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HomeCruiseLetter to the Editor: Anchoring Scope? What is right?

Letter to the Editor: Anchoring Scope? What is right?

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Good day,

Fatty’s article of a few years back, on anchoring, was well written and filled with facts and figures. It was no doubt very informative to those less knowledgeable on the “art” of anchoring effectively.

Your latest series though, “Anchoring Games”, which was no doubt also for the benefit of those less knowledgeable, is an interesting read, although with, in particular, one very poor piece of advice.

“Gently reversing, we pay out chain until we achieve twice the water depth, then we set the anchor with reverse thrust…”

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There is no context as to whether the “water depth” she refers to is bowroller to seabed, or simply depth of water. If the former, she is suggesting setting the anchor at 2:1 scope (around 31 degrees angle off the seabed), or if the latter, then it is around 1.5:1 scope (around 43 degrees angle off seabed). So in 3m of water, one should properly and effectively set the anchor with a whopping 6m of chain paid out?

Compare these with setting at 6:1 scope, which gives an angle of 10 degrees, or 7:1, which is around 8 degrees, and allows the anchor to dig in properly, at the optimum angle.

Readers would do well to rather refer to Peter Smith’s excellent site on anchors/anchoring, angles and how they effect anchoring.

As a full time cruiser for the past 7 years, I can take this with a pinch of salt, but what if you and I start getting newbies anchoring in front of us, having actually taken this advice seriously?

Regards, Carl

Dear Carl,

When you are right you are right … Thank you for holding us accountable!  

As you pointed out, Cap’n Fatty Goodlander addressed this quite well in his earlier article.  Without much ado let’s defer to his wisdom.  

What is anchor scope? Why? How much do you need?

Okay, scope is the amount of rode (chain or nylon or combo) you deploy between boat and anchor. How to determine how much scope? Take the depth of the water add the height of the bow roller above water—and times it by five to get the correct scope in light to moderate winds. Let’s say that you anchor in 15 feet of water, and your bow roller height is five feet. You need 100 feet of rode to anchor. No less. Nearly all anchor dragging is because of too little scope. 5 to 1 is minimum. 7 or 8 to 1 is recommended in a blow. I deploy 10 to 1 during hurricanes (dozens of which I’ve ridden out successfully, two of which I haven’t).”

For those curious to read the whole article: https://www.allatsea.net/anchoring-a-boat-the-ultimate-guide/

We would also highly recommend a deeper dive into Fatty’s book: http://www.fattygoodlander.com/creative_anchoring

Thanks Carl!


Letters to the Editor are always welcome!  Send email to editor@allatsea.net

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