Anchor / Chain / Boat sizing

[ddavis4464]

The idea of a heavy anchor makes my heart happy. I might go a different way on the chain. A lot of folks like to go up the food chain to high test chain. For me, proof chain is the way to go. Why the heresy? Well the working load is about 2.5 times more for the grade 70. The breaking force is ratio is the same (2.5). Before the lower strength proof coil chain breaks the windlass and gear are probably going to tear off the bow. If the chain is properly sized to the wind profile of the boat the working load should handle anything up to a Cat II. All the extra strength is basically unusable.
All the chain rusts away at about the same rate so you don't get any advantage there. Only buy chain by the barrel or half barrel, it is vastly less expensive. Buy it from a amenable hardware store for the best price. We're talking half to a third of the boat store price for the same item. Only use double dipped American galvanized chain.
If you happen to get into a hurricane and stretch the proof coil you get to buy the replacement chain with the money you saved the first time around. I have anchored through two glancing blows, but have never stretched the chain. Rusting however has gotten me a few times over the years.
Two pounds of anchor for every thousand of displacement seems to work well. You know that if you laid out enough chain you wouldn't need and anchor... no not suggesting that, but enough chain for a 7:1 scope takes a lot of work off the anchor. The chain drag will keep the anchor from popping out with a wind or tide change while it resettles. Good Luck.

[roverhi]

A 35# Manson Supreme or equivalent would be just fine for all around use. Had a 45# CQR on our 20,000# plus displacement boat and never had a problem including reported 50k plus winds from a tropical storm. If you had an electric windlass that was guaranteed not to quit when you most needed it, anchor size is not much of an issue. From experience at a much younger age, hauling in chain rode and a heavy anchor with a manual windlass gets old in a hurry. Why waste the energy if you won't ever need it. The FX23 can serve as an additional anchor in survival conditions if you should need it. FWIW, on a similar displacement boat, have a 35# Mantus on 130' of 5/16" chain plus rope rode and an electric windlass. Have an FX23 as a backup and FX16 as a stern anchor in the lazarette. The FX23 is huge in comparison to the Danforth 20H that served me well for many years on another boat of similar displacement.

Not a fan of having a storm anchor. What's on the bow is the anchor that I'll feel safe with in all but survival conditions. For me, that would be a 35# anchor. In those conditions want a second anchor to be as sure as possible that one of them will hold in case of a rode failure. It's been my experience that the rode is more of an issue than the size of the anchor. Lose a boat or two a year here to rode/mooring pendant chafe. What's on the bottom seemed to do just fine.

[Jim Cate]

Originally Posted by laika

Jim, why don't you like the storm anchor in the bilge? Because it's just not used in practice and quietly collects rust?

Thx

Others have already explained this philosophy, but in general, one never can be sure that during a period at anchor one might suddenly need the larger anchor due to a change in conditions. This is a lousy time to be dragging that rusty storm anchor out of the bilge and trying to rig it usefully.

Put your best bower on the bow and use it all the time. If it is too heavy to recover in normal use, just think how hard it will be to recover when dug i n by storm force winds!

Jim

[Cheechako]

Originally Posted by roverhi

A 35# Manson Supreme or equivalent would be just fine for all around use. Had a 45# CQR on our 20,000# plus displacement boat and never had a problem including reported 50k plus winds from a tropical storm. If you had an electric windlass that was guaranteed not to quit when you most needed it, anchor size is not much of an issue. From experience at a much younger age, hauling in chain rode and a heavy anchor with a manual windlass gets old in a hurry. Why waste the energy if you won't ever need it. The FX23 can serve as an additional anchor in survival conditions if you should need it. FWIW, on a similar displacement boat, have a 35# Mantus on 130' of 5/16" chain plus rope rode and an electric windlass. Have an FX23 as a backup and FX16 as a stern anchor in the lazarette. The FX23 is huge in comparison to the Danforth 20H that served me well for many years on another boat of similar displacement.

Not a fan of having a storm anchor. What's on the bow is the anchor that I'll feel safe with in all but survival conditions. For me, that would be a 35# anchor. In those conditions want a second anchor to be as sure as possible that one of them will hold in case of a rode failure. It's been my experience that the rode is more of an issue than the size of the anchor. Lose a boat or two a year here to rode/mooring pendant chafe. What's on the bottom seemed to do just fine.

totally agree. a 35# new gen anchor is plenty for that 27 ft boat.
Sometimes you can over think this. When fitting out my 47' years ago, the only Delta anchors available were 66# and 80 something #. I opted for the 80#. when I got it down to the boat, I realized just how big it really was. ........carried it back to the store and exchange it.

