Why a halyard can slip in a winch?

You've just changed your halyard and had a nasty surprise: it doesn't hold well in the clutch or the winch.

Here are a few ideas to solve your problem.

Check the diameter of the line

To avoid mistakes when replacing halyards and sheets on your sailboat, the simplest way is to buy ropes identical to the original ones.
Because when it leaves the manufacturer, the boat is designed to sail correctly.

Check your deck hardware and the old line, and make sure the newly purchased halyard has the same diameter as the old one.

If the original rope on the boat was 10mm polyester, then get 10mm polyester again.
If you bought a halyard with too small a diameter, it may not be suitable for your deck hardware.

Covering the halyard

Replacing a worn line with a more technical rope can be tempting, even interesting, depending on your use and sailing style.

A Dyneema halyard has many advantages and is a very technical product, ideal for those seeking performance and feel at sea.
Since Dyneema has a very high breaking load, you can try to reduce the diameter of the rope while remaining within the constraints of the clutches.

However, while high-modulus polyethylene has the advantage of being very resistant to chafing, it is also a more slippery material than polyester.
And at the clutches, a smooth and slippery fiber is not ideal.

The solution is then very simple: cover the halyard with a polyester sheath, of course, of the same diameter as the line.
Polyester has a much higher friction coefficient and will compensate for this lack of friction in the clutches.

This way, you get the best of both textile fibers: lightness, resistance to friction, breaking strength, and high performance of Dyneema over most of the halyard's length; while optimizing its hold in the clutches by using polyester only where it is really necessary.

Check the winch

Remember to check the wear of the winch drum.

Like all elements on a sailboat, deck hardware is subject to UV rays, friction, salt... in short, it eventually wears out over time.

If the winch drum is worn (this is the part in contact with the rope), there will be less friction and your halyard may slip.

This is also true for clutches, which wear out quickly.
When new, deck hardware is often given with a diameter tolerance of plus or minus 1. Of course, as soon as the equipment has been used a little and starts to wear, this is no longer true.