In the previous chapters we wrote about anchors we like. Now let’s move on to our recommendations for the size and material for our best bower (primary anchor).
Specifying Primary Anchor Size
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More Articles From Online Book: Anchoring Made Easy:
- Introduction
- 4 Vital Anchor Selection Criteria and a Review of SPADE
- SARCA Excel Anchor—A Real World Test
- SPADE, SARCA Excel, or Some Other Anchor?
- Rocna Resetting Failures and Evaluation of Vulcan and Mantus
- Ultra Anchor Review
- Specifying Primary Anchor Size
- Kedge (Secondary Anchor)—Recommended Type and Size
- Third Anchors, Storm Anchors and Spare Anchors
- Anchor Tests—The Good, The Bad, and The Downright Silly
- Making Anchor Tests More Meaningful
- We Love The Way Our Anchor Drags
- Things to Know About Anchor Chain
- Selecting a Chain Grade
- Anchor Chain Catenary, When it Matters and When it Doesn’t
- Anchoring—Snubbers
- Anchor Rode Questions and Answers
- Q&A: Hybrid Rope And Chain Anchor Rodes
- Anchor Swivels, Just Say No
- A Windlass That Makes The Grade
- The Perfect Anchor Roller
- Install A Wash-down Pump—And Save Money!
- Anchoring—Kellets
- Anchoring—Chain: Stoppers, Termination and Marking
- 20 Tips To Get Anchored and Stay Anchored
- Choosing an Anchorage
- Choosing a Spot
- 15 Steps To Getting Securely Anchored
- One Anchor or Two?
- Two Anchors Done Right
- Yawing at Anchor, The Theory and The Solution
- Yawing at The Anchor, an Alternative Cure
- How To Use An Anchor Trip Line
- ShoreFasts—Part 1, When to Use Them
- ShoreFasts—Part 2, Example Setups Plus Tips and Tricks
- ShoreFasts—Part 3, The Gear
- A Small-Boat Anchoring System
We also like it BIG. and heavy.
We had a 20 kg Rockna for our Lagoon380 and it worked very well, but it did not give me the good sleep at nigth when wind was blowing hard, So i changed it to the biggest i have space for a 33kg Rockna, and setting it well, i sleep very well.
Big is Better.
We also have a Spade 15kg just as an ekstra , what we call an Coffe anchor to just sett out on the back when needed. its so nice as is it just to remove the bolt an flat pack it. 8 meters of chain and then rope, and we use our Mainsail (EL) winch on it. Life is good 🙂
Hi Geir Ove,
Thanks very much for the confirmation from a catamaran owner, very useful.
Hi John,
As someone sailing the boat used for you example, I concur with all you have said. I have used the 66 pound SPADE for 7-8 years now and have been very happy. It was the biggest I could get short time, and I have been thinking for a couple of years now that the next size bigger would have been better.
As to weight, the difference is not significant. This is particularly the case if you forgo the many advice givers who put anchor size and chain size together. So the 3/8 or even 7/16 inch chain that many might think would go with this anchor weight can easily be dropped to 5/16 G4 as, in the higher wind ranges, strength of the chain is far the most important criteria when compared to weight. At least that is my take. This gives a big weight savings and the weight goes where it really counts: in the anchor.
Cheers, Dick Stevenson, s/v Alchemy
Hi Dick,
I picked the Valiant as my example boat because I knew we had real world experience to draw on—you—but I’m always a little nervous when I put words in someone else’s mouth…or an anchor on their boat! Great to have your confirmation on the size recommendation, thank you.
I agree with the comments about weight and penetrating the surface. I am fairly sure that my 60kilo does a much better job of this than the old 34kilo.
The winch should be big enough to pull the anchor up in marginal conditions. You can test if its big enough by doing the following… next time its blowing 18kts, use the winch to slowly pull your boat to the anchor and retrieve it. If it smells or burns out , its too small.
I am sure that on a dark stormy night, it will get alot more stress than that if you decided to retrieve the anchor.
The amount of bow rollers that stick out miles and are very thin is amazing, I only hope they have a snubber that works without the bow roller. I tried to make mine very short and it has small fins so the chain does not have to come in absolutely straight.
The one area that makes me a little uncomfortable with my current setup is that it takes me 1 minute of work to deploy my anchor. I cant do it instantly. I have to give it a small push. I think that if I had a 50kilo then it might be better as 60 is slightly too big.
Hi Fuss,
I like your windlass test, very much to our way of thinking.
Also, a good point on the launching tradeoffs.
Hi John
I had an aluminum Spade on my last boat and it was good and reliable. But I think the aluminum reacted with the zinc on my chain, and one foot of chain rusted severely every year. I kept chopping off chain. Not a good situation.
I would never recommend an aluminum anchor used with chain. I now carry a 44kg galvanized Rocna on a Trintella 47 with displacement about 37,000 pounds. It seems ok so far, but like you, I always question about whether I should have chosen bigger or the Spade (which I loved except for the chain issue. )
Best wishes
Charles
s/v Dawnpiper
Hi Charles,
That’s interesting and something I had never thought of.
At first I was confused since the steal chain is less active than the aluminium anchor, but then it struck me that probably what’s happening here is that the zinc galvanizing on the chain is acting as a sacrificial anode for the anchor.
I guess you must have been anchored for quite some time before that happened?
Hi John
We did the typical anchoring- overnight. Nothing long term. I think salt spray also contributes to the zinc reacting with the aluminum. The zinc disappeared regularly and the steel underneath rusted fairly quickly.
I loved the Spade and the aluminum made it easy to carry bigger but I did not like the disappearing chain!
Best wishes
Charles
Hi Charles,
Really interesting that just the spray of being on the bow would do it. Just another strike against aluminium anchors as best bowers.
Also good to know that using aluminium in secondary anchors will not be a problem. More on that coming up in the next chapter.
Another reason to eschew stainless anchors, chain and fittings: Stainless is bright and shiny due to the oxide film on the surface which, surprising as it might seem, needs oxygen to maintain its integrity. Once immersed in seawater, however, the oxide film cannot be maintained and the SS will soon turn to mush as the bright and shiny deteriorates. Besides, who wants a rusty SS anchor on display at the marina?
