An anchors holding power is based on two things. One, its ability to dig into various bottoms, and two, the surface area that is in contact with that bottom thus transferring the load over a greater area. One anchor is likely to not be optimal in all bottoms and all conditions. I now carry 3 anchors on board. I have a 22lb danforth buried in the aft locker, a Fortress-FX23 as a second anchor, and a Rocna 25 (55lbs) that I use as my primary anchor on my 42' sloop.
Please remember that my explanations here are based primarily on my opinion and experiences and that I am not writing for any anchor company. Also, I make no guarantees that I know everything or that this article is the sum total of what you need to know to anchor well. Read, read, read some more, talk with experienced cruisers, and experiment yourself. Above all don't skimp on the equipment and over time you will be able to sleep better at night.
My 35lb Delta anchor has failed to dig in for me on some bottoms, primarily really hard bottoms and really soft bottoms. It has been a good anchor for this lake and I have used it on the last two boats for about 15 years. A couple weeks ago, my boat swung in a sudden wind shift and the Delta did not reset and I had to ride to the boat at top speed in my tender to rescue it before it drifted onto the rocks. This was not necessarily the fault of the anchor. I could have anchored farther from shore in an area that was more exposed but had more room for the anchor to reset and possibly better bottom conditions. It is hard to say what the cause was.
I began researching new anchors rather than waiting for my cruising lifestyle to require me to get a bigger hook. My anchor was also just big enough for my boat, and was not over sized which often helps them hold more due to the increased weight and the surface area that bigger hooks provide.
I came down to two choices, one was the Rocna 25 (55lbs) which was significantly heavier than my current anchor and the other was an outsider called the Mantus which has some very interesting videos which demonstrate its superior setting ability according to the manufacturer. The Rocna was recommended by many liveaboards who own the same boat as me and I ended up choosing it because of those recommendations. The Mantus is untested by most consumer groups so far and also recommended a 65lb anchor which had a longer shank that was likely to make it hard to fit on my bow. I haven't used it so I have no opinion on it.
The big test was when a storm front went through and I experienced winds in the 40s. The Rocna held. A boat with a Bruce did not, and one with a Delta did not while another with a Delta held just fine. The bottom was very deep mud. I loaned my Fortress, which doesn't have any chain, to a 37' boat whose Delta had failed to hold while trying to originally set it and the Fortress didn't budge despite the boat putting the rail in the water as it sailed back and forth in the storm. I believe soft mud needs surface area like Danforth designs have so I expected the Fortress to hold well. There were other circumstances that made this an unscientific test. One of the Deltas had limited chain, and the Bruce was on a limited scope when compared to me, so you see that how you set the anchor and the entire system is part of the equation more so than just buying a good hook and everything will be anchoring heaven.
My opinions:
1. Use chain if you can with a nylon snubber to reduce the shock loads. Chain forms a cantenary which causes the pull on the anchor to be horizontal to the bottom or even downward. The more the better. I will switch from 80' to 300' of all chain rode before leaving Lake Champlain with its ideal bottom conditions. However, once the wind blows hard, the chain straightens out and does little good.
2. More scope is better when hanging on the hook or setting it. A 5 to 1 scope (including the distance from the bow to the bottom) is what is usually recommended as a minimum. Up to 10 to one or above in a storm, and less may work in a very protected area. For years I had 50' of chain with 200' of nylon on a Delta and did just fine. I could lift the 5/16" chain and the light anchor that was on my 30' sailboat without a winch. I could set on a long rode and pull up to the chain in a tight anchorage if it was protected. Bigger is better so if you can go up one size and still handle the tackle, consider it.
3. Set the anchor. Not with your hands and back Danforth owners! Tie it to the boat and back down with lots of power while you rest your hand on the line. I use 2000 rpms and I know I have exerted as much force as most wind conditions will so I can rest more easily. It doesn't hurt to leave it in reverse for a couple minutes at those higher rpms to let the anchor settle in. If the line jumps or moves and fails to stop your backward momentum then it isn't digging in and you will have to try again in a different spot. Take a bearing on nearby shoreline to determine where you left the hook. I mark the spot I dropped the hook on the GPS for an estimate of how much line I have out and to tell if I have drifted.
4. Waves are probably worse than wind. The sudden shock loads that a boat can apply to its ground tackle when it is sideways to the wind in wavy conditions are considerable. Look for protection in an anchorage with enough room to reset if the wind switches unexpectedly.
5. Have a plan for what to do if there is a sudden problem. I have buoyed an anchor as someone dragged toward me in the middle of the night and left it in order to anchor on my secondary. I have bugged out at 3AM in a sudden wind shift with 30+ knot winds and rain in seas that quickly built to 4' or more. Have your boat ready to leave when you go to bed. I pull up the outboard on the dinghy but leave it tied on well. I put the ladder away and make sure the boat is ship shape before sleeping. I have clothing ready to put on when I go to bed. I use a GPS with an anchor alarm that tells me if the boat has swung or dragged. If it swings, I restart the engine and reset it.
6. I personally do not use two anchors at a time as they always end up twisted which can make picking them up in an emergency a mess. I do carry more than one type and like the light weight aluminum Fortress anchor as I can deploy it over the bow with a mostly rope rode by hand. An anchor design is a trade-off, there are good ones, but no perfect ones.
7. I only use an anchor float in rocky conditions where I fear not being able to get the anchor out. By the way, I break the anchor out with my boat on the shortest scope possible, not my back. I digress, anchor floats can get hooked on your prop in a wind shift. Someone else can get hooked on them, and they limit the number of boats that can fit in an anchorage. Under some conditions it is difficult to tell where a boat's anchor is; if this is the case, hail the boat anchoring near you and inform them of it if they do not have it marked. I have a new product I use that can be disconnected and has not rope, only an elastomeric rubber band. The elastather works well. I added a snap hook to it to let it down to the bottom before bed so it doesn't hook your boat if you spin.
8. I consider rafting to be primarily for calm conditions in protected waters where I can swing on one hook, or tie to shore with several hooks out.
9. If you are having trouble with communications get some two way anchoring headsets.
10. The first person with the anchor down has the rights. They can tell you to move if they feel you are too close and if you anchor with too much scope or bump into them at night, it is your fault. Additionally you can not anchor on a 15 to 1 scope when everyone around you has a 5 to one chain rode. If you don't like how the rest of the fleet is anchored, move to a new location away from them.
11. If you come in late, do not motor up to the front of the fleet and anchor where the real estate has already been taken. Try an alarm clock and get up and leave earlier if you want the best spot.
12. Be respectful. Once the hook is down, neither you nor your music should be heard on the other boats in the anchorage. Go below if you are loud. Just like your car in high school, no one is impressed with your stereo as much as you are!
Read and learn! There are many good books. It only took a simple google search to find this link. I have not read this particular book.
Nothing in this article represents my acceptance of liability for your anchoring. These are my opinions and are not intended to train you to anchor or tell you the best way to anchor.
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