Picture a thousand words

The preventer is not at all used to control the gybe, it is only (!) to prevent an accidential gybe. Take a long and sturdy line, knot a double eight or something like that at the half length and then attach it to the boom, i.e. were the sheet is attached (or further aft if possible). Now take each end of the line through a block on the toerail roughly abeam the mast and lead the line aft.

Now when sailing with the boom on starboard, set tight the starboard preventer. Enjoy your downwind sailing.
When gybing, release the preventer, perform the gybe. When on the new tack, set the port preventer....

When chartering I always take two heavy blocks with me and use a spare mooring rope as preventer...
 
unless I'm missing something the preventer runs from the boom on the same side as the boom is lying (starboard tack on the port side), to a foredeck car and then onto the lazy headsheet winch back in the cockpit. This means that if need to alter mainsale trim you can ease or take up the slack on the winch.

when gybing you untie from the boom end, this goes onto your new lazy headsale winch and the other end off the winch onto the boom.

I hope that makes sense?
 
I don't have a preventer permantly fixed to my boat, but I do use one when running. In this case I run it from the kicker attachment to a forward cleat on the same side as the boom. You'd be surprised how much stretch there is in 8 foot of mylar rope.
 
Excuse my scabby drawing, but we find the simplest way is to rig a block at the bow, and run a line from the cockpit, outside of the shrouds, round the block, back to the cockpit on each side (we have two winches on each side so it's a simple setup). This means you can gybe with ease by
<ul type="square"> freeing the preventer line
gybing
tensioning the line from the opposite end. [/list]
Works for us, but the other method may be better depending on the dimensions of the boat and the length of the boom. Hope this helps.

preventer.jpg
 
Don't forget that if the boat gets gybed with a preventer fitted the forces on the boom and preventer can be enormous. If the boom is small it could very easily break. I would not recommend using one over F6.
 
Toryboy - I inherited a Dutchman Boom Brake with my boat. Haven't used it yet but hope to over the next couple of weeks. Happy to let you take a close look to see if it's something you want to make up. Looks to be a good piece of kit and I've read a few good comments so looking forward giving it a go.
 
I think the story with preventers is that neither of them is any use as the boom comes across.


What you should be doing is sheeting in the main to hard in and then letting it run out again after the boom comes across. In other words you never let it slam all the way out, but you do have to let it run out fairly fast on the new side. Of course without a proper kicking strap/vang this process can lead to a chinese gybe.

The effect of not being able to release the main once the boom crossed the centreline was quite clear when I was watching the J class Endeavour in 2001 from the top of the Needles Battery when they did this in 30 knots true with a full main and the mainsail neatly spun them round 135 degrees. Nothing major broke and they carried on sailing.

Unfortunately my camcorder battery was flat so I didnt get the manoever on tape.
 
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No, apparantly it cannot be used with a roller reefing boom like I have. I am going to put some more thought into alternatives....

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There was a thread a while ago about using a climbing "Figure of Eight" as a boom brake. (If you don't already know, a small amount of tension in a rope threaded through an '8' generates a huge resistance to movement).

The scheme as described consisted of an '8' shackled to the boom (could be boom end, or kicker attachment, etc.) running on a length of line strung between the chainplates. One end of this line was fixed, the other ran through a block and back to the cockpit so that the tension on the line could be controlled. Haul it tight to act as a preventer, release it to gybe, or moderate tension to slow down the boom.

It struck me as an elegant solution, but I've not got around to trying it. (Fig. of 8s are about £10-00 and usually work on 10-12mm line).

Andy
 
Seems to me that one of the problems using a preventer is that if you do accidently gybe and end up with the main completely backed and the boat out of control, then you need to be able to quickly release the preventer but preferably under control so that the boom doesn't slam across (the main will be fully out, of course). For this reason you need to have the preventer on a winch so that you can release it easily but under control.
We just use a line temporarily rigged from a winch in the cockpit, through the appropriate bow fairlead (w/o any form of block or pulley) and then to the outer end of the boom.
 
the preventer is to hold the boom forward .... and stop it swinging across in an accidental gybe.

Therefore if boom is out to starboard - preventer is forward to starboard.......

You can rig two lines .... so that you can clip / unclip as necessary. with the ends coming back to cockpit to tighten / slack as required.

Myself .... I use a light line from boom kicking strap point to cleat forward ... the line would break if any real force came on it ...
 
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