Jibing The Mainsail

Jan 7, 2011
4,726
Oday 322 East Chicago, IN
I have enjoyed Christian‘s videos, and he has made the sail to/from Hawaii a few times.

He broke his carbon fiber pole on this trip (during that 1 minute of video).

It certainly looked like those gybes were “less than controlled”.

Greg
 
  • Like
Likes: Hayden Watson
May 17, 2004
5,028
Beneteau Oceanis 37 Havre de Grace
there are a couple of jibes he does from 19:00 to 20:00 that just made me nervous to watch. What do you think?
The one at 19:00 I was ok with - the sail was reefed and the wind was low enough that the impact wasn’t bad. But yeah the one at 20:00 was more than I’d be comfortable with.
 

Alfa

.
Mar 19, 2015
38
Beneteau 31 North Vancouver
More than quarter century ago decided to buy a boat and go solo offshore (competent mountaineer, backcountry skier and ocean kayaker but green in sailing). I equipped my double ender JASON 35 with Walder boom brake and this device saved my skin few times when making mistakes or in dark with squalls coming down. Now, at 82, i cruse Salish Sea on Beneteau 31 with my old Fig 8 Descender attached to the boom with control line via block, led to the cockpit winch. Not perfect but cheep, simple and allows to control jibes. I keep Fig 8 dangling loose when sailing to wind, to much friction. On pic: motor sailing in light breeze.
 
  • Like
Likes: jon hansen
Oct 22, 2014
20,992
CAL 35 Cruiser #21 moored EVERETT WA
but there are a couple of jibes he does
Those are uncontrolled jibes. I can understand your concern. I would not jibe in that fashion.

First, I set a preventer to stop that from happening.

Even though the conditions in the video are benign to moderate, it can make for a real bad day should something break.

The preventer creates a way to control the jibe by use of the sheets, both Main and preventer.
 
  • Like
Likes: Hayden Watson
Apr 5, 2009
2,774
Catalina '88 C30 tr/bs Oak Harbor, WA
For the sake of this discussion, I will limit my comments to single or double handed in moderate breeze 15-25 in non-racing conditions where safety is more important than speed
  • On a broad reach or below, I have a preventer rigged to hold the boom out. I do not have standing preventers rigged to both sides but would if I was sailing offshore.
  • When preparing to jibe set autopilot to steer a course no greater than 160º true and release the preventer. and make sure that the traveler is locked to prevent movement in either direction. (center is best)
  • trim in both jib sheets so that the clew of the jib is near the forward lower shroud.
  • hand trim the main to bring near centerline and hold line in gloved hand but out of cleat.
  • turn boat through the wind and as the boom comes across the boat allow the sheet to take some length to absorb the impact.
  • Ease traveler down and ease mainsheet as needed for proper trim.
  • ease old working jib sheet while taking up the new sheet to bring the sail across the bow and trim to new course.
If the wind was really blowing +30 to whatever the best jibe is no jibe. I would chicken jibe. For those not familiar with the name that means to jibe by tacking the boat up and through the eye of the wind through an angle of 270º. That way both sails come across the boat in a very controlled manner with no wild swing, crash, bang. Turn the helm aggressively because you want to make the 270º turn as fast as possible to keep the speed up. Just ignore the main and work the jib sheets to get the foresail across to the other side and the main will completely take care of itself.
 
Jul 27, 2011
4,988
Bavaria 38E Alamitos Bay
Those are uncontrolled jibes. I can understand your concern. I would not jibe in that fashion.

First, I set a preventer to stop that from happening.

Even though the conditions in the video are benign to moderate, it can make for a real bad day should something break.

The preventer creates a way to control the jibe by use of the sheets, both Main and preventer.
I like to use a boom brake; Wichard’s Gyb’easy. If an accidental gybe does occur the effect is tamped down some; perhaps a lot.
 
Last edited:
Oct 22, 2014
20,992
CAL 35 Cruiser #21 moored EVERETT WA
One can accomplish the same by pulling the Mainsheet in and letting it out.

With a preventer you have complete control. You let out on the preventer line while you haul in on the Mainsheet. When the sail crosses mid line you let out on the Mainsheet. You then need to reset the preventer. In doing this you get the opportunity to inspect the boat. Secure any loose lines, make adjustments then settle in on the new tack. You see he goes forward and adjusts the jib pole for the new wing and wing tack. Going forward to reset the preventer is no big deal.
 
