# Mainsheet size?



## MedSailor (Mar 30, 2008)

The mainsheet that came with my boat wasn't long enough to get the boom all the way out.  I've been getting by with a line that I believe is 7/16 stay-set from my old boat. 

I'm about to re-lead the mainsheet forward, and back to a winch, and am pricing out the associated hardware. What size, and strength should my mainsheet be? Hardware has "safe working load" stamped on it, but the lines only have %stretch and breaking strength. Any guidelines out there that I can use?

According to Harken's mainsheet load calculator I can expect to frequently be seeing loads of 1,500lbs and see up to 3,000lbs on occasion. With the blocks and deck organizers that I'm looking at, there is a decent size price increase, if I go from blocks that will accept 1/2" line to ones that will accept 5/8" line. 

MedSailor

PS. When sizing the safe working load of a deck organizer, does it really need to be able to take the full load? Surely with a 30deg deflection it won't be that severely loaded right?


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## Faster (Sep 13, 2005)

First, the deflection adds to the load, eg a 180 turn doubles the load.. But for deck organizers I don't think you need to worry too much- I reckon if your line fits it'll be fine. I think the biggest issue with a cheap organizer would be weakness of the sheave itself.

For the sheet itself with the multipart nature of the tackle the rope is usually chosen for its hand rather than strength.. i.e. what's easiest/most comfortable to hold onto..what's comfy is usually plenty strong.


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## sailordave (Jun 26, 2001)

well looking up a FORMOSA 41 and using 15 and 43 for the E and P and a sheeting position 4 feet fwd of the end of the boom... and 25 knots of AWS you're looking at 2237 pounds of force.

I'd go w/ 1/2" sta-set or better yet 1/2" VPC (less stretch and about 10% higher load) Plus it will fit better in your hands.

My Main is 281 ft^2 and I use 7/16"; w/ your main at 322 ft^2 this should work.


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## MedSailor (Mar 30, 2008)

sailordave said:


> well looking up a FORMOSA 41 and using 15 and 43 for the E and P and a sheeting position 4 feet fwd of the end of the boom... and 25 knots of AWS you're looking at 2237 pounds of force.
> 
> I'd go w/ 1/2" sta-set or better yet 1/2" VPC (less stretch and about 10% higher load) Plus it will fit better in your hands.
> 
> My Main is 281 ft^2 and I use 7/16"; w/ your main at 322 ft^2 this should work.


Thanks for looking up the particulars on my boat! I should have posted them. My new main is going to be 400sqft almost exactly. 41' luff, 17'3"foot and lots of roach. 

So nobody minds the stretch on the round trip to the mast and back? Sounds good to me! I don't want to have to size my blocks to take larger than 1/2" line. In fact, it looks like I'd end up coming out ahead (cost wise) if I keep everything to 1/2" and if I need to, just upgrade the line to high-tech. That'll be cheaper than bigger blocks and less stretch....

MedSailor


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## MedSailor (Mar 30, 2008)

Faster said:


> First, the deflection adds to the load, eg a 180 turn doubles the load..* But for deck organizers I don't think you need to worry too much- I reckon if your line fits it'll be fine. *I think the biggest issue with a cheap organizer would be weakness of the sheave itself.


I don't know about this. On one hand, I've been on all kinds of raceboats that didn't have oversized gear and we stressed the CRAP out of it and nothing ever broke. Hoepfully that means that their ratings are conservative. Still, some of the ratings are pitiful....

Harken's 40mm carbo blocks (up to 1/2" line) have a MWL (max working load) or under 500lbs for a single block!  Their 40mm Cruising ESP deck organizer is a little better at a MWL of 2000lbs... Seems to me that if I use a Harken 40mm block (sized for 1/2" line) to do a 180deg turn at the mast I might blow up the block in short order. Garhauer, on the other hand, has single blocks rated to MWL 2800lbs...

Then, there is the "it hasn't broken yet" evidence. Apparently the plastic cam cleat that currently holds my mainsheet is only rated to 500lbs. Hmmm..... Why didn't it break when that 30+kt squall hit us with the main fully up? Seem like it should have been blowing shrapnel all over the boat.

MedSailor


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## Alex W (Nov 1, 2012)

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.


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## overbored (Oct 8, 2010)

the cleat is holding the same as the amount of load that you will be holding which is about 200 lbs. max. after it goes around a winch the cleat should not be seeing much load. the blocks on the other hand will be seeing a lot higher load if before the winch. 40 mm is a bit small for a 400 ' main. 40mm will add a bit of friction to the system. 57 mm is what you need on that main.


