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-   -   mainsheet sizing/load (http://www.sailnet.com/forums/gear-maintenance/53880-mainsheet-sizing-load.html)

huguley3 04-27-2009 01:56 PM

mainsheet sizing/load
 
My mainsheet currently uses a dock cleat to secure it. It seems kind of scary to me to use something like that for a sheet so I am looking at replacing it with a rope clutch. I will need to move the winch and possibly the sheave. Also planning to move the main halyard back to a second clutch so its not on the mast. I have a pretty good plan for doing all of that.

I am wondering about the size of line for the mainsheet? I have looked for some kind of sizing chart but they are all based on boat size which seems like you would end up with a line that may be off. My traveler is about in the middle of the boom so I am guessing the boom will be generating more leverage on the sheet than if it was toward the end of the boom. Or is it just a rule of thumb and if the sheet breaks you get a stronger line next time? :) I was just going to replace the line with a similer diameter but I had Mack sails out to replace my main halyard and they said it was oversized(was 7/16 replaced with 3/8) and replaced it with a smaller diameter line. The larger line is easier to hold onto but harder to keep tidy. Always a trade off but I would rather only have to buy the rope clutch once. The current mainsheet is 1/2 inch.

If I could replace the 1/2 inch mainsheet with 3/8 or 7/16 then I can get a single double clutch. 7/16 can get up to 6100 lbs in strength while 1/2 inch is 8700 lbs. The current line on the mainsheet is very old and has not broken yet. I don't know what kind it is but it is ready to be retired.

Anyway long post for a simple question about how strong of line I need for a 30' sailboats mainsheet. :)

mitiempo 04-27-2009 02:38 PM

I'd downsize it to 3/8 or 7/16 as that is plenty strong enough. Most modern line has enough strength that people go large enough to make the line easy to handle and end up with a much stronger line than they need. 1/2 is too big in my opinion.
Brian

sailingfool 04-27-2009 02:53 PM

I've never seen a rope clutch used on a mainsheet, I cant' say why not, nor quite provide an explanation for why not, but I would not use a clutch. The mainsheet is the one line on a boat most often played, ie.e repeatedly eased and trimmed, and a rope clutch is not good gear for such an application.

As to size, given the above statement I'd generally go with as large a size as cleanly fits in the sheaves. If the 1/2 fits cleanly I'd use that size again. While the 3/8 would probably be fine to carry the load, the crew's hands will like the 1/2 a lot more...

sailingdog 04-27-2009 03:24 PM

Quote:

Originally Posted by huguley3 (Post 480271)
My mainsheet currently uses a dock cleat to secure it. It seems kind of scary to me to use something like that for a sheet so I am looking at replacing it with a rope clutch. I will need to move the winch and possibly the sheave. Also planning to move the main halyard back to a second clutch so its not on the mast. I have a pretty good plan for doing all of that.

You should be using a cam cleat, clam cleat or something similar for a main sheet. A rope clutch doesn't always release under load, nor does it release anywhere near fast enough to be safe on a mainsheet.

Quote:

I am wondering about the size of line for the mainsheet? I have looked for some kind of sizing chart but they are all based on boat size which seems like you would end up with a line that may be off. My traveler is about in the middle of the boom so I am guessing the boom will be generating more leverage on the sheet than if it was toward the end of the boom. Or is it just a rule of thumb and if the sheet breaks you get a stronger line next time? :) I was just going to replace the line with a similer diameter but I had Mack sails out to replace my main halyard and they said it was oversized(was 7/16 replaced with 3/8) and replaced it with a smaller diameter line. The larger line is easier to hold onto but harder to keep tidy. Always a trade off but I would rather only have to buy the rope clutch once. The current mainsheet is 1/2 inch.

If I could replace the 1/2 inch mainsheet with 3/8 or 7/16 then I can get a single double clutch. 7/16 can get up to 6100 lbs in strength while 1/2 inch is 8700 lbs. The current line on the mainsheet is very old and has not broken yet. I don't know what kind it is but it is ready to be retired.

