2 Main sheets

[Tranquil42]

Hi. I'm a relative novice but have a question regarding larger cats. I noticed that some of the larger ones use 2 sheets to control the main sail. I've heard that one should use the windward one to effectively trim the sale and the leeward to bring the boom down and increase the leech tension. Is that correct? I ask because when thinking about controlling the jib one uses the leeward side to control the sail, and the windward side is slack (opposite of how I was told to trim the main with two sheets). Any guidance would be appreciated!

[Bean Counter]

Catanas have a dual sheet system - see link

http://www.cruisersforum.com/forums/...tem-51165.html

[tp12]

Originally Posted by Tranquil42

Hi. I'm a relative novice but have a question regarding larger cats. I noticed that some of the larger ones use 2 sheets to control the main sail. I've heard that one should use the windward one to effectively trim the sale and the leeward to bring the boom down and increase the leech tension. Is that correct? I ask because when thinking about controlling the jib one uses the leeward side to control the sail, and the windward side is slack (opposite of how I was told to trim the main with two sheets). Any guidance would be appreciated!

That's essentially it. I've only sailed one boat like that, so I'm no expert, but I found you just couldn't get the leech tension necessary for pretty much any point of sail and the sail shape suffered. The charter boat I had would just flap high up, rather annoyingly, and even pulling the leech line down hard didn't resolve it.

[LoudMusic]

Originally Posted by tp12

That's essentially it. I've only sailed one boat like that, so I'm no expert, but I found you just couldn't get the leech tension necessary for pretty much any point of sail and the sail shape suffered. The charter boat I had would just flap high up, rather annoyingly, and even pulling the leech line down hard didn't resolve it.

I've asked about dual main sheets in multiple locations and never got what I found to be helpful responses. This is the best information I've seen so far.

Though I have to wonder how much of that was due to the cut of the sail. Have you sailed the same model boat with traditional sheet and traveler?

[tp12]

Originally Posted by LoudMusic

I've asked about dual main sheets in multiple locations and never got what I found to be helpful responses. This is the best information I've seen so far.

Though I have to wonder how much of that was due to the cut of the sail. Have you sailed the same model boat with traditional sheet and traveler?

No, I haven't. It was a charter boat in Greece. The cut will play a role, I'm sure, but you just can't get the downward force on the boom that you need to get the top of the sail working properly, in my experience. I had the vang on hard as well.

It's not a mainsail config I'd put on a boat or want on a boat. A nice long traveller is needed to get the best control on the main, in my opinion.

For quite a few cruisers, though, it's good enough and the lack of maintenance compared to a traveler setup is preferred. It just depends on what you want and where you place your priorities.

Maybe some cruisers with this setup would like to comment and provide more experience than I can on this one?

[Matt Johnson]

Not a large cat, but I set-up dual mainsheet on our 37' monohull. The original traveller was only three feet long and almost totally blocked our view forward over the cabin top. So, I cut it off and went to dual mainsheets as an experiment to see if we'd like it.

With the two lower mainsheet legs spread about 8' apart on our cabin top, pulling hard on both side with the boom centered doesn't have enough downward force to fully tighten the leech without hard vanging. We've yet to do it, but I plan on welding sheeting points close together for those times when I'm sailing hard to windward.

At points of sail with the boom off of center and downwind until reaching, the boom is under great control with dual mainsheets. But, it is a multiple step process to get the main trimmed and not for constant adjusting.

I'd rather have a long traveller, but it would require obscuring our view forward and a lot of welding to accomplish.

Matt

[GordMay]

Greetings and welcome aboard the CF, Tranquil.

... one should use the windward one to effectively trim the sale and the leeward to bring the boom down and increase the leech tension ...

As I understand it, this is correct.

[Tranquil42]

Thanks for everyone's comments. I'll be sailing a 48 with this set up in the spring.

[billknny]

Originally Posted by Tranquil42

Hi. I'm a relative novice but have a question regarding larger cats. I noticed that some of the larger ones use 2 sheets to control the main sail. I've heard that one should use the windward one to effectively trim the sale and the leeward to bring the boom down and increase the leech tension. Is that correct? I ask because when thinking about controlling the jib one uses the leeward side to control the sail, and the windward side is slack (opposite of how I was told to trim the main with two sheets). Any guidance would be appreciated!

