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gybe preventers

9K views 18 replies 12 participants last post by  Guesser 
#1 · (Edited)
Hey all,

When running, when is it SAFE to rig main and jib preventers and when is it NOT SAFE?

I've heard of people being stuck and being knocked down because of wind shifts or something else.

Also, when is it a good idea to put your jib out on a pole, and how do you do this exactly? I have never tried it, and running wing and wing is the most difficult tack for me.

When running I release my main as much as possible (so it's almost touching the spreader), but it seems to jerk around quite a bit.

Thanks,

Kacper
 
#2 · (Edited)
Generally, a boom preventer is only used on longer dead-downwind runs. Rigging it for short ones can be a nuisance. A boom preventer isn't going to cause the boat to be knocked down unless you come around quite a bit... from a downwind run to a beam reach or so on the opposite tack. If your sailing skills are so poor that you can't keep on a downwind run, then you probably should be out there as that's over a 90 degree shift in wind and boat direction combined. Granted, it does happen, but should be pretty unusual, especially on open water. I prefer a boom brake to a boom preventer, as I believe a properly setup and designed boom brake is better and safer than a preventer is.

If you're running almost dead-downwind, you should probably have a boom preventer rigged, to prevent the boom from crossing the boat and injuring people in the case of an accidental gybe.

I've never heard of a jib preventer... The jib isn't all that dangerous, given that it doesn't have a large metal boom attached to the bottom of it to wield like a club.

To pole out a jib, you have to have a ring setup on the mast, like you would for a symetrical spinnaker. Then you take one end of the pole and attach it to the jib sheets, like you would on a spinnaker, and then make the other end to the ring on the mast. Now, if you're going DDW, then you might want to pole the jib out on the side opposite the mainsail, and sail wing-on-wing, to increase the effective sail area.

As for the main sail jerking around... can you describe what you mean by "jerking around" a bit more clearly, it's a bit vague.
 
#3 ·
hey sailindog,
Sorry, when I said "jib preventer" I meant poling out the jib, which I've never done.

Yes, in this case I am always doing DDW. I find that in light winds, say if my boom is on starboard, and I turn to starboard just by 10 degrees this causes an accidental gybe.

By jerking I mean, it the boom comes aft and forward in a violent kind of way, espcially if we go over a wake or over a wave. This usually happens in lighter winds.


Kacper
 
#4 ·
Using a preventer and tightening up on the boomvang, if you have one, will help prevent the boom from doing that.
 
#5 · (Edited)
The boom vang will stop the boom rising. If you are ddw your boom as you describe it maybe at say 100 -110. Altering course 10 gives you 110 -120, whereas the wind must be at >135 to give a gybe. A minimum change of 15. You could get some movement from a wake or very likely flukely winds in the light which could set off a gybe but in the light it wouldn't matter too much but it can be disconcerting. You wouldn't need a preventer then.
In fact what can easily happen with minor wind fluctuation and steering wanderings is that rather than being ddw you are sailing by the lee and and a further small turn that way is added to by the resultant change in apparent wind easily accumulating in total to put the wind ahead of the boom and gybe you.
You would be better off not sailing ddw in those conditions but bearing off say 20-30 and gaining boatspeed and vmg. Then you would find that having the boom to leeward gives you some extra degrees of margin, a minimum change of 45, making a gybe unlikely.
 
#6 ·
I use a modified sort of preventer set-up. I rig a pair of four-part tackles, with cam cleats on the bottom blocks, to a mid-boom bail. One tackle leads to a port mid-ship cleat, forward of the boom and one leads starboard. To gybe or wear the boat in heavy air, I can loose the weather preventer, and haul in the lee as I steer with my legs on the tiller. I use the mainsheet as a boom brake to fine tune the process when I am on my new broad reaching course.

This differs from the usual preventer-to-the-bow and back set up, but it's worked for me in 30 knots. Here's a picture of the set up prior to hoisting the main. I suppose you could call it a "split vang", as well, except that these are rigged for the whole day of downwind sailing.
 
#7 · (Edited)
Dead downwind, twin headsails are much better. If you must use your main you might find that sailing slightly off dead downwind is both faster to your waypoint and much more comfortable. Or you might try just dousing the main and sailing with a big headsail only. Downwind the main is a pain. There is also a product called a BoomBrake that basically adds a friction system to keep the boom from slamming over.
 
