The quality of DV Jammer
Author: Antal Date Posted:1 January 2019
Traditional lever clutches have restrictions on holding capacity. Jammers however offer superior holding capacity compared to that of clutches.
Jammers stand out for their performance; specifically the max working load may be higher than that of some commercial lines. It is a question of quality, not of size.
Antal’s Double V-Grip Jammers, (DVJ) offers superior quality in a small and extremely powerful line holding jammer. The mechanism is based on Antal’s successful V-Grip system and takes it one step further. The DVJ relies on two opposing V shaped wedges which interlock, grasping the line and evenly distributing the load on 4 sides. The result is a jammer that offers increased surface area grip as opposed to the traditional 2 flat jaws.
Clutch VS Jammer System
Deck gear is often measured by holding capacity.
Clutches and Jammers should rather be measured together with the line they lock, i.e as a clutch-line system or a jammer-line system. Both elements of the system (clutch or jammer and line) should be of the highest quality for the system to give great performances.
Traditionally clutches are used for maneuvers where the line often passes through them. This is also because they can even be opened under certain loads, thanks to their lever. Jammers, however, offer superior holding capacity and have replaced clutches where loads may be intense and the good condition of lines is essential: halyards, for instance.
The DVJ’s superior quality lies precisely in its design. Using the V-Grip technology the DVJ’s wedges offer increased surface area that evenly grips the line on 4 different sides.
Quality of the jammer
From a mechanical point of view the DVJ’s strength is that it distributes pressure on a wide surface and keeps pressure low ‘on each single point of the wedge’. As a result potential line damage is reduced.
Thanks to its qualities the DVJ accomplishes three things at the same time: it does not let the line slip, it does not wear the line and it offers the highest holding capacity.
DVJ Tests (quality of the line)
Because a clutch is always part of a clutch-line system, the propoerties of the lines are of great importance, too. The DVJ’s load capacity was tested on a variety of line compositions. Tests reveal best results on Dyneema cored lines with composite Kevlar-Polyester covers. The max working load values of the DVJ is based on the load tests on this kind of lines. Dyneema lines with composite Kevlar-Polyester covers combine all required properties: rigidity, abrasion resistance and a great diameter-load ratio.
The main body and the wedges inside are hard black anodized aluminum while the handle is resin made. The jaws can be opened with either a handle mounted on the DVJ, or it can be opened by hand with remote control line. Maintenance of DVJ is easy thanks to the rear cover that can be opened by two fasteners.
The DV Jammers are produced for 4 different line sizes: 8, 10, 12and 14 mm. Their MWL are 1500, 2000, 3000 and 4000 kg respectively. Test results on different line materials, together with all specs, are available on the DV Jammer User Guide.
The jammer is secured by 4 studs from underneath. Note that the 8 and 10 share the same drilling template, just as the 12 and 14. Mast mounting is possible thanks to a lower base provided by Antal. Finally, side mounting jammers are fitted with a special side plate.