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Old 30-09-2010, 16:20   #1
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Main Sheet System: Conventional or . . . ?

I am considering updating the mainsheet system on Insatiable.

This is a 40' long, 25 year old IOR "1-ton" racer-cruiser, so we have a reasonably large mainsail - approx 50 square metres (540 square feet).

We currently have a faily conventional mainsheet system, with an 8:1 purchase system, with 4 sheaves on the boom (1 double block and 2 singles), and a traiple and a single on the traveller.

I am considering going to an "admirals cup" (a.k.a. "German") mainsheet system, with a single block on the traveller,, and a double on the boom, with the mainsheet running formard along the boom, down to the deck either side of the mast, and back to the secondary winches.

This Admirals Cup type system is increasingly common on racing boats of around our size (Farr 40 OD, for example), but less common on cruising boats. I'm not sure whether this is because technology on crusing boats tends to lag behind racing boats, or because cruisers are, in general, inherently more conservative than racers, or whether it is simply a less suitable system for boats that are primarily used for cruising.

Any thoughts on the relative merits of this verus the more conventional system?
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Old 30-09-2010, 18:01   #2
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That system should work well for you. We used it on a 35 footer with a biggish main. I like the fact that there are no blocks from a fine trim to clock you upside the head.
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Old 30-09-2010, 18:13   #3
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Fewer blocks means less friction. Even a top of the line block increases the friction load by about 8-10%. That, plus the fact that fewer blocks means faster sheet up-take (less line) explains the trend (in part). The question then becomes whether your boom is sufficiently robust to take all of the sheet loading at a single point of contact; and, whether you have the winches and turning blocks to carry the load in the sheet.

FWIW...
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Old 30-09-2010, 18:14   #4
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Hi Patrick
Have you considered these: Google Image Result for http://www.ar-marine.co.uk/media/catalog/product/cache/1/image/5e06319eda06f020e43594a9c230972d/3/3/332.jpg

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Old 30-09-2010, 18:52   #5
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G'day Ian,

No I haven't, and to be honest I think that particular version would be sending a boy to do a man's work. But that isn't the point. The system you linked is another version of a conventional mainsheet system. It is essentially a 6:1 conventional system. I could replace the current (worn-out, gradually breaking) 8:1 system with a fancy new 8:1 (or 6:1 with a fine tune), system from Harken or Lewmar (or whoever) and it would, no doubt, work well... better than the old, for sure.

But, given that I am going to replace the system, I have the option of going to a completely different style of system, such as you use trimming main on Blue Chip, or on Eurocentral (and Wired and most of the bigger perfomance boats around here). So the question is what are the advantages and disadvantages of this system relative to the more conventional (such as the one that you linked).

I am not saying that I am hell-bent on converting to the Admirals Cup style system, merely considering the options.
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Old 30-09-2010, 19:19   #6
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svHylyte has a good point about your boom taking the load from a single point, although you could still but two blocks on the boom, eh?

What do you really want? Is it having the mainsheet lead down to both sides of the cockpit? Or are you trying to reduce the mechanical advantage of you 8:1 system?
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Old 30-09-2010, 19:49   #7
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Use big ball bearing blocks. Big sheaves relative to sheet diameter gives low friction. Many sailor cheat here to their regret.
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Old 30-09-2010, 19:52   #8
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The boom is fairly substantial, I would be reasonably confident of coming up with a way of distributing the load. Using a conventional system, we can't really reduce the purchase without re-intorducing a fine tune of some sort (short of employing an olympic weightlifter to trim the main). I probably could add a fine tune and drop to a 6:1 purchase.

But the point ins't to reduce the mechanical advantage, per se. The point is that if an Admirals Cup type mainsheet system is an inherently better way to trim the main, I should consider whether or not we should employ it.

More and more modern yachts have this mainsail system, there must be a reason why, no?
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Old 30-09-2010, 21:07   #9
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I used a version of the Admiral's Cup rigging on another boat for three months, end-of-boom sheet with the traveler aft of the cockpit. The problem I encountered was the sheet keep accumulating on one side or the other, so had to be moved daily through the blocks with the main idle to even up. Otherwise OK...

