Adding a proper cunningham - SailNet Community
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post #1 of 5 Old 02-22-2012 Thread Starter
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Adding a proper cunningham

Right now the main just has a cunningham line that goes from a cleat on one side of the main, to the other. As it's hard to use, it never gets used!

I would like to bring the line back to the cockpit, and I think I would like to add some blocks at the mast to give some reduction/mechanical advantage. So if you have this, what reduction do you have and, ideally, could you post a pic of the arrangement?

Thanks.

Bristol 31.1, San Francisco Bay
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post #2 of 5 Old 02-22-2012
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Here's the page out of the Harken catalogue with some examples:

Harken Hardware Catalog

We are using a 3:1... on a former 24 foot race boat we used 6:1 for ease of adjustment.. you can use relatively small line and blocks for this.

Ron

1984 Fast/Nicholson 345 "FastForward"

".. there is much you could do at sea with common sense.. and very little you could do without it.."
Capt G E Ericson (from "The Cruel Sea" by Nicholas Monsarrat)
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post #3 of 5 Old 02-22-2012
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I've used a 6:1 on a J24. Should be enough for your bristol. The 6:1 on the 24 was that way for fine tuning, not b/c it needed the purchase. They used Harken micro blocks. You could use the ti-lite blocks, carbos, I'd suggest Garhauer, but they don't make anything small.

You could do a cascade, but might be more trouble than its worth.

Merit 25 # 764 "Audrey"
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post #4 of 5 Old 02-22-2012
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I have a 6:1 arrangement, with some fancy schmancy dyneema type stuff. Can't remember exactly, but it's strong enough to lift the boat up, and plenty to put some significant tension on the luff.

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1974 C&C27 MkII

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post #5 of 5 Old 02-22-2012
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I use a direct dyneema line to a 20:1 coachroof mounted winch / Garhauer gang of rope clutches ... on a 440 sq. ft mainsail.

gooseneck fitting ---> cunningham (strap eye on sewn web .. one side of sail's luff reinforcement patch) ---> mast base sheeve ---> deck organizer ---> clutch ---> 20:1 winch.

If your main's headboard is NOT above the 'black mast top band' .....'If the halyard is properly tensioned to remove boltrope 'preload' in a dacron sail (normal preload is ~1" strain per 10-11ft. of luff length) - all to get a proper luff hoist / stretch-out ........ you wont need 'much' cunningham strain *distance* to affect the position of max draft location adjustment in the lower panels. All depends on how well the mast track is lubricated !!!!
If the headboard is AT the black band, then of course youll need all the cunningham 'movement' you can get ... still at about 1" per 10-11 ft. of luff length.

------
On my sport boat, the cunningham is a sewn cringle: deck cleat ---> mast base block ---> (stainless 'strap' through the cringle with block on each side/end of the 'strap') first block ---> block attached to mast base -----> second block on strap (on opposite side of sail) ---> mast base block (opposite side) ---> deck cleat. Allows setting cunningham from 'either' side of the boat w/ 4:1 purchase
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Last edited by RichH; 02-23-2012 at 12:02 AM.
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