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Re: Reduction in anchor scope with chain use
There is only the rule of common sense. The weight of chain rather than length is important--but in deep water you have to use nylon or you will simply not be able to recover all the chain if it is heavy short link chain--which is the best to buy.
If you have such chain, you need to put out as much as you can in the circumstances. I know that is stating the obvious, but after reading the first post the obvious seems to have been overlooked. The comparison in weight of chain and nylon is completely irrelevant. The weight of chain is relevant--because you need to ensure you put out no more than your winch can handle in a vertical lift plus the force necessary to pull the pick out of the mud plus the weight of said pick and an angel of you use one. If you put out more than that you will be unable to get it back. If you regularly set anchors in deep water fifty feet of heavy short link chain with an angel of about twenty pounds set in the chain about ten feet from the rode end, then a five-to one scope to the end of the chain with the angel fitted is a minimum and ten is better. What pulls out the anchor is the weight of the boat and the speed it builds up as it surges backwards between waves in a storm, because when the chain pulls taut this is transferred to the ground tackle. An angel plus chain softens this and the elasticity of a 20mm nylon rode softens it still further. Even so--such an anchor can still drag--sometimes anchors land on sea beds where they will not grip. In such a situation, if the water is shallow, say twenty feet or so--the more chain you can let out the better.
My boat weight five tons, and with stores and fuel more than six when cruising. My anchor is sixty pounds and I use at least thirty metres of 13mm short link chain, to which is lock-spliced one hundred metres of 20mm hard woven nylon rode. Even so, I would hate to have to ride out a storm at anchor. I am just experienced and pessimistic enough to realise that if I am wearing cast-iron pants, fate does not often try to kick my arse.
Last edited by Mike Banks; 10-17-2012 at 03:24 AM.