[hamburking]

When you add up all that weight, anchors and chain, thats a lot of weight...and most of it up on the bow. I agree with the other posters...its overkill. I'd put one big hook on the bow, with chain and nylon. And stow another twin to that below. If you overload your boat with weight, you'll run into other problems.

I have a 30' Pearson. I carry a 10kg bruce on the bow with 10' of heavy chain, and 200' of nylon braid. I have an identical spare stashed below. One night when it blew 40 knots at my favorite anchorage, the bruce dragged. I reset it, and then set the second bruce in a V off the bow. It held well. All the other boats dragged (about 20)...made quite a show. Only one boat, a little grampian held fast and looked totally relaxed...he had a rocna.

With all that new investment on the bow...do you set a tripline on a marker when you anchor? I've caught a powerline, a dead tree, and a car frame with my hooks, and had a terrible time getting them back because I didn't set a trip line. The thought in my head is always...do I just cut it loose and take the loss?

[Bulawayo]

Originally Posted by Cheechako

totally agree. a 35# new gen anchor is plenty for that 27 ft boat.
Sometimes you can over think this. When fitting out my 47' years ago, the only Delta anchors available were 66# and 80 something #. I opted for the 80#. when I got it down to the boat, I realized just how big it really was. ........carried it back to the store and exchange it.

Isn't that the whole point, Cheechako? I dont think anyone would argue that the recommended weight anchor shall hold the majority of the time. The big however is the extreme. I would hazard that a number of cruisers who wonder the planet have experienced the sudden squall that usually occurs after dusk. When you get 60 knots suddenly hit you from no-where you tend to re-evaluate your anchoring arrangement. The first time it happened to us was in northern Madagascar and I spent two hours with both engines taking the load off a dragging anchor. We had a storm anchor but there was no way to set it. An adjacent Australian cat, which had a massive CQR anchor stayed put. When we spoke to the owner the following morning he grinned and told us he had also learnt the hard way to forget using a recommended weight and to always use his storm anchor. We sold our recommended weight anchor soon after and used our storm weight routinely after that.
I would hazard that if you keep to an area that does not experience such weather then your comments shall be correct but if you look at many anchoring forums, especially of cruising boats then you shall read a number of stories of people that have dragged unexpectedly and do not have any opportunity to adjust their anchoring arrangment. We do have a single hander friend, also on a cat who prefers yet another arrangement; he anchors his 38ft cat using a tandem arrangement. He swears by a Fortress anchor followed by 25ft of chain to a CQR. Personally, I would not be able to get on with the hassle of bringing this back on board constantly, especially single handing.

[DMCantor]

You need to think a bit about cruising grounds, as well. Over the years, we have rarely had difficulty anchoring across the whole Eastern Caribbean chain. Some harbors you have to be smart about where you locate (Bequia is a good example), and in some harbors its just easier to pick up a mooring (but be careful because many moorings are in really poor condition). But generally, you can get dug in and be secure without any heroics on anchor size.

Rode length is another story. Harbors get crowded, and that often pushes you out into deeper water. We have 200 feet of chain rode, which gives us 40' depth (including bow height) for a 5:1 scope. Plenty of places where it would be preferable to anchor in 50' or even 60', and I don't recommend skimping on the scope.

If you stick with 200' of chain, I suggest you get set up to easily and securely add a length of nylon rode. If you use this, increase the scope beyond 5:1.

[Cheechako]

Originally Posted by Bulawayo

Isn't that the whole point, Cheechako? I dont think anyone would argue that the recommended weight anchor shall hold the majority of the time. The big however is the extreme. I would hazard that a number of cruisers who wonder the planet have experienced the sudden squall that usually occurs after dusk. When you get 60 knots suddenly hit you from no-where you tend to re-evaluate your anchoring arrangement. The first time it happened to us was in northern Madagascar and I spent two hours with both engines taking the load off a dragging anchor. We had a storm anchor but there was no way to set it. An adjacent Australian cat, which had a massive CQR anchor stayed put. When we spoke to the owner the following morning he grinned and told us he had also learnt the hard way to forget using a recommended weight and to always use his storm anchor. We sold our recommended weight anchor soon after and used our storm weight routinely after that.
I would hazard that if you keep to an area that does not experience such weather then your comments shall be correct but if you look at many anchoring forums, especially of cruising boats then you shall read a number of stories of people that have dragged unexpectedly and do not have any opportunity to adjust their anchoring arrangment. We do have a single hander friend, also on a cat who prefers yet another arrangement; he anchors his 38ft cat using a tandem arrangement. He swears by a Fortress anchor followed by 25ft of chain to a CQR. Personally, I would not be able to get on with the hassle of bringing this back on board constantly, especially single handing.

