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Old 15-07-2017, 03:41   #1
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Multihull Anchoring Techniques - Ingenious or Ridiculous

Wondering if any multi hull owners, especially tri owners, have used multiple anchors to protect them in various situations.

Personally, I have used a bow anchor on chain along with a heavy anchor on a line aft to secure my trimaran and to keep the stern from drifting into a shallow reef during a wind or tide change. I carried the aft anchor out on a dinghy and ran the anchor line through an eye on the starboard side, a solution which worked in the conditions I faced - changing winds of up to 20 knots and reversing tides in a steep-sided channel.

Though this solution worked, I can imagine potential downside to such an arrangement. What think ye of such an arrangement, and has anyone else experimented with or successfully used multi-anchor solutions on their multihull? If so, when, why, where, and what was the outcome.?

Thanks,

G2L
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Old 15-07-2017, 06:05   #2
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Re: Multihull Anchoring Techniques - Ingenious or Ridiculous

Mark Johnson anchoring book goes into a lot of detail regarding such. Kindle version too.
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Old 16-07-2017, 11:08   #3
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Re: Multihull Anchoring Techniques - Ingenious or Ridiculous

If it holds a boat well without obstructing others or causing harm and is fairly easy to retrieve after the unusual conditions have passed, any system has my respect. I created an unconventional anchoring system - with great success - to secure a catamaran during a hurricane. It may have been more than necessary but that question only came up once the storm left the area with the boat completely unscathed.
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Old 21-07-2017, 05:18   #4
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Thanks folks- Re: Multihull Anchoring Techniques - Ingenious or Ridiculous

Thanks, you guys for your input. Much appreciated.

G2L
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Old 21-07-2017, 13:29   #5
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Re: Multihull Anchoring Techniques - Ingenious or Ridiculous

Yes. I like the options that multiple anchors opens up. Add the limited swing of multiple anchors plus shoal draft and it opens up a lot of options.

On cats Ive used two off the bow, bahamian moor, tandem, and fore and aft.

There are threads here discussing multiple anchor use...on which many have stated their religious opposition to such.
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Old 21-07-2017, 13:47   #6
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Re: Multihull Anchoring Techniques - Ingenious or Ridiculous

Used fore and aft to anchor here (star on map)...what an awesome spot...just behind the reef, minimal swing room, great snorkeling a few boat lengths away, shallow enough to stand up...wade to the beach...no one is going to anchor on top of you either.

BTW, the place name is wrong on Bing...its not Narganá, but it is in the San Blas.
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Old 21-07-2017, 19:02   #7
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Re: Multihull Anchoring Techniques - Ingenious or Ridiculous

Ditto on the Bahamian moor.

It's a lot easier with rope rodes. I learned of a special knot in Multihulls Magazine years ago that secures the two rodes together and you can then use the two tails to make the legs of the bridle.
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Old 21-07-2017, 19:57   #8
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Re: Multihull Anchoring Techniques - Ingenious or Ridiculous

Quote:
Originally Posted by ggray View Post
Ditto on the Bahamian moor.

It's a lot easier with rope rodes. I learned of a special knot in Multihulls Magazine years ago that secures the two rodes together and you can then use the two tails to make the legs of the bridle.
Oh goody, more knots! Care to share how to tie it?
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Old 21-07-2017, 23:57   #9
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Re: Multihull Anchoring Techniques - Ingenious or Ridiculous

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Originally Posted by Gone2long View Post
Personally, I have used a bow anchor on chain along with a heavy anchor on a line aft to secure my trimaran and to keep the stern from drifting into a shallow reef during a wind or tide change. I carried the aft anchor out on a dinghy and ran the anchor line through an eye on the starboard side, a solution which worked in the conditions I faced - changing winds of up to 20 knots and reversing tides in a steep-sided channel.
In an anchorage with limited swinging, the options are:

1. Bow and stern anchor
2. Bahamian moor
3. A single anchor on a short scope
4. A single anchor with the stern tied to shore (as a variation you can lead the shore line to the bow)

There are some variations on the above, where multiple anchors are used.

