer can be mounted in small, inaccessible spaces.


Simple separation of body and base- Due to its clever design, the body is held to its base by only a single screw and can be separated from the base in less than 30 seconds making regular maintenance quick and easy. It also means the base is easy to mount securely, in difficult to reach locations on the mast, boom or deck, without the body in place.


The Karver KJ Jammer truly stands out from the crowd and its unique features offer some interesting and unique rope holding applications which are gradually being appreciated by a growing number of cruising and club race customers.


Still in two minds?

Don’t worry! On our website you can find detailed product information on all our clutches and jammers. If you are still unsure, you can always contact us on; support@upffront.com and we would be happy to help.

 clutches and jammers online


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