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Technical Manual

Side Cleats Or Center Jammer?

by Hedley Fletcher

This may be a question many of you have not even considered. It has been a tendency for many years to mount a single block in the cockpit base and to cleat the mainsheet on the side decks. Many of you may have noticed several boats now sporting a centre main jammer in the cockpit base, thus doing away with the need for side deck cleats. In this article, I will endeavour to outline the advantages of using a centre jammer and the problems one might encounter.

Whilst sailing during the World Qualifiers last year it became apparent to me that I was extremely uncomfortable when hiked out over long beats. Looking at why this should be, I noticed to my astonishment my legs were in an awkward position. This occurs when sailing to windward and trying to push your weight forward in the cockpit. The legs are restricted in the cockpit by the mainsheet passing from the floor to the side deck cleats. As you will see from the diagram, the area of restricted movement in the cockpit is substantial.

The size of the restricted area does, of course, depend considerably on the position of side deck cleats. The tendency to have cutaway side decks for the traveller has meant cleats are mounted further aft, increasing this restricted area. The cleats in this position also means you have a tendency to sit on them, making it even more uncomfortable.

By using a centre-jammer this problem of restricted movement can be overcome. It is then possible to hike with legs in line with the body and as far forward as the traveller allows. Hiking in such a position will be considerably more comfortable and will not place unnecessary strain on the knees.

If at this point you are beginning to consider the possibilities of a centre-jammer, it must be pointed out that there are problems you may encounter. Firstly the point at which the mainsheet is cleated is not at hand and it is therefore important that the cleat angle is set correctly. A good starting point is to set the jammer up so that when the sheet is pulled just clear of the side deck it cleats. Secondly, there is a tendency for the mainsheet to become tangled around the base unless you are careful.

There are two variations of good quality centrebase jammers available on the market, from Harken and Northfix. Both retail at around £40. Unfortunately, neither of these are ideally suited for an OK. They are designed for boats with shallower cockpits or for mounting off the floor. The problem is being able to situate the cleat at a steep enough angle so the mainsheet is cleated when pulled just clear of the side deck. The Harken base has no adjustment for the cleat angle and it is necessary to build the cleat on a wooden base. The Northfix cleat angle can be adjusted to a certain degree by means of a curved plate on which the cleat is mounted. However, it may still be necessary to build it up a little.

It is very difficult without using a centre jammer for some time to know how it would suit individuals. The cost of the bases may discourage some from trying the system. However, by sailing in a steady force 2 - 3 and holding the sheet without cleating it, you can soon see how much more space there is available to you.

Finally, I have heard it said that centre jammers are useful on a windy reach to give the hands a rest, but this is one reason for not using one!



As a result of Hedley Fletcher and David Rose's advocacy, centre jammers are now (1998) quite popular with leading British boats.