Latest News: Forums Technical Upgrading genoa sheet jammers

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  • #4319

    I’ve moved from my trusty old MKI which had a full racing setup, to a newer and simpler World, which suits my style of sailing better.
    One thing I really miss, though, is the old boat’s genoa sheet setup. It had what I believe are called ‘H tracks’ with a BB floating block, led to a 76mm ratchet BB block, and from there to the jammer.
    The new boat has these fitted instead:

    I do actually like the low profile and simplicity of these jammers, but in stronger winds I miss my BB blocks! Is there are a way to modify these jammers to incorporate some sort of roller? Or do I just need to get used to putting a bit more effort into sheeting in…

    Colin Parkstone

    Yes! You can take the slider off and turn it upside down.

    On the rear are screws, holding the plate with the jammer on to the fairlead.

    Remove the plate and cleat and put the slider back on the track with a BB block tied to it with strong string.

    Then use this block to lead the sheet to your ratchet block and in turn to a cleat like your last boat.

    Or, remove the whole cleat and fairlead from the track and replace with new slider and block.

    You would not need 75mm ratchet blocks, 54mm work just as well.



    If you remove the plate and cleat you will notice the rear leg is a little longer then the two front legs of the fairlead. You need to add washers to compensate for the removal of the plate.

    Another nice way to convert the existing sliders is to cut of the front leg of the fairlead after removing the plate and cleat. When you file the front of the remaining U, containing the knob and spring, carefully to a nice rounded shape it will look as if designed that way by the manufacturer. Then use a Harken 2652 which has a clip pitch (32 mm) equal to the distance of the now unused screw holes in the slider. The rear of the Harken clip fits nicely under the remaining part of the fairlead but you may want to add a washer to fill up the gap to the same thickness as the plate that used to be there. while the back of the Harken clip is fixed with the existing screw, the front of the clip is fixed with the old screw cut and filed to the required length and a locking nut. You could use a new, shorter screw but you still would have to file it plane with the top of the lock-nut as you would not want any sharp parts there, trying to pinch a hole in your clothes.[attachment=1:300xiner]fix.jpg[/attachment:300xiner] Obviously other brands can be used too but I have used Harken and I know it fits from experience.

    Here is what my thwart looks like: [attachment=0:300xiner]thwart.jpg[/attachment:300xiner] The set-up is made with a Harken 2640 – 40 mm ratchet cheek block on a slightly angled, well painted piece of plywood. The swivel cleat is a Harken 240 (or is it a 241?). A swivel is nice for single handed sailing, a simple cleat on a pedestal should be good enough for a two person crew.


    Thanks for the advice. Still contemplating how to upgrade the genoa sheeting.
    I don’t really want to go down the route of a race-type setup which takes up space on the thwart, although I will admit that, having previously owned a boat which was set up like that, it is a very good system.

    I’ve come across these sheet leads, apparently these are an Allen part, but I cannot find any reference to them anywhere. Has anybody used this design before? I am concerned that the apparently free-floating cleats will be impossible to uncleat. Also the tracks are only 220mm long- the existing ones are about 350mm.


    I had to take the hacksaw to the bridge at the top of the cleat because the sheet was prone to re-cleat itself in the course of a tack with wet results !!

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