Our quick and easy preventer explained

When I recently wrote about some helpful upgrades that we’ve made to Yahtzee, I included a new preventer setup that I think needs some clarification. Well, I finally had the time to set it up at the dock and take some photos that will help explain it a bit better.

In my mind — and experience sailing downwind — a well devised and rigged preventer is an essential piece of gear aboard. And if it’s done right, it should be easy to set up, release and switch sides after an intentional jibe.

What any good preventer should do is catch the boom in the unfortunate event of an accidental jibe. That being the case, I like to lead the preventer line as far forward as possible. But, and this is the big caveat, every boat’s setup will be different. There is no one size fits all. After safe ease of use, what you want to achieve is a fair lead so the the preventer isn’t chafing.

Here’s Yahtzee’s preventer explained:

When installing a permanent preventer that can be quickly deployed on either side of the boat, the first thing I wanted to achieve was making it so that it could be stowed easily out of the way on the boom. To make this happen on Yahtzee, I measured and cut a length of Dyneema, attached the aft end to the bail at the end of the boom and then ran it about 3/4 of the way forward towards a cleat. At the forward end of the Dyneema I spliced in a stainless ring. This ring can then be attached to a short piece of bungee from the cleat to hold it taut, or to the second portion of the preventer line when it’s fully rigged.

Dyneema runs from the end of the boom forward when not in use.
A short length of bungee cord with a clip on the end can attach to the ring on the Dyneema or hold the coiled preventer that will run forward to the bow while deployed.

When it’s time to rig the full preventer for use, I can simply unhook the coil or Dyneema line and ease the boom out to where I want it while broad reaching or running. The secondary line then runs forward to a low friction ring on a snap shackle that I can move from the bow to the toe rail depending on how and where I want the line to lead.

Boom eased out over the starboard side with the preventer fully rigged.
Preventer running forward to the bow.
At the bow the preventer can get cleated on either side or led through a low friction ring and run aft.

The great thing about this setup is that when it comes time to jibe, Jill or I can un-attach the two lines without having to lean out over the side of the boat. The Dyneema can get quickly stowed on the boom with the bungee and then we can move the other section of the preventer to the new side. Once the jibe has been completed, the ring-end of the Dyneema section gets taken off the boom and re-attach it to the secondary line. When it’s all set, we can tighten the whole thing up and sail on without worry. Simple, quick and efficient.

If you have any questions, please feel free to email me (andrewcross8@gmail.com) or ask in the comments below.

8 thoughts on “Our quick and easy preventer explained

  1. I need to set one of these up and I really like your setup for ease of use and stowability. Curious about the attachment that you use when you lead the line aft assuming you run the control line back to the cockpit for cleating.

    1. Good question. I didn’t mention where we secure it because we’ve experimented with lots of places and it kind of depends on conditions. In the real boisterous stuff we can run it back to a clutch or cleat in the cockpit. Other times I’ve just cleated it on the port or starboard bow cleat. And in a few situations I’ve run back down the deck to a cleat we have that slides forward and aft on the genoa track.

  2. Similar to our setup, except instead of a two part line we use a single line on each side – port and stbd preventers.
    It’s really nice not to have to go forward when jibing – the less excuse we have for not setting the preventer, the better.

    1. Yeah, that’s a good setup. I’ve done the double preventer rig before and have thought about rigging an extra line that will be ready to switch easier. In the end I haven’t done it because I’ve found that the times when we actually use a preventer are when we’re sailing long haul on one tack and not even jibing that often. Also, when using it we’re sailing downwind in following seas and going on deck hasn’t presented a huge safety issue.

  3. We have two three part vang /preventers, port and starboard. They are attached to a padeye on the boom and two padeyes on the deck . The bitter ends leads to cam cleats on the outboard side of the cockpit coaming. If we do take an accidental jibe the boom stops short of center line. To get out of this situation we usually have to jibe back as the cam cleat is jammed pretty hard.

    Being vangs as well as preventers, they are always set up. No going forward, no strange lines line on the deck. Also stabilizes the boom when docked, anchored or powering.

    1. Sounds like a great all-around solution. Thanks for sharing, Steve!

      Since so many people do preventers in different ways, I was hoping to get people sharing how they make it work aboard their boats.

  4. Two improvements I can suggest to your setup.

    1. It is a simple exercise to install a length of shock cord inside the 12-strand Dyneema so that it has a bungee effect to allow it to be hooked to a truncated cleat on the boom, but has full strength when stretched to its limit. This eliminates the short length of shock cord you have on the boom. (The “truncated cleat” is a plastic cleat with the forward horn shortened so the preventer can be easily removed). Instead of the ring at the end, just make a tuck-and-bury eye splice.

    2. There is a point on the cap rail where going forward has NO EFFECT on the angle of the preventer line with the boom. This means you can attaché the preventer line to the rail at a place further aft which allows a fair lead to the winch in the cockpit.

    I have had some issues with turning blocks forward so I have been planning to incorporate the “low friction ring” in my system.


    s/v BEATRIX
    Hobart, Tasmania

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