Anchor sizing questions

[evm1024]

Manufactures recommendations are just that, recommendations. They have no special insight into your boat size, type, anchoring grounds, rode etc.

They do use a number of tables, rules and math that have typically been worked out by others. And they do a bit of but not exhaustive testing on their products to establish roughly where their anchors fit into the tables, rules and math.

Many of you remember the fiasco of Rocna moving their production from NZ and Canada to China - And many do not. Their anchors were bending like pretzels - I had one of the Rocna with weak steel shanks and returned it to West Marine.

And some posting in this thread were pivotal in exposing the flaw in Rocna anchors at the time. This was the same time frame where CMP took over Rocna.

The point being that anchor manufactures screw up, have no true insight, and have a vested interest in selling anchors for profit. Which means that suggesting that you put a huge anchor on your bow is not the best sales tactic. Big enough to do the job >>> most <<< of the time but not so big as to look bad.

Food for thought.

[Bon Temps]

I changed to a Rocha 3 years ago after dragging on my spade and a weird 3 blade monster that I can’t even remember the name now. I researched the hell out of it and decided on the Rocha and used one size bigger for my 38 ft cat. I use 8 mm chain. I have dragged once but n 3 years.

[Mike OReilly]

These discussions seem to boil down to a clash between two approaches.

#1. Those who seek a definite, clear and universal answer. They want a formula that you can input the parameters, and get the RIGHT ANSWER.

#2. Those who say anchoring is a complex problem that defies simple approaches. Therefore, the best approach is to do the BEST that you can.

I obviously fall into the second category. I don’t dismiss the data-driven approach. I’m a science guy; I love data. But after much anchoring experience I’ve come to realize the range of variables is such than the simple formulaic approach is likely never going to capture the reality of — reality.

I don’t dismiss the formulaic approach, but I recognize it is based on a set of simple variables, and simple inputs (tests), that don’t capture the range of what I actually encounter in the real anchoring world.

Therefore, recognizing that more holding power is better than less, but also recognizing that each boat and crew have limitations with regard to how much mass they can manage, I come to the simple approach that says: JUST DO THE BEST YOU CAN.

In this case, the BEST, is getting the largest new-gen anchor that fits your boat and your crew’s capabilities. Match it with as much chain as you can manage.

[evm1024]

Very well said Mike.

I just want to remind people that anchoring can be divided into 3 modes:

SNAFU

TARFU

FUBAR

[boom23]

This thread is going around and around in circles...

All I have to say is that everyone is entitled to his opinion. But, please, if you are one of the "get the smallest required anchor/rode" people, do not anchor close to me. If you drag, even if you do not hit my boat, I will have to come and help you, which can endanger my life.

I really wish no one's anchor drags, ever. I also wish I could control every possible anchoring variable, but that is not possible. That is why I like to err on the side of extra holding power (anchor size and chain weight/length). I am not a racer.

Let's all be safe. Cruising is supposed to be fun.

[Stu Jackson]

Originally Posted by JDWS

>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>>>>>>>>>>>


What I haven’t finished yet is setting up the rest of the ground tackle. For now, we are still swinging off of the original nylon rode plus 35 ft of 5/16 chain. In the PNW, being choosy about weather, abundant well-protected coves, and good mud holding this is working for now, but before moving onto the boat for the 2019 season, I want to upgrade. My current thinking, based on a lot of reading and chatting with other sailors (and our own overnight-to-2 wk cruises in the area) is 30 meters of 5/16 backed my nylon, and move the existing rode plus the 10kg claw to the stern. We plan to stay in the region for the next couple of years, but may also jump to the sea of Cortez at some point.

Any thoughts?

Sounds right. Have you read Smitty's website, he has a C310, too.


I may have posted this earlier in this thread, but it applies to your thinking, from a friend of mine:


Steve’s Anchoring 101

The Rocna. All 20kg of it with 100ft of chain. The rest of the world can debate all they like. When I pull into a place like Bodega Bay at midnight and the fog is so thick I can't see the jetty 50 feet away to make an entrance, I drop my hook in the rolling ocean swells with the surf crashing (Foster says it's like staying in a cheap Best Western beside the highway), and I sleep. And in the morning I have a windlass to pull the beast up and I wouldn't trade it for anything. (I also wouldn't add more chain - this works perfectly in 25 to 30 feet of water - you let all the chain out and you tie off nylon at the preferred scope and don't bother with snubbers and chain hooks and all that stuff...)

[Jim Cate]

Originally Posted by Souzag818

Hey Jim and Ann- I value your opinion, and most of the time I completely agree with your comments. You're one of a handful of people here that are doing it full time and I respect that. I've got a Spade S100 and have never been happier or felt more secure and safe whenever I've used it. It's held my boat in 30 knots, with 100' of chain and about 30 of nylon rode let out, and I had another 220' of line I could have let out, but didn't need to. My question is what do you have for an anchor? I'm not planning on giving up my Spade, I'm just curious.