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## blt2ski (May 5, 2005)

I have 1/2" on my 195# main. with a 4-1 sheet option, and 1/4" on the 4-1 micro. ALso all XLS extra! I would not put sta set on my boat or equal, granted I race a bit, but the stretch is more than I want even on a cruise style boat! I prefer higher tech a bit thinner vs larger and strethier/same strength per say. Folks on dingy's are using lines in the 4-6 mm in diam, granted less loads, but still on the small diam size. 

One thing I like about the XLS extra and XLS extra T, is the multiple color options, so one can easily color code the different lines etc on your boat.

Marty


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## Gust14882 (Nov 30, 2010)

First off, it appears that Harken is more conservative with their MWL's than other suppliers. They use a safety factor of at least 3 or 4, compared to others who use a factor of just 2. (Safety factor is breaking load divided by working load.)

Secondly, a mainsheet with a bit of 'give' helps to protect the rest of your gear in the event of an accidental gybe or other overload situation. The line absorbs the shock load by stretching a bit. Far easier to have to grind in a little more once in a while than to have to replace broken gear. Leave the low-stretch stuff for halyards and such that are under constant high load.

Third, 40mm blocks for a 400sf main? Get real, at least 57mm or better yet 75. The smaller blocks impart a sharper bend, with more friction, smaller bearing surfaces, and fewer bearings to boot.

Plus, if you need a winch to trim your main, you better build stout tackle to handle the loads.


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## knuterikt (Aug 7, 2006)

MedSailor said:


> The mainsheet that came with my boat wasn't long enough to get the boom all the way out.  I've been getting by with a line that I believe is 7/16 stay-set from my old boat.
> 
> I'm about to re-lead the mainsheet forward, and back to a winch, and am pricing out the associated hardware. What size, and strength should my mainsheet be? Hardware has "safe working load" stamped on it, but the lines only have %stretch and breaking strength. Any guidelines out there that I can use?
> 
> ...


you must look at all the different componets in your sheet arrangement to get this right.

The load from the load calculator give the load at the fixing point at the boom.
So if you have one block at the boom you should size the block for the load.
I have three blocks at the boom - so the load is divided between those three - each block sized for 50% of the total load (I have a geerman main sheet set up).
At the traveller I have a fiddle block that must take the whole load alone.

A turning block (a block that only change direction of the line w/o gaining advantage) deflecting 180 degrees, need to be sized for double line load (not the boom load) - but it will not increase the load on the rope..

For rope size, handling often is more important to size than strenght. But I would at least have a safety factor of 1:3

If you post i diagram or pictures it's easier to see  what you are planning to do.

A good source for block load's http://www.lewmar.com/cms/assets/1/categories/hardware-tech-ref.pdf

Some figures from my boat:
Mainsheet load 1000kg
Fiddle block at traveller 1000kg
The middle boom block get a load of 500 kg
The other two get 250kg * 141% = 352kg
With a 1:4 system the load on the rope and and cleats/cluthes is 250kg

This is a picture of the turning block at the mast, attached with a Dyneema loop - load 352 kg (block & loop)









My mainsheet


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## sailordave (Jun 26, 2001)

Alex W said:


> 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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## chucklesR (Sep 17, 2007)

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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## MarkofSeaLife (Nov 7, 2010)

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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## Faster (Sep 13, 2005)

MarkofSeaLife said:


> 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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## Stumble (Feb 2, 2012)

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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## Alex W (Nov 1, 2012)

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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## zz4gta (Aug 15, 2007)

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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## zz4gta (Aug 15, 2007)

Another tip
Harken

That's for all blocks. Deck organizers included.


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## MedSailor (Mar 30, 2008)

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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## Stumble (Feb 2, 2012)

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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## MedSailor (Mar 30, 2008)

Stumble said:


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


By double ended do you mean european or german mainsheet where it goes to 2 winches? I don't have 2 winches.... What I would like to be able to do is hand sheet until it is blowing a bit, then use the winch when needed. As others have pointed out, the main is the first sail on my boat to be reefed, so I expect that with modest purchase I could be sheeting it by hand on most days.

MedSailor


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## Stumble (Feb 2, 2012)

Med, if you want to be able to hand sheet it primarily, with the winch available as a backup, then you should probably size it based upon controlling it that way. Assuming a 1500lbs max load trimmed by hand, you would need something like a 30:1 purchase arrangement. This is why on mid boom sheeted mains they pretty much have to be winch controlled. The rough number is that a person can exert around 50lbs of force on a line for brief periods. Beyond this it isn't practical. On my Trip 40 we had a 24:1 and a cascade 48:1 on the main, but it was still pretty marginal. 

