Unmanageable Mainsheet - Page 8 - SailNet Community
Old 09-26-2007
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Quote:
Originally Posted by SEMIJim View Post
So what we're experiencing here, or likely to experience here, isn't necessarily what we'll experience elsewhere. Indeed: Even just going across the state, to Lake Michigan, will be quite different. (I understand Lake Michigan can become quite harsh, quite quickly, quite unexpectedly.)
Now you are thinking more "globally"

Quote:
I mutinied. I called up and canceled the order late yesterday afternoon. (Made it just in time, too.)

60mm, actually. It's not so much the 60mm, but the SWL and breaking strength.

Wait... You quoted SWL at 19kts; breaking at 27. I put the following numbers into the Harken Mainsheet Calculator

E = 11.8
P = 33.5
V = 27
X = 4

With those numbers I get a mainsheet load of 1772 lbs. Since you stated the blocks you selected will fail at 27kts; I assumed that you were talking about the 50mm blocks. The 60mm blocks have a SWL of 1760 lbs; not failure load. I think the confusion lies where they show SWL in both KG and LBS on their spec sheet, but they don't quote failure loads. Since the 60mm specs don't include failure load I can't tell you at what windspeed you would expect a failure at; but the Lewmar Selection Guide shows the 60mm blocks as being suitable for mid-boom use on boats up to 34 feet; with 72mm blocks also suggested. However, the header states "for hand held and winch control" which suggests that a mid-boom setup should have a dedicated winch (or extra leverage that their 6:1 blocks are not well suited for).

Quote:
Now I just need to decide between the Lewmar 80mm fiddles, the Harken 4:1 solution (57mm dual block, 76mm fiddle), the Harken 6:1 solution, or maybe the Harken 4:1/8:1 self-contained system. (I'd really like to go w/Lewmar, but they don't appear to do anything with a ratchet, other than fiddle blocks.) Decisions, decisions. The lower I go, the faster I can move the boom and the less mainsheet I'll have on the cockpit sole, but the more strength it'll take to use. The higher I go, the slower the boom moves, the more sheet on the cockpit sole, but the more likely The Admiral, and perhaps I, will be able to deal with it. I think a tour of the club's slips is in order, as Sailormann suggested.
I'm thinking your biggest consideration among these choices is the amount of leverage that will be needed. I don't think the Admiral wants to develop ape-arms while trimming the main; and as for the additional sheet you could get a sheet bag to hold the excess when you are sailing upwind.

If you want to minimize the amount of sheet you need, you would want a 4:1/16:1 setup but it looks to require two mounting points on the boom for single blocks. (You should check that mount on the boom BTW to be sure it is properly sized, since it was retrofitted in).

The 4:1/8:1 that Harken sells is essentially an 8:1 system that has double bitter ends. It works by pulling on both lines to get a 4:1 sheeting speed/force, but you will need 8:1 line length to make the sheet long enough. They also make a 3:1/6:1 but it might be too small for your mainsail. If it were me; I would go with the 4:1/8:1 or a 4:1/16:1 with separate sheets.
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Quote:
Originally Posted by KeelHaulin View Post
With those numbers I get a mainsheet load of 1772 lbs. Since you stated the blocks you selected will fail at 27kts; I assumed that you were talking about the 50mm blocks. The 60mm blocks have a SWL of 1760 lbs; not failure load.
I'm looking at Lewmar's 2006/7 dead tree material catalogue. The 29901624 (60mm fiddle, cam/becket/ratchet) is shown with a 400 kg SWL (882 lbs) and a 800 kg breaking load (1764 lbs).

Quote:
Originally Posted by KeelHaulin View Post
I'm thinking your biggest consideration among these choices is the amount of leverage that will be needed. I don't think the Admiral wants to develop ape-arms while trimming the main;
No

Quote:
Originally Posted by KeelHaulin View Post
and as for the additional sheet you could get a sheet bag to hold the excess when you are sailing upwind.
There's a thought.

Quote:
Originally Posted by KeelHaulin View Post
(You should check that mount on the boom BTW to be sure it is properly sized, since it was retrofitted in).
Will do.

Quote:
Originally Posted by KeelHaulin View Post
The 4:1/8:1 that Harken sells is essentially an 8:1 system that has double bitter ends. It works by pulling on both lines to get a 4:1 sheeting speed/force, but you will need 8:1 line length to make the sheet long enough. They also make a 3:1/6:1 but it might be too small for your mainsail. If it were me; I would go with the 4:1/8:1 or a 4:1/16:1 with separate sheets.
Yeah, the 3:1/6:1 is not suitable for the amount of sail we have with mid-boom sheeting.

I'm thinking of the KISS principle, here. I'm thinking maybe just going 6:1 and being done with it.

What do you think of this combo (discovered by The Admiral, I would note):
Harken 2141 57 mm Carbo Triple Ratchet w/Cam, Becket
Harken 2604 BLK-57MM CARBO TRPL

The limits are imposed by the traveler-mounted end, the 2141, and are based on the cam cleat. We'd have an SWL good to 27 kts and a breaking load good to 43 kts, based on Harken's mainsheet loading calculator.

