Slipping Main Halyard

Originally posted by NickA The mast and hence cleat are pretty new (15 months) and the halyard is routed so that it doesn't run through the cleat when hoisting.  Shouldn't have worn out yet. My first boat (a laser 2) had a hook rack for the jib halyard and it was a right pain in the bum - but that was because the halyard also set the rig tension - I could never get enough rig tension on.  Not an issue on the main of a boat with independent rake and rig tension adjusters. Various knotty solutions will work for now - JohnJack's slipknot under the cleat appeals, and yes a picture would be a help!  Should think it's essential with a D12 halyard; didn't think D12 would cleat at all.

I don't know what loads your mainsail take s but I solved this problem by going back to basic seamanship.  Fit an old-fashioned horned cleat. Swig up the main with the kicker,cunningham and outhaul off, take a round turn ,a figure of eight, and finish with a locking turn. You could make a mock up horizantally on a scrap piece of timber. I'll think you will find it won't slip.

I would have thought a Jav would have a wire halyard....I am sure mine did. Why not have an external halyard and the cleat at the top? Tasar has a wire with a 'pip' on it and a metal 'V' cleat 3" from the sheave at the top.There is only 6' of wire to stretch. Byte has a similar solution but with string and a cleat. The only problem is that you need to change your glasses to see up there and on the Byte which runs with loaded cunningham it tends to jam.

If you thicken the halyard with an insert please remember to taper the insert by cutting away strands gradually

This makes the insert roll over you sheave block at the top easier and prevents creating a hard point where the rope thickens that massively reduces the strength of the rope.

Nick, if you are thickening D12 with a core then you need to do it for the region in the cleat + an inch or two on either side. This is standard practice on spinnaker halyards but I have to say I dont know many people using D12 for main halyards.
I have found that boats which rely on standing rigging to provide mast pre-bend are suitable for hook racks and those which rely on main halyard tension for pre-bend need a cleat such that additional purchases can be added to the halyard once nearly up to assist with increased tension to induce bend. The RS600 being a case in point.
One solution sometimes used is to use two cleats or pack out the top end of the cleat to get a better bite angle.