Twin Anchors at the Bow

[Gludy]

Why is having a pair of anchors at the bow so popular in other countries eg USA but not used over here?

At what angle to each other are they deployed?

Surely as you turn with the tide a pair of anchors can get into a fair mess?

 

[Pinnacle]

The big Nordhaven at Hamble point has two ENORMOUS ones fitted into a truly massive ss fabricated protection plate. They look the biz, but I too wondered if they were intended for simultaneous deployment, or if one was a back-up for the other? /forums/images/graemlins/confused.gif

 

[Gludy]

Deploying two anchors is apparantlyy called the 'Bahamian' technique but i do not understand the logic - if the tide turns surely it would get into a mess?

Here is a link explaining the technique
Click here

 

[Pinnacle]

Quite.......

 

[jfm]

I agree, it must be mess if/when tide/wind turns. But seems sensible only to deploy 2 anchors if really needed, and in that case you'd be on anchor watch and could weigh anchors if big windshift, and redeploy.

Lots of boats have 2 anchors (eg all Ferretti above 70 feet or so) but that's more of a back up in case equipment failure. Not to set two anchors every time you stop for a swim. I'd love a 2 anchor set up - would feel like a "proper" boat

On the question of angle, it depends what you are trying to achieve. If you want to achieve max holding in a very strong wind/tide, then as a matter of geometry, the angle should be as small as possible so the anchors are just not fouling each other. The greater the angle, the greater the tension on each anchor for any given wind/tide load on the boat, and hence the earlier you reach the point at which anchor fails. So something close to zero degrees. In reality, I'd put the anchors about 3 metres apart if expect a force 12. But I bet lots of salty dog sailors write 30 degrees and other old-wives-tale nonsense on this subject

But if you just want to stop the boat pendulum-swinging around the anchor then you should space them wide apart. 180 degrees apart in theory gives minimum swinging but 90deg would be pretty good.

 

[Gludy]

The marlows hjave two anchors so i thought I shouldm find out why before just accepting them.

Which two anchor types are best to go for including the new styles?

 

[jfm]

I edited and added a bit more above. I think the Delta shape are the biz. Those bruce types just dont look right for weedy bottoms, whereas the Delta point cuts through a weed carpet. Though this is a bit unscientific gut instinct ... others may know better

 

[Gludy]

But the idea is two have two types and thus a choice.

 

[jfm]

Also, 2 anchors is very handy for med mooring. helps keep a stern to boat striaght in an either-way cross wind if the 2 anchors are deployed 30deg apart or whatever. And if you use divers to weigh anchor (like in monaco) you can get them to lift the leeward (slack) anchor first and then you hold position all very tidily.

 

[jfm]

I'd have two the same, two Deltas!

In fact I've never noticed twin anchor boats having different anchors. Most use the same each side. mirabella has a big one and a small one (relatively) but most are perfectly matched i think.

Looks tidier too

 

[Gludy]

[ QUOTE ]
And if you use divers to weigh anchor (like in monaco)

[/ QUOTE ]

Tell me more?? I have never heard of that.

 

[jfm]

Just typed expl and it crashed, urgh- will do tomorrow, gotta run now for a train

 

[Medskipper]

My brother has been sailing the med waters for the last ten years, summer months are always at anchor and as the med can blow up quite badly at times he has often used the two anchor method described. Sometimes sitting up on anchor watch for 48 hours at a time! he swears by this type of anchoring and says it has saved his vessel from being washed up on a beach or even rocks on numerous occasions.
When in this situation he also will take the strain off the anchors by just having the engine ticking over in gear.

Not sure if this is a practical method with a tide that rises and falls as much as our coasts though!

Barry

By the way, did they take back your Trader in the end? sorry I have not kept up with your woes.

 

[Gludy]

Yes they took her back BUT I still have the £140k plus to come and another £50k in post dated cheques. There is another story building for the manner in which the agreement we reached is being executed and I am on the point of pressing the publicity buttons again. So its not all over yet!