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Old 21-10-2010, 17:06   #10
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I'm liking this (Admiral's Cup; German) mainsheet approach but before I start making boat mods. can anyone come back on how the mainsail cover is handled? Is there a slot in the cover to allow the mainsheet to come out at an angle?
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Old 21-10-2010, 17:47   #11
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We use this mainsheet setup as well on our Farr 44 racer and I am the mainsheet trimmer and really like this system. I do not have the problem of the sheet accumulating on the one side by using the two winches but you could do if you kept on using the same winch to ease the sheets.

As far as the sail cover goes yes we have a slot in the cover where the sheet comes off the boom up near the gooseneck. You can probably make this out in the photo I've shown below.
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Old 21-10-2010, 23:36   #12
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It's a very good system:
Much less friction
Big dumps are quicker
Gybes are easier
Much less rope clutter
You can get over the sheet accumulating on one side by having an endless sheet.

Downsides:
You may need to buy 2no. extra winches and strengthen the decks (unless you have 2 dedicated main sheet winches already in the right place)
You will somehow need to strengthen the deck up near the mast to accommodate the deck-blocks.
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Old 22-10-2010, 01:24   #13
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Hi Pat,

Dunno if you have made your decison yet, but here is my .02c worth...

Having trimmed with both mainsheet systems on many different styles of boats I'm thinking that you may want to trial it if possible with some sort of temporary rig before committing to it to see if it works for you.

With your boat being rather heavier in disp it may not be as easy to gybe in cruising mode. On lighter displacement boats with swept rigs (no runners...) and lots crew it is really easy to gybe as you can literally throw the main over easily in anything up to 25kts. From my one tonner days you couldn't do that as there was too much load and you need to control the gybe more due to having to have the new runner "made" before dumping the old one. You should also check the gearing with winches you intend to use - on the F40 the high gear is nearly 1:1 and the low gear allows easy trimming under load upwind.

On a boat I sailed on (Mumm 36) with a mainsheet conversion like you are contemplating, the old runner winches were used for the mainsheet did not have the correct ratio and you could not trim rapidly enough on reaches/mark roundings etc.

Best main sheet system I have sailed with (racing) would have been with a traditional purchase but with the fine tune inside the boom giving almost limitless adjustment, but probably not ideal for mixed cruising/racing... With your style of boat, you tend to use the traveller more upwind and the tendancy with the lighter boats is to use vang sheeting with the traveller way up to windward and use the mainsheet for fine adjustments.

On my boat, I just remove the fine tune for cruising and simply terminate the dead end of the mainsheet on a pad eye on the cockpit floor - 30 second job...

Hope this helps.
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Old 26-10-2010, 23:21   #14
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Originally Posted by Spirit28 View Post
Hi Pat,

Dunno if you have made your decison yet, but here is my .02c worth...

Having trimmed with both mainsheet systems on many different styles of boats I'm thinking that you may want to trial it if possible with some sort of temporary rig before committing to it to see if it works for you.

With your boat being rather heavier in disp it may not be as easy to gybe in cruising mode. On lighter displacement boats with swept rigs (no runners...) and lots crew it is really easy to gybe as you can literally throw the main over easily in anything up to 25kts. From my one tonner days you couldn't do that as there was too much load and you need to control the gybe more due to having to have the new runner "made" before dumping the old one. You should also check the gearing with winches you intend to use - on the F40 the high gear is nearly 1:1 and the low gear allows easy trimming under load upwind.

On a boat I sailed on (Mumm 36) with a mainsheet conversion like you are contemplating, the old runner winches were used for the mainsheet did not have the correct ratio and you could not trim rapidly enough on reaches/mark roundings etc.

Best main sheet system I have sailed with (racing) would have been with a traditional purchase but with the fine tune inside the boom giving almost limitless adjustment, but probably not ideal for mixed cruising/racing... With your style of boat, you tend to use the traveller more upwind and the tendancy with the lighter boats is to use vang sheeting with the traveller way up to windward and use the mainsheet for fine adjustments.

On my boat, I just remove the fine tune for cruising and simply terminate the dead end of the mainsheet on a pad eye on the cockpit floor - 30 second job...

Hope this helps.
Bill,

Thanks for that - it is a great help, although it asks almost as many questions as it answers! Heh.

I am still mulling over the options. I have gone out and ordered parts for a new mainsheet traveller car, and associated controls, but this will work with either system, so should not necessarily impact the final decision.
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