Anyway long post for a simple question about how strong of line I need for a 30' sailboats mainsheet. :)
Depends on the amount of purchase/leverage your mainsheet gives you as well as what line you're using. On a 30' boat, a 1/2" polyester double braid is quite common... but if you go up to a spectra or dyneema based line, you might be able to drop down to a 3/8" or 7/16" line. One advantage of a smaller line is that they generally run out with less friction—smalller diameter==> less friction. One disadvantage is that they're harder on your hands.

huguley3 04-27-2009 06:11 PM

Oh great sure make it even more complicated for me. :)

I saw rope clutches on a 36' islander in the great lakes. He was not racing the boat so maybe that is why he was using the rope clutch for the mainsheet? he had about 5 clutches setup for the lines and even the reef points it was pretty slick. I will look into a cam for it and see how it will fit. I guess it would solve the problem of having differently sized lines for the various functions. If it did stick on occasion I think a clutch is better than the dock cleat I have on it now.

The crew is basically me and the SO and whoever happens to be along for the ride. So I am guessing if I choose small lines I will be the one that ends up paying because the SO will refuse to deal with it and I will be the one cursing at them as they slip through my hands and chew up my baby soft hands. :)

padean 04-27-2009 06:50 PM

Quote:

Originally Posted by sailingfool (Post 480302)
I've never seen a rope clutch used on a mainsheet, I cant' say why not, nor quite provide an explanation for why not, but I would not use a clutch. The mainsheet is the one line on a boat most often played, ie.e repeatedly eased and trimmed, and a rope clutch is not good gear for such an application.

As to size, given the above statement I'd generally go with as large a size as cleanly fits in the sheaves. If the 1/2 fits cleanly I'd use that size again. While the 3/8 would probably be fine to carry the load, the crew's hands will like the 1/2 a lot more...


I use a rope clutch for my mainsheet. It works out well with my deck layout, where all lines are led to the cockpit. I use Lewmar D2 clutches, and they release very nicely under load. Original sheet blocks were old and the loads were too heavy for my wife to ease the line, but she can do it nicely with the clutch. With new sheet blocks the loads are much lower, but the clutch still works fine. I would rather have an end boom traveler with a gross and fine adjustment lines for the mainsheet, but the current set-up works well for us.

For the size boat huguley3 is talking about, 3/8 line should be more than adequate, although it will depend on the forces on the line, which will depend on the number of blocks and mechanical advantage on the sheet. If the forces are high, a thicker line such as 7/16 is a little easier on the hands.

sailingdog 04-27-2009 07:46 PM

Quote:

Originally Posted by huguley3 (Post 480425)
Oh great sure make it even more complicated for me. :)

I saw rope clutches on a 36' islander in the great lakes. He was not racing the boat so maybe that is why he was using the rope clutch for the mainsheet? he had about 5 clutches setup for the lines and even the reef points it was pretty slick. I will look into a cam for it and see how it will fit. I guess it would solve the problem of having differently sized lines for the various functions. If it did stick on occasion I think a clutch is better than the dock cleat I have on it now.

Most likely, you're a bit confused. If the reefing lines were there, chances are much more likely that the line in question was the MAIN HALYARD, not the mainsheet. The main halyard, outhaul, topping lift, boomvang, and reefing lines are often brought back to the cockpit so that the mainsail can be reefed and shaped from the cockpit.

Quote:

The crew is basically me and the SO and whoever happens to be along for the ride. So I am guessing if I choose small lines I will be the one that ends up paying because the SO will refuse to deal with it and I will be the one cursing at them as they slip through my hands and chew up my baby soft hands. :)
Go with 7/16" or 1/2" lines then.

blt2ski 04-27-2009 08:19 PM

huguley,

Do you have a picture of what you are trying to modify? Not that I would want a cleat either, a cam cleat is best. Not sure I would want a clutch, altho I have to admit, I do have a clutch for how I can operate my 110 and smaller jibs with the way those lines come to the top of the cabin top. I may change this option at some point in time. Not sure I would want a clutch or equal with a main sheet, a jam cleat could/would be quicker to release than a clutch in most cases. Are you sure you do not have a jam cleat?

Marty

sailingfool 04-27-2009 09:04 PM

I think the OP is referring to a horn cleat as a "dock cleat". If so, the horn cleat is certainly the most traditional means for securing sheets, although racers may like clam cleats. Cam cleats for sheets are common on smaller boats, especially one designs., and often for the mainsheet when used on a block tackle.

For sheets used with winches on a non-racing boat, stick with the horn cleats installed by the builder...

blt2ski 04-27-2009 09:17 PM

SF,

I may not have said the type of cleat I was thinking of very well, I was thinking of a cross between a Horn and a ham, where one side the line with jam between the deck and that horn, the other the line will not jam, on can wrap around it lose. I have some of these my self, and do like them, in that one does not have to use a figure 8 to Cinch/tighten the line, but a (usually) a quick flick will unloosen the sheet.

marty


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