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Old 30-05-2012, 19:06   #1
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Sea Anchor line

i recently bOught myself a sea anchor which I hope I never have to use. I have a good anchor line with chain of some 200 feet to attach to it but for my size boat I could need more than 300 feet. I have another 200 foot anchor line. What is the best way to attach to each other these two long lines that may be exposed to tremendous strain?
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Old 30-05-2012, 19:15   #2
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Re: Sea Anchor line

I would use thimbles in the ends of the line, and then join the two lines with a heavy shackle.

I don't think it is the loading on the line that would result in breaking the line. The problem is chafe from recurrent loading.

When I laid to an 18 foot diameters ParaAnchor north of New Zealand in a winter storm, I never felt that the loading was all the great because the line had so much stretch. Chafe was the real enemy.

Focus on chafe prevention.
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Old 06-06-2012, 02:15   #3
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Re: Sea Anchor line

yeah Ive just been reading eric hiscock on this very subject and he says chafe is the big problem - he recommends putting heavy plastic hosing over the inboard end of the lines to protect them - failing that wrap them with towels taped over.
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Old 06-06-2012, 10:57   #4
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Re: Sea Anchor line

I have recently loaded a mooring line with plenty of load (measured, I am that smart). It did not snap. Why I loaded it was because of the knot there was in it.

Now I think if the line is strong enough (enough= plenty of margin) then you can tie them together. (Maybe, though, you cannot untie them later).

Eyes spliced onto thimbles & shackle are probably the strongest and least destructive way though - use welded ones (not open ones) or plastic closed ones. Open ones sometimes cut the rope.

Make sure your deck fittings are stronger than the line too!

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Old 06-06-2012, 12:10   #5
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Re: Sea Anchor line

Is there not a case for a swivel at the parachute too? I imagine the parachute revolving under strain and resulting in a bird's nest! IMO, I would go for the thimble and shackle join, the inboard ends of the anchor lines would surely have the thimbles already, for attaching to the boat. Chafe, - Plastic hose is good, but if loose on the warp can result in chafe inside the pipe too, ongoing monitoring through the storm is essential.
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Old 06-06-2012, 15:10   #6
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Re: Sea Anchor line

Assuming the line you are planning on using is nylon, the worst thing you can do is add a plastic cover Over it for chaff protection.

While it used to be thought that plastic sleaving would protect against chaff, reviews of the primary failure mechanism of dock lines during hurricanes has shown a few things relavent to sea anchors.

1) strength was almost never the problem
2) chaff, particularly chaff at the chock where the line came onto the boat was overwhelmingly the favorite point of breaking.
3) the primary cause of breaking has been ascribed to a few things.
a) as the nylon stretches over the chock it is doing so under tremendous loads. This friction of course causes significant heat in the line.
b) plastic covers act detrimentally in two ways, first they act as an insulator to keep the heat from being carried away by water and air convection currents. And they add another friction point for the line to rub against.

Currently there are a number of systems in the works for dock lines that use a two piece line. Nylon from the piling to just before the chock, and then dyneema/spectra spliced onto the end that carries the load aboard.

Unfortunately there just isn't a way to do this for a sea anchor, but it does inform the decision of how to use it. First keep coverings as far as possible from nylon lines as you can. If you use use one, ensure it is a breathable one that will allow heat to dissipate. Finally try to keep the bending angle between the cleat and the load point (the anchor) at as shallow a bend as possible. This reduces the friction load at the chock.

For a sea anchor my advice would be to start with more line out than you feel you need (let the boat rest one wave more downwind than you could), and slowly over time shorten the line. This will keep moving the damaged portion of line onboard instead of further out (like letting the line out over time will). Even a few inches an hour could make the difference, and probably won't change the ride of the boat much.

If you can, moving the cleat to the toe rail would probably be the best option, but that is obviously a major job.

Quote:
Originally Posted by charliehows View Post
yeah Ive just been reading eric hiscock on this very subject and he says chafe is the big problem - he recommends putting heavy plastic hosing over the inboard end of the lines to protect them - failing that wrap them with towels taped over.
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Old 06-06-2012, 15:40   #7
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Re: Sea Anchor line

Re plastic hose: I found a cut piece of canvas firehose easier to manage to protect boat lines from chafe.

Hugs,
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Old 06-06-2012, 16:34   #8
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Re: Sea Anchor line

Fire hose has the same problem at plastic tubing, it is water proof. Heavy canvas, or some of the specialty chaff protection items will work much better.
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Old 06-06-2012, 17:54   #9
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Re: Sea Anchor line

Just two ideas:

- perhaps there is a way to pre-modify the bow fittings avoiding any too sharp endes and turns,
- if the line is to be taken IN by inches then it may also be a good idea to plan this in advance - during the storm the pressure on the line may be too high to allow for doing this by hand.

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