Yeah, everyone has to make their own decision. I think a 35# is well above the recommended weight for that 27 footer right? BTW: A Fortress FX37 with 25 ft of chain held that same 47 foot boat I mentioned in winds of 71+ mph. That's the anchor I would have for Storm conditions.

[kas_1611]

Talking of storm conditions I'll share the experience from Thursday that we had here in Croatia. I'm tied up in my home marina right now in a large sheltered bay.

Lovely day, sunny and clear all day. Some cloud building over land but that's pretty normal for this time of year. Wind non existent to bugger all.

Suddenly out of nowhere, and I mean that in all honesty, the wind goes from 1kt to 38kts and swings round through 90º from NW to NE as a massive storm front hits. Torrential rain followed and within 10 minutes we were heeled over at about 20º and bouncing around like a cork in a jacuzzi (remember I'm tied to the quay!). Given the bay is cut in 2 by a causeway there isn't much fetch but the chop that was driven up by the wind was impressive.

As is normal at this time of day (5pm) it was busy with charter boats coming in so you can imagine the chaos. Even the 100ft superyacht that moors up in the marina had to make 2 attempts to come in with all her horsepower and multiple thrusters.

Imagine instead of being tied to the wall in the marina that you were sitting on your 16kg Delta (our old hook) thinking isn't this lovely. Then WHAM! you are broadsided by 38kts and quickly getting bashed by quite steep chop. Odds on dragging? Pretty blooming high and odds of deploying a secondary storm anchor? Pretty bloody low I'd guess.

Hence always anchor for the worst possible conditions with the biggest anchor you can carry on your bow and sufficient chain/rode out to hold you. It's easier and safer to do this in quiet conditions than trying to do it as the tempest tries to flay the skin from your body or blow you overboard whilst your boat goes backwards.

That's why I carry a 33kg Vulcan with 60m of 8mm G70 spliced to 45m of 16mm anchorplait up front. My old Delta did indeed drag twice at 45kts and 35kts previously and it's not an experience I want to repeat.

Keiron

[Stu Jackson]

Good advice here about anchor sizing. The Rocna information is very good.

What always seems to be missing in these discussions are the entire anchoring SYSTEM.

Calder's Cruising Handbook has a great discussion. The baiscs are size of boat and ANTICIPATED wind strengths.

ONLY YOU can make these decisions.

Here's some discussion about that with the tables from Calder's book.

Anchor System Sizing Tables (Reply #6) & Why Swivels are a bad idea Ground Tackle & Anchor System Sizing TABLES & Swivels

[laika]

Really appreciate all the various input. Tons of good stuff. And thanks for the link Stu. I usually cringe at tables and graphs and just operate on the "overbuilt it" principle, but accordingly, a 30ft boat will see about 2800lbs on the tackle and hardware at 60kts of windspeed. The WLL of 5/16 BBB is 1900lbs. UBS much higher. The hundreds of feet of 3/4" double-braid that I have has a WLL of 1800libbys.

My bow cleats and windlass are all backed by large g10 backing plates. The cleat arms will sheer off before it pulls through the deck. I am planning on using 3/8" 209A crosby industrial shackles, WLL of 2000lbs, and no swivels. Planning on buying the mantus bridle and hook along with the anchor.

I like ddavis's rationale for the BBB. After all, the UBS is substantial, it's gonna rust either way, and you can always buy more. 5/16 BBB is already a good size for my boat and that's what I'm setup for. As of now, I'm planning on buying some fresh stuff and new shackles when I get back down to FL and calling it good.

If I get caught in a 60kt+ blow the WLL of the system would have been exceeded by a decent margin and it would seem prudent to replace chain and shackles.

In terms of weight, the boat was designed to cruise and I've done a lot to keep her simple. With all her chain out, she actually squats a bit. She's 5 tons empty and while not beamy (yet w/ a lovely tumblehome) has the freeboard of boats 10' longer. Probably not a game changer, but seems worth mentioning. It's fairly large boat in a little package.

I've scratched the 65# super-storm anchor, but think I'm gonna see the conservativism through with the 45#. PLanning on getting an fx23 as well, but if the mantus is to serve as the defacto storm anchor, that's what they recommend for boats in my displacement range. I also reckon I'm hauling chain w/ a manual either way, and it's only the last bit where the anchor comes into play. It may be I'll rethink that after a couple months on the hook!