Stainless is nice for frequent short stays in sticky bottoms. (The mud just slides right off a well polished SS fluke.) Other than that, I think galvanized steel is by far the best option. Stronger, more predictable, cheaper, fewer insidious corrosion quirks.
Excellent article. The Valiant 40 is a great benchmark, especially for us (Perry 43 @ 24k lbs disp.). Will size Spade accordingly (S160 it is). Thank you.
Hi Brian,
Glad it was useful.
Hi John,
I agree with all your conclusions, (except that one, and you know which one)
I’m one of those guys that need to look at budget. My criteria is that budget costs are not allowed to reduce safety, reliability or increase working hours to do upkeep of the boat.
As you have read in another post recently, I’m one of those that does believe in modern anchors, but I refuse to pay for it as there is no justification for them being so expensive. I have chosen an anchor that has served me and the family I come from, for multiple decades with a perfect track record, although the type is no longer approved by fellow long distance sailors 😉
I did choose a size or 6-7 up from recommended size, and use an 80kg on my 55.000 lbs/52ft boat (fully loaded). If I were to buy a type of anchor that is approved by fellow sailors, I would probably still opt for a size or 3-4 bigger than adviced, rather than the 1 possibly 2 sized John is referring to. But I have to admit that I have little to no experience with the expensive anchors.
I also replaced the chain this winter, and where I used to use a 13mm chain of regular steel, I found out this winter that prices of G40 chain have come down quite a bit, and a 10mm G40 chain costs actually less than a normal grade 13mm chain, but weighs practically 40% less and saves on shipping as well. So upgrading chain to higher strength is a much better choice to reduce weight than opting for a smaller anchor.
Hi Erik,
I think you are right about size and that really there is almost no limit, other than stowing, to the benefits of upsizing, particularly for boats going to extreme places.
Also, a very good point on the benefits of G40 chain, and the fact that it is very often cheaper than BBB, something that often gets missed.
In fact I was amazed to find that our new G70 was cheeper again than G40 in our application for the same reason. Of course that does not account for the cost of a new custom wildcat…Ouch!
That’s interesting and important information, John. May I suggest that if you come across that sort of information concerning costs of recommended gear, that it gets passed on in some format? While we would all like to have the best, the reality is that not all readers are planning “make or break” voyages, but if I learn something non-intuitive like “G70 is cheaper than G40 now”, it makes me far more open to the cost of a new wildcat as there’s very little to object to when it comes to the price of a chain.
It may surprise you to know that some of us read “attainable” as “affordable” (although that’s wishful thinking at times) and that you represent a sort of offshore-orientated “Consumer Reports” when you advocate one type of boat gear over another.
Hi Marc,
I did, and in detail.
Thanks, John…as compelling as your posts are, I can’t remember all of them individually *and* remember which Perko catalogue number refers to the raw water strainer body cork gasket and which to the neoprene…
I suspect I’m not alone in this! Anyway, yes, that article advocating G70 is exactly what I wanted. May I ask if you are happy with the G70 performance in the intervening time?
Hi Marc,
I would suggest getting into the habit of using the search option at the top of the sidebar, that’s what I do. We use (and pay for) the Google search engine and it is quite extraordinary what a good job it does of finding what one is looking for.
Phyllis has also put a huge amount of work into curating our content. You can use the categories at the top and drill down, or the Online Library in the side bar to find what you are looking for.
The point being that you don’t have to remember where stuff is and two minutes searching will find pretty much anything.
And yes, we are very happy with our G70 chain…after we got over paying $1100 for a custom wildcat!
Hello John,
I came across the wildcat cost when specifying the windlass for our boat. We ended up going a winch size up because it had more wildcat options but also for power, of course. It pays to really look at the fine print and the tables.
Otherwise, if the windlass is already there, it can be a painful gotcha.
When we priced chain recently, G40 is very reasonably priced; G70 considerably more.
Hi John,
I do have a large Spade anchor and it is a stanless steel anchor. I knew your position before I purchased it and I discussed it with the US importer when I met them in Newport and again in Miami. They do not agree that their stainless steel anchors would not perform the same as their galvanized anchor and it would be interesting if they could provide additional comments on this item. I have 2 anchors and they are stanless steel! And yes, they look great!
Jean
Hi Jean,
Well, as long as they are SPADE, I’m pretty sure you will be fine. However it is just as well to be aware that, assuming they are made of the same gauge as their galvanized counterparts of the same size and assuming that said counterparts are made from good quality high strength steel, I think I’m right in saying that your anchors will have a lower yield strength particularly in the stock.
This is something that the manufactures of stainless anchors often fail to mention. This was highlighted in a recent Practical Sailor article. I quote:
“Of the materials used, 316 stainless steel has the lowest yield strength, followed by the aluminum alloys. The ASTM 514 galvanized steel is approximately 70-percent stronger than the 316 stainless steel.”
“The results clearly illustrate the significant advantages of a well-engineered shank of high-tensile steel. The failure of the stainless-steel Spade also reinforces our point that using the same template for different material necessarily imparts variability in shank yield strength. (We would not have expected to see the same degree of a failure in the much stronger galvanized or even the aluminum version of the Spade, which has a beefed-up shank to account for the difference in tensile strength.)”
Hi John,
To add one more data point, we use a 65 lb anchor which we are very happy with. This is on a 36′, 17000lb fully loaded displacement boat. I suspect that a 50lb anchor would work for 99% of the anchoring that we do but the 65 is still easy to handle so there really was not reason not to upsize a bit more. We know that we will occasionally anchor out in nor’easters and tropical storms so we size our anchors to give us a fairly high confidence of staying put in those conditions.
I think that your recommendation to upsize 1 or 2 sizes for these anchors is very reasonable. The only caution that I would have is if someone forgets that your recommendations only pertain to these anchors and their sizing charts. For example, the Lewmar Delta sizing chart recommends a 22lb anchor for our boat which is really too small for anything beyond ideal conditions. If we upsized twice, we would have a 44lb anchor with significantly less holding power per pound than our Mantus. Using your guidelines, we would be choosing between a 55/66lb Spade and a 55/73lb Rocna which is very reasonable.
