preventer line - what rope/from where?

[gregcope]

Hi,

Looking to make a preventer - basically a long line, one each side, around 2xboat lengths to go from cockpit to a point forward of the mast, then aft each side to the end of boom, one side being make tight/fast depending on tack.

Want something with a bit of stretch if we do gybe/broach. Also want a solid colour, like red, so that it is easy to see/identify/reference.

Been looking for 8mm Red Braided Nylon. Found lots of "interesting" sources... and in 10M length (need 2 double that approx).

Ideas?

 

[bedouin]

Why on earth do you want stretch? Surely the whole point of a preventer is to stop the boom moving if the wind gets on the wrong side of the sail?

 

[gregcope]

Why on earth do you want stretch? Surely the whole point of a preventer is to stop the boom moving if the wind gets on the wrong side of the sail?

In an accidental gybe, or a broach where the boom hits the water, there will be large loads on the preventer, and I want it to "give" a bit, rather than bits of boat breaking. Even 8mm will not stretch that much.

Also Saint Cunliffe suggests it... (Stretch/nylon)

 

[dulcibella]

Large shock loads could break very low stretch ropes such as Dyneema, though I don't imagine there would be any problem with using a polyester braid-on-braid or something similar. Nylon too is fine, and won't stretch too much unless it is much too thin.

 

[Dockhead]

Dyneema would be massive overkill for such an application. Most people use ordinary double braid polyester. On my boat, a surplus 12mm furling line, or whatever is at hand. Run it over the lifelines around a cleat forward of the mast, and back to a winch. Simples.

We always rig a preventer whenever the mainsheet is eased enough that the boom could fly around in a gybe.

 

[Leighb]

One good tip I picked up from this forum some time ago. Rig a line along the boom fixed at the outboard end, and clipped with a strong shackle to the centre of the boom, at the kicker attachment for example. The preventer is then clipped to this. The advantage is that you can easily rig the preventer with the mainsheet fully eased, perhaps when the wind has started to pick up unexpectedly when off the wind.

 

[bedouin]

For us we use pretty much any length of line around - usually a spinnaker sheet.

I would have thought the ideal rope to meet the OPs requirements would be a climbing rope. They are designed to stretch a lot more than a sailing rope in the event of a snatch load, and not having the marine premium they may even work out cheaper

 

[Bobc]

One good tip I picked up from this forum some time ago. Rig a line along the boom fixed at the outboard end, and clipped with a strong shackle to the centre of the boom, at the kicker attachment for example. The preventer is then clipped to this. The advantage is that you can easily rig the preventer with the mainsheet fully eased, perhaps when the wind has started to pick up unexpectedly when off the wind.

Now, that's a damn fine idea.

 

[Leighb]

A further advantage is if you need to gybe. We have our preventer ridges with a snap shackle each end, it runs from the side deck adjacent to the cockpit forward through a block on the foredeck and back down the other side.

To gybe, just let go the active preventer, gybe the boat as normal, and then unclip the now lazy preventer from the boom end line, which is to hand from the companionway no need to go on deck, clip on the new active preventer, tension it and make fast.

It all makes going downwind much more comfortable especially for us less agile "older" sailors.

 

[Poecheng]

No discounting the good ideas above but there has been an article about this on the morganscloud site (which is very good indeed) and may be worth finding

 

[Leighb]

No discounting the good ideas above but there has been an article about this on the morganscloud site (which is very good indeed) and may be worth finding

It is quite possible that that is where I found the advice originally, I can't remember exactly.

 

[gregcope]

No discounting the good ideas above but there has been an article about this on the morganscloud site (which is very good indeed) and may be worth finding

Thanks for the tip;

http://www.morganscloud.com/2014/03/13/rigging-a-proper-preventer-part-2/

Morganscloud view (which I support) is a line from the boom forward (not to the toerail) for various reasons - the two mains ones;

- Forward of the mast is the only direction that prevents the boom moving (toerail mounts allow movement)
- Loads are much lower

They have a permeant arrangement down each side of the boom, which is handy if you want to rig up a Preventer whilst off the wind (ie end of boom is already out).

Couple of interesting points;
- The inclusion of a designed in weak point (the know) to break in a way that sends any debris forward;
- Mount point should be near the main sheet to reduce sideways loads on the boom.

So I think I will mount mine, with a small soft shackle or something similar that is weak and then run the lines forward and back to the cockpit.

 

[Tintin]

You have to pay to read the article.

 

[captainboo]

You have to pay to read the article.

I have searched for "morganscloud" and "preventer" and can read the full article without logging in or paying, but if I cut and paste the link it dosen't work!