Traveler vs Twin Mainsheets

[Jeff_H]

I have sailed on boats with the double tackle set up that the Original Poster mentions. In effect the windward sheet sets the horizontal position of the boom and the leeward sheet acts like a vang and sets the vertical position of the boom. This system works well on extremely beamy boats like catamarans or open class boats, but it is a very difficult system to sail with on more conventional boats, where the new windward sheet must be eased and the new leeward sheet taken in on every tack. While tacking is difficult, jibing has some really serious issues since both sheets need to be brought in and then eased during the jibe. Also in a conventional situation, the leeward sheet is way too far inboard to serve as a preventer and if taken to the rail an d used as a preventer, the leeward sheet becomes a real hazzard offshore in terms of potential damage to the boom in big waves.

I would agree with the general comments and further suggest that on a boat of a length much over 30 feet, the mainsheet should be no further forward on the than a 1/3 of the length of the boom towards the mast, which typically makes the bridge deck the furtherest forward postion before you are faced with a situation where you are wrestling with excessive friction and a lot of line to handle or else every adjustment of the mainsail into an operation that requires a winch.

Jeff

[Valiente]

Originally Posted by Sasha_V

I can see an advantage is being able to use the twin mainsheets as preventers against accidental jibing... And they are a great way to lock the boom in place so the boom tent / awning really doesn't go anywhere when you are at anchor!

Sasha

I use twin purchases in this fashion when going downwind to more safely gybe the main. Friction on both sides of the boom allows a more controlled movement, and with the tiller moved with my legs, I can gybe solo smoothly in heavy air.

(I think I've posted this photo before...)

[Sailormann]

The sheets have been led to the center of the cockpit in order to allow the helmsman to sit near the boat's COG. The arrangement shown is pretty serviceable. The location of the centreline sheet will assist in flattening the main. The double-ended traveller sheet is common to a lot of boats.

The maximum span of a traveller track is going to be dependent on the size and shape of the track. Ideally, the sheet will rise from the traveller car at a 90 degree angle. Sometimes this is not possible, but I think that the reason some boats are not rigged that way has more to do with economy than anything else.

[KeelHaulin]

Originally Posted by Valiente

I use twin purchases in this fashion when going downwind to more safely gybe the main...I can gybe solo smoothly in heavy air.

Yeah; gybes are MUCH easier when the main is flaked!!

Just kidding; noticed the lowered main in your nice picture that shows the preventers. I have the blocks on order for my boat; we sailed another like ours a few weeks ago that had this set-up and it was so nice to have a preventer in light air that we are doing the same. In light wind they can be used for upwind controls similar to a twin mainsheet. Swivel cam- cleats on the cockpit coaming will allow for adjustment at the helm. If the situation becomes heavy wind and big waves; just release the cam cleats on the preventers so you don't have to worry about boom damage.

I agree with Jeff_H that double mainsheets instead of a mainsheet/traveler/(preventer) would be a big PITA for most cruising boats. In addition I think the sheet loads would be higher to get the correct upwind trim at higher windspeeds because they are pulling at a diagonal instead of vertically against the boom.

[Valiente]

Originally Posted by KeelHaulin

I agree with Jeff_H that double mainsheets instead of a mainsheet/traveler/(preventer) would be a big PITA for most cruising boats. In addition I think the sheet loads would be higher to get the correct upwind trim at higher windspeeds because they are pulling at a diagonal instead of vertically against the boom.

Glad to see you were paying attention : that picture was purely to show "the system" from above. You can't get the whole set-up in frame unless it's from above.

You can see that the farther out the boom is from center, the more vertical the pull downward. The key is that the mainsheet is *still on* and functioning. You slack it off to use the dual semi-preventer-things to make the gybe, and then you can move the traveller cars and tension the mainsheet afterwards. The "working preventer" then works exactly like the old style vangs that would have a shackle on the lower block taken to the rail.

EDIT: We were likely making 6.5 knots under a No. 3 alone at that point; I recall that a strong 25-30 knot northeast wind pushed us west south west from Cobourg to Toronto in just under 10 hours, a record for that boat. We had to hoist the main later in the day to keep up speed

I have found this simple and relatively inexpensive system has made downwind work considerably safer, because the purchase provided means you can ease with one hand and tension with the other. Even in 35 knots, I can keep a reefed main moving slowly to the new course, saving damage, noise and possible injury (a guy was killed here in a crash gybe a few years back because preventers were not rigged).

Of course if you broach or otherwise screw up, these preventers could save your boom and main. Admittedly, they are not as useful in this as the usual preventers run from boom-end forward to the bow and back to the cockpit, but they are good enough as they are for my purposes.