Eric
Anchor makers used to like to advertise their anchors as being the most efficient by weight – touting yours as “holds as well as a 20lb larger Brand X” was common. I find the sizing charts on most anchors designed since the late 90s / early 00s to be considerably more accurate than those for 1960s-80s designs.
Hi Eric and Matt,
Thanks for highlighting that my recommendation depends very heavily on the accuracy of the size table you start off with. I should have punched that up.
Really scary that the Delta table yields an anchor that is smaller than the SPADE and Rocna since the latter set better and have much higher ultimate holding than the Delta—I suspect that the Delta table was the result of applied marketing, rather than applied engineering!
Size charts are living documents.
I think it was in the 50’s that Lloyd’s register had 40 knots of wind in relatively sheltered waters as their requirement for anchor holding limits. That is what many sizing charts have been based on in the days and was perfectly legit. LR has come to other conclusions by now, based on incidents no doubt, and their requirements have changed. 40 knots with little swell is not all that much and should be a walk in the park for any main anchor.
The sizing charts remained as is, and often manufacturers of newer types of anchors did not want to give customers the idea that their anchor needed to be heavier and have exaggerated the holding power of their anchors.
Now that much more cruisers are getting out there and knowledge is much easier shared due to the internet, real life info is much easier to get and educating yourself on any subject is much easier.
And last but not least, people like Peter Smith have taken a leading role in anchor education based on experience. Invaluable if you ask me.
Hi Charles and John,
Just an FYI. I have had an aluminum Fortress anchor as a kedge on the with the same hank of Acco galvanized chain on the bow for 12+ years now. Admittedly, the anchor has seen little sustained underwater life, but it has seen a lot of salt spray with no discernible problem for the chain.
Dick Stevenson, s/v Alchemy
Hi Dick,
Hum, curiouser and curiouser, only thing I can guess is a difference in galvanizing quality, but that could easily be wrong—a lot of variables here.
Hi John,
Thanks for this chapter.
I have a boat under construction. An aluminium 47ft (14.3m) lifting keel. Weight is 16 metric tonnes. The spec for the ‘best bower’ is a Rocna 33kg. The chain will be 100m long, and stored in a central locker (under the mast). Having read this I am thinking that potentially I need to upgrade to the 40kg. This said it does look like overkill. Can an anchor be too heavy, or should I not worry as the chain locker is in the centre of the yacht so weight may not be such an issue.
Look forward to your comments.
Hi Tim,
I think I would go with Erik’s thinking (see above) and say that there is no such thing as an anchor that is too big, and that would go double for you an Erik who have managed to take the very sensible step of moving your chain lockers aft.
After all, how much difference is 7 kg really going to make in terms of weight on the bow? But on the other hand, said 7kg will make a huge difference to setting and holding.
Thanks John,
Spec being changed as I type !!!!
Tim
if you have the space up there even for a 55kg, Go for it, as you have al the chain w, in the senter. BIGGER IS BETTER. Sleep better. remember it is holding you life, and al the once you love.
To me when i walk the marinas, and se a boat with a big anchor, then i always say to myself, there is a boat that belongs to a real ocean sailor.
Geir and John,
Done already. I thought the 7kg difference was so little I opted for the 55 given the chain locker is aft.
One day I know I will be somewhere in a howler thinking how grateful I am to this advice !!!!
Thanks
Hi Tim,
Sounds good. One thought, have you taken a close look at the dimensions of the Rocna? A 55kg Rocna is HUGE so there maybe interference issues particularly with the roll bar, or it may hit the bow when being deployed or retrieved. Point being that a lot of thought is going to have to go into the bow roller design to make this work. Of course since you are building a new boat, all of this is solvable at the design stage. If that all gets too much you may wish to consider a 55 kg SPADE instead.
Hi Tim,
This is funny, we are currently building a lifting keel boat, aluminium, a tad larger and heavier than yours. Rocna 33 is what the chart said, it got sized up to 40; I said I wanted 55.
Are you happy with your choice?
Then I came across the Rocna issues discussed here in depth and said, no point settling for a Rocna now, so probably going for a Vulcan 55. But that did require a bit of rework of the bowsprit.
Well done, TIM.
if i ever do by one more boat, i think that how big an anchor it can use is what i will check first.
If i spend a lot of money on a boat/ship, i want to make sure that when i anchor, our life, money, is well taken care of. Life is so much better with a BIG anchor. Sail safe. and have a nice summer al.
Hi John,
Thanks for the perfect post at the perfect time. I am currently in the process of adding my long-awaited ideal anchor setup, and it’s your example exactly except that my 40-ft cruising boat is a Caliber.
My wife was starting to get a bit embarrassed when she saw the actual size of the anchor and I think beginning to question my sanity a bit. Thanks to your post, we’re all good.
Besides, I’ve always been from the Steve Dashew school of anchoring: When people begin to laugh at the size of your ground tackle, you’re probably starting to get it right.
Hi Alan,
Glad it was useful.
The strange thing is that the same people don’t seem to be laughing as they drag past you at 3:00 am!
Nice boat you have.
Here is a manual that provides an extremely detailed analysis of anchoring theory, gear and techniques for the big guys in the offshore oil and gas business. We are just scraping the surface, so to speak.
http://vryhof.com
Hi Wilson,
Yikes, that will keep us all occupied for a rainy day!
Hi John,
Nice article, as usual. One rule of thumb that I like to use is that if people at the marina point and giggle over how large your anchor is, then you’ve got it about right.
We upgraded from a 35# CQR to our 45# Manson Boss for our Niagara 35 and were astounded by the difference in surface area. It is probably 4x the area and is huge under the bowsprit.
We sleep well now, but I”m glad I didn’t go two sizes up for the 55# as it wouldn’t have fit. Different anchor types scale very differently.
Chris
Hi Chris,
As you say, different anchors scale differently, that’s why we limit our recommendations to the two anchor size tables we have studied (Rocna and SPADE) and also bias the Rocna down a bit, see the post above.
