noelex
Well-known member
There is a persistent claim that is repeated continuously on this forum (in three posts on the last short anchor thread alone) suggesting that any modern 15 kg anchor (Rocna is often quoted) has been tested to consistently produce 2000 kg of holding power.
This statement is misleading and needs correcting. Let’s examine the numbers in detail:
The large and often quoted anchor test conducted by Yachting Monthly and Sail magazine in 2006 measured the holding power of a 15 kg Rocna at three locations and recorded an average holding power of 2300 kg in location one, 1200 kg in location two and 680 kg in location three.
Rocna listed the holding power of their 15 kg anchor as 381 kg, obviously taking into account that the vast majority of substrates are not as good as those included in the 2006 test and reporting the correct SHC.
The Rocna was one of the very best anchors in this 2006 test. Many other 15 kg anchors did far worse, even the steel Spade only recorded an average hold of 230 kg in one of the three substrates. These tests were all in very good substrates. There was no attempt to test in common but difficult substrates such weed, gravel, cobblestones, soft mud etc where the results would be lower, much lower.
These tests were all conducted with a straight line pull. In real life nature is not so accommodating and changes in the direction of pull will significantly reduce the holding power.
Note that they are average results with quite a high standard deviation. If three pulls result in holding figures of, for example, 1000 kg, 1500 kg and 500 kg, the holding power will be reported as 1000 kg, but can the anchor be trusted over 500 kg when it will fail at anything over 500kg on every third deployment in this substrate? We need our anchor to be secure on every occasion. The lowest holding value in a particular substrate is important, but this is not quoted.
There are some other factors such as the important differences between DHC (dynamic holding capacity) and SHC (static holding capacity) that I will outline in a future post, but in summary don’t be mislead by the 2000kg myth.
This statement is misleading and needs correcting. Let’s examine the numbers in detail:
The large and often quoted anchor test conducted by Yachting Monthly and Sail magazine in 2006 measured the holding power of a 15 kg Rocna at three locations and recorded an average holding power of 2300 kg in location one, 1200 kg in location two and 680 kg in location three.
Rocna listed the holding power of their 15 kg anchor as 381 kg, obviously taking into account that the vast majority of substrates are not as good as those included in the 2006 test and reporting the correct SHC.
The Rocna was one of the very best anchors in this 2006 test. Many other 15 kg anchors did far worse, even the steel Spade only recorded an average hold of 230 kg in one of the three substrates. These tests were all in very good substrates. There was no attempt to test in common but difficult substrates such weed, gravel, cobblestones, soft mud etc where the results would be lower, much lower.
These tests were all conducted with a straight line pull. In real life nature is not so accommodating and changes in the direction of pull will significantly reduce the holding power.
Note that they are average results with quite a high standard deviation. If three pulls result in holding figures of, for example, 1000 kg, 1500 kg and 500 kg, the holding power will be reported as 1000 kg, but can the anchor be trusted over 500 kg when it will fail at anything over 500kg on every third deployment in this substrate? We need our anchor to be secure on every occasion. The lowest holding value in a particular substrate is important, but this is not quoted.
There are some other factors such as the important differences between DHC (dynamic holding capacity) and SHC (static holding capacity) that I will outline in a future post, but in summary don’t be mislead by the 2000kg myth.
Last edited:
.
.
