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My wife and I are returning to BVI, chartering a 38' with a twin mainsheet config. I get that there might be some benefit in the set-up as a gybe preventer, but not much else. The vessel is supposedly brand new(ish). Why am I not seeing this twin set up as more than buttons on a balloon?

Any thoughts appreciated.
 

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My wife and I are returning to BVI, chartering a 38' with a twin mainsheet config. I get that there might be some benefit in the set-up as a gybe preventer, but not much else. The vessel is supposedly brand new(ish). Why am I not seeing this twin set up as more than buttons on a balloon?

Any thoughts appreciated.
Twin mainsheet. Do you mean two separate systems with separate blocks or do you mean it has two ends, not tied off, through the same block system?
 

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I have a mainsheet rigged as both 8:1 and 4:1... for fine tune you use one line and for coarse trim you use both. For gybing you haul both.
 

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It is just a different way of achieving the sail control that a single mainsheet and traveller would provide. We just got a boat with a dual mainsheet, so I'm just getting used to it. It really doesn't do anything for jibe prevention because they don't project far enough for that.

Essentially, one sheet is used to position the boom, and the other to control the leach tension and twist. Catana is one popular brand that has used dual mainsheets for many years.

Our other boat has no traveller and a mainsheet on the hardtop inline with the boom. However, it has a rigid vang. So this system works by using the mainsheet to control the boom position, and the vang to control the leach and twist. One advantage it has over a traveller or dual sheet is that the sail can be controlled deep off wind using the vang.

So AFAIK, there are three ways to do the same thing regarding mainsail control: traveller and mainsheet, dual mainsheets, mainsheet and vang.

Mark
 

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If is a newer Jeanneau then you might be referring to a German Sheeting system, which is a double ended mainsheet run to both sides of the boat. They are typically led to both primary winches. The main benefit of the setup is so that both the Genoa and the main can be trimmed from the helm position, and both share the primary winches. Since the leeward winch is being used for the Genoa, the leeward mainsheet is cleated off, and the other end is on the windward winch.

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twin main - or German mainsheet - lets you control main sail from winches at either helm position. I'm assuming your 38 has dual helms like most newer charter boats. Just don't trim from the same side all the time - you'll run out of sheet.
 

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twin main - or German mainsheet - lets you control main sail from winches at either helm position. I'm assuming your 38 has dual helms like most newer charter boats. Just don't trim from the same side all the time - you'll run out of sheet.
The mainsheet system I have (see below) is a continuous double ended sheet. Either end could be led to a winch. This would be for 8:1 fine tuning. However if you use both end... you have 4:1. There is a traveler as well and they too can be led to a winch. I built this system in 1985 unaware of the German System from available hardware. The line could be spliced end to end making it a continuous line. I don't see the point aside from you can't loose the sheet. But a stopper knot at the end prevents that.

This is a good system for my large main fractional rig... especially because the main is the main source of power in the rig.
 

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Discussion Starter #13
Again, thanks,

If I've got this right, basically the "German" system, which is probably what we'll be using, works kind of like this: if you are on a starboard tack, the mainsheet is controlled by a starboard winch. At the same time, on the port side the sheet is wrapped, but "lazy."
And then vice-versa on the port tack.
Is it that simple?
 

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Again, thanks,



If I've got this right, basically the "German" system, which is probably what we'll be using, works kind of like this: if you are on a starboard tack, the mainsheet is controlled by a starboard winch. At the same time, on the port side the sheet is wrapped, but "lazy."

And then vice-versa on the port tack.

Is it that simple?
Yes, both the Genoa sheet and the main sheet are lead through a double cheek block on each side. The cheek blocks have clutches so you can lock off the "lazy" end and free up the winch for use with the other sail.



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Separate twin main sheets are best for controlling the shape of the mainsail. Instead of moving the sheet on the traveler, you can control the fullness of the sail with twin sheets.
 

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Earlier in the thread someone commented that German style sheet with a vang works as well as a more typical layout that has the mainsheet attached to a traveler. With a single sheet setup and without a traveler, you cannot control twist and still be able to center the boom. The issue becomes if the leech is eased enough to allow the leech to open for the gradient wind, the boom is well to leeward of its ideal position. That is an issue until the wind is blowing enough that the sail needs to be bladed out, in which case vang sheeting works fine.

There is an old school set up with a separate mainsheet tackle on each side of the boat. This allows twist and rotation to be adjusted independent of each other and allows the same range of sail trim as a mainsheet and traveller. In practice it is a pain in the butt to use since the type of adjustment that would normally be made with the traveler, is made by adjusting the tackle on both sides of the boat, and it is a bit of a trial and error proposition since you don't know whether the adjustment on one tackle is right until you adjust the other, so you end up making a lot more adjustments.

All that said, for some reason almost all new European boats are being delivered without travelers these days. I think that results from the trend of mounting travelers on the cabin top and mid-boom travelers are relatively so ineffective that there isn't much loss to eliminating the traveler.

Jeff
 
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Actually, my traveler is used almost as much for moving the main aside at anchor as it is for trimming the main. It's a fractional rig so main trim is a biggie.
 

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It is unclear what kind of "double mainsheet" the OP is going to be dealing with, but what I am talking about is more of a "double ended" mainsheet that is standard on the Jeanneau 379, 389, 409 etc. As these boats are popular in charter fleets there is a good chance this is what he will be encountering.

Jeanneau has not eliminated the traveller, they have just added German sheeting. this the boat easier to single hand without sacrificing the superior trimming ability the traveller offers.

https://youtu.be/LDxSQPryS4k


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Earlier in the thread someone commented that German style sheet with a vang works as well as a more typical layout that has the mainsheet attached to a traveler. With a single sheet setup and without a traveler, you cannot control twist and still be able to center the boom. The issue becomes if the leech is eased enough to allow the leech to open for the gradient wind, the boom is well to leeward of its ideal position. That is an issue until the wind is blowing enough that the sail needs to be bladed out, in which case vang sheeting works fine.

There is an old school set up with a separate mainsheet tackle on each side of the boat. This allows twist and rotation to be adjusted independent of each other and allows the same range of sail trim as a mainsheet and traveller. In practice it is a pain in the butt to use since the type of adjustment that would normally be made with the traveler, is made by adjusting the tackle on both sides of the boat, and it is a bit of a trial and error proposition since you don't know whether the adjustment on one tackle is right until you adjust the other, so you end up making a lot more adjustments.

All that said, for some reason almost all new European boats are being delivered without travelers these days. I think that results from the trend of mounting travelers on the cabin top and mid-boom travelers are relatively so ineffective that there isn't much loss to eliminating the traveler.

Jeff
I think it was me who said we had a boat with a single mainsheet and traveller - but I don't know what a German style is.

I don't understand why you say the boom can't be centered and twist controlled. The twist is controlled by the vang, and the mainsheet can bring the boom to center. You need to readjust the mainsheet after letting out the vang, but the boom does come to center.

The shortcoming is that the boom cannot be positioned to windward of centerline. This is helpful in certain conditions. However, the vastly superior control of a vang compared to a traveller or twin sheet setup when deep off the wind more than makes up for it in a cruising situation.

Best of all worlds would be a traveller or twin sheet with a vang. More complicated, though.

Mark
 
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