#8 ·
Boom Brake

To prevent gybes I really like the Dutchman boom brake. Especially since I have a lot of guests that like to "drive". Holding +/- 15 degrees is not a bad job for a rookie. Downwind I love it. If an accidential gybe occurrs, the boom is managed and will come across slowly if it has to. Dutchman info is http://www.mvbinfo.com/dp_03_BB_brochure.html
 
#13 ·
I use a simplified version of Valiente's preventer. I attach a snatch block forward of the mast on either side of the boat. I'll use my spare jib sheets, if I have nothing else, and tie one end to the boom, lead it through the snatch blocks, and then lead them aft to my two aft winches. That setup, and a whisker pole, makes for a pretty easy run sailing wing on wing.

The double headsail idea isn't too bad, either, if you have an extra halyard up front (you should have a spare, anyway). I just don't like unfurling the extra sail, only to have to stuff it back in the bag later.
 
#14 ·
That will work fine in all but very heavy air cases, but I add the mechanical advantage in case of a situation that might crash gybe the boom, like weak winds but relatively high following seas, like from a front that's passed over but left a lot of slop behind. That sort of thing can roll the boat enough to turn the boom into a bam.

When sailing very broadly downwind, if I want to gybe/wear the boat smoothly, I'll use both rigged preventers instead of the mainsheet to transit the boom under some friction as I give a little nudge with my knees holding the tiller.

I've just found it's a nice way to handle things alone and I've transferred "the system" to the new, larger boat, although the boom is high enough that it's not half the hazard it was on the 33 footer...and I will have a pretty heavy traveller on the deck as opposed to the cabin top just aft of mid boom.
 
#15 ·
I know that this is a really obvious question to most but what exactly is a preventer and how does it work? Is it a couple ropes there to hold the boom back? or that boom brake? I am way off owning my first real boat, but am looking into getting a 16' Nacra or hobie cat so brushing up on the terms is prolly a good start :p
 
#16 ·
A preventer is a line attached to the boom and some point forward on the boat. Its purpose is to prevent the boom from crossing the boat in an accidental gybe and hitting you in the head—hence the name, preventer. Usually, there is one on each side of the boat, and they have to be released and re-tensioned after each intentional gybe.

A boom brake, serves a similar purpose, to reduce the chance of injury from the boom in an accidental gybe, but as it is named, it works by slowing the movement of the boom, rather than preventing it altogether. It is usually a device—essentially a rope clutch of a sort, that is attached to the boom and has a line that is attached forward and outboard of the boom on either side that runs through it. By adjusting the tension of the rope and the clutch mechanism, you can control how much braking force is applied to the boom.

IMHO, a boom brake is a better solution than the preventers, since it requires less user intervention once it is setup than do the preventers. It also has fewer dangers associated with it than do the preventers, which, in certain instances can cause the mainsail to backwind and "pin" the boat down, possibly leading to a capsize situation.
 
#17 ·
sailingdog said:
IMHO, a boom brake is a better solution than the preventers, since it requires less user intervention once it is setup than do the preventers. It also has fewer dangers associated with it than do the preventers, which, in certain instances can cause the mainsail to backwind and "pin" the boat down, possibly leading to a capsize situation.
It seems like many of the preventer rigs also require someone to go forward to release the line at the snatch block in the forepeak, prior to any gybe....

No real expience - adjust confidence accordingly!

Cheers!
 
#18 ·
It depends. If you're using a snatch block forward, and the line is long enough, you can have it run aft to the cockpit and just slacken it when you need to gybe. This would avoid the need to leave the cockpit to adjust the preventers, but would leave two more long lines underfoot in the cockpit. If you're sailing with a jib and a spinnaker, now you've got eight lines sitting in the cockpit—not including the mainsheet or any traveler or track control lines.
 
#19 ·
I'm a bit lazy, so when I'm sailing downwind in in light air I just take the end of a jib sheet (or any handy line) and lash the boom to a stantion or cleat; this generally provides enough protection and keeps the main from floundering about. I also have a 4 to 1 preventer for use in heavier winds, but usually it's overkill and not worth the effort.

On a side note...I recently added a boom kicker and I gotta tell ya, it is the coolest thing ever.
 
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