Thanks for the kind words. Both Ann and I are happy to share our experiences and hope that they are useful to others... realizing that they may well not apply to other situations.

As to our anchor, well, we have been using a 60 lb Supreme for the past decade or so. It is on ~80 m of 10 mm short link ("Grade L") chain.Happy in general, but have had a problem with it in bottoms consisting of low sheer strength mud/silt in storm conditions. Have used a second anchor, an old Hi-tensile Danforth 20-H on a second rope rode in those situations, and that has worked well. We know that it will have problems in heavy weed and try to avoid such bottoms.

I think we would be equally happy with any of the modern anchors of similar size, but if I were to replace it today, I'd likely try to increase the fluke area a bit, either by changing to a different design or by increasing size to the next available one.

Jim

[JDWS]

Thanks Stu- love the Steve’s anchoring 101 quote - classic! I read a lot of Smitty’s blog when we were thinking about the C310; they seem great. I’ll have to hit him up on the scope and chain issue. I seem to recall they had similar tackle to ours when the first headed out.

[Jim Cate]

(or elsewhere)

(I also wouldn't add more chain - this works perfectly in 25 to 30 feet of water - you let all the chain out and you tie off nylon at the preferred scope and don't bother with snubbers and chain hooks and all that stuff...)

works perfectly... until the nylon chafes at the chocks (or elsewhere) and parts. If it was all chain with a snubber then when the snubber chafes and parts, you are still anchored.

Think this is fantasy? I've seen it happen... happily only on OPBs.

Jim

[GRIT]

I'm not sure why I'm posting here, an anchor thread of all things!

To skip the drivle, just read the paragraphs in red.

However, for the poster who asked: "if you were building a new boat, and could choose any anchor"... (I'm paraphrasing here.)

Well, we did just that; we built a new boat, and chose an anchor for her.

Here's my story.

We've always had rather large primary anchors: 35 foot S&S (6 tonnes) had a 33 lb Genuine Bruce anchor. 39 foot Corbin (12 tonnes) had a 66 lb Genuine Bruce anchor. Both boats had all chain g40, in 5/16.

We'd been very happy with both of our previous anchors, and boats. We were full time cruisers (always at anchor), for 14 years, from Nova Scotia, to Trinidad, to France, Spain, UK etc...

Our new boat is a cat, with a lot of windage. Cats are new to us, so we were very apprehensive in choosing the "proper anchor".

I studied all the "recommended sizes" from several anchor manufacturers, and noted their surface area, as well as the anchor's weight. I came to the conclusion that most manufacturers seem to recommend between 1700 cm2 and 2000 cm2 for our boat, spade recommended 1200 cm2. The weights were between 25kg and 45kg with most being above 35 kg.

Using these figures, and information gathered from reading several blogs, and questioning several cruisers, with similar boats, and adding my own personal preferences, we finally chose our new anchor. This, by the way, took several months of research.

Before I mention the anchor we chose, I should start by saying: I don't like the hoop, it's a personal thing, it just makes me nervous. I won't bother getting into it, but I'm uncomfortable with a hoop. Having said that, I'm also uncomfortable with anchors that are not built all in one piece, though that's what we bought.

We purchased a Spade S200. It has a mass of 55kg, and a surface area of 2000 cm2, which was actually the deciding factor for which model to buy. We have 80m of G40, 10mm Titan chain, and a Lofrans X3, 1700 watt windlass.

I might have bought an Ultra anchor, but I'm not sure I'm comfortable with using stainless for an anchor. It's a personal thing. If the Spade starts to rust earlier than we think it should, we'll switch to an Ultra.

In regards to using a larger anchor than recommended: We were in hurricane Juan, in Halifax, a direct hit. We were anchored on two anchors, the Bruce, and a Fortress. We had to ditch the Fortress, as it was caught by a passing group of boats, still attached to their docks. The "oversized" Bruce proved it's value that night, and not for the first time!

So there you have it. If I were to build a new 50 foot catamaran, with a maximum displacement of 9.5 tonnes, and could choose any anchor I wanted, because I'll build the roller to suit; I'd pick a Spade S200. Our secondary is yet to be chosen (Probably an Aluminum Spade), our kedge is a Fortress, and our stern anchor is a 66lb Genuine Bruce, with hurricane experience.

That's my opinion, which is worth exactly what you paid for it.

Cheers all.
Paul.

[thinwater]

BTW, I didn't mean to imply there was one answer. Heck no, since I've been all over the place on this myself, from heavy rigs with chain, to rope and aluminum anchors. Each suited the boat and the situation, and they were not interchangeable.



I just wanted to hear the "from scratch" responses.

[GRIT]

Thinwater. I took your post as you meant it. I figured you just wanted to know what folks would choose, "from scratch" and I'm sharing my choice, and thought process.

I've not yet found a real life problem with one sole solution. There are usually several solutions to every problem.

I'm just sharing mine.

Cheers.
Paul.