 

[jfm]

In many med ports boats use ground lines not anchors at the bow, but in Port of Monaco and St Trop they use anchors. Monaco has ground lines even for the biggest boats, but they're flimsy and superyachts use anchors.

When I say "groundline" I mean a rope tied to a concrete block on the seabed, and the free end is tied to the moored boat's bow, so holding the bow when the boat is berthed in stern-to

When leaving monaco berths the big boats do not cast off at the stern and weigh anchor using their own windlass. The place is too busy to have boats swinging around doing that.

Instead, the bow is made temporarily secure using one of the groundlines (which a diver retrieves from the seabed, and hands to the crew). Then the diver attahces an airbag to the anchor and lifts it clear of the seabed. Then the crew wind in the anchor with the boat's windlass. Then the anchors are fully stowed before the boat casts off and leaves its berth

Often anchors get tangled. If another anchor chain is crossed over the chain of the boat that is trying to leave port, the diver attachs an airbag to the crossing chain and lifts it a few metres above sea bed. Then he attaches another airbag to the anchor of the boat that wants to leave port, then the crew wind the windlass,and the anchor is threaded under the crossing chain.

All pretty intricate stuff. I have been thru this process on board Mirabella5 a few times, including the crossed chain scenario. Her anchors are 600kg and 400kg, so big airbags. It is quite a palava and can take nearly an hour. Costs money too - the divers do ok!

 

[Deleted User YDKXO]

I changed the hook on my current boat from a Bruce to a Delta because the Bruce dragged regularly on weedy bottoms. The Delta is much better but Mr Rocna will be along in a minute to tell us that his hook is better still
The Bruce looks like a good anchor for mud and clay so maybe it's still the way to go for Gludy depending on where he plans to cruise. Praps with a 2 anchor set up, you could have one of each?
Personally I don't really understand the 2 anchor system. I think I'd rather have one monster feck off anchor with some heavy chain and an over powered windlass
I did try the 2 anchor system on a mobo that we once chartered in the BVI and it certainly seems to reduce swing but it's a bit of a pita to use and would be a nightmare IMHO in areas where the tide/wind changes regularly. OK in the Windies where you get prevailing winds from one direction mainly but not the UK

 

[Salty John]

This article explains the options: http://www.saltyjohn.co.uk/resources/haphook.pdf
Written for raggies, but the same principles apply.
The Bahamian moor is for anchoring where there are reversing currents; the boat lies first to one anchor and, when the current reverses, lies to the other anchor. In the Bahamas this situation often prevails so I suppose that's why this system was develpoed there. I've used it many, many times with great success.
In heavy weather I like two anchors off the bow about 50 degrees apart because it cuts yawing and feels very secure because of the redundancy.
One good anchor of the right size on all chain should be secure in most conditions if set right.

 

[benjenbav]

It's worth mentioning that not everywhere had the same pattern of semi-diurnal tides as the UK. In the UK I think it would be more trouble than it's worth to bahamian moor because of the twisting every time the tide changed - unless you have plenty of crew to row out and reset at least one anchor every tide.

 

[Gludy]

Thanks jfm - fascinating.

 

[jfm]

Ah, I even have a picture. This is Mirabella5's anchor that was laid out to the port side being brought in, in Port of Monaco. It's hanging from that airbag, while M5's crew wind it in on the windlass. The diver is under the water, and his support boat is the small boat whizzing around in the background. M5 is firmly engines-off still on her berth at this point, held by stern lines, and temporary ground lines for the bow

I took that photo just after the Monaco yacht show, 24/9/06. Maltese Falcon had left 20 minutes before, was berthed port side of M5. This was the day the two yachts had a bit of a "race", and despite the calm looking water in the pic the wind was really strong in the afternoon and M5 broke her speed record at 18.5kts. Also on the same sail the discovery channel chopper shot the video that was on TV, and these videos (stored on marian's website) were taken

http://www.bymnews.com/photos/thumbnails.php?album=314