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Our bareboat trip to Antigua was the first time anyone aboard had ever anchored a cruising catamaran. There was a bit of learning curve involved (the anchor dropped just forward of the mast so we had to keep the bows into the wind, the bridle needed to be set before any set checking could happen and more) but I think we got the hang of the catamaran nuances eventually.

We did have a lot of trouble getting the anchor to set the second time in Five Island Harbour. The first time we anchored we just did so as practice while waiting for our friends to pick their spot. Our helmsman had some trouble keeping the bows into the wind using the engines but the anchor set well once we were on the bridle and backing down both engines at 1800rpm gave us confidence in our set. 11' under the boat + 3' gave us 60 seconds of windlassing the chain out. (even at 1800rpm the bridle still kept it's attachment point to the chain below the waterline so I figured the bridle was enough to compensate for our freeboard.)

We went for a swim to cool off before our friends (in a monohull, more sensitive to depth and swell) chose the night's anchoring location.

We raised anchor and tried to reset where they and a few other boats were anchored on the north side of the harbor. This was a disaster. The anchor would not set. The depth was right around 15' every time we tried to set.

We tried:
  • Anchoring at least 5 times
  • Letting out all our chain (about 120' according to our briefing)
  • Backing down on the anchor
  • Not backing down on the anchor
  • Lastly: Going back to where we had set successfully and anchoring there

Our friends on the monohull confirmed that we were dragging (I was worried it was in our heads but it didn't turn out to be). Every time the anchor came up clean (no weeds or clay).

Eventually, as sunset approached 2 hours later, we gave up and moved back near where we had originally anchored on the south side of the harbour. It set and held all night but we didn't have the courage to back down on it and possibly pull it out of the bottom. I tried to dive the anchor but the visibility was bad enough it was basically dark at the bottom (the sun was low in the sky as well). It was a restless night for me.

We anchored just west of Coco Point in Barbuda. We pulled the anchor out backing down on it at 1200rpm the first time, the second time it set and held though we only backed down on it with both engines in idle reverse. That held for two nights in about 15' of water. I was able to snorkel down to it and the set looked good.

In Mamora bay it set and held the first time. I dove on the anchor, it had dug completely into the bottom. Before leaving we backed down on the anchor at 1800rpm and it held.


I hardly have extensive experience anchoring but I've never been nervous about an anchor's set; especially not when using all chain. Needless to say this troubled me the whole trip.

One potential explanation I came up with is that, because we were actively using the throttle to control the boat's orientation while setting that we wound up dropping the chain on the anchor and the tangled mess wouldn't set. I watched for this (and quick jerks in the chain once it was straight up and down that would indicate a tangle un-tangling) while we brought up the anchor but didn't notice anything suspicious.

During the day of anchoring in Five Island Harbour I thought I noticed the anchor wasn't true but I dismissed it as an optical illusion due to the way it sat in the rollers. The 5th day of our trip on a mooring in Nonsuch Bay I examined the anchor more closely and confirmed it wasn't true, the plow was bent about 10° to port where it attached to the shank. (I really should have gotten a picture of the anchor but one of the other equipment failures of this trip was my waterproof camera proved to be less than waterproof.) I am starting to think this might have been the culprit.

In soft bottoms the anchor would have tended to rotate clockwise eventually orienting itself on it's side; hardly ideal for holding. This would explain why backing down hard resulted in pulling the anchor out instead of a good set. I wanted to snorkel down to the anchor while the boat was backing down on it to observe it's motion but with as little visibility as we had this seemed unwise (nobody aboard could see me and I'd have to be really close).

On harder bottoms I expect the anchor wouldn't have dug in if it landed on the bottom on it's right side because the center of the plow wouldn't have been a point of contact.

Or perhaps we were just terribly unlucky? Anyone else have experience with bent anchors not holding? Is there something else I missed here? I'd love to put this one to bed...
 

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Had a Danforth that had a slight bend in the shaft. Never would set right.
In 15' of water with 120' of chain out considering you probably had about 5' of free board would give you a 6to1 scope all chain, sounds sufficient to me.
 

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Discussion Starter #4
Had a Danforth that had a slight bend in the shaft. Never would set right.
Thanks. That's good to know.

In 15' of water with 120' of chain out considering you probably had about 5' of free board would give you a 6to1 scope all chain, sounds sufficient to me.
The charter company suggested 4to1 which is what I've heard for all chain before.

I should mention that, at anchor, we never had more than 15 knots. It was generally around 10.
 

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Had a Danforth that had a slight bend in the shaft. Never would set right.
In 15' of water with 120' of chain out considering you probably had about 5' of free board would give you a 6to1 scope all chain, sounds sufficient to me.
+1

We had an aluminium Spade that the shank got slightly bent, it made a major difference to try to get the anchor to hold/set, replaced under warranty and problem sorted
 

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Discussion Starter #6
I really dug deep into these anchoring problems and I wanted to share my takeaways with the forums that aided me in my quest:
  • Set the bridle before you put tension on the rode when the rode is dropped from the middle of the boat
  • Keep an eye on the chain in your locker when letting it out; don’t let it all out!
  • Measure the rate that the windlass puts out chain. We were told it was 1’/second but after we measured 10 seconds of chain we calculated more like 1.5’/second
  • In addition to bearings on fixed objects, start a new GPS track just before you drop anchor so you know if you’re holding, swinging or dragging anchor
  • “All a bent anchor is good for is scrap. It cannot and will not hold properly.” – Capt. Alex Blackwell, Happy Hooking
  • When power setting with all chain, either refrain from pulling the chain bar tight when counting on the catenary (5:1 scope) or let out more scope (7:1) when setting with bar tight chain.
  • Aim to start making sternway, dead slow, just as your anchor touches the bottom taking the windlasses speed into account. Err on the side of being moving when it takes the bottom so it doesn’t get tangled in the chain (hat tip to Ozsailor)
  • Limit yourself to three anchoring attempts in one place, especially if you know of somewhere nearby that you’ve had better holding before.
  • I have kindle books downloaded to your phone always with me; they have lots of anchoring information. USE THEM FOOL!

There some detail about how I reached these conclusions and some additional nuances here: Quixotic Catamaran Anchoring I figured it best not to post the entire 10+ page exposition.
 

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See the book 'How To Anchor Safely - So You Sleep Well!' Most anchoring advice is the length of a short article, rather than a comprehensive look at the subject only a full size book can provide.
 

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The old anchors depended more on weight than shape. The new anchors (scoop type) work on very carefully worked out engineering principles. A bent anchor (plow, fluke or scoop) will never hold properly. It will always roll out. We've written extensively on anchors and anchoring. There are a few articles on our website cruising.coastalboating.net/Seamanship/Anchoring/index.html based on our book "Happy Hooking. The Art of Anchoring".

Out of curiosity, I don't see that you mention the type of anchor except that it was a plow. Did you happen to notice what make it was?
 

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In soft bottoms and with plow-type anchors (not the 'danforth types) one usually must WAIT for the anchor to settle down though muck and slime by its own weight, sometimes waiting for up to 1/2 hour, before pulling strain on the rode. This is important especially when using the 'weighted tip' plow type anchors.
 

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Guys without knowing what kind of anchor he was using, we're just guessing here. From the instructions he was given it sounds like a Danforth or a Fortress style. They are wonderful anchors (I own 3 Fortress anchors) in sand but are too light to punch through seagrass.
 
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