Anchor battles, more SPADE versus Rocna
posted by John & Phyllis Web Site
A few weeks ago, while buried in launching and commissioning “Morgan’s Cloud”, we received an e-mail from Alain Poiraud, inventor of the SPADE anchor, questioning the validity of a graph of relative anchor holding power provided by Rocna and our decision to use it in this post.
I should point out that we were posting Craig Smith’s (a principal at Rocna) comments in there entirety (as we had done some weeks before for Alain) and therefore we were not making any comment on the validity of the graph by posting it. In fact we placed the following editorial comment under it: “The chart above was adjusted by Rocna based on the original SAIL Magazine chart, which you can see on the third page of this PDF.”
Now that we have a few moments, I have had another look at the original chart from the SAIL Magazine anchor tests and the chart that Rocna derived from it. The two charts give a somewhat different overall impression, although the Rocna still just beats out the SPADE on the original, but by a narrower margin.
As I understand it, Rocna scaled the original findings in proportion to anchor weight to generate their chart. I would be the first to admit that I’m no engineer, but it seems to me that this kind of scaling of results is not really valid. For example such treatment would slaughter a fisherman type which, none the less, can be a very useful anchor in rock and kelp covered bottoms. (See this post)
When it comes to the Rocna to SPADE comparison, surely Rocna are scaling apples and oranges since the SPADE is ballasted with lead and the Rocna is not. Sure if SPADE were trying to recommending an anchor of twice the weight for the test, Rocna would have a point to question the results, but we are talking 3 pounds difference here. It would even be possible for SPADE to turn the tables on Rocna and scale the same graph by surface area and thereby come up with a completely different result.
Chart that Rocna derived from the original SAIL magazine test.
In our opinion, choosing anchors is hard enough without the manufacturers changing the results of independent studies in ways that benefit their products.
As we have said before, we have no opinion on which of these anchors is better. We gather that in some other tests the SPADE has done marginally better than the Rocna (depending on how you read the results), the opposite of the SAIL test.
Frankly we think that these small testing differences are pretty meaningless in the real world. The point is that both are fine anchors that are dramatically better than the old style anchors we were all using up until a few years ago. And, if you are still using an old style anchor, the purchase of either a Rocna or a SPADE will definitely increase your safety and enjoyment of cruising.
Labels: Anchoring
5 Comments:
Just mentioning the Rocna or Spade is a great way to build web traffic--well at least you'll get Alain and Craig! It's kind of amusing once you realize that these guys just can't stay away from an opportunity to criticize the other. We did a little post on this: http://www.navagear.com/2007/04/lets-talk-about-the-rocna/
Both good anchors, though! Enjoying your blog...
Aaron Tinling
Navagear.com
I will ignore Poiraud's fingerprints here, other than to point out for the record his frequent and consistent attempts to discredit Rocna in public at any opportunity and by any means - and I do mean any - since the SAIL testing. That aside:
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.
Sorry, I can't resist posting this here:
CS-BB post on Spade, Manson Rocna copy, and genuine Rocna
Look at the guy's transition from one anchor to another. This is one of the very few users who can claim to have experience with most anchor types including almost all the new generation contenders.
This post has been removed by the author.
For our complete reply to Craig's comment see this post.
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