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post #50 of Old 11-10-2013
Courtney the Dancer
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Location: San Juan Islands., WA, USA
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Re: Caternary & Chain...

I think what is missing in this discussion about all chain or chain/rope is that the lighter chain/rope will be a straight line to the anchor, and therefore starting to lift the shank, in much less wind than the all chain. If it takes 160 lbs of force to lift the chain in PS's test it would take a small fraction of that to lift a length of nylon line and 30-40' of chain. So it would seem to follow that the same dynamics on the anchor would happen sooner (much lower wind speeds) than with all chain. Increasing the scope would lower the angle of pull somewhat but would not add weight (catenary) at all compared to all chain. No argument that when the wind speed increases to the point where the chain is bar tight there will be no catenary, but 300' of 3/8" chain is going to keep the pull on the anchor horizontal at much higher wind speeds than an equivalent length of nylon line. So I would assume that the same anchor wouldn't start dragging until the wind maintained enough force to lift the chain.
We use a 66 lb Bruce with 300' of 3/8" BBB as our main anchor on a 40' 24,000lb boat.

SV Laurie Anne

1988 Brewer 40 Pilothouse

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