Working on the same principle as the Chinese finger trap, the Cousin Trestec Constrictor 10 is a simple yet effective means of securing relatively highly loaded lines.

This principle of rope holding is already in use on almost every line on a modern racing yacht. A rope splice in any braided line achieves its high strength by the line’s tendency to close down and grip on itself under tension. The difference here is the ability of the clutch to allow the line to pass through the rope braid easily when required.

Most rope clutches rely on a metal surface squeezing down on the line. These have limitations; almost every racer who has served their time in the ‘pit’ will have experienced highly loaded lines (especially jib halyards) slip under high loads. Also they will have probably struggled to release a loaded line quickly, normally having to take it up on a winch.

Release under load

The Constrictor clutch is designed to alleviate these issues, providing high holding power yet the ability to release lines under load easily. Its operation is relatively simple: as the working line (a halyard, for example) is eased onto the clutch the textile sock grips the line and constricts to hold it firmly.

To release the load you need simply to pull on the control line; this prevents the clutch’s rope braid from extending, and therefore constricting and gripping the working line. A simple knot and notch allows the control line to be held in the open position, allowing the working line to pass in either direction.

In the ‘jammed’ mode a line may still be taken up, much like a one-way valve.
We tested this clutch on Scarlet Oyster during the ARC and Caribbean race circuit. Once crew were familiar with its operation, we found it reliable and effective.

We used it on the spinnaker pole downhaul, as it was the only single clutch we have (the rest are in banks of three or more). While the ultimate holding power was not tested for this task, its ability to be released under load easily was found to be very useful. Out of curiosity I did winch a larger load onto the clutch, and it showed no hint of allowing the line to slip.

Installation was very simple. We used the same fastenings as the existing Spinlock clutch, making retrofitting straightforward.

The Constrictor would, I am sure, prove very effective for dealing with halyards and would allow a controlled spinnaker drop without a winch. My only concerns are that, as the force required to release a line is so small, it is easy to release a highly loaded line accidentally, so user familiarisation is particularly important.

The other potential drawback is that there is a little ‘backlash’ as the clutch stretches out to grip the line – this could be an issue on the precise holding of a jib halyard, say.

It is a much kinder grip on a line than a conventional clutch, reducing wear on what can be very expensive running rigging. And having no metal moving parts means there is little to worry about in terms of corrosion or maintenance.