Hi John
Here is the recommendation from Rocna on over-sizing, interested in your thoughts, it does concern me as my boat, a Contest 37, is close to the top end of a 20kg anchor so am considering 25kg, but wary of the extra loads on chain and windlass
regards
Myron
“Many Rocna customers, in improving their anchor type by switching to a Rocna from an older anchor which they have learned to be unreliable, make doubly sure about their upgrade by also increasing the weight of their anchor. We see this tendency a lot, and try to discourage it. As above, our official sizing is very conservative, and in many cases it’s a case of “don’t over-size – we already did that for you!”
On a weight-for-weight basis, the Rocna represents a very significant step up from most other types, and doubling the size (for example) could inadvertently cause serious problems with retrieval and other handling issues.
Our sizing is conservative
Unlike other manufacturers, our sizing recommendations are intended to provide an anchor adequate for use in most all conditions. We base our calculations on 50 knots of wind, associated surge, and poor holding bottoms. For more on our philosophy and rationale, please consult our Knowledge Base article on our sizing recommendations.”
Hi Myron,
As I said in the post above, I’m writing about offshore voyaging boats here, which may be required to anchor in far worse conditions than 50 knots. In my some 25 years of full time cruising I have anchored in more wind than that (sustained) at least a dozen times. Given that, the Rocna quote above just confirms my sizing recommendations. Keep in mind that my key recommendation here is that your best bower also be your storm anchor.
On windlass load. First off, I am recommending going up one to two sizes, not doubling the size. Again the key here is that we are sizing a complete system that will keep an offshore boat safe in any conditions she is likely to be exposed to. Therefore, as I say in the post, if the windlass is not up to the job it should be replaced. Downsizing the anchor to compensate for a poor windlass is just compounding the problem. Ditto the chain.
Having said all that, given the size of your boat, the other option would be to go with the Rocna recommended size and then have a massive Fortress or SPADE as a storm anchor, and possibly doubling as a kedge. However, for the reasons I state in the post above, this is definitely a second grade solution.
John, I can’t recall, but does your windlass have a manual function and do you ever bother using it? Were we in relatively shallow waters, I would tend to up chain electrically until we were 1:1 and broken out and then finish the last five metres or so via cranking, as I feel this allows one to inspect the chain most likely in contact with the bottom and to just stow the anchor at the end of the roller more carefully. But then my background in sailing features non-self-tailing winches, manual pumps and other primitive forms of mechanical advantage.
Hi Marc,
Yes it does have a manual backup, but, like most electric windlasses said backup is not very functional and incredibly slow, so we never use it.
Also, when you sail a 25 ton boat with no electric winches and just two people you don’t look for things to crank by hand!
Hi Myron,
I suspect you will be quite happy with either anchor, but happier with the 25kg.
As to the chain, to my way of thinking the chain should only be sized by strength and not weight. This sometimes makes for a visual effect of too small chain (when G40 or G70) on an “oversize” anchor, but as you sleep well at night, it will start to look better and better.
As to the windlass, it depends on its “bollard” pull. You (and the windlass) will definitely have to work harder to get the new generation anchor out of the seabed, but that is a matter of a bit of patience when the anchor is up and down and then some extra time for cleaning it. A deck wash pump will be a blessing. But those are the prices paid for being nailed to the bottom.
I am really uncertain what Rocna means by “serious problems with retrieval” in this context of additional size/weight.
My best, Dick Stevenson, s/v Alchemy
HI Dick
Thanks for the comments, I should add that I was considering upgrading to G70 chain
Regards
Myron
John, I’ve been reading your posts on anchor selection, etc. as I have been thinking about upgrading this capability for some time. Besides anchor selection, two pieces of the system that seem equally important are anchor rode and windlass. I’ve read the articles on catenary and scope (Petesmith.net) and come away with the idea that the value of chain is primarily chafe related. With respect to windlass capabilities, the typical suppliers don’t seem to carry ones with the capabilities you recommend . I know you are in the process of updating your anchoring material – will you be addressing these aspects of anchoring systems in upcoming posts?
Hi Robert,
Absolutely, it’s we will be updating with our latest thoughts on chain and windlasses.
You guys are over the top, again!
I have a Rocna 25 on my Catalina 42, 13ish tonnes and have NEVER had a problem with the anchor being too small. I’ve been sailing in the South Pacific for three years and don’t agree that I need a 33 or a 40, first of all my windless couldn’t handle it, and mostly it is the design of the anchor and how you set it. Back up on it in reverse and when the bow swings, it is set! Cocktail time!
I have a back up Rocna 15, which is the model they use in all the testing. That anchor would hold me just as well.
Sure, I’m not sailing in Nova Scotia or Greenland, thank you, I prefer the tropics, but my Rocna 25 will never fail me, can’t say that about my chain or rode.
Hi Michael,
I’m sure you are right that your Rocna 25 is fine 99% of the time. At one point we were using a 66 pound SPADE, which would be the equivalent scaled by boat size, and it worked fine for us.
However, as I say in the post, my sizing recommendations are based on my thinking that our primary anchors should also be our storm anchors and that is why we use a SPADE that is two sized larger at 121 pounds. We also size our chain accordingly. In the final analysis I guess it comes down to where you are sailing and your risk tolerance. Also, perhaps you have a larger storm anchor in your inventory?
Having said all that, as Dick says, I really can’t see that going up one or two sizes would cause your windlass any problems. After all we are only talking 12 pounds difference.
John,
Risk tolerance is an interesting term, but the reductio ad absurdem argument is going to sea in a battleship or not going at all.
You use the term 99%, again, a mathematical probability based on what?
You have no quantifiable information that a Rocna 33 will hold better than my Rochna 25 for my boat.
As one of your posters mention, “I sleep better at night with the heavier Rocna!” Perhaps he should have tried more nights on the Rocna 25?
I sleep better at anchorages having three years of perfect holding in different situations on my Rocna25.
I expect more from you and this site, I have and continue to learn ways of doing things better and being safer from your knowledge base of cruising but chafe at unsupported conjecture and opinion.
Keeping my boat light and fast also makes me safer and more nimble.
I’d like to hear more from the Rocna people, but fear there is no testing that has been done between these two anchors and as I stated before, most if not all the different style anchor testing I have seen uses the Rocna 15.
Let’s also forget the windless issue as it has little to do with holding and the comforting idea of how we all sleep at night!