There is no perfect answer and all options can be useful at times, depending on the situation. Personally, I find with an oversized main anchor that has good short scope performance, I find myself most commonly using option 3 or 4 when presented with an anchorage that has limited swinging room, but there are a lot of different situations so it pays to consider all the alternatives rather than becoming wedded to one or two techniques.

What you have described is 1. Although it sounds like you attached the "stern anchor" closer to the bow, which does allow some weathercocking.

Bow and stern anchors (1.) is the simplest way to set out multiple anchors used to reduce swing. It has the drawback that with a crosswind component the vessel is not free to rotate into the wind. Boats have a much higher drag coefficient with wind from the side rather than ahead, so the force on the anchors can become quite high.

This does not mean I would not use this technique, but it does need some care if there is risk of any significant side wind component. The slightly more complicated Bahamian moor is sometimes a better choice although there can be some twisting of the two rodes.

Using two anchors in either the manner you describe or with a Bahamian moor to reduce swing also has the drawback that both anchors must hold. If one anchor fails the boat can get into trouble. This doubles the chance of failure even if you have two good quality anchors (unlike the situation where an extra anchor is deployed as back up). Often boats only have one modern anchor so they are relying on an second tier anchor to hold when using these techniques.

The other drawback to consider is that you will swing differently to other boats that are only using a single anchor.
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Old 22-07-2017, 06:45   #10
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Re: Multihull Anchoring Techniques - Ingenious or Ridiculous

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Oh goody, more knots! Care to share how to tie it?
Ive used bowline-in-a-bight for this purpose.
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Old 23-07-2017, 06:37   #11
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Re: Multihull Anchoring Techniques - Ingenious or Ridiculous

I'll look tomorrow for a drawing I made of it, but I can describe it here.

Its principle is that of a bowline, so like a bowline , the lines can't have tension using the process so this needs to be done quickly.

You need a short piece of line, maybe 3 feet, that is larger (say, 1 1/2 times the diameter of each of your rodes, or even bigger if you want). I like to use braided line.

Take the two rodes coming from the anchors in one hand, and make a loop of both lines together as in making a bowline.

Then take your short piece on line, and be like the rabbit coming out of the hole, around the tree and back in the hole.

Then you take the other end of the short line, go around the two ends (that you can consider the tap root of the tree, and will become the legs of the bridle) and come back up through the same hole.

Snug it up and you are done. The unfortunate thing is it's a pain to make adjustments

I have made my bridle of two lines tied with this knot. One end has a chain hook on it, the other just a bare tail that should I want to use both anchors (done very infrequently now that I no longer have two anchors with rope rodes) it can be tied to the rope with a rolling hitch, or if in the unlikely event I had to use only the anchor with the rope rode.

I'm sorry I don't remember the name of the person to give credit for this knot.
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Old 23-07-2017, 07:46   #12
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Re: Multihull Anchoring Techniques - Ingenious or Ridiculous

Nice in theory but a PITA to set and retrieve two bow anchors from a multi unless well and truly rigged for it - and most ain't.
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Old 23-07-2017, 08:07   #13
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Re: Multihull Anchoring Techniques - Ingenious or Ridiculous

You are right, that a bridle must be used on a multi makes it a PITA for two anchors off the bow. But on a bridle, she is rock steady, so that justifies some effort.

If you know a way to well and truly rig for two bow anchors that's not a PITA, I'm all ears.
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Old 23-07-2017, 09:23   #14
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Re: Multihull Anchoring Techniques - Ingenious or Ridiculous

True, most production cats are not rigged for two anchors on the bow. I added a second bow roller to mine. Only the primary has a fair lead to the windlass, but my secondary is a Fortress on a combination rode so not hard to handle by hand. I also added a second large cleat so now both have a nice big cleat properly aligned with the rode.
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Old 23-07-2017, 11:02   #15
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Re: Multihull Anchoring Techniques - Ingenious or Ridiculous

I believe I misunderstood Nekos point to think he had a scheme to easily RIG two bow anchors to a bridle, not to launch the anchors.

I have no problem launching them as I added a second anchor roller, and a manual windlass for it.

Figured that was better than back surgery. No point in having a second anchor if you can't or aren't inclined to use it.
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