Apr 5, 2009
2,774
Catalina '88 C30 tr/bs Oak Harbor, WA
One can accomplish the same by pulling the Mainsheet in and letting it out.

With a preventer you have complete control. You let out on the preventer line while you haul in on the Mainsheet. When the sail crosses mid line you let out on the Mainsheet. You then need to reset the preventer. In doing this you get the opportunity to inspect the boat. Secure any loose lines, make adjustments then settle in on the new tack. You see he goes forward and adjusts the jib pole for the new wing and wing tack. Going forward to reset the preventer is no big deal.
Not when your boat has mid-boom sheeting, and the sheet is all in front of the dodger.

As you say, the best way to control it is a full preventer with a cockpit-controlled line to the end of the boom. I am planning to do something like that for distance races, but the brake would be nice for everyday control albeit to a lesser degree.
 

Mifeo

.
Mar 27, 2022
12
Dufour 365 Grand Large 0 Barcelona
PST.
Preventer
Sheet
Traveler
And the reverse after the gybe.
 
Jul 27, 2011
4,988
Bavaria 38E Alamitos Bay
Must keep in mind the difference between a controlled and uncontrolled gybe. The “preventer” prevents the uncontrolled gybe. If you are using a preventer, traveler, and mainsheet, you are controlling the gybe, etc. At that point, a preventer is not preventing anything. A boom brake “brakes” an uncontrolled or accidental gybe. Typically does not prevent it unless it is a weak one and the brake is set strong. If you ease the preventer to trim the mainsheet to bring the boom to mid-ship for the gybe, you are controlling it. If you tension a boom brake prior to gybing in anticipation, you are controlling it, etc.

If planning or anticipating a gybe in strong wind, a boom brake is a better device to use IMO. Most likely you will still trim the mainsheet to close the boom’s swing angle. But in moderate air (15 - 18 kt) with minimal crew, say double-handed, the brake allows you to gybe the boat from a reach or run w/o having to tend to it much. This is good when maneuvering at the start of a race where the helm is concentrating on the course and start line, and the other crew principally on headsail trim. To control the gybe using the mainsheet only would require a third crew to complete the gybe efficiently.

We’ve gybed the boat directly from a starboard to port reach in about 15 kt apparent rounding a leeward turning mark during a race. Of course we were reefed, but I will say it was still a bit scary. :yikes: Boom comes over fast then the brakes sets in. We had two trimmers plus helm and we were both busy getting the headsail across and back into in trim; whereas the mainsail did its own thing. Even with self-tailing winches, I appreciated help trimming the 120% Genoa back in!
 
Last edited:
  • Like
Likes: jssailem
Jul 27, 2011
4,988
Bavaria 38E Alamitos Bay
As you can see, when the boom gybes you must reset the preventer to the other side of the boat; i.e. to the port bow strong point. You must detach the boom from the starboard preventer line then attach to a port preventer line. To stablize the boom for this action, you'd likely need to trim the mainsheet to remove slack. Most users would have a "lazy preventer" set up and ready to go following completion of the gybe. As the boom nears amidships the "holding power" of the preventer diminishes.
 
  • Like
Likes: Mifeo
Oct 22, 2014
20,992
CAL 35 Cruiser #21 moored EVERETT WA
Ok, this is new to me, how do you rig a preventer?
what is needed?
@Mifeo 's diagram shows the the attachment points
  1. Boom end
  2. Bow strong point
  3. Long line run to the cockpit
  4. Secured in cockpit by winch and or cleat.
You ease the main sheet and snug up the preventer, you ease the preventer and snug up the mainsheet. I want a little stretch in the preventer so I use a line like yacht braid. It is polyester double braid with a polyester core.
5-8% stretch serves as a buffer to the strains the boom and main will give the preventer.

I have a strong block that I secure to the forward dock line cleat with a soft shackle (about $5.00). If a wave hits the boom in a foul sea you can get tremendous forces on this rig. The 1/4" diameter dyneema soft shackle has a breaking strength of plus 10,000 lbs. The block matches that strength.