I’m sure that we don’t need Rocna to tell us that the 33 will hold better than the 25 for any boat, not just yours. Physics tells us that. In fact, the improvement is usually non-linear due to the soil mechanics involved (a 50% improvement in weight or surface area will give a better than 50% improvement in holding).
Anchoring is a very tricky business because bottoms are so inconsistent. No matter what a manufacturer might claim, it’s impossible to know that any anchor will hold in a certain wind speed because it depends on the bottom and the set.
We all have to make our individual decisions about how much safety factor we want to put into this uncertainty. Most cruising sailors decide that an extra 20# on the bow is negligible and worth the peace of mind.
You obviously disagree. It’s your boat and your right, but jumping on John for agreeing with the vast majority of sailors seems to be a bit unfair.
Hi Michael,
When we were picking ground tackle, I took a different approach than John but ended up with basically the same result for anchor sizing. I wish there was a standard like an ASTM one where the anchors were rated for holding power in different substrates and then a table was published similar to the one that Fortress publishes of holding power in different substrates as this would allow a much more informed decision. Since this doesn’t exist, here are a couple of factors that I don’t often hear people discuss which are part of the reason why we chose the size we purchased.
Being an engineer, I generally work with safety factors. With anchors, I think that this is not the correct way to go about it because the loads and the holding power are so variable, it is not like tensile testing steel which is highly predictable. Therefore, I think that the best way to think about it is in terms of probability. Short of carrying a several ton piece of granite, we can’t expect to get 100% reliability in anchoring but 99.9+% should be the goal. Where I am really interested though is in the challenging conditions that are rarely encountered but where the chances of dragging are the highest and the difficulty and danger in dealing with that dragging are also the highest. For the way we cruise, I would state this as a 95% success rate (no dragging) in 60 knot sustained winds in a medium mud bottom with less than 1/2 mile fetch. Even this isn’t nearly specific enough but I think that it would be a good starting point and it would mean that we would drag 1 out of 20 times in those conditions which is a bit alarming but probably realistic. My favorite explanation of sizing is by Rocna who choose 50 knots and “poor holding bottoms” but this is still a bit ambiguous and it doesn’t meet my requirements anyways so I would need to go larger. Of course, we don’t have the data to actually figure out exact probabilities but I still find it a useful tool for starters.
One of the reasons that we chose a big anchor is that the holding power generated is highly variable even in the same substrate. If we take the West Marine anchor test from a few years ago, the Delta held an average of 1925 but had a standard deviation of 1384 which is very alarming as it suggests the data was all over the place. Statistically, many of our sets will be significantly below the average holding power for that substrate. Since it is very hard to tell if your current set is one of the bad ones, you need to have an average holding power that far exceeds the loads (one area that I find very interesting is what happens when you have occasional load peaks that exceed the holding power). If we then look at the most recent Fortress anchor tests, we can see that if we include other substrates, the results are even more variable. Our anchors are sized around medium mud substrates as there are a lot of them where we anchor but if you stuck to sand bottoms, you might get away with a far smaller anchor. My take on John’s recommendation is that it will work for anywhere provided that common sense is used which includes incredibly variable conditions.
Thankfully, there isn’t that big of a pool of knowledge on anchoring in extreme conditions. Many people extrapolate from relative benign conditions up to storm force but this is a really bad practice. We don’t anchor in storm force conditions often but we do anchor in them. I try to pay close attention to how deep the anchor buried as that is my best indicator of how the sizing is and I have had the entire roll bar under the surface in conditions that are not at all extreme. Unfortunately, even the new generation anchors drag. I have yet to drag one myself but I have friends who have and I have witnessed others do it as well. Even with our large anchor, I consider it likely that we will end up dragging it at some point in the future. Anchor size is a compromise like anything else but we felt that it was easy to justify a 65lb anchor on our 36′ 17,000lb boat as there really was no downside.
Eric
I find this a very coherent comment, Eric, and thank you.
Of course, sometimes the best anchoring choice is not to anchor at all, but to head to sea where there are generally fewer hard things to damage your boat.
These days, it is relatively rare to be “surprised” by weather, also local conditions can vary enormously and not all places are well-forecast. But personally, having seen the destruction even the most minor of hurricanes (Gonzalo over Antigua, Oct. 2014) was able to make of a crowded anchorage/harbour, I would feel safer well offshore. Another point is that today’s boats have relatively greater windage in the past, and this ultimately increases the loads on any ground tackle. How many people, even with proper warning, strip off their sails and cockpit canvas? Secure their tenders with lashings? Put up storm covers? I found the airborne debris more dangerous than the wind, myself. Apart from devising an “ideal” boat that would exhibit a “windage constant”, it is hard to apply some holding figures meaningfully to such a dynamic and variable situation as multiple boats ranging from “unprepared” to “fully battened down” together in a gale-struck harbour. Even if everything else is equal…it isn’t.
Hi Marc,
While I’m a great believer in the old adage that “it’s not the sea that kills sailors, it’s the hard bits around the edges” I’m extremely uncomfortable with any suggestion that a yacht should head offshore to ride out a hurricane.
Even if said hurricane is just a cat 1, very few cruising boats are equipped or the crews experienced enough to safely manage that at sea. And worse still, any hurricane has the potential to increase in intensity dramatically and in contravention of the forcast.
Bottom line, if your boat drags ashore in a hurricane you have a good chance of surviving, but if you are offshore and the boat is overwhelmed by the same storm you die, it’s that simple. Therefore I think leaving an anchorage for sea in a yacht to ride out a hurricane or even a storm is an extremely poor and unseamanlike choice.
Hi John,
Thanks for confirming that. I have thankfully never experienced a full on storm at sea but I would definitely be worried doing so based on how exciting a strong gale can be. I have sat out a few at anchor and while I find the noise to be pretty nerve wracking, I do not become overly concerned for my own life provided I have picked a spot with soft edges where I could walk ashore.
Eric
With all due respect, were the storm and tide coming directly into a crowded harbour, I would consider all options, John. There are too many variables, such as the availability of the lee side of an island, the proximity of a hurricane hole nearby, but not in, an anchorage that is getting smacked, and the experience of the crew and the presence of equipment, such as drogues/sea anchors, to mitigate effects. Even the speed of the storm, and thus its destructive duration, would play a role.
