Anchoring confidently is always a challenge on a charter boat. You’re dealing with ground tackle that you haven’t selected, setup or tested. Add the complications of being new to catamarans and unfamiliar with chain rode and we had an unfailing recipe for drama. That said we anchored four of our eight nights in Antigua and, once we managed to get our anchor to set, we had no issues with dragging or swinging. Successful in hindsight but we certainly would up dealing with more drama and uncertainty than I had anticipated.
Once I got back to high speed internet I consulted SailNet and Sailing Anarchy to try to get to the bottom of the trouble we had. Here is a copy of that post, slightly edited for clarity (if you’ve found your way here via one of those posts, skip to the next section):
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 the helmsman could stop actively orienting the boat) 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 its 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.
- 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 with no weeds, clay or shells.
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 successfully dove on the anchor for the first time, it had dug completely into the bottom and was under the sand. 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 after power setting; 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 an illusion, the plow was bent about 10° to port where it attached to the shank. (I got 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 starboard 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 its 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…
One thing that I forgot to mention in my post is that the anchor was a delta. The boat specs list it as 45lbs but it seemed really light for 45lbs.
Here is what a few hours of not getting your anchor to set looks like as a GPS track:
Scope Schools of Thought
The forums disagreed on whether we had sufficient rode for the depth:
- 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.
- I carry 300′ of chain. Doubt 120′ is enough. In 18′ of water I would have at least 140′ overnight.
This and doubts about how much throttle to use to power set the anchor sent me down the anchoring rabbit hole, re-reading the anchoring sections of my favorite sailing books and seeking out additional resources.
More scope is better, there is no debate about that and plenty of research backing it up. On the other hand these days there is an old school and new school philosophy when using all chain rode. The old school says that, because of the catenary you need less scope when using all chain. The new school argues that a well set anchor in high wind conditions will remove the catenary, making the chain “bar tight”, meaning the angle of pull will be determined solely by the scope used. Accordingly, the old school suggests less scope with chain rode than with rope rode while the new school insists that ultimately the same scope should be used for chain and rope.
For anchoring in heavy conditions I wholeheartedly buy into the new school. I’ve seen enough pictures from anchor tests to know that chain rodes can be pulled bar tight by modern anchors. In normal conditions, however, in a crowded anchorage in it makes sense to take the catenary into account when dropping the hook. It also makes sense to anchor so that you swing similarly to nearby boats which usually means utilizing similar scope.
I got a few replies on SailNet that confirmed our experience that slightly bent anchors are troublesome to set:
- Had a Danforth that had a slight bend in the shaft. Never would set right.
- 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
I found these posts reassuring but I still wanted to go deeper, to get to the heart of this issue. I reached out to Capt. Alex Blackwell, the author of Happy Hooking; I was very excited when I received a prompt reply! Capt. Alex put the matter to bed in no uncertain terms:
All a bent anchor is good for is scrap. It cannot and will not hold properly.
Power Setting/Checking your Set
When it comes to Power Setting, different books recommend different ways to power set and use the engine to check your anchor’s set. It runs the gamut from vague to conflicting:
- “pay out a 5 to 1 scope, dig the anchor in well by putting the engine into reverse, and then shorten the scope to 3 to 1.” – John Vigor, The Seaworthy Offshore Sailboat
- “Now make sure the anchor is securely set by carefully backing your boat gently under power. Applying too much power may simply pull the anchor out. A good anchor will go deep at this time and keep your boat securely hooked.” – Capt. Alex Blackwell, Happy Hooking
- “We leave the boat in dead slow astern for a minute or so to allow the anchor to fully settle. Then Evans gently increases reverse until we reach half throttle. If the boat still doesn’t move, the anchor is set and can withstand winds of gale force.” – Beth Leonard, The Voyager’s Handbook
- “I believe the most important use of an auxiliary engine is to try to drag the yacht astern at full throttle to check that the holding ground, anchor, shackles, chain, line, bow roller, anchor spring and windlass are doing their job.” – Hal Roth, How to Sail Around the World
This hardly settles the matter. My experience anchoring comes predominantly from boats without windlasses that have a bit of chain at the anchor end and a the rest rope rode and without a working tachometer. We usually test the anchor in reverse with the throttle up to the level that sounds like cruising RPMs, I’d estimate around 2000RPM. We use 7:1 scope and while setting you can see the highly tensioned rode slice through the water if the boat is pitching at all. The stretch in the rode makes it easy to see if the anchor breaks free, the tension disappears instantly. If that happens we move a bit and try again with a bit more line out.
