Bristol Channel Cutter "Angelsea" (Shanti)

To chain or not to chain

 

First, for reference: go to Tuning an anchor rode by Al Frasse and take a read, or after you read this blog. It is the best article I have ever seen on using chain, line or chain/line for anchoring. He gives some GREAT mathematical scenarios for the use of chain and/or line for anchoring. All of my samples in this article are derived from running the spreed sheets he provides on the site.

Ok…ladies and gentlemen, grab a cup of joe and listen to my reasoning regarding too much weight in your bow. You may not agree which is fine. In the end you are responsible for the safety of your vessel and those who sail with you. So what you do is up to you. I will not fault anyone for that. This is all my theory and I’m stickin’ to it mainly because it has worked well for me. Isn’t that the way it usually works in the end?

Let’s start with a situation and a realization.
My wife (then) and I were on a cruise from L.A. to the Sea of Cortez. This is aboard Angelsea, our 22’engineless Falmouth Cutter. We had been anchored in Cabo San Lucas and departed for La Paz which is about 150 miles up into the Sea of Cortez. Our first leg was to a bay called Los Frailes about 50 miles up the coast. The last 30 miles into the anchorage we were headed on a course that is pretty much due north. The sail started out a pleasant one…close reaching in about 12 kts of wind. But that was soon to change. We had a tail wind and a current at about 1 kt to help us along. Everything was cool, or so it seemed. Now about 15 miles from the anchorage it looked like we would make it in by night fall. Then the wind started to pick up out of the north, and blowing contrary to the current that was helping us along.
North winds this time of year in the Cortez happen and usually can be quite strong. Well, this was a doozey of a norther. By nightfall it was blowing 35-40 against the current. We were reefed down to the 3rd in the main and the first or second in the staysail, depending on the state of the wind. The seas were square. At the time we were carrying a 65lb ABI windlass and 200′ of 5/16 BBB right up in the bow. This was 310 pounds total w/anchor or like having 2 average sized men sitting right on the bow. This proved to be too much weight for Angelsea. She would nose dive into the oncoming swells and almost come to a stop. Of course because of our course to destination and the direction of the wind we were beating. (I then realized why they called it beating).
We beat off Los Frailes for 3 days and made 5 miles to weather. Finally we turned tail and sailed back to Cabo. We promptly went ashore to have an ice cream cone  😎

Now to the analysis:
Not only is anchoring and the gear to do it important for one’s safety, but a vessel MUST also be able to beat off a lee shore in most circumstances. Sure, there are times when things go so bad it’s “bring out the sea anchor!”, and hopefully you have enough sea room through prudent planning to survive. So weight in the bow is an important consideration balanced with the gear to keep you put in one place. It’s not an easy decision really.

So what did I change on Angelsea?
I took the ABI bronze windlass off and went to 100′ of 1/4″ HT and ½” multi-plait line. That took 200 lbs out of my bow. Angelsea now sailed like a witch to weather easily lifting her bow over the seas. It was an entirely different boat. This setup for my primary working anchor worked well for over 10 years in the Caribbean.

Let’s look at trade offs, specifications and scenarios for going lighter with the anchor gear. After all we all want to sleep well at anchor.

¼ G4 is rated at 2600lbs. WLL (working load limit) with a safety factor of 3 giving us a breaking strength of 7800lbs

5/16 G3 is rated at 1900lbs WLL with a safety factor of 4 giving us a breaking strength of 7600lbs.

I have no idea what the reasoning is for the different safety factors used for the different materials.

So as far as strength goes we can use either ¼ G4 (HT) or 5/16 G3 (BBB).

Now to shackles to hook this all up with. Shackles have been a weak link in the past for ¼” chain, as equivalent strength has not been available. Most shackles with equivalent strength will not fit 1/4″ chain. So we have a weak link so to speak. But there are shackles out there that do. Look up Van Beest shackles from Holland. They are sold here in the US. Their 9mm shackle looks like it will fit  ¼” chain. It is rated at 1500lbs WLL, but that is with a safety factor of 6. Again no idea why this safety factor, but they are the Dutch and the government may require a higher safety factor. So the breaking load is at 9000lbs. If we use the same safety factor as the HT chain, that would be a WLL of 3000lbs. If anybody knows the reasoning for the different safety factors, please speak up,

Now for some sample scenarios I ran with the excel sheets from France.

Lyle Hess 26′ Falmouth Cutter (12000Lbs). Inspired by a forum post at the Bristol Channel Cutter forum for a 26′ Falmouth Cutter.

Scenarios:

Anchored in 22′ of water and freeboard of 3′ = 25′ total

All chain 5/16 G3 (BBB) – Labeled 5G3
100′ of 1/4″ G4 chain w/1/2 nylon line – Labeled 4G4

Working load limit for 5/16 BBB is 1900 lbs,
WLL for 1/4 HT is 2600 lbs

Wind 20 knots, gusting to 25 knots – over 30kts I deploy a second anchor.
Force of wind calculated for 30′ boat, as a safety factor and to take into account the extra rigging and spars of a Lyle Hess design.

