Anchors, is one big one better than 2 small ones

[Chris_Robb]

Read the Alain Fraysse website, which most authorities recognise as giving an accurate mathematical assessment of catenary and other anchoring forces. Above a wind strength of about force 6-7 catenary pretty much disappears as a useful device. The rode will not be straight of course as its own weight will always give it some curve, but the whole lot of it will be off the bottom. I have confirmed this by diving on my anchor in winds of around that strength many times, but particularly in Cala Lupe in Sardinia, where we were anchored in shallow water, 2 - 2.5 metres, with 35 metres of chain out. The whole length of it was off the bottom for large periods of time.

[QUOTE

Originally Posted by Uricanejack http://www.ybw.com/forums/showthread.php?p=4113533#post4113533
Hmm somebody might actually know what he is talking about.

Its the catenary which counts.[/QUOTE]

+We have had this argument before here. I concur with Vyv's argument. I have seen exactly the same happening when I have dived on the anchor. What is essential though once chain is off the bottom (and therefore not providing any drag) is to cushion the shock loads on the anchor as a yacht yaws from side to side. So essential to have a 20meter nylon snubber suitably protected from shafe. Amazing to see the stretch in it when its really blowing!

 

[Neeves]

Jonathan. For me, being a bit of a swinger, I prefer one large anchor to take account of the change of wind. You however have what appears to be an entirely different set of circumstances as defined above.

In the Med, anchored and stern to rocks, I would be happier with say 2 large anchors, but I would, for the simplicity of laying and leaving in an emergency, much prefer 1 single large one. I bought the recommended size for my boat which was 45LBS, but If I was buying again, I would buy at least one size up. I have no problems handling this one, so one might as well go bigger.

People often mention the ease with which one large anchor can be lifted against 2 smaller ones, thank goodness for electric windlass! When we are anchored in strong winds the last thing we want to do it move - so I do wonder what emergency develops to necessitate a move? Someone mentioned earlier: forecasting 3 months ahead is not all its cracked up to be but 24 hour forecast are pretty good. They might be out by a few hours but if the forecast says strong winds, that's what you get. When we hear a strong wind forecast we find the most secure place available and take every precaution (and if that means 2 anchors and a line ashore, that's what we do. To demand relying on one big anchors seems to suggest people do try to challenge but there are very few anchorsages that do not provide shelter (that's why they are anchorages) and getting tucked in seems sensible. Circular storms are a different issue (my view is you need many anchors and many securements). Winds veer, in storms, but seldom through 180 degrees and anything less can usually be catered for, which might necessitate a move (but not an emergency move). The only need to move quickly is when a yacht upwind drags. If we had 2 anchors out I'd simply buoy the second anchor and drop the bitter end over the side, this would allow us to swing out of the way of the dragging yacht without lifting the primary. But there is another issue, the implication now seems to be you need to keep an anchor watch in case other boats upwind drag, not for your own yacht. Part of the basis of BIB was better sleep, that seems to have been lost (maybe Broadband radar is the answer)?

Jonathan

 

[Neeves]

I think one of the advocates of 'small' is John Knox though he is restricting his support for 'small' to his own anchor. Does anyone have any experience, at all, of the KnoxAnchor?

 

[Neeves]

Oldbilbo,


Why 2 sizes bigger, the original thesis was proposed by Morgan's Cloud and in the debate, I recall, were specifically applying their discussion with reference to their own Rocna anchor (interestingly they carry 2 anchors, 2 bow rollers, the second is a Spade). In the image on their website they actually show the bow of a yacht with old gen anchors, but they note the discussion is limited to new gen. Basically I am taking Morgan's Cloud thesis, 2 steps larger, based on Rocna sizing, and then applying that size differential across the crude list of anchors.

Hi, a quick correction here in the interests of clarity.

Morgan's Cloud is equipped with two Spades, a bower of 55kgs and a kedge of around 35kgs. They don't carry a Rocna, but our boat (which also features on the site) does, a 33kg bower and a 25kg kedge, for our 43ft Ovni.

Best wishes

Colin

The original image on the Morgan's Cloud 'Opening Thesis' was a bow roller with a Spade and Rocna, it was subsequently changed to the current image with a CQR and 'another'. The initial discussion was centred round use of a Rocna. There has been some editing of the thread. I do understand that Spade are a supporter of Morgan's Cloud (it says so on the American website of Spade.


The paste below is part of the debate on the subject. You will note I queried 'Spade and Rocna' but if you read everything earlier there is now no mention - its been edited out.