Jim
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Old 09-26-2007
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Now, I’m probably way out of line here, but are you sure the single point loading the DPO mounted on the boom is sufficient? For example, Catalina 30’s distribute their mid-boom sheeting across two load points on the boom. Not that this makes any difference as you plan to sail only on calm days, but you may inadvertently break your boom during an accidental (inadvertent?) gybe. Heck, here in windy S.F. Bay, I know a guy who broke his boom during an accidental gybe with three load points on his mid boom sheeting. And I, myself, have drug the ol’ boom in the water a time or two.
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Old 09-27-2007
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It sounds like an acceptable setup Jim. The only thing better I could suggest is the 1556 triple (3800# SWL); but it is much more expensive. I think a breaking load of 43 kts is much better for safety as you will probably have reefed down or spilled the sheets before experiencing that much wind; and you will have 6:1 with ratchet which is certainly an upgrade over your current setup. Unfortunately I don't think you can add a fine trim setup to the 57mm Carbo Triple if you ever decided to upgrade (where you probably could with the 1556). But; there are other ways to get the added purchase if you ever decided there is need for it.

I agree that double attachment points on the boom would be good also; it reduces load on each attachment and really reduces the chance of a failure. If your boom does not have internal reefing lines you might consider going to a heavy bail if you don't want to switch to double blocks.
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Quote:
Originally Posted by KeelHaulin View Post
It sounds like an acceptable setup Jim. The only thing better I could suggest is the 1556 triple (3800# SWL); but it is much more expensive.
Yes. Using Harken's "Compu Spec," it comes up with the 1556 and 1954 if I specify mid-boom sheeting, the 2141 and 2604 if I specify 3/4 boom sheeting. Ours is actually more like 2/3. (Boom is 13' long, attachment point is about 4' from the end.)

Quote:
Originally Posted by KeelHaulin View Post
I agree that double attachment points on the boom would be good also; it reduces load on each attachment and really reduces the chance of a failure. If your boom does not have internal reefing lines you might consider going to a heavy bail if you don't want to switch to double blocks.
Going from memory: It's already got a bail that resembles the bail on those blocks. I'll have to double-check.

Edit: Wait--don't have to go from memory. One of the pictures I posted in my original post at the start of this thread shows the bail on the bottom of the boom quite clearly.

How the heck would one add a bail? I wouldn't mind going to separate single blocks on the boom and distributing the load. Boom's hollow, I know, but... how do you get the hardware to fasten anything in there all the way down there, much less tighten it down? Hire mice?

Jim

Last edited by SEMIJim; 09-27-2007 at 10:27 AM.
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Old 09-27-2007
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It looks like a standard 3/8" internal boom bail. Probably no worries about the bail itself failing; the concern would be about the bail pulling out due to metal fatigue of the aluminum boom. I have not installed one of these bails, it seems to me that you would cut/drill the holes to fit the part and then slide the bail down from the end of the boom. Run a fish wire down and wrap it around the bail before sending it down through the boom so you can pull the eye out when it is in position. The bail should have threaded fittings so you don't have to hold nuts on from behind. www.ballengerspars.com shows both 3/8" and 1/2" internal bails on their parts list. Give them a call and ask about suitable sizes and if it would be a good decision to add a second block/bail to your boom.

As for the size of the block hardware; when in doubt it's always best to oversize. If you do double blocks on the boom you could go with the 57mm blocks on the boom because the load is distributed to two separate load points. So for a 6:1 you could do a 2602 double, 2600 single, and the 1564 triple.
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Hmmm... Surgery like that on the boom is a bit more than I'm prepared to tackle atm. I'll inspect the boom carefully for signs of fatigue in the area of that bail and ask at the club if we either have any riggers amongst the membership (I'm betting we do) or if the club has a relationship with a local rigger, and have them inspect it. I have to find a rigger, anyway, as my aft port lower shroud has a couple busted strands and needs replacement.

Providing nobody comes up with any show-stopper comments regarding the latest (Harken) components we've selected, I'll order them this weekend and get 'em on their way.

Thanks again for your help, KeelHaulin, and everybody else.

Jim
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Old 09-28-2007
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SEMIJim-

Just be aware that you don't need a rigger to replace a shroud with broken strands. You can often take the old shround down (if you've got double lowers) without much risk to the rig...as long as you don't sail the boat, and get a piece of 1x19 stainless and the modular terminal hardware, like StaLok, Hayn HiMOD or Norseman, and install it yourself. You'll probably want a Loos rigging tension guage to properly re-tension the shroud.

If you don't have double lowers, you probably should lead a halyard from the masthead and use it as a temporary shroud, while doing the replacement.

However, if the lower shroud has broken strands in it, and it wasn't due to impact or some other type of damage to that specific shroud, then there's a very good chance that much of your rigging is in need of replacement—especially if it is all of the same age. Did you have a rigging survey done when you bought the boat??

Sailingdog

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Last edited by sailingdog; 09-28-2007 at 10:32 AM.
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I'm going to reply to the standing rigging issue in a new thread, rather then haul this one off in a new direction.

Jim
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Old 10-02-2007
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blocks

FYI.....Jims suggestion of the 2604 and 2141 triple blocks work well. found them both on ebay for \$55 and \$80 dollars respectively. we race with it on a contention 30, end boom, and it has comfortably kept good control up to 45kts.

we have found that 10mm main sheet is kind on the hands, but with the 6:1 purchase does not run as freely as i would like in light winds....here is a compromise.....i am tempted by 8mm replacement sheet but it will need full fingered gloves if you are going to play it aggressively.

hope this helps

Rob
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