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Old 03-25-2013
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Mainsheet size?

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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Old 03-25-2013
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Re: Mainsheet size?

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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Re: Mainsheet size?

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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Old 03-26-2013
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Re: Mainsheet size?

Quote:
Originally Posted by sailordave View Post
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....

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Re: Mainsheet size?

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Originally Posted by Faster View Post
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.

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Last edited by MedSailor; 03-26-2013 at 12:36 AM.
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Re: Mainsheet size?

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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Last edited by Alex W; 03-26-2013 at 01:29 AM.
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Re: Mainsheet size?

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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Re: Mainsheet size?

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.

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Re: Mainsheet size?

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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Re: Mainsheet size?

Quote:
Originally Posted by MedSailor View Post
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?
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/c...e-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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Last edited by knuterikt; 03-26-2013 at 07:20 AM.
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