Quote from AAC

'Jonathan Neeves December 15, 2012 at 3:28 am EDIT

You had suggested stirring things up

It might have been in an earlier thread but why this fascination with Rocna and Spade? The same pairing appears in (an)other thread(s). What is wrong with Spade and Supreme or Boss or Excel or SARCA or Fortress. All (named brands) have holding capacity beyond anything most people will need (if sized correctly). 2 concave anchors looks like overkill, roll bars are very 1970′s, two galvanised anchors (spine threatening – depends on yacht size and strength of partners). Just seems parochial and ‘restrictive(?)’ but – its your website

But I was never considered as a mover and shaker.

REPLY

John December 15, 2012 at 9:20 am EDIT
Hi Jonathan,

Note that I say “new generation anchors LIKE the SPADE and Rocna” which clearly implies that there are other options.

Having said that, here at AAC, we only recommend products that we have extensive first hand experience with, or verified second hand experience from multiple sources who we know personally and trust.

Our readers come to AAC for experienced based facts, not speculation. They can get enough of the latter on the forums.

Incidentally, if you look under anchors in the menu, you will find our thoughts on the Luke and Fortress.

end of quote

For information I believe a Luke is a demountable Fishermans

Jonathan

 

[oldbilbo]

Apropos guidance from some retailers and how much reliance may be placed on it…..

In recent days I’ve been exploring the perceived merits of several anchors, and the experiences and preferences of a number of well-seasoned sailors…. oh, and I’ve been sailing myself for over 40 years. In part due to interesting comment on threads/sites such as this one, I’ve queried with retailers some details of products I’m interested in – including the publicised metallurgical composition. I’m pleased to say that folk at Piplers and at Bainbridge, both in the UK, have been helpful.

However, I’ve been digging for info on the Plastimo Kobra 2, and was directed by the Head Office of a sizeable chain-chandlery to ‘one of our experts’. I asked him my question “Given that this product is probably made in China and that there has been controversy over the mix of metals in another anchor type, what’s the make-up of the metal?"

His reply included “I’ve been in this trade for decades and I don’t think I have been asked that before. Why do you want to know?” ….followed by “Most of our customers are perfectly happy with the anchors we sell them, and I think I’d soon know if something wasn’t quite right. You can follow our recommendations with confidence.” At this point I started to smell a rat and asked him what kind of boat he sailed and whether he did much anchoring. His reply was ‘No, not me. I don’t have a boat.”

Needless to say…..

 

[Neeves]

I was in the UK and walked round a few marinas. I saw one or two Kobras in most marinas, 10kg-20kg, a number had shanks that were off centre by a few degrees. I could not work out if this was how they were made, they had bent slightly and the owners did not know or they had bent a lot and the owners bent them back as well as they could.

Sorry I had to send you off to find out yourself but if I'd posted this first someone somewhere would have said I have an axe to grind.

I do own a little one, for testing, its shank is a 'mild steel' but it is common for small anchors to be made with their shanks of a lesser quility than bigger ones so I was reluctant to quote mine as an example. They are great anchor, good holding, set quickly and cheap. But I' suspicious and think you get what you pay for.

Jonathan

 

[oldbilbo]

.... is one big one better than 2 small ones

OK, I'll bite.

Yes.

I have it on good authority ( or so she tells me... )

 

[geem]

I thought I would offer my experience of two anchors. This applies to my last boat which we have recently sold. The boat was a Prout Snowgoose 37 Cat. In cruising trim she is about 6 ton. We had 30m of 8mm chain, 20m of anchorplait and a 20kg pattern Bruce anchor. In addition we had a 10kg aluminium anchor (ex-military). This anchor looked like a Fortress that had been on steroids!

Whilst in Mindelo in Cape Verdes we got caught out. We were in a crowded anchorage with just the Bruce set. Our neighbours who we were cruising in company with us had set two anchors in a mooring pattern. In the middle of the night the wind shifted 180 degrees rising from about 10 knots to 50 in a violent (but warm) rain squall. We were anchored near the beach so ended up almost on it with about 2 inches of water under the keel. Our friends with the twin anchor set up were fine having had one anchor out to sea. The rest of the anchorage was in turmoil due to dragging anchors. Our shallow draft protected us as we had deep draft boats near that ran aground before they hit us!!
A few days later we were anchored off another Cape Verde island. Weather forecasts were hard to come by and not reliable. We set our Bruce on the leeward side of this deserted island and we went to bed. The wind picked up in the night and was blowing hard. Due to the mountainous terrain we were getting violent gusts of over 50 knots and big wind shifts. We let out all of our chain and rope but then experienced huge snatching that threatened to rip the anchor from the sea bed or snap our gear. The snatching would knock you off your feet.

After this experience we would always set two anchors if we were staying overnight.

Setting the second anchor could be a pain but we have a rib with a powerful engine and a large effective lightweight anchor. We don’t use chain on this anchor as it would make it difficult to handle. Our experience of using our second anchor would suggest that chain is not necessary.

