Re: How much anchor chain?



I am writing this to clarify something in your recent post about anchor scope. I am sure you know this, but there wasn't enough detail in your post that newbies will certainly need. 

10 meters indicated on the depth instrument is actually 10 meters of water, only if you have the depth Datum set to water depth rather than actual transducer depth, or keel depth. If you have the Datum set to keel depth (as many do), you need to add this to the scope computation. Unless the Datum is set to indicate actual water depth, you are probably closer to 12 meters. You can find information on the Datum offset in your depth instrument manual. 

FYI, I was recently in an Amel that someone had attempted to set the Datum to indicate the depth of the keel. That person then relied on his depth instrument in shallow water, but because he set the Datum wrong, when his keel touched bottom, his instruments indicated 3 meters. When this boat was hauled out, there were more than 10 large chips on the cast iron ballast and a large chips in the rudder.

Additionally, your bow roller is about 2 meters above the water, so when computing scope you'll need to add this to the computation. The easiest way is to add it to the indicated depth.

Also, many of us like to have a lazy loop of chain between the snubber connection to the chain and the bow roller.

Chances are that with 10 meters depth indicated on your depth sounder, you need to use somewhere between 12 and 14 as depth in the scope computation. I doubt that you can get 7:1 in 10 meters of water with 60 meters of chain...I believe that the most that you could have is between 4 and 5:1.


CW Bill Rouse
Admiral, Texas Navy
Commander Emeritus
Amel School
720 Winnie St
Galveston Island, TX 77550
+1(832) 380-4970

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