Posted on by Alex

Anchors n’ Chains

Of all systems in a voyaging sailboat, the Anchoring System is one of the most important, IMHO.

A good, well designed anchoring system will save a sailor’s bacon if he/she is ever caught at the wrong place at the wrong time. And for the 99%+ of situations when he/she is at the right place at the right time (knock wood), such a system will warrant wonderful, worry-free nights of sleep.

For these reasons, i spent a considerable amount of time redesigning Pesto’s anchoring system for this journey. It was a bit more comprehensive than the picture below suggests:

Pesto - Aug14 1 (2)

 

Arguably, a good and well designed anchoring system is safer than a mooring buoy. And i would say, when conditions are really nasty, possibly even safer than being at a marina (if you want to dive deeper, read this and this for a reported case of a sailboat that withstood a category 4 hurricane lying at anchor – a properly sized one).

Pesto’s original anchoring system was perfectly OK for regular use and the occasional vacations trip. But i knew it was not properly sized for long term offshore cruising. This meant we might be exposed if we ever get caught at the wrong place at the wrong time. So, as soon as i arrived here, i started a project to upgrade it.

But before i get started, just a few definitions: imagine the anchor lying on the seabed. At it’s very tip there is a shackle, which connects the anchor to the chain. The chain goes up out of the water and around a roller at the tip of Pesto’s bow. On Pesto’s deck there is a large dedicated winch to pull the chain and the anchor up from the bottom (it is impossible to pull it by hand). This winch has an element called gypsy, which is what “grabs” the chain and cranks it up and into the chain locker – there are pictures of each of these elements below.

Ok. The first step was easy – to replace the anchor itself. Pesto was awarded a new-generation anchor (Rocna), which is 20% heavier than the original one, has a much higher holding power, and has a very successful track record of not failing once it is set.

First, i had to set the old anchor free. The shackle was oxidized and frozen, and so i had to saw the chain.
First, i had to set the old anchor free. The shackle was oxidized and frozen, and so i had to saw the chain.
The old guy - Thank You for its dedicated service!
The old guy – Thank You for its dedicated service!
Next, i had to stow the old anchor. I used a system of turning blocks and Pesto's halyards to hoist it fem place, and then drop it gently inside Pesto's cabin (later on i decided to get rid of this anchor altogether, and a similar system was employed to take it our of the cabin and onto a cart at the dock)
Next, i had to remove and stow the old anchor. I used a system of turning blocks and Pesto’s halyards to hoist it, and then place it gently inside Pesto’s cabin for storage (later on i decided to get rid of this anchor altogether, and a similar system was employed to take it our of the cabin and onto a cart at the dock).
Pesto's new anchor came gift-wrapped
Pesto’s new anchor. “Gift-wrapping” has a different concept in the marine element.
Putting the new anchor in place was much easier. I simply attached the chain to it, dropped it on the water, and used Pesto's winch (called "windlass") to crank the chain (and the anchor) in place.
Putting the new anchor in place was much easier. I simply attached the chain to it, dropped it on the water, and used Pesto’s winch (called “windlass”) to crank the chain (and the anchor) in place.

 

The next stage of this project was less straight forward. Pesto’s chain had 3 issues:

  • nobody knew the specification of its steel, and it was likely the “BBB” type – the “least strong” of marine-grade specs.
  • the links were of an odd sizing. Whereas the link wire was pretty thick (1/2 inch), the link itself was quite narrow. And this limited the size of the shackle that could be used to attach this chain to the anchor.
  • it was short for our intended use, at 200ft.

(wow – it’s been a while since i last used bullets!)

That grey thing up there is the original shackle (between the silver element to the left - anchor - and the ocre thing to the right - chain). Way too small, constrained by the chain link sizing.
That grey thing up there is the original shackle (between the silver element to the left – anchor – and the ocre thing to the right – chain). Way too small, constrained by the chain link sizing.

 

The chain had to go!

The first step was to test a similarly thick chain (1/2 inch) but with a regular sizing. I went to a chandlery and got a sample:

 

As expected, the regular-sized chain (silver, left) is quite wider than my original chain.
As expected, the regular-sized 1/2 inch chain (silver, right) is quite wider than my original chain. There were good news and bad news from this experiment. The good – this new chain would allow for a much larger (and stronger) shackle. The bad – this chain would not fit the windlass’ gypsy. And replacing the gypsy (or the windlass) was out of question.

 

Therefore, a regular-sized 1/2 inch chain was not suitable.

My challenge now was to find a different type of chain which would at the same time:

  1. fit the windlass gypsy
  2. allow for a larger, stronger shackle
  3. be stronger than the existing chain

(did you notice? Bullets again !)