When we expected a blow we would deploy the aluminium anchor in addition to the Bruce. We did this by motoring out in the rib and dropping the anchor a few meters to one side of the Bruce anchor, unless we were expecting a wind shift. The Aluminium anchor would be set on stretchy 3 strand nylon with no chain. The main anchor would usually be set with a bridle to the bows to stop the boat sheering around. This worked very well.
The rode on the aluminium anchor was adjusted so that tension was primarily on this anchor first. The gusts of wind would stretch out the rope then apply load to the main anchor. This acted like a great shock absorber. We used this system generally and with more regularity as we completed our Atlantic circuit in 2004/05.

I think there is a time and place for two anchors or more.
Our friends from the Bahamas carry 12 anchors and hundreds of feet of spare chain. Their normal anchor is a Bruce. Their storm anchor is a cast iron fisherman anchor that weighs 75lbs. Their other anchors are all folding fisherman types. Their boat is 17 ton monohull and they have to contend with hurricanes on a fairly regular basis. They bed themselves into the mangroves and deploy their chain and anchors. They have done this several times and always come off unscathed. Different solutions for different circumstances.

On my new boat I will be carrying at least 3 anchors. I am sure there will be times when I deploy more than just one.

 

[Neeves]

Thanks, Geem,

Good to have first hand experiences. Our history is not too dissimilar to yours - as we too have a cat. Based on your experience would you change your practice if you had a mono (accepting you might not use (need) a bridle). Or do you think, your and our practice, multi -specific (I don't think it multispecific - but like broader opinion). We like alloy in a 2 anchor situation easy to deploy either from a dinghy or over the lifelines but confess have never tried one without some chain - but had never thought of using the nylon rode as the 'first line of defense' anchor, thus allowing the chain rode to cut in once some elasticity was taken up - good idea (necessity the mother of invention). We can commend hanging a buckets between the transoms, say between 2 sheet winches, as a drogue to stop the stern swinging and another anchor simply hanging off the bow as a friction brake, just dragging on the seabed.

I'm specifically not asking about your next anchor choices! - it can upset the current valuable equanimity

Again thanks!

Jonathan

 

[geem]

my prout catamaran didn’t swing around much. I suspect that the bridle helped but the fact that the mast is well aft helps to reduce the sailing at anchor effect some cats experience.
I have made up a bridle for the mono. For nothing else, I like that fact that it takes the load off the windlass and stops to chain grating on the gypsy and keeping me awake.
My new boat is heavy and a ketch. In theory the main Rocna anchor is undersized at 25kg. I may purchase a new larger anchor but I will still be carrying my aluminium landing craft anchor, the heavy cast iron kedge that was original to the boat and probably a couple of smaller fortress anchors I have. You never know when they will come in handy.
if i am stuck somewhere and its blowing hard, you can bet I will be deploying more than one anchor

 

[DaveS]

I'm coming a bit late to this - apologies. Bilbo has already quoted my experience and posted the Delta size recommendations: from these it would appear that I am in the "one size up" bracket but, as has been pointed out, with different manufacturers offering different size steps, "one" or "two sizes up" will not give reliable comparisons across manufacturers. To clarify, while I would expect to use only my "oversized" anchor 99% of the time, I do carry aboard a variety of others as possible back-ups. I have once set a second bower in "fork" formation but with a much narrower angle than the 30deg usually shown in the books. This was when anchoring in a gale with wind varying rapidly in force and direction. (I do not recommend Loch Harport in strong SE: the wind from the Cuillin is very unstable.) In retrospect I'm not sure that having the second anchor down really achieved much once the primary was well embedded, and in subsequent wind shifts it was more nuisance than help. I certainly agree with using nylon snubbers and I would really like to try a stabilising riding sail.

I'd seen the Alain Poiroid anchor test report some time ago in one of the heated anchor threads, but had lost track of it. Would I be guessing correctly the anonymised identities of the "unstable" anchors as Bruce, Danforth, Fortress and CQR respectively, and the "stable" anchors as Delta, Bugel (and of course Spade)?

 

[Neeves]

I'd hesitate to list unstable anchors, I value the equanimity, but some good anchors include, Fortress, Spade (Al and Gal), Rocna, Supreme, Excel (Al and Gal). There are some new ones champing at the bit for inclusion, Boss, Mantus, KnoxAnchor and rumour has it a few more just over the horizon. People have preferences, some subjective, (in the foregoing list) as they had of other brands, Bruce vs Delta for example - I suspect much depends on where, how and why you anchor and what's actually on the yacht. Its inordinately difficult for the individual to compare, not many have opportunity to test a variety of anchors on the same yacht, in the same seabed, in the same conditions.

Thanks for the post.

Jonathan