I don’t care to rule out anything on general principles, having observed to date that life on the water seems to be a series of special exceptions.
Hi Michael,
I am glad you have had such success with your size Rockna.
I suspect you might feel differently were you attempting to get your size/weight anchor squirreling through the weeds of the Med or the Kelp of Scotland and Norway. There, I believe, added weight makes a big difference. Once well set, you may be quite right that a Rocna 25 will do the job, Sometimes the issue is getting the anchor to a place where it can get well set.
I am surprised you feel your windlass will not handle the added weight of the next size anchor. What brand/size is it? In the scheme of things, we are not talking about much additional weight so I would think ,at worst, it might slow down retrieval, but not make things impossible or lead to damage of the windlass.
My best, Dick Stevenson, s/v Alchemy
John,
As I sit on my anchor in Suva, Fiji, after a very wet beam reach from Opua, NZ which took 8 days, a fast run considering we lost our Genoa halyard half way.
My latest thought on your oversized anchor idea is that you have no empirical evidence for your argument.
‘If anchor manufacturer recommends X, then X + 2 must be better’
Here is my challenge to you.:
Buy, steal or borrow a Rocna 15 kg, 200 ft of ACCO 5/16″ G4 chain and the appropriate Crosby shackle.
Anchor with this set up in no more than 40 ft ( 5-1 ratio) in any condition that you “theorize” may fail. Now I’m not asking you to anchor to a lee shore, but I think you get my challenge.
While I cannot guarantee an outcome, I think you maybe surprised at the results.
Hi Michael,
I’m sure you are right, the Rocna is a great anchor. Likewise my 66 pound SPADE has held our 25 ton boat in gale force winds without issues. But would I want to try that in storm force winds? No.
Back before we had the 55kg SPADE I relied on setting other storm anchors when I expected very strong winds, perhaps this is your approach? And that’s fine.
But I prefer, for the reasons outlined in the post, an anchor on the bow ready to go that will, and has, handled winds of hurricane force on several occasions. Each to their own.
Hi Michael,
For you tropic sailors who prefer to stick to recommended anchor sizes here is an empirical case to consider. I can’t remember the exact details, but a few years back Grenada was hit by a cat 3-4 hurricane in spite of being “outside” of the hurricane belt. After the wind shift one of the few surviving boats at anchor was one of Steve Dashew’s designs, equipped with an “oversize” anchor as per his usual specifications.
Hard to see how an extra 20# or so is going to effect the load on a windlass that is already being asked to lift several hundred pounds of chain. So the main difference in weight is a somewhat lighter wallet if you choose to go up in size.
Within a given ground tackle weight budget, it always makes sense to put as much of that as possible in the anchor, even if the tables say it’s overkill.
Say you can handle up to 250 pounds for the whole setup. The anchor salesman says that a 40-pounder is about right for your boat, and offers 210 lb of 3/8″ BBB chain (130 ft) to go with it.
Having read AAC, you instead choose 5/16″ G43 chain, which is 50% stonger and weghs half a pound less per foot. The same 250 pound weight budget now gives you 170 ft of chain and a whopping 70 pound anchor.
The difference in practical, real-world performance between these two setups – both of which weigh the same – is night and day.
Hi John,
I will say that you are correct that most electric windlasses perform pretty poorly in their manual mode. In actuality, I did not choose the windlass that came with my boat so I can claim no good judgment, only good luck.
It is a Lighthouse which performs superbly as an electric windlass, but they have also taken the time to design it so it performs quite well in manual mode and has a kedging off mode that is quite incredibly powerful. The manual anchor mode benefits from having a ratcheting winch handle, something not so easy to locate these days, but not impossible. Clearly it should be said that neither manual mode will please you if you are in a hurry, but, in a pinch, they are more than adequate and just takes a bit of time, but no real effort.
Dick Stevenson, s/v Alchemy
Hi Dick,
Thanks, that’s worth knowing. I will put it in the mix when I write more about windlasses.
Hi Marc,
In my observation, one of the most dangerous things in a hurricane are other people’s boats. The four anchored boats in Onset harbor for Hurricane Bob were fine (the latecomer who barged in upsetting our planned layout caused a problem, but the boats ended up fine). The mooring field was predominantly onshore and the marina was pretty much totaled including all boats. In inspecting the boats on shore from the mooring field many showed signs of being beat on by other boats. Interestingly also, there mooring pennants were still quite long and intact off their bow indicating to me that their neighbors had pulled/dragged down on them and the rudder or prop had chafed/cut the pennants setting the boats free to find shore, luckily on sand.
My best, Dick Stevenson, s/v Alchemy
Dick, it was having observed this at uncomfortably close first-hand, that was the place from which my observation came. Boats bashing boats can not only cause obvious damage, from “that’ll buff out” to crippling holings, but can either wreck one’s mooring or cause a ground tackle failure, and then you’ve got possibly entangled and damaged boats heading for the rocks, the beach or out to sea. Lest I give the impression that I too strongly advocate “cut and run”, I would not rule out a deliberate grounding on the right sort of sloped beach if I thought it would save our lives and our boat (a full-keeler with a supported transom-hung rudder with which it’s possible to consider this tactic). For us, it all depends on the surrounding circumstances whether to hang tough or to bale out.
Hi Marc,
I would support finding a place where there are fewer or no other boats during preparation for a major storm or hurricane. That is what we did for Isabel when in the Chesapeake where there are lots of hidey-holes to choose from. Our final choice was to be far more exposed, but had no other boats about and we had the room to do what we wanted with our ground tackle.
When we realized that Hurricane Bob was aiming to put us in its worst quadrant (which did come to pass) and Ginger heard something vague that indicated I was contemplating staying aboard, she gave me a look and said that our 3 children and she were going to a motel and that I was coming with her. A non-committal “Oh” emerged from my mouth and she declared, “That is why we have insurance!” She was right, of course. Losing one’s life trying to save a child is one thing, a boat is another.
Of the 3 anchored boats with whom I prepared for the storm, 2 men stayed aboard. One had built his boat himself: his wife and children went with us to the motel. The other was a single-hander. Both were quite experienced and competent. The first was fine the next morning when I went by early. The other was badly injured, unable to help himself, and I got the CG to take him to the hospital. I was later told he was within several hours of dying because of internal damage.
