'Til the butter melts

Pursuing the cruising dream in 32' of sailing ketch

The Art and Science of Anchoring

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(Note: This is what we call a “technical” post. If you think discussions of gear and techniques that are directly applicable to sailing and cruising are “Deadly Boring”, you might want to move on to one of my normal, funny offerings. Really, I won’t be offended.)
In this post, I’m going to outline my patented, never fail system for choosing anchoring gear, selecting a location, and setting your anchor for a secure night or an extended stay. Ready?

Just kidding. There’s no such thing.

But if there were, and if I had it, I could make a killing. Wherever two or more cruising boats gather, the talk will – eventually – turn to the subject of anchors and anchoring, and the opinions will sometimes be as diverse and contradictory as the subjects of an election cycle. 

Well, maybe not THAT contradictory, but I promise there will be strongly held yet conflicting opinions and methods. 


Take this boat, for example. These poor guys have been having a hell of a time the last 48 hours, having anchored, dragged, re-anchored and even moved to a marina for the night (see the blown fender hanging at the side? Likely a victim of a dock bash during the night) before returning to the area where we rode out the storm without moving an inch. And at that they had to try to anchor three times before it held…

If it holds…
So what can you do to increase the odds of staying put? There are some basics that I’ve learned from reading and experimenting, but before I do that, let’s look at the picture above more carefully. I see (or saw) three things straight away that could be done better, and those deal with Scope, Shock, and Windage.
Scope: Scope is the length of rode (chain or rope or both) deployed. The more scope out, the more likely your anchor is to catch and hold well. Recommendations for scope are given as a ratio between the depth from bow to the bottom and the amount of rode deployed, with 3:1 is a minimum for chain rode. 5:1 is better, and 7:1 is reasonable for a gale of 40 knot winds. But more than a minimum is better, always.

But in the case of this boat, we watched them let the anchor out the first time they tried this morning. One fellow at the bow was holding the anchor chain with the anchor dragging in the water, probably 5 or 6 feet down. When they’d picked their spot, he released the chain he was holding, and the chain ran out for maybe 20 feet before it stopped. Since we’re here in 12-15 feet of water, and the distance from the surface of the water to their bow is close to 4 feet, that means they have – at the most – a scope ratio of 2:1. Not even enough to stop for lunch, much less for the night.

Shock: Boats move at anchor. Some even sail back and forth, tugging at the anchor at the end of each swing, and the boat pictured above is a sailer. The problem with that is that chain doesn’t stretch – not even a little. As soon as the chain comes taught, there’s an enormous shock as 14000 pounds of boat is suddenly denied its freedom of motion.

The answer to that problem is a snubber (described below) or – as we’re using right now – a combination of chain and nylon line in your anchor rode. For the last two days we’ve been riding to 75 feet of heavy (⅜”) chain plus 35 feet of ⅝” nylon line. Now nylon is wonderfully stretchy, as much as 20%, so on the occasions when Sionna decides to swing, that line acts like a shock absorber, easing the load onto the anchor progressively and spreading the load over time. The anchor is therefore much more likely to stay put.

And what’s a “snubber”? Simply a short (15-20 feet) length of nylon line with a hook on one end. The hook gets attached to the chain, the end of the line is attached to the boat, and enough chain is let out so that the nylon line is taking the load, with the excess of chain loose in the middle. 

Windage: The wind is a powerful force – a force to be reckoned with. And the stronger it blows, the greater the force it can exert. Not only that, but it’s power increases at twice its speed, meaning that if the wind speed doubles, the force it exerts is multiplied by four. In situations where you expect strong winds, therefore, it’s very important to reduce your windage as much as you can. Look at the picture again:


They removed the main sail – that was a good idea, as sails can create a lot of drag, but see the dinghy? It’s hanging from the stern like a glorified wind scoop – the worst possible position from a windage standpoint. Laying flat on deck, yes, or even trailing in the water behind, but this…

So aboard Sionna (I’ll stop picking on our neighbors now) we have a list of things we do to reduce windage, reduce shock loading, and maximize the holding power of our anchor when we’re expecting significant winds at anchor, but it began long before, when we were choosing the anchoring equipment we have aboard. 

You see, when it comes to anchors, heavier is always better, up to the point when the crew is not able to handle the weight. Same for the chain attached to it – so we chose a 35# anchor (slightly over-sized according to the books) and ⅜” chain – one size larger than normal. To that we attached ⅝” nylon line, again slightly over-sized, but also easier to handle than a finer line.  

The business end of the 35# CQR anchor


Chain and snubber deployed. The snubber takes the load while the chain acts as a backup.
What else? Anything on deck that might come loose, or which presents a significant amount of resistance to the wind. This includes our stays’l (which is stored in a bag on deck when not in use), the sun awning, the sailing rig for the dinghy, fenders, BBQ grill, throwable life ring…

Dinghy sail and mast on the starboard side deck.


Sun awning on the port side deck.
Stays’l (Stay Sail) on the port side deck forward.
BBQ grill (green) and the fenders (blue opposite, usually there are three tied there).
Throwable life ring (“Lifesling”) in it’s bag.

And finally there are the sails themselves. These enormous pieces of cloth can become dangerous should they begin to catch the wind. In a minor blow (say, less than 40 knots) we take lengths of spare line and snugly wrap them, inside their covers.
Wrapped sails in preparation for Tropical Storm Hermine.
We also tie a heavy line around the rolling head sail to be sure it doesn’t decide to unroll – something that has frequently resulted (on other boats) in loss of the whole mast.  
And for stronger winds? Or even a hurricane? The sails come off entirely and are stowed below, along with everything else previously mentioned. Yes, a storm-prepped sailboat is a mite cozy below! But all of these things add to your chances of staying anchored and undamaged in a real storm.
And that, really, is the point. Keep the boat attached to the ground and in safe water, and keep the crew safe aboard or – if it’s a better option – in shelter ashore. Safety first.

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Author: s/v sionna

Living the dream in 32'. We left Maine on August 18th, 2016, and have gradually worked our way south until we felt warm enough. We've paused in Boot Key Harbor, and are now exploring the Keys until we leave the boat and return to Maine for a summer of employment. Follow our blog here, and follow our progress in map form by joining www.Farkwar.com!

2 thoughts on “The Art and Science of Anchoring

  1. Interesting and informative – with photographic examples! Nice one. (I take it you’ve been given permission to read and write – I’m sure you’d never risk a dope-slap from Nicki which could end you up back in eye surgery)

    And speaking of election cycles, I’m stealing from you guys, if you don’t mind… “Scope, Shock, and Windage” is going to be my campaign slogan in the NEXT big contest. I can’t lose…

    Like

    • Limited duty, Matt. I actually wrote 95% of this in Ocean City, before the eye became critical.
      I’d vote for you based on that slogan alone!

      Like

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