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Old 09 July 2019, 17:00   #1
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Overnight Anchoring

Hello everyone, Iím after some advice please, Iím planning on leaving my 22ft rib on anchor over night (sand seabed), Iím using 10 meters of 8mm chain with 12mm 36mtr rope what anchor/weight should I be using? Any recommendations welcomed. Thanks
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Old 09 July 2019, 18:21   #2
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Depends on the conditions you expects etc. The weight depends on the design you choose. Some people would suggest 1kg per m of length. If you were operating commercially then the size of anchor would depend how far from shore you plan to go - presumably however if you are planning to anchor overnight then it will be in benign conditions and it might be fair to compare to the least challenging coding requirement - 4kg.

There have been many threads on this so searching should bring you suggestions on designs to avoid etc.
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Old 10 July 2019, 01:11   #3
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10m of 8mm is 14kg - if you deploy it all.

How deep is the water?

In case it's not obvious a grapnel & fisherman are both the wrong design if you are making a choice for sand specifically.

This time it's sand. Will it always be sand?

You need to consider storage on board. Anchor locker size? Space left with chain and rope?

Are you staying aboard?

Do you have a plan if the wind / tide change overnight and she slips?

How are you getting ashore once anchored?
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Old 10 July 2019, 01:32   #4
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Maximum tide height will be about 9-10 meters.

I currently use a danforth whilst anchored in the day and watching the boat from the beach & yes it will always be sand.

I’m planning on attaching a marker buoy to the other end of the rope so basically be a temporary mooring and I have a small sib which I use to get back and forth from the rib.

Thanks.
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Old 10 July 2019, 02:11   #5
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Davos

Welcome to the forum.

For your size RIB I'd suggest a 7kg'ish anchor. Jimmy Green have a large range and anchor types have been discussed on here recently.

Your anchor will need to fit in your anchor locker unless you can tie it to the deck.

When you deploy the anchor you will need to ensure that the intersection between the rope and the chain and the rope and the boat can't chafe.
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Old 10 July 2019, 04:45   #6
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At 10m water depth but only 46m of rode I'd suggest that you need a longer line by the same again bar any tail. Your chain seems about right.


An anchor weight of about 7.5kg should be fine, but is there space to stow that shank?


Anchoring is as much art and compromise as science and there are plenty of rules of thumb about weights per metre of vessel and length per metre of water depth. All I would say - in the absence of any information about location and conditions - is to err on the side of caution. It might be overkill but that's better than waking up and finding out that your boat is either gone or ashore on rocks.


Hope it works out and have a great time!
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Old 10 July 2019, 12:24   #7
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Originally Posted by Dr. Hook View Post
At 10m water depth but only 46m of rode I'd suggest that you need a longer line by the same again bar any tail. Your chain seems about right.

The RYA recommend 4x for chain only, and 6x for a mix of chain and rope (with 5m+ of chain) so I donít think he needs double - but a bit more would be wise if it really is a 9-10m depth. Worth keeping in mind though that the boat will swing so simply chucking out more scope isnít always a good idea.
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Old 10 July 2019, 13:17   #8
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The RYA recommend 4x for chain only, and 6x for a mix of chain and rope (with 5m+ of chain) so I donít think he needs double - but a bit more would be wise if it really is a 9-10m depth. Worth keeping in mind though that the boat will swing so simply chucking out more scope isnít always a good idea.

As I said above ref. art and compromise. Anywhere between 5:1 and 12:1 depending where you are, what you're doing and who's rule of thumb you're following. So 8:1 is a happy medium and the diff between this and 6 ain't worth arguing about. I don't really care, it's not my boat and I certainly don't try to help to be snarled up in pedantics. After all I think we both agree his line is a bit short!!!!!



As I'm sure wiser members know, if you're worried about swing, there are more than half a dozen different ways to use your kedge............
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Old 10 July 2019, 13:32   #9
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Thank you everyone for all the advice!
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Old 10 July 2019, 13:37   #10
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I certainly don't try to help to be snarled up in pedantics.
You've given them too much scope.

Cheer up though - it's a long rode that has no turning!
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