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  #11  
Old 03-26-2013
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Re: Mainsheet size?

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Originally Posted by Alex W View Post
What is your mainsheet rigging? The cam cleat probably never sees loads higher than 500lbs if your mainsheet has 2200lbs of load and goes through a 6:1 or 8:1 tackle.

I do think that 25 knots of AWS is too low of a number to use as the maximum. That is the same as close hauled into a 20 knot wind. I'd do the calculations at 35 knots AWS. For me that comes up with ~2200lbs on my Pearson 28-2 (P=32, E=11). I'm using 7/16" XLS Extra (I think it feels nicer in the hand than XLS, and it has much less stretch) with a 4:1 tackle.
AGREED.
I was picking a typical number when I ran the calcs for MEDSAILOR. With a safety factor of probably at least 3:1 he can handle the occasional gust to 30+. The other thing to consider is a Formosa 41 is a ketch and if the wind is getting up there, the first thing he is probably going to do as far as shortening sail is reef the main. That right there will lessen the load on the mainsheet system.
(And it's not like he's going to be RACING and pushing the limits on that boat!)
And I would definitely try out several different types of line to see how they FEEL in your hand, then evaluate their strength.

As an aside though, if your new main is pushing 400 ft^2 you're probably going to want/need 9/16" line for that sheet!
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Old 03-26-2013
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Re: Mainsheet size?

Dave,
I think you have it right - hand first - then size for strength.

One other thing to think about regarding type and make of the line is how clean it runs, especially mainsheets. Kinking and hockling can ruin your day when you get a jam.

Some of the new high tech low stretch geewhiz lines feel like ice (no grip) and hockle like a stray dog's coat.
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Old 03-26-2013
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Re: Mainsheet size?

I wouldn't worry about working loads etc at all.

Think about what's comfortable in your hand and the coil not too heavy to coil up.

Any double braid apart from the very skinny stuff will be fine. But I like 12 mm, that's 1/2 inch, the best. It fits the palm of the hand, fingers can tighten around it easily, a long fall can be easily made up because its light.
Whereas 14 mm, the next size up is getting bug and fat, try stretching your arms out at when you tidy up the cockpit! It's like a gym workout.

Mark
PS I made an error when I first bought Sea Life, a discount of the reel price of 8 mm braid was so good I bought the whole roll. Now every control line is red and white. "Grab the red one! NO the OTHER red one!"
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Re: Mainsheet size?

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Originally Posted by MarkofSeaLife View Post
PS I made an error when I first bought Sea Life, a discount of the reel price of 8 mm braid was so good I bought the whole roll. Now every control line is red and white. "Grab the red one! NO the OTHER red one!"
Did the same thing years back.... regretted it too!
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Re: Mainsheet size?

For this I would be looking at 8mm endurabraid. It will be a little more than a 1/2" sta-set (I just paid $.01 more) but it will run cleaner, has less stretch, and is plenty big enough to hand work.
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Old 03-26-2013
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Re: Mainsheet size?

I always shop cutoffs to get roll-like pricing in a variety of colors. It's hard to do the whole boat in one weekend that way, but not hard to upgrade the running rigging over a period of 6 months.
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Old 03-26-2013
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Re: Mainsheet size?

Medsailor and all, please keep in mind what you're buying and how these objects are rated. They will be rated for the weakest point in the system. For example, the Harken blocks (57mm) that are rated at 300 lbs SWL are rated that way b/c of it's cam cleat. The cleat is only rated to 300 lbs.
Harken 57mm Carbo AirBlock
The same size and type of block without a cam cleat has no weak point but the block itself and has a SWL of 793 lbs.
Harken 57 mm Carbo AirBlock

Harken also uses a safety factor of 2 or 3:1. Garhauer uses something like 4 to 5:1 which is why their stuff is so heavy.

IMHO for a 41' boat you can use 3/8" line for a mainsheet and be fine. This is a good size for winches or hand trimming. Is the mainsheet on a winch? Or will it be trimmed by hand?
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Re: Mainsheet size?

Another tip
Harken

That's for all blocks. Deck organizers included.
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Old 03-26-2013
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Re: Mainsheet size?

Thanks all for the replies so far. Special thanks to Knut for the drawings and the link to the Lewmar PDF.

So it sounds like the consensus is that nobody cares much about low stretch on a mainsheet. I can get on board with that and it certainly simplifies things. Glad to hear also that 1/2" seems to be a good candidate, that also makes things simpler and cheaper.

To the comment about "getting real" because 40mm blocks would induce too much friction, I find that this is exactly the kind of information that is hard to find in the product guides. So is a 40mm block too much friction because of something on MY boat, or is it too much friction for 1/2" line, or just too much friction for everyone? Why, if the block is rated for 1/2" line would they make a 40mm block at all? How will I know if the sheves are big enough to have a low enough friction level? If my choice is worthy of ridicule, is there a more salient guideline that I can be pointed to?

As many, and the Lewmar PDF have outlined, I'm missing the DECREASE in load that goes along with purchase. Yes, my brain knows that 6:1 means that you end up pulling 1/6 of the load, but somehow I didn't connect that it also means you can size some of the blocks for the reduced load they will see. Currently the mainsheet isn't on a winch at all, but my 6:1 purchase answers the question as to why my plastic cam-cleat hasn't exploded yet.

My new setup will be going from the boom, through a fiddle block a couple times, then forward to the mast, down to the deck, around a deck organizer, then to a rope clutch and finally a winch. Any thoughts on how much purchase I should have for my 400sqft sail before the winch?

This is what I have in mind, though I'm really hoping that I don't need a deck organizer near the mast AND at the winch....


Thanks for all the help so far.

MedSailor
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Last edited by MedSailor; 03-27-2013 at 12:13 AM.
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Re: Mainsheet size?

Med,

If its going to be trimmed from the winch, then none. Perhaps 2:1 at the most.

If we assume that a maximum sheet load is 3,000lbs, and the winch has a 40:1 purchase that means the max handle load should be around 10lbs. Add in a little extra for friction loss and you still have way more purchase than you need.

The typical design for a winch trimmed main is to have a double ended sheet so you can fast trim at 1:2, then at 1:1, then on the winch at 40:1. More than this is just silly on a moderate size main like yours.

Edit: my math was wrong... Assuming a 3,000 sheet load, a 40:1 winch would have 75lbs of load on the handle.
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Last edited by Stumble; 03-30-2013 at 01:49 AM.
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