By switching to a winch, you immediately get somewhere in the 40:1 range in low gear, meaning even a 2:1 or 3:1 additionally while nice, isn't really necessary. The downside to additional purchases is that you also increase the amount of line you need to crank in, and the amount of tale left in the cockpit. Which may or may not be an issue depending on your boat. 

If I was setting up a winch driven system, I would just assume that I was going to use it most of the time. Otherwise on a sail this big you have to have a major increase in necessary purchase.


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## knuterikt (Aug 7, 2006)

MedSailor said:


> 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....
> 
> ...


I think my main is aproximately the same size as yours.
I have a German double ended system, when we rigged this the choice was 1:2 or 1:4, chose 1:4 (with a 1:40 winch). Reasoning was that it would be easier to go from 1:4 to 1:2 if we wanted to change....
We still use 1:4 as it give some more leverage while sheeting in by hand.

As for leading the sheet to the winch it all depends on where the winch is located.
We use a the secondary cockpit winches, so the sheet go from the goose neck down to a block at the chain plate (see picture - note the attachment is at the *bottom* of the turnbuckle - and this solution have been cleared with a competent rigger)
Used a Dyneema loop 









The best advice is to try out the lead using some blocks and rope.
Remember to test all boom positions, you don't want the sheet self adjust while tacking.

My sheet winch (one)


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## MedSailor (Mar 30, 2008)

Stumble said:


> Med, if you want to be able to hand sheet it primarily, with the winch available as a backup, then you should probably size it based upon controlling it that way. Assuming a 1500lbs max load trimmed by hand, you would need something like a 30:1 purchase arrangement. This is why on mid boom sheeted mains they pretty much have to be winch controlled. The rough number is that a person can exert around 50lbs of force on a line for brief periods. Beyond this it isn't practical. On my Trip 40 we had a 24:1 and a cascade 48:1 on the main, but it was still pretty marginal.
> 
> By switching to a winch, you immediately get somewhere in the 40:1 range in low gear, meaning even a 2:1 or 3:1 additionally while nice, isn't really necessary. The downside to additional purchases is that you also increase the amount of line you need to crank in, and the amount of tale left in the cockpit. Which may or may not be an issue depending on your boat.
> 
> If I was setting up a winch driven system, I would just assume that I was going to use it most of the time. Otherwise on a sail this big you have to have a major increase in necessary purchase.


All good points, though as I work though both winch, and winch-less systems I still think there is an argument for a moderate amount of purchase. With a 4:1, by the math, it looks like I might be able to hand sheet up to 10kts. I realize that the reality will be different as friction from blocks will make it harder, the rope clutch adds resistance but generally makes hand sheeting easier etc. I will probably also be able to hand sheet off the wind.

Even without any hand sheeting, the 3/4:1 purchase has the advantage of being easier on my blocks and cabin-top hardware (except the traveler car) Without some purchse I would need a turning block at the mast rated for 6000lbs and rope clutches rated to 3000lbs. I'm finding that those are hard to find in the size line (and cost bracket) that I'm using.

MedSaillor


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## Faster (Sep 13, 2005)

We started out with a 4 part winchless sheeting system.. we're now up to 6 parts for better control. The good bearing blocks reduce friction considerably. 

Makes controlling gybes much easier/less scary too.

btw our main is 41P/14E.. similar to yours??


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## MedSailor (Mar 30, 2008)

Faster said:


> We started out with a 4 part winchless sheeting system.. we're now up to 6 parts for better control. The good bearing blocks reduce friction considerably.
> 
> Makes controlling gybes much easier/less scary too.
> 
> btw our main is 41P/14E.. similar to yours??


I'm a little lower aspect.  42'P (luff will be 41) 17'9" E (foot will be 17'3"). Lots of roach, especially at the head of the sail for a total of 398.25sqft. (400 square feet to me)

MedSailor


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## MedSailor (Mar 30, 2008)

For the traveler car end, is there an advantage of this kind of block








over this one?









Less friction???

MedSailor


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## overbored (Oct 8, 2010)

no difference. the double sheave is done on the larger sizes because if you have lower sheave that is 4" then the top one would need to be 6" and that makes a very tall block. it done to keep the assembly as low a profile as possible


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## Stumble (Feb 2, 2012)

Med,

As overboard mentioned they are used to try and control the block size. When dealing with large line size (1/2" or larger) keeping a 8:1 turning radius means the smaller block should be at least 4" which would mean a 6" upper wheel minimum to give enough clearance.


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