How can I stop 12mm mainsheet slipping in my Lewmar cleats, and can they be serviced?
My mainsheet slips in its Lewmar cleats, even after replacing it with new 12mm rope. Can I adjust the grip, or are there springs or other parts I should service or replace?
Answer
If your Lewmar mainsheet cleats have two spring-loaded jaws, they normally have no grip adjustment: persistent slipping with new 12mm rope points to the wrong cleat size, poor rope entry, sticking cams or worn teeth. Check the model and its rope range, then clean and inspect both cams before buying more rope or replacement hardware.
Check cleat and rope size
A cam cleat has two toothed jaws that open as you pull the sheet through and close when the load reverses. A rope clutch has a lever handle and an enclosed gripping mechanism. Its servicing procedure differs, so identify the fitting before dismantling it.
Look for a moulded or stamped part number on the body or underside, then check the specified rope diameter range. A 12mm mainsheet is at the upper limit of some larger cam cleats and exceeds the capacity of many smaller ones. The diameter on the rope label alone does not tell you whether the cleat is suitable.
With the sheet unloaded, push it fully down between the jaws. Both cams should grip the cover firmly, with room to wedge tighter when you pull the loaded side. If the rope rides high, holds the jaws almost fully open or will not seat properly, check size compatibility first.
Secure the boom and remove all mainsheet load before dismantling the cleat or its supporting block.
Check sheet entry and grip
Follow the loaded sheet from the last sheave into the cleat. It should enter centrally and close to the cleat's working plane, without pulling upwards out of the jaws. On a mainsheet block with an adjustable cleat platform, you may be able to change the platform angle even though the gripping pressure is fixed.
- Check both jaws: open each cam separately and release it. Each should return promptly under spring pressure.
- Inspect the teeth: look for rounded crests, chipped edges, cracks and one jaw noticeably smoother than the other.
- Watch under modest hand tension: check whether the rope slides through closed jaws or lifts out of them.
- Check the mounting: a loose platform, distorted base or binding pivot can prevent proper engagement.
Rope construction matters too. A firm, slippery cover can grip less effectively than a supple polyester double braid of the same nominal diameter. If available, try a short length of another suitable 12mm polyester sheet under controlled hand load. A difference helps identify cover compatibility, but does not prove the cleat will hold sailing loads.