Jibe preventer rigging

[Dockhead]

Originally Posted by Joli

I read that report, mostly they had never sailed the boat in a breeze. Stuff wasn't sorted.

Yep. It certainly wasn't sorted. Most importantly, as the report said, the geometry of the preventer was all wrong - from mid boom to midships. Crazy.

[barryglewis]

We have two 3 to 1 tackles with blocks lashed to the boom where the boom vang attaches, and the other blocks to the toerail just after of the chain plates.
The rig is 3/4 with smallish headsails and comparatively large mainsail (500sq ft, 50 ft luff) and has a full width traveller. Once sheets are freed past a very close reach the lee preventer is used to control twist, in preference to the boom vang which makes an angle to the boom of about 30°, ok for short races, but not for making passages. The preventer tackle also stop the 5.9m boom slamming around, reducing wear. And on a run, they stop the boom falling in, acting as a boom preventer. The tackles are lead to the 2ndary winches. We have had accidental gybes and been able to recover gracefully, easing the boom across with the preventer after shifting the running backstay.
This has worked well on Risky Business for the 50,000nmiles we have logged to date. Note we use cheap and used polyester as I want some give in the system, and a "weak link".
Does have drawback as have to shift tether clips on the jackstay when going forward of the mast.
Used a boom brake on a 47ft steel yawl on a trip to the entrance to the Ross Sea in 1986, and was very pleased with it. I would try a modern climbing descender as a boom brake when we next go cruising except there isn't really enough clearance between boom and small dinghy when carried on cabin top, which we do for short passages.

[Brian Renwick]

Originally Posted by GiaPet

I had an inadvertent jibe and snapped my traveler car on my 49 Jeaneau DS. Any advoce on the easiest and least expensive way to rig a Jibe preventer?

I strongly recommend you read the "Platino accident report". You'll find it with an Internet search. Lots of useful information and highly relevant to what you're wanting.
Enjoy!

[Dockhead]

Originally Posted by requiem

Agree. I see the point that the geometry would might with the midcleat attachment and even worsen with the bow attachment as the boom moves, but the point is to prevent the boom from moving to begin with, so that shouldn't come into play.

I don't see how rigging to the bow is not better in every case. Even more so when you consider the preventer angle in the vertical plane.

And remember to always right to the boom end. Selden strongly forbids rigging preventers to it's booms otherwise than the the end. "You will break the boom" Surely this is pretty obvious.

Originally Posted by requiem

I recall such a discussion in older threads, and I think good reasoning was provided, but I could use a recap here as my instinct is that shock loads on static line would be far worse. (This comes from the climbing world, e.g. reference funkness devices, how to break dyneema slings, etc.)

Yes, this is certainly true. And for that reason I always keep my preventers good and tight.

[requiem]

Originally Posted by Dockhead

I don't see how rigging to the bow is not better in every case. Even more so when you consider the preventer angle in the vertical plane.

When the boom is centered, a line to the bow has the more acute angle compared to a line to a midship cleat. Thus, as the boom is brought in, at some point which angle is "worse" would swap. (Viewed from top down; I'm not thinking in 3D yet.)

But, it shouldn't matter because the boom should never move far enough for that to happen!

[Dockhead]

Originally Posted by requiem

When the boom is centered, a line to the bow has the more acute angle compared to a line to a midship cleat. Thus, as the boom is brought in, at some point which angle is "worse" would swap. (Viewed from top down; I'm not thinking in 3D yet.)



But, it shouldn't matter because the boom should never move far enough for that to happen!

Well, sure, but who needs a preventer when the boom is centered?

[wingssail]

Originally Posted by requiem

When the boom is centered, a line to the bow has the more acute angle compared to a line to a midship cleat. Thus, as the boom is brought in, at some point which angle is "worse" would swap. (Viewed from top down; I'm not thinking in 3D yet.)

But, it shouldn't matter because the boom should never move far enough for that to happen!

I am glad requiem has stated this so clearly, and yes it is true. Look at the diagrams below. Of course the geometry depends on the length:width of the boat and the length of the boom and in which position you are trying to fix the boom. In most positions the downward pull assists the fixing of the boom's position. Securing the preventer in the deck closer to the end of the boom adds more downward force.

Originally Posted by Dockhead

Well, sure, but who needs a preventer when the boom is centered?

We all do, not to prevent a jibe but to stabilize the boom when the wind is light and the seas are lumpy.

VERY often we encounter these conditions when reaching, close reaching or even on the wind. The boat moves around in the waves and the boom is thrown from side to side. The mainsail flogs and slaps. If you can stabilize the boom with a preventer rigged with a good angle to the deck forward you can often quiet the mainsail and get some productive drive out of it.

I find that stabilizing the boom in sloppy conditions is needed far more often than simply a prevention of a jibe.

When rigging a preventer to stabilize the boom it is important to avoid the acute angle of the preventer from the end of the boom to the bow of the boat. In the diagrams view 3A and 4A have the worst angles.

None of these diagrams show the lines back to the cockpit but is is not hard ti imagine that the route for preventers fixed to the bow crosses more of the boat's superstructure. Also, going to the side deck to run the preventer is simpler and safer than going to the bow.

Either solution will work and it is the choice of the skipper to decide what they like best. But to totally dismiss any method other than rigging to the bow does not reveal an open, objective, mind.