I've been reading through Noelex's excellent anchor photos thread lately and one of the things that also strikes me about having an unduly large anchor is the potential to open up otherwise questionable anchorages.
If you can lift it and it fits on the boat the positives just seem to far outweigh the negatives. Plus I'm 6'2", 32yo and in good shape.

A hearty thanks again to all! Easy to get lost in the weeds on some of this stuff. CF proves time and again to be a great resource.

[sailnow2011]

When cornell setup his boat he did a 33KG rocna. Mantus is almost the same anchor, so thats good. However his boat was 45' with a lot of windage. He may know what he is talking about. I only question his use of 3/8" chain. A good G40 5/16" is all you really need under 50', as their are no recorded failures of an anchor chain that was not due to age and neglect.

[Bluebeard]

Over many years I've read the discussions about anchor/chain sizing with interest. I've spend a significant part of my life engineering anchor systems for oil rigs. Using chain that is sized in inches not millimetres! Like 3 or 4 inch diameter. When you start analysing what is happening, there are several factors that don't ever get discussed:-
There is a quasi steady state loading due to wind and current, and a transient loading due to wave and swell surge. In the latter case the overall strength of the system is secondary and what is important is the ability of the system to absorb the energy of the wave as it passes through.
In both cases the anchor rode should not be above horizontal at the anchor.

There is real value in having an all chain anchor rode. When it is working it forms a caterary, with varying lengths of chain still on the seabed. As it is loaded the caterary is flattened and chain is lifted off the seabed close to the anchor. It is not generally understood that this sytem is very elastic and absorbs energy by lifting the chain through the water. So there are significant advantages in using all chain, and the heaviest chain possible at that. Whether you want extra weight of chain, especially if it is in a chain locker at deck level and in the bow is another question.

For me, put the weight into chain, not the anchor. As ddavis4464 says above, if you have enough chain out you don't need the anchor. My judgement is that before you ever get anywhere near loading an all chain system to it's braking point you will have pulled any realistic anchor out of the ground.

It worries me that people use an all/mainly rope rode as this will have very little catenary effect, I doubt that the elasticity of rope is adequate.
An answer of course is to use angels, weight lowered down the rode to create a catenary, but you would have to use a similar weight to the chain you are replacing.

What we need is for some young thing whose brain still works to run the numbers.

[Cheechako]

Originally Posted by Bluebeard

Over many years I've read the discussions about anchor/chain sizing with interest. I've spend a significant part of my life engineering anchor systems for oil rigs. Using chain that is sized in inches not millimetres! Like 3 or 4 inch diameter. When you start analysing what is happening, there are several factors that don't ever get discussed:-
There is a quasi steady state loading due to wind and current, and a transient loading due to wave and swell surge. In the latter case the overall strength of the system is secondary and what is important is the ability of the system to absorb the energy of the wave as it passes through.
In both cases the anchor rode should not be above horizontal at the anchor.

There is real value in having an all chain anchor rode. When it is working it forms a caterary, with varying lengths of chain still on the seabed. As it is loaded the caterary is flattened and chain is lifted off the seabed close to the anchor. It is not generally understood that this sytem is very elastic and absorbs energy by lifting the chain through the water. So there are significant advantages in using all chain, and the heaviest chain possible at that. Whether you want extra weight of chain, especially if it is in a chain locker at deck level and in the bow is another question.

For me, put the weight into chain, not the anchor. As ddavis4464 says above, if you have enough chain out you don't need the anchor. My judgement is that before you ever get anywhere near loading an all chain system to it's braking point you will have pulled any realistic anchor out of the ground.

It worries me that people use an all/mainly rope rode as this will have very little catenary effect, I doubt that the elasticity of rope is adequate.
An answer of course is to use angels, weight lowered down the rode to create a catenary, but you would have to use a similar weight to the chain you are replacing.

What we need is for some young thing whose brain still works to run the numbers.

Interesting for sure. Chain does matter, when I was in the Tobago cays on my catamaran, one day it blew a steady 30 with gusts in the high 30's. Shallow and mostly flat water as it's completely protected. I snorkled a lot and in those conditions the chain was not taught and had a pretty good catenary in it. I would have thought it would be bar tight!

[Chuck Hawley]

I have a similar sized boat, albeit without a windlass so I can't use a long length of chain.

After doing a lot of anchor testing over the last 25 years, I'd go with a "modern" Rocna/Supreme/Mantus design in the 33-35# range, and 5/16" HT chain. My preference is the Manson Supreme, but that's a personal bias and not based on hard evidence.

I think you'll find that the "scoop" type anchors hold dramatically more than the plow style anchors, and that they are extremely strong and resist bending from veering loads.

Chuck