Circumstances vary, in the Chesapeake with marshy and sandy stuff around, we stayed aboard (it ended up in the tropical storm range): were I Maine with rocks all around, I would do all I could and likely leave the boat. It is certainly possible that being aboard could make a difference, but I believe that to be unlikely: the chances being much greater that we/I would get hurt: unacceptable odds when there are choices.
My best, Dick Stevenson, s/v Alchemy
My goodness, Bob was a big ‘un. Dick, I don’t want to give the impression I am either casual or gung-ho on this topic. I largely agree with you that staying with the boat is not ideal and could be positively dangerous in some conditions. On the other hand, in many places of the world, the accomodations ashore are simply not built to withstand much in the way of wind (the recent Vanuatu typhoon comes to mind).
I also agree that going up a creek or into a secluded inlet with few or no other boats is preferable to a crowded harbour, particularly if you can run multiple strong lines to rocks or trees ashore. I would not casually run out to sea without a damn good reason, but then I’ve seen some damn good reasons now: I’ve watched docks literally split in front of me, and big boats smash into the shore still carrying large chunks of dock.
http://alchemy2009.blogspot.ca/2014/10/skipper-by-name-windy-by-nature.html
Like you, however, I would like to have options beyond one chain and one anchor, even if it did hold our particular vessel, because I do not have confidence in other people’s preparation. I also know that if our steel boat dragged because someone hit us, it’s us hitting others that would probably lead to more sinkings. Thank you for your experience.
For my Tartan 37C (15,500 lbs) I choose one size over what was recommended by Rocna, so I have the 25KG with 5/16″ G40 chain. It has worked perfect for 7 years or so. Last year we left from Nova Scotia, down the ICW and spent the winter in the Bahamas. I started diving on the anchor once we got down to the Bahamas and was very surprised to see that it wasn’t always fully dug in for some situations where the sand was hard packed (I could dive and put a knife in the sand and no rock beneath) I have a feathering kiwi prop and I would reverse until black smoke was coming out of the W40 engine, it seemed like lots of torque with the 5/8″ snubbers stretched quite tight. If there was to be any wind I would add our 40 lb kellet and put on the riding sail (to keep the bow to the wind) and we did not drag like others when some strong fronts came through. My long winded point to think about is that with an oversized anchor the square area is much larger and there may be times when you may not have the engine power to fully set the anchor under some conditions. Actually in Spanish Wells I carted the anchor to a boat repair place, borrowed a grinder and put a sharper edge to the sides of the Rocna which seemed to help. The sharper edges of a Spade would probably make this a moot point, but for me and our oversized Rocna, it was a concern.
Hi Richard,
Hum, that’s a really interesting thought. However, I think that the fact that the anchor is not fully buried by the load you can exert with your engine does not matter. My thinking being that a partially buried larger anchor will have the same fluke area bearing on the seabed (the parameter that governs ultimate holding) as a smaller anchor fully buried. After all it resisted the same force from the engine while in that state.
Assuming I have that right, then if the wind comes up to the point that your boat is exerting more load on the anchor than your engine did, then the larger anchor will dig in even further, and thereby increase its ultimate holding, whereas a smaller anchor fully buried might be at it’s maximum holding and therefore would drag sooner and at a lower force.
A thought experiment that helped me with this was to imagine that you anchored on say a 5 pound dingy anchor. Sure, you could bury it easily the engine, but it would still drag in any sort of wind.
I base this on an article on the actual mechanics of holding that Matt, our engineering correspondent is working on that I have seen a draft of.
Do any of the engineers out there have any thoughts on this? Matt, Eric, Chris?
Good points John, I had also thought that it would continue to bury itself if the wind came up. Of course if the wind shifted then came up, it may be more of a concern when not fully buried. It did help when I sharpened the edge of the Rocna (I’m sure there are a lot of groans going on….) but I am not opposed to modifying items if I feel it will help. I really like the sharper edges of the Spade and it may be in my future. I also feel strongly that anything I can do when the wind pipes up to ease the load on the anchor is worthwhile, thus the “delta” shaped riding sail I made (the boat dances around like John Travolta without it) plus the kellet help. Of course so would 3/8″ chain….
Richard
Hi Richard,
I’m sure the riding sail is great. On the other hand I’m not a big fan of kellets and suspect that it’s not adding much, if anything, to your security. More in a future post.
After reading this and other places we bought a Vulcan. One size bigger than recommended. A 25kg for a 41 Irwin.
First time we dropped it in Belhaven NC in deep black puff mud I let the boat fall off in 20 knots and smugly waited for the anchor to set its in own length like they said in the accompanying instruction booklet!
And watched that anchor drag though the mud like I was plowing a row for corn. I couldn’t believe it. Picked it up and tried to set it by backing down. 10 feet of water 60 feet of chain. It would not set. I was not even be living this.
The third time I set it down gently and made sure to let it pay out as I fell off in the now 25 knot breeze, and this time it caught and I backed down on it to make sure.
Within 30 minutes we had sustained 37 knots in a storm, and it held fine.
I wonder if having just one shackle somehow allowed it to kink and not set? At any rate I added another 5/8 shackle and last night it set as advertised. I am still going to be uneasy for a bit though.
We will see!
Hi Miami
Had the exact same experience. a 25 kg Rocna (with roll bar) plus 220′ of 7/16″ chain for my 39′ LOD 16 T ketch. Where I now moor, before I got the mooring, I used the Roc, in the slightest breeze, mild current, up an enclosed bay. It dragged twice, drifting along as if there was no anchor or chain.
There is a fish farm very close by. The bottom is the finest soft mud, very deep, extremely slick, almost like oil.
Maybe the Roc has a weakness in superfine deep soft mud.
Hi Nick,
Were those dragging experiences after the anchor was set, or while trying to set it?
Hi John
I always set it, meaning testing it by putting the engine in reverse, or have a good wind do this for me. This makes no sense; perhaps I omitted to test the set. It was quite a few years ago & I don’t remember much else, other than the mild breeze & light current. A local diver said the mud was like soup – he could push his arm straight down, no resistance.