The biggest difference between anchoring our chartered catamaran with all chain and the monohulls we’re used to is the way you handle the boat as you let out the rode. On the monohull you put her in neutral, drift to a stop and drop the anchor off the bow. You then let the boat drift backwards; naturally the bow will drift off the wind. To start the anchor digging in you snub the rode which puts tension on the rode and pulls the bow back into the wind. Then you let out more rode, snubbing as necessary to keep the boat mostly pointed into the wind until you’ve let out appropriate scope. Finally you check your set by motoring in reverse. Only at this point would you worry about a snubber or bridle were your rode all chain.
On the catamaran the anchor was dropped from right in front of the mast; once the necessary scope was let out the bridle was hooked to the chain and more chain was let out to allow the boat to lie to the bridle. This necessitated keeping the hulls pointed into the wind using power while we “drifted” back until the bridle was set.
We did try to snub once when the boat was perfectly aligned with the rode before the bridle was attached. The chain clearly loaded up and seemed to be holding but the boat quickly swung out of alignment and the chain headed toward the starboard hull so we quickly let out more chain and motored forward a touch to save the bottom paint. After this one attempt we learned not to take up tension on the rode until the bridle was set.
With the helmsman focusing on the boat’s alignment to the wind and using the windlass to let out the chain it was difficult to make sure we were paying out the rode along the bottom at the right rate. The inability to snub the rode as it went out made anchoring an all or nothing affair; before we could check if anything was holding everything had to be set with the boat lying to the bridle. We didn’t have the option of letting out more scope after we set the bridle; we had to decide how much rode to put out before we checked our holding. So we had to get everything setup like this before we started taking bearings, watching the behavior of the ground tackle at the surface and the GPS:
The main difficulty was that, whether we were dragging or set, the weight of the chain between the windlass and bridle attachment point (let’s call this “lazy chain”) would cause the bridle to swing back and forth between 45° and straight up and down quite regularly. With this gentle swinging motion it was difficult to tell if the boat was sailing up to the bridle, losing tension and then drifting back or if the boat was taking up tension on the anchor, pulling it free and then the weight of the “lazy chain” dragging it further along the bottom. It was difficult to put your hand on the bridle to feel for vibrations and it was impossible to reach the chain. I observed this bridle swing when I was sure we were dragging as well as when we weren’t (after more than 24 hours anchored in the same place).
The bridle’s swing being so difficult to read it made checking the set by backing under power almost imperative. With some reverse the bridle angle brought the chain attachment point near enough to the surface to be seen. You could observe the bridle under tension slicing through the water. If the anchor broke free the “lazy chain” induced swinging would resume. Then we’d pick up the assembly and try again.
Anchoring off Coco point in Barbuda I couldn’t tell if the anchor had set due to the bridle swing and some swell. Our first power set at 1200RPMs broke free while the second, in idle reverse, held. In Mamora Bay we power set at 1200RPMs which held. This was the first time I was able to closely inspect the anchor on the bottom and the set looked very good, the whole plow was buried, only the shank was visible. The “lazy chain” induced swing was ever present in all three anchoring spots.
Back(ing) Aboard our Catamaran
In Antigua, experiencing at most 17 knots at anchor catenary was always a factor once the anchor was set. On the other hand, when we were setting the anchor with both engines in reverse we might have pulled most of the catenary out (as I mentioned the visibility was very poor so it was hard to tell). I believe we underestimated the power of the catamaran’s dual engine and dual prop setup which lead us to pull the rode bar tight and the anchor free when we tried to power set with only 5:1 scope. When we were power setting we were using “old school” scope in “new school” conditions which held half the time and pulled out half the time.
Furthermore, this West Marine anchor test suggests that our Delta anchor was very sensitive to scope.
Next time if a power set fails at 5:1 scope the second time we try it will be with 7:1 scope or better.
Five Island Frustration:
I still believe that the bend in the anchor shaft to plow connection combined with a soft bottom caused our setting problems. Everyone who weighed in seemed to agree that a bent anchor would have difficultly setting and holding.
We drug anchor with all 120’ of chain out without backing down at all. Twice. Instead of digging in deeper the anchor must have spun onto its side and drug along if it didn’t set in the first anchor length or so.
Unfortunately that will have to remain a hypothesis. I wish the visibility was better or the water was shallower so I could have swum down and verified for myself but that didn’t work out. Or that I had thought to take the anchor ashore and try it from a beach near the problem anchoring area. The strongest statement I will make is that none of my research into anchoring calls this hypothesis into question.
There are some things we definitely got right immediately or learned very quickly:
- 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
Some things that I learned once I got back to reliable internet access:
Lessons Learned Later
- “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!