Twisting halyard on a screecher with 2:1 purchase

[TradewindSailor]

I have a screecher of around 1000 sq ft on my catamaran. I hoist it furled on a Profurl furler. As the sail is hauled up the halyard twists around itself (it has a 2:1 purchase .... i.e. a block at the head of the sail ..... leading the halyard to be dead-ended at the top of the mast).

This usually locks the sail half way up /forums/images/graemlins/confused.gif /forums/images/graemlins/frown.gif

The old halyard is now completely wrecked ...... I believe it was braid-on-braid polyester. I'm sure it had some bias in the lay-up to cause the twist under load.

Can anyone recommend a rope that will not twist under load? It has been suggested that Spectra - cruising or racing versions - may be suitable; but I don't want to make any mistakes as I need about 200' of the stuff! /forums/images/graemlins/ooo.gif

Cheers

 

[michael_w]

Why do you need a 2:1 purchase? I appreciate that you need loads of halyard tension to get the furler to work. Can't you just wind the sh*t out of the halyard with a winch?

 

[TradewindSailor]

The reason for having a 2:1 is that it halves the loads on the sheave and significantly reduces the chafe on the halyard at the masthead. Even a 18mm halyard wouldn't last a days sail without the 2:1 system.

By the way ..... this cruising cat goes 16 kts!!! /forums/images/graemlins/cool.gif Not at fast as an Outremer though /forums/images/graemlins/ooo.gif

 

[michael_w]

What about a bit of old skool technology, wire pennant and metal sheaves? Or the way the Volvo 60s do it with a halyard jammer at the top of the mast, operated remotely.

16kts 'aint that quick these days. /forums/images/graemlins/cool.gif

FWIW my old International 14 used to twist the kite halyard all the time. The only effective cure was to remove the halyard (with mouse) drag it along the ground until all the twists had gone and re-reeve. Usually I had to do this every race.

 

[TradewindSailor]

Thanks Michael ..... but the mast head jammer won't help me haul the sail up ...... it's only there to prevent a significant amount of stretch that would be present if the jammer was at the bottom of the mast.

With a wire halyard you are still looking at a considerable increase in stress and hence chafe at the sheave. Without a 2:1 the wire will have too free a movement resulting in accelerated chafe ...... with a 2:1 the wire will twist.

As for 16kts ....... It's pretty quick for a cruising cat. Gunboats and Outremers do get up into the early 20's though. However ..... if I could get my hands on B and Q .... /forums/images/graemlins/cool.gif

Cheers