Hi Nick,
I’m guessing you did set it but experienced a problem with the Rocna that Practical Sailor documented in testing and that we have been hearing of anecdotally: if the wind or tide switches 180 degrees the anchor can, in rare instances, be flipped over on it’s back and stay there balanced on the roll bar. My guess (and it is just that) is that this problem is more likely in very soft mud and if the anchor has been set and the blade is foul with mud.
Hi Miami,
This is very useful information about this new anchor, thank you. Please keep the reports coming.
I don’t think the problem was the single shackle, that is as long as it was on the correct way around with the bow through the anchor and the pin through the chain.
No matter what anchor type you have, very thin mud is a challenge to set. The secret is to come back very slowly and gently to work the anchor into the thicker mud deeper down, as you found on your third attempt. Of course doing that is easier said than done when the breeze is up, as it was for you!
Hi Miami,
Having thought more about your report, this is at least partial confirmation that it is difficult to do an anchor without a roll bar without going the expensive fabrication and lead in the tip way of the SPADE, The point being that although I have had a SPADE fail to set on me (less that a dozed times in 20 years) it has never ever dragged back without providing substantial resistance on the rode indicating that it was setting, but that the bottom material was not providing enough drag resistance to withstand our 3/4 power set.
In fact the few times it has dragged slowly back it has taken in excess of 35 hp at the prop to do it.
Disclosure: Both SPADE and Rocna advertise here at AAC, but SPADE have been with us longer and once gave us an anchor.
Good morning John et al,
These are interesting comments (now that I have bought the anchor!) – but I can’t add much yet.
It has been so friggin hot the last few days moving north we have been fortunate to borrow docks with power for the ac. (Came with the boat and are awfully nice right now)
Starting tomorrow we will be anchoring again a lot exploring the Chesapeake on the way to Philly and should have lots of opportunities to play in the mud. We will see.
Had a friend over last night who said ‘an old salt’ told him he dropped his spade and plenty of rode then went and had a drink – came back in 15-20 minutes and set the anchor after it had time to dig in. A capt on a 36 cat with a spade told me the exact same thing (he watched me try to set the vulcan.)
We will see! And let you know.
Thanks for the feedback. (Great for SEO too!)
Hi Miami,
I hear that “leaving the anchor to soak wisdom a lot, but actually I have never found it helped much. Rather we have found the secret in soft mud is to make sure that we run the chain so no load is put on the the anchor while backing down (requires the right windlass) and then very slowly and gently work the anchor in with the engine at idle revs in reverse, once we have 5:1 scope out. This may take as much as 5 minutes at idle revs before very gently increasing the revs to 3/4 power. Again this may take a while.
This is only required in soft mud with the SPADE. Normally we just dump it, run the chain to 5:1 and then take the engine right up to 3/4 power—5 minutes, soup to nuts.
More in this excellent chapter from Colin.
Update on the 25 kg Vulcan.
We have now anchored for the last month with the Vulcan from Beaufort NC up to Annapolis and through the Chesapeake.
Sheesh it’s muddy up here!
I have much more confidence in the anchor. When I drop it, I just let the boat settle back and pay out the chain 6-1 or so and let it sit while I tidy up. Then I will back down slow with 60 hp and slowly add power until 1800 rpm or so – a pretty good pull. I never did this with the plow or the barnacle I had as it would just pull them out!
The other difference is when I pull it up invariably I have to use the boat and not the windlass to break it out. It will hold the boat straight up and down.
So thanks for the recommendation and the followup!
Miami
Hi Miami,
Thanks very much for the Vulcan update. Please keep them coming. I will be very interested to hear how it does in the hard sand of the Bahamas, if you are heading that way.
Hi Miami, I agree with John re the “soaking” (nice way of putting it) of the anchor: never did much for me. My regimen is pretty similar to John’s to get my anchor in. If I think it may be a a bit of a challenge, I will give extra rode initially and then shorten up later once I have a good stick. I often do this anyway as I like to get the anchor in as quickly as possible. The more it moves while finding its way in, the more likely it may find trouble (fish apparatus, cables, etc).
Dick Stevenson, s/v Alchemy
Same here, irrespective of the anchor. Plenty of rode out until I feel well stuck in, and then I shorten up to conditions of weather and, if applicable, crowding. This also allows me the proper “vector” regarding the wind at the time of anchoring, so I’m dug in perpendicularly to the prevailing breeze.
Hi John, great info as always, thank you! I’m thinking about my ability to physically handle large, heavy objects, especially as I age. How do you and Phyllis find managing your 100+ pound anchor? Clearly you must be getting by ok since you’re using it. Have there been times when an anchor of that weight has been a physical challenge for you?
Best,
Chuck
Hi Chuck,
The way we are set up there is never any need to physically handle the anchor. It’s hauled and set with a windlass. We also have the bow set up so that we don’t need to remove it to go on a mooring. That said, if we do need to move it off the bow roller, we use a halyard, but that is a very rare event.
Hello,
When we bought our Hallberg Rassy 46 (around 20metric Tons) it came with a galvanized CQR I guess around 40kg with 100m of 3/8′ or 10 mm stainless steel chain. The junction chain to anchor is a WASI SS ball swivel, that seems adaquately sized. The windlass is a Lofrans 1200W 24 V.
I have had bad experience with CQR with a previous AMEL Meltem (the predecessor of ther Super Maramu).
I am thinking of upgrading to a ROCNA after checking it fits on the bow roller abd doesn’t interfere with the SS HR bowsprit. Do you think we should go for a 40kg ROCNA ?
We also carry a Fortress FX37 and a Spade Aluminium 100 as kedge anchors.
We will be anchoring mostly in the Med for the moment. Most often hard sand or mud. Some times rock. We try not to Anchor on Posidonia grass. It can be quickly 20m deep although we try to be in the 3 to 10m sand / rock if possible so we can manage some Anchor fowling in apnea.
Thank you for your real world advice.
Denis
s/y Hibernia II
Hi Foster,
Just use the selection criteria in the post above and you will be good. I would also get rid of that swivel, here’s why: https://www.morganscloud.com/2010/09/12/anchor-swivels/