How do you run two anchors?

[thinwater]

Originally Posted by belizesailor

Thinwater, can you post a link to your testing?

I am particularly interested in what amount of pulling force hauls the primary out of the bottom. Seems to me that's got to be a very large load. Is it within realistic loads for mid sized boat anchoring (IMHO, most estimates are way over stated)?

Anecdotally (no structured testing), Ive used inline tandem anchors successfully (didn't drag), but who knows without structured testing...the primary alone may have still done the job.

The testing is for an article in Practical Sailor, so I will only post bits and pieces. Sorry. However, there is always more on my blog (in signature, below).

How much is required to lift the secondary? Like everything in anchoring there are MANY variables. In this case the secondary was a Guardian, and because it drags less, was carrying all of the load. The force was perhaps 1/2 what the Mantus could have held on it's own, and a small fraction of the Guardian's capacity. As a general rule, however, this becomes a serious problem as soon as the rode lifts off the bottom, since the front anchor is seeing 100% of the lifting load and ~ 1/2 of the horizontal load. Thus, a 20:1 scope is the bare minimum.

Yes, this will be a problem for any boat in any thunderstorm, depending on the bottom and anchor selection. It was well below the normal holding strength of the anchor.

[thinwater]

Originally Posted by SVNeko

After several multiple anchor fiascos, I would like to try this technique. However, for those with rope rodes for their secondary, how would you propose attaching the secondary rope rode to the primary chain? Not many multis carry two all chain rodes.

A soft shackle through a link is well proven. A prussic works (my favorite). Though I would use a rolling hitch for a snubber, I would not trust it for this.

[thinwater]

Originally Posted by mikereed100

We use a loop of dyneema/polyester double braid to attach our bridle to our chain. It would be a simple matter to add another loop the the bridle and attach this to the rope rode of a second anchor. The loop is made by tying a double fisherman's bend (Double Fisherman's Bend | How to tie a Double Fisherman's, or Grapevine, Bend | Rescue Knots..) and is attached to the bridle with a prusik hitch (Prusik Knot | How to tie the Prusik Knot | Climbing Knots), locating the fisherman's bend in the middle of the prusik. The bight of the loop is then tied to the chain (or rope) with a rolling hitch. The diameter of the loop of dyneema is less than that of the chain or rope which aids in holding. Also, using a loop to tie the rolling hitch doubles the turns around the chain/rope from 3 to 6. I also put a figure 8 in the end of the loop just to be sure it does not pull through, but this is probably unnecessary paranoia.

I've done this (I had a bridle plate with an extra hole for this purpose and used a very large carabiner), but it is not the preferred way for a Bahamian moor. If the boat does a few 360s, the legs start to wrap around the bridle, which makes an awkward mess, difficult to undo if loaded. This is the reason they should be connected to the rode, as much as 6' down. The reason I like the prusik (other than being fast and secure) is that it would not break my hear to cut it if the load was too high to disconnect. A few $ worth of scrap line.

It could also be I am not visualizing your rig correctly. If the loop has some length it could be brilliant.

[thinwater]

Originally Posted by mstrebe

A screw-pin shackle? Seems rather simple to me.

Easy to drop, requires 3 hands, leaning over the bow. But it would work.

This is why I use the prusik. One hand, in the dark.

[SVNeko]

Originally Posted by mstrebe

A screw-pin shackle? Seems rather simple to me.

Sent from my iPad using Cruisers Sailing Forum

Read the thread and the question closely before you pipe up.

[belizesailor]

Originally Posted by thinwater

A soft shackle through a link is well proven. A prussic works (my favorite). Though I would use a rolling hitch for a snubber, I would not trust it for this.

What would be your concern about a rolling hitch in this scenario?

[thinwater]

Originally Posted by belizesailor

What would be your concern about a rolling hitch in this scenario?

I've used a rolling hitch for snubber many times without trouble. I'm sure it is all in my head, but it just isn't a knot I naturally trust with something this critical. It often seems unreliable when tied to another line of the same size, depending on stiffness. Like a pruisik, it works better if the knotted line is either very limp (my polyester double braid rode is not) or smaller (it is not). With a prusik I can use Dyneema, which is small and limp. When I attached a snubber, the snubber line was always smaller (for stretch).

That is all, and I could be very wrong.

[44'cruisingcat]

How I run two anchors.


Set the first normally, then at low tide walk the second one out from the stern. The stern anchor is there only to prevent the boat from drifting over the bow anchor, then maybe settling on top of it on the next low tide.

[Cheechako]

And .........be careful where you choose to use a stern anchor; in an area with strong currents or winds... it can cause the main /bow anchor to drag or pull out due to the higher loads created by the boat being broadside to current or wind. Don't ask me how I know!

[44'cruisingcat]

Our stern anchor has less holding power than the bow one, so theoretically it would be the one to drag.

[monte]

For stern anchoring we usually set the bow anchor at about 5:1, then let out another 30m of chain and reverse 30m and drop the fortress on 30m of rode, then take up 30m of chain, fit the bridle and tension the stern rode. Reverse the sequence to pull it up. This works well and we often do it instead of tying to a tree. Saves swimming or using the dinghy to drop the stern anchor. Occasionally we swim the stern anchor out, which is easy enough. Even easier if we tie a fender on to float it.
Good point about not wanting to settle on the main anchor 44, I'd probably want the stern anchor out before low tide in that case though..

[svmariane]

Originally Posted by elaak

Hey all,
For those who run two anchors, whats your preference on how to do it?

Specifically:

- How are you storing your second anchor?

Underway: Lashed to the aft rail. Chain is disconnected & man-handled into dedicated box inside lazarette.

At anchor: Lashed with a Parachute rip-cord arrangement outboard on the stbd bow pulpit, with 50 metres chain then 50 metres 1" line laid for instant deployment. All led from the anchor, outboard, then back on board through the 2nd bow roller. Bitter end secured. Pull ripcord - anchor deploys, chain/line deploys. Five year old child could handle it. Adult would calculate, then cleat off the line prior to full extension. (As/if needed.)

Reasoning: Stuff happens in high winds. Somebody else drifts down upon us, yanking out our primary anchor. (We've experienced that firsthand.) Or, the primary anchor holds just fine in winds of 50 kn, but drags when gusts hit 55 knots. And etc. Stuff happens. We prefer to be ready.

- If the secondary anchor is run from the bow, how is each anchor attached to the bridle?

Sorry. Monohull here. No bridle.

- How do you deal with avoid twist? Mitigating twist once its happened?

Twist? Don't deploy the second anchor unless/until needed. Bring anchor back aboard at first opportunity. One or two twists overnight or until situation stabilized? Don't care - I'll sort it out later.


- Any issue keeping rode out of the underwater appendages? (dagger board, rudder, etc)

That might be a multihull problem. We've not encountered that.

- Setting them

Emergency: Pull ripcord. And hope to hell she grabs.
Sensing emergency bearing down: Motor fwd & slightly aside towards clear(er) water. Drop anchor and set as if t'were the only anchor involved.

- Unsetting them

One at a time. Second anchor retrieved first.

Anyway - That's kept us off the shoals these many odd years.