Originally Posted by BrianFortress
In the case of the Fortress anchor bending during an anchor test, it is almost ALWAYS under a load that occurs long after the steel anchors have pulled out of the sea bottom.
Or put in a different way, the steel anchors don't often bend in the anchor tests because they will pull out of a sea bottom first.
That is a generalization that not only is true but yes I can accept that. At least it happened in some tests with some bottoms but that regards only badly bent flukes.
The problem with aluminum anchors has not to do with bent flukes but with the forces on the long shank in a veering moment. Regarding that, what you say is not accurate. About the test carried out by west marine Yachtingmonthly say :
" we subjected it to a further test at 3/1 scope and it cave an amaising 4.500 lb plus resistance though the shank bent slightly during our veering test."
. They don't say at what force the shank bent but their conclusion is "This is a lightweight anchor wich should prove dependable in an emergency"
This seems to me like a recommendation as a secondary anchor and a not recommendation as a primary anchor and I believe it has to do with the inferior resistance showed on the tests comparing with steel anchors. For instance they say about the Spade : At 5/1 it repeatedly held at the maximum 5,000 lb and on the veering test we recorded up to 5,400 lb!
and about the Mason: "Even 3:1 scope it held to an astonishing 4,612 lb. It was unfased by the veering tests – refusing to budge at 5,000 lb from all angles".
Neither the Mason or the Spade were affected (bent) by the veering test even if they hold as much or more on a veering test than what the Fortress on a forward pull. Again, they don't say at what force the Fortress shank bent, they say only : "though the shank bent slightly during our veering test"
Regarding the French test that also had a veering test they could not test on that regard the Fortress because it was been destroyed already by a frontal pull (with a huge holding force, I agree) but they had tested several other aluminum anchors and also bent the Spade shank on the veering test. They finally opted not to test the aluminum anchors on the veering test anymore and they opted to recommend on their conclusion the use of Aluminum anchors only as secondary anchors and that is after all also the use that Spade recommends for their aluminum anchors.
Originally Posted by BrianFortress
And Paulo, I will see if I can locate pictures of the high grade steel anchors that were destroyed in the US Navy tests, while the Fortress anchors tested had minimal damage.
These tests proved beyond a doubt that just because an anchor is manufactured from a high grade of steel does not guarantee that they will be able to withstand heavy loads, or even provide good holding power for that matter.
As you pointed out with the bent Rocna made with an inappropriate steel grade, if a Steel anchor is not well designed and made with a proper steel grade it can bent as easily as an aluminum anchor and has no guarantee of being stronger than an aluminum one. However a proper grade steel in a similar sized and designed anchor will make it stronger than if you apply an identically appropriate aluminum high grade as it is showed on the Spade that has two similar anchors, one made of steel another from aluminum.
Show me on that navy tests a Steel Spade or a Mason supreme destroyed by a force that a Fortress could sustain without damage and you prove your point. Show that happened with any other different designed or made with lower steel grade steel grade anchor and that proves nothing regarding the superior steel resistance, except that you should not buy any of those destroyed anchors
The opposite is true. It was proven that the Fortress would be rendered useless and bent its shank by veering forces inferior to the ones that had no effect on steel anchors, namely the Spade and the Mason.