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Following is an email I received from Craig at Rocna anchors, in response to a query I sent asking for data showing the holding power on larger/heavier vessels. - Ken W
July 10, 2007
Hi Ken,
Nordhavns in our experience tend to be more sensible than some designs, and Rocnas always fit well. From the pics on your website I would assume this to be the case with your boat also.
We have a general dimensions sheet here:
www.rocna.com/distributable/rocna_anchors_dimensions.pdf
Please check that out, and let me know if it is inadequate. We are currently actually working on some distributable patterns, which would allow you to make up a 1:1 pattern of the side profile of the anchor (at the expense of quite a few sheets of paper!).
The other thing we can do is generate a drawing for you of the anchor on your bow, if you are able to get CAD of the roller and platform profile to us. Happy to do what we can.
On the sizing, note that you are well within our sizing range – for a 72’ monohull, we rate the 110 up to 150 tonnes in terms of displacement. Your extra windage will use a little of that margin, but there is still plenty.
We don’t have any hard data sorry, or comparison testing. The gear required to test anchors of this size to their limit is heavy duty stuff. We are however very familiar with the type behavior, and from industry standard models the 110 should even in soft mud (assuming well set) hold far more than the forces your boat could exert.
I don’t have the data from every 110 out there, as we do not sell much direct, but a brief trawl through recent sales finds a boat in Sweden of 100’ (a sloop) displacing 90 tonnes, and in NZ a 72’ high-profile motor sailor of 82 tonnes. Actually we have something of a testimonial from the latter, which I have attached. Anyway these are around the mark.
One thing I should do is get you to compare the dimensions of the anchor from the above sheet to your plow, if you can. The Rocna is a physically large anchor, and most are surprised when they see it in person. Put next to your 300lb plow, it would probably seem of equal size if not a little larger.
I’ve also attached some photos of other 110s. Feel free to forward these on to your friends or put them on your website.
We are currently working on the design for a Rocna 150 (330lb) but I really think this will be terrible overkill for your boat. If you are still concerned, I can try to pull Peter (our designer) aside and get his personal opinion, or even get him to phone you if you wish.
I hope that helps. Regards,
Craig @ Rocna
July 10, 2007
Hi Ken,
Noticed your mention of tandem anchors on your website.
Boy do we have some input on that topic.
You may notice that the Rocna is (to our knowledge anyway) the only anchor on the market designed with a specific attachment point for a tandem anchor (refer our User’s Guide under “printable information” on our site).
I will say no more but direct you to the article on the topic (make a cup of coffee, it’s a long one):
http://www.rocna.com/boat-anchors/tandem-anchoring.php
I really urge you study that thoroughly. We have done a great deal of testing and research on the matter. While the article speaks for itself, I will reiterate the dangers involved with the technique: an excellent understanding of it is very important.
Also, if you’re interested in seeing a demonstration, there is a video here which shows two small Rocna 10s in tandem, being set:
http://www.rocna.com/images/remote/rocna_tandem_demonstration.mov
Hope you find that interesting. Don’t get information overload!
- Craig @ Rocna
---> Check out the Rocna in stainless steel: ROCNA IN STAINLESS PDF
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