Force of wind at 20kts 163 lbs, Force of wind at 25kts 741 lbs (gusts) w/ boat at 30 degrees yaw

Note: we do not want to exceed a 10 degree pulling angle at the anchor. After that point we will lose way too much holding power.

20-25 kts of wind

4G4 100′ chain and 25′ line (5 to 1) – Angle ranges from 0 to 8.8 in the gusts with a max dynamic force of 1096 lbs

5G3 with 125′ chain (5 to 1) – Angle ranges from 0 to 9.9 in the gusts with a max dynamic force of 2568 lbs

Now we increase our scope by 25′ with either chain or line to 150′ (6-1)

4G4 – Angle ranges from 0 to 6.3 in the gusts with a max dynamic force of 1033 lbs

5G3 – Angle ranges from 0 to 7.7 in the gusts with a max dynamic force of 2433 lbs

Lastly, go to http://alain.fraysse.free.fr/sail/rode/rode_b.htm and run some of your own scenarios through the spread sheets there. It’s a good exercise and very informative.

Last year anchored in Charlotte Amalie Harbor I experienced one of my wildest times at anchor, even worse than riding out a Cat 4 hurricane in the mangroves. I was anchored in 30’ of water with my 100’ of chain and 50’ of line out (5-1). The wind was blowing 10-50 knots (confirmed by some Mega yachts close by at the marina). The large range of wind speed was what caused all the problems. After a major gust, and the chain and line had been stretched out, the boat would spring forward then go beam to the wind because the rode was so slack. So when one of the 40-50kt gusts hit it was right on the beam. A couple of times I was knocked down to about 40 degrees, or visually my side decks were underwater. Stuff flying all over my cabin below. IT WAS WILD!
I would normally have put out a second anchor, but I was clear astern and wanted to see how well the system would hold. The bottom was excellent holding by the way. This wind condition went on most of the day. I didn’t budge an inch.

Chafe!
Now to last last and final argument in the chain line debate, chafe. One of the reasons I use 100′ for the first part of my rode is for the chafe factor. Here in the Caribbean we have coral rubble bottoms and coral heads that the rode can chafe against. Although I try not to anchor to close to coral heads. First, you don’t want to damage the coral. Second if you do get close and the wind shifts, you can wrap the chain around the head. This makes for a bad situation if you get something bad in the night. With the chain effectively shortened you can easily have a shock load when the load comes up short on the chain. This can easily break the chain.

With the chain/line combo, you get the best of both worlds. In most cases when you are anchoring close to coral heads it is fairly shallow. So you can use all chain at 5 to 1 in 20′ of water. Oh, and put out 6 or7 feet of line instead of using a snubber. In 30 feet of water you can deploy all your chain and 20′ of line to give 4 to 1, or 50′ of line if it is going to be blowy. With the wind blowing and the angle of the rode, the line is still fairly shallow and not even near the bottom. In 25 years of sailing the Caribbean this has always worked well for me.

On my present boat, Shanti, which is a 15000 lb 28’ Bristol Channel Cutter I use 100’ of 5/16 HT, hooked up to 200’ 5/8 multi-plait nylon. This is handled by an all bronze manual ABI windlass. The windlass is located about 8’ aft of the bow and dumps the chain in the bilge right in front of the mast. I use a 22’ Delta anchor, which as far as I can figure equals the holding power of a 35lb CQR. And as you can see with line in the equation I have a lot less dynamic load on the anchor.

Now I’m going to go get some sleep!

Gary

2 thoughts on “To chain or not to chain

  1. dwkentsr

    Gary,
    I concur with your analysis and conclusions. I found a lcoal supplier for 5/8 inch Gleistein 8 plait polyester that should minimize the bungee cord springy behavior of the equivalent nylon rode.

    I bought a bronze stem head anchor roller with roller extensions to allow stowage of a Rocna. It is way too heavy and puts the bowsprit traveller out of reach. You have a stemhead anchor roller. Any photos on your site? Is it custom built? Where can I buy one?
    Thanks
    David Kent
    BCC Rose

  2. Douglas

    Hi Gary , often it is recommended to dive on your anchor to see how it is set .

    I did this one time and found that my 25 lb CQR was lying on it’s side.
    The anchor tip caught on a low rock protruding up out of the sand, when I was backing down, then fell back on it’s side on the sand bottom near-by .
    This time I did dive on my anchor with scuba gear, and was easily able to lift the anchor off the bottom and re-set it in sand a few yards away.
    My surprise was that the anchor weighed half as much as it did on deck in open air.

    You must have experienced this too at some point in your cruising.

    Heavy things submerged in water seem to weigh a lot less .

    I did look to see what the comercial dive boats were using in the area, and they all used a Bruce, so I switched to a Bruce too.

    Not familiar with a Rocna yet , but many European boats seem to use this one .