Yet MORE Anchor Stuff
posted by John & Phyllis Web Site
[Not surprisingly, our post suggesting that Rocna should not have scaled the results of the SAIL Magazine anchor test got a comment from Craig Smith at Rocna, which we have printed below, together with our response.]
"To compare results from a 32lb anchor directly to those from a 35lb anchor is conceptually little different to Practical Sailor drawing the insightful conclusion in their 1999 testing that the CQR is better than the Delta, because it held 583lbs average vs. the Delta's 496lbs.
The sizes tested? 35lb CQR, 22lb Delta. No, really.
(I'll say the obvious: work out the performance per lb).
The variation of anchor sizes in the sample of contenders chosen by West Marine is most unfortunate. It is also however unavoidable, because it is impossible to find the same size produced by all manufacturers. Variance around a median must be accepted in any real world test.
West Marine have in the past analyzed their results on a ratio of holding power to weight. SAIL in this case have regrettably elected not to.
Your comment John that "if SPADE were recommending an anchor of twice the weight for the test" our correction would be valid immediately conceeds that this adjustment is justified. It would be illogical to argue otherwise, even though the difference is smaller. If it is valid for that extreme, then it is valid for any variance whatsoever. In fact, the variance is about 10% which is in fact quite significant if the results are close.
The fact that the Spade requires a lead tip-weight is one flaw of the Spade which directly affects performance - as seen here. It is no excuse, no more so than the presence of the Rocna's roll-bar would be if the situation were reversed. Indeed, the fact that the Rocna of smaller weight features more surface area than the Spade at no expense of other factors is one of our sales points in advantage.
It would be logical to consider the performance on a surface-area to surface-area basis only if this was an intrinsically important factor. If one cares how much paint is required to turn one's anchor pink, then this may be so. However, weight is typically the definining factor of anchors of the same material, and is most critical on the bow of any boat. It also directly affects cost.
It is more regrettable that SAIL's analysis of their own data leaves much to be desired. In any case, a brief look at West Marine's own comments on the matter may be more appropriate than debating figures. In their current catalog is a table with summary comments of all anchors tested.
On the Spade:
"Somewhat mixed results with three OK pulls, and three maximum pulls. Set immediately each time."
On the Rocna:
"Superb, consistent performance. Held a minimum of 4,500lb and engaged immediately."
Those quotes are verbatim and complete. There I will leave it, unless you John would like a more in depth debate on the matter on your site. I am happy to discuss our analysis of the data, which is intended to be a fairer and more representative picture of the testing data."
Our Response:
I still don’t think it is a good idea for manufacturers to unilaterally change the result of independent tests. The Rocna is a great anchor and I don’t think that it needs this kind of manipulation of the data to sell; in fact I think it may even be detrimental in the long run.
I would also question the implied assertion that holding power to weight is the only valid criterion for anchor evaluation. If this were so, aluminum anchors like those from SPADE and Fortress would be clear winners. (Yes I know that Craig said “anchors of the same material", but that seems a convenient qualification to me.) However, as a long term user of an aluminum Fortress as a kedge I would never suggest that it was a superior all round anchor to a steel SPADE or Rocna. See this post for more some of our thoughts on aluminum anchors.
There are many other factors that make a good anchor including ease of stowing on the bow roller, ability to exhaust rocks from the blade, susceptibility to break out in a wind shift, strength and, most of all, ability to set and hold in many different bottom types.
We know the SPADE is a good anchor and a breakthrough in performance over traditional anchors because we have used it several hundred times in many different bottom types from the Bahamas to Greenland and many places in-between on both sides of the Atlantic; the same places where we used a CQR, Luke and Fortress in the past.
From the anecdotal information we are getting, we suspect that the Rocna would have done as well as the SPADE for us. Who knows, it might even have done better, although it is hard to imagine how since the SPADE has never dragged once set and has only failed to set twice in all that time. However, to use one test, done with a few pulls in three similar locations and scaled by weight, to say that the Rocna is the best anchor is, I think, a leap way too far.
Labels: Anchoring
2 Comments:
John, that's a fair response, although I will protest we are not adjusting the results of the test - only submitting a different presentation of the same data. Our chart measures the ratio, not the data. The raw data is free to be seen in the SAIL article on our site. This data, however it is presented, may speak for itself and of course may not be "adjusted".
I'll also pick up on the fact that you've avoided my example from Practical Sailor. This is important to illustrate the problem with testing varying anchor sizes. The point is, most people reading the article are not interested in the particular sizes tested (~15Kg steel anchors), but sizes either larger or smaller. They are therefore interested in a fair comparison of type, other factors notwithstanding, which may be applied as at least one input to 25Kg anchors or 5Kg anchors.
Do you agree with Practical Sailor that the CQR is the "better anchor" than the Delta on the basis of the test and results outlined in my example?
I am amused by all this. My 2 cents - who cares about holding power of one type of anchor verses another in a consistent type of holding ground - the real test is the ability to hold in a variety of holding grounds. The Rocna videos are interesting, but the relative measure of how fast an anchor sets (the thing they emphasize so much ) is a lot less relevant than the binary question of did or didn't it set at all. Ditto holding strength. To run a "real world" test with even a modicum of statistical validity they are going to have to do a lot of tests in a lot of different holding ground. The generic test with the strain gauge, pick-up truck, and anchor set in the sand strike me as only highly relevant to holding ones pickup truck in place. No one seems to address that the test ignores the angle of pull and given how often cruisers are choking up on the rode because of a tight quarters - maybe we should be measuring which anchor does the best on the lowest ratio rode.
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