Took all measurements from the existing chain (and also the windlass gypsy)
Took measurements from the existing chain (and also the windlass gypsy)
Compared these measurements with a number of alternative chain models that would meet the criteria above
Compared these measurements with a number of alternative chain models that would meet the criteria above

 

This exercise suggested that a 7/16 inch chain made of G43 steel might fit the gypsy. Such chain would be a staggering 60% stronger than the incumbent, allow for a proper shackle, and still 300ft of it would weight roughly the same as the current 200ft of the existing chain – a home run!

However this was all a hypothesis at that stage – i had to find a practical way to confirm whether this new chain would fit the gypsy or not. And what’s better to verify a hypothesis than an experiment?

So i went to the chandlery again and bought 20ft of the 7/16 G43 chain. I was an special order and i had to wait a week for it top arrive.
So i went to the chandlery again and bought 20ft of the 7/16 G43 chain. It was a special order and i had to wait a week for it to arrive.
The first thing i did was to wrap it around the gypsy - it fits!
The first thing i did was to wrap it around the gypsy – it fits!
Then i connected it to the anchor (still using the small shackle), let it all go into the water, and brought jot back with the windlass. I did this exercise to confirm that the new chain would not skip a link in the gypsy (that's why i bought a 20ft length for the test)
Then i connected it to the anchor (still using the small shackle), let it all go into the water, and brought it back with the windlass. I did this exercise to confirm that the new chain would not skip a link in the gypsy under load (that’s why i bought a 20ft length for the test)

 

With the chain-gypsy fit confirmed, i went again to the chandlery and placed an order for a full length of 300ft of this chain. At this stage i was already popular there. Not only did i get a substantial discount, they were also nice enough to deliver it at Pesto’s bow, with no additional cost (the drum weighted in excess of 600lbs – i had no clue how i would bring it on to the dock by myself!):

Seems like the end of the project? So it did to me at this stage ... and i was wrong!
Seems like the end of the project? So it did to me at this stage … and i was wrong!
First of all, i took the chain out of the drum and laid it on the dock for two purposes - visually check each and every link, and place a marker every 20ft, so that i know the length of chain paid out at anchorages (the other cables underneath the chain, i laid them there to act as a "bedding" to protect the chain from chaffing against the abrasive dock).
First of all, i took the chain out of the drum and laid it on the dock for two purposes – visually check each and every link, and place a marker every 20ft, so that i know the length of chain paid out at anchorages (the other cables underneath the chain, i laid them there to act as a “bedding” to protect the chain from chaffing against the abrasive dock).
Well, but for the new chain to go in, the old chain needs to get out first. SO i did, only to encounter a bed of mud accumulated at the bottom of the chain locker. This thing has been deposited there over the years, and was sedimented enough to be clogging the locker's drain.
Well, but for the new chain to go in, the old chain needs to get out first. So i did, only to encounter a bed of mud accumulated at the bottom of the chain locker.

 

Before i could put the new chain in, i had to clean the chain locker. The sediments at its bottom were already clogging the locker’s drain, transforming it in a giant bucket. Right at the bow. Dangerous. Cleaning it was a P.I.T.A. quite unpleasant job and took a whole morning, as documented here.

Anyway, the old chain went out, the new chain came in, and we were close to finishing this project. The next step was the Shackle. I had researched before what would be the strongest and most reliable shackle i could fit into this chain (Crosby Shackle – model 209.a), but finding it was another thing. No chandlery had it and in the end, you won’t believe it, i found it at Amazon.com!

The crosby shackle - a really strong and reliable piece of equipment
The crosby shackle – a really strong and reliable piece of equipment
I applied seizing, to ensure it never un-screws indadvertedly.
Special seizing applied (“monel”), to ensure it never un-screws by itself.

 

And then the very last element of this project – the Snubber. This is a piece of rode, specifically 3-strand nylon, which is tied between the anchor and the boat. Since all other components of this system are very stiff, it is prone to shock loads, which can destroy it. The snubber is the shock-absorber on this system.

Sizing the rode for the snubber required resurrecting the concepts of Forces at an Angle from my olden days of engineering.
Sizing the rode for the snubber required resurrecting the concepts of Forces at an Angle from my olden days of engineering.
The final splicing for the snubber.
The final splicing for the snubber.

 

And with that we now have a solid anchoring system for our journey (and granted wonderful worry-free nights of sleep).

I appreciate it was a long, technical post. But at least once i wanted to share an end-to-end view of how my new “work” looks like 🙂

Have a great week!