What you describe is not new at all, but has been around for centuries, long before travelers were practical and booms were strong enough to survive a mast rigged Vang.

They way you describe using twin main sheets is kind of right, but it is a touch more complex in practice because one sheet does not only pull down, and the other in, but both do both to an extent that varies on the boom angle.

If you think about trimming a mainsail, it is really all about putting the end of the boom in the correct spot to get the twist, wind angle, and leech tension you want. With two sheets—rigged correctly—you can put the end of the boom anywhere you wish between the attachment points of the sheets to the hull. It is an ideal set up for many catamarans.

If you can’t get the leech tension you need with such a setup the problem is the sail is blown out, not the setup.

[Palarran]

What would seem to be difficult with the two sheet set up IMO is running downwind with a triple reefed main and the boom out as far as possible. How does the windward sheet handle this distance? It must be nearly 30'.

[mark_morwood]

Originally Posted by Palarran

What would seem to be difficult with the two sheet set up IMO is running downwind with a triple reefed main and the boom out as far as possible. How does the windward sheet handle this distance? It must be nearly 30'.

Not sure if you are wondering about how to keep the boom in the right position, or just managing the length of the sheet required. Apologies if I'm answering the wrong question that you already know the answer to, however if it was the former:

As soon as the boom is outboard of the leeward main sheet deck block, the windward sheet is no longer effective, so doesn't matter as long it is long enough. You are then in the same position as with a traveller with the car all the way to the end, and may want to rig something that looks like a boom preventer to pull the boom down and give you the shape you want and to keep the sail off the shrouds.

A slightly off topic comment I would make is after cruising our Catana 48 for a couple of years, whenever we were sailing off the wind in anything but light conditions we started dropping the main and sailing only on genoa, jib or spinnaker. It was much more relaxing and practically just as fast. We had a full width traveler, not dual sheets, but I don't think there would be much difference.

[LoudMusic]

Originally Posted by Palarran

What would seem to be difficult with the two sheet set up IMO is running downwind with a triple reefed main and the boom out as far as possible. How does the windward sheet handle this distance? It must be nearly 30'.

That's a good point, and on a wide catamaran (where I see them mostly employed) it could be FAR more than 30'. My boat is 24' wide. The windward mainsheet on a downwind run would need to be probably close to 60' long.

I *think* the solution would be to have blocks you can release from the boom. But that sounds ludicrously cumbersome for jibing. Though I do spend a fair amount of time shifting the traveler back and forth its full run, which is probably 14', each time we jib.

[rbk]

We have dual main sheets along with a 7’ traveller (monohull) and absolutely love it. Not so much if we didn’t have the traveller, but with it, it is super flexible on all points, acts as a vang and preventer (to some degree) and when gybing it allows you to easily float the main across center. You can twist and shape the main in ways you can’t with a single and get plenty of leech tension (again without the traveller it would be difficult) one of the best parts is being able to lock the boom in mid air (topping lift included in this) at anchor and on many points of sail (anywhere but running or a deep broad reach).

[Palarran]

To those who responded to my question. It would maybe make sense if you still had a traveler, and a split main sheet, where if you are moving the boom lets say more than 3' past the leeward point of the traveler, you can release the windward side and use both to leeward. But most that I've seen have a two to one purchase, at least that is how I'd see it. The sheet goes up to the boom and back down. We have a 4 to one and there have been times that I need all of that leverage.

I just can't imagine the amount of line that would be splayed out across my boat though. Well, in our case, it just wouldn't be a good option. It really must be just for boat's that sheet off their hard top. I've never done that but have seen several boats that had jybed and destroyed their hard tops or arches. I love that my main is sheeted to a traveler that is bolted right into the main rear frame of the boat.

[Chablis 1]

Hi,
On the Catanas equipped with dual mainsheets there is an extra pad eye in front of the steering wheels where you can also attach the mainsheet block. You do this on a downwind reach, when you want to open up the mainsail completely. At the same time it acts as a preventer.
Thomas