Anchor Scope

Anchoring is a pretty simple concept. The boat is floating in the water and will float away if not tied down to something. The anchor is a fancy hook that grabs onto the sea floor and you are tied to the anchor, thus tied to the sea floor! 

If only it were so simple. 

There are many different styles of anchors and many different ways to attach the boat to the anchor, but if you comb through all of this information, you will find one common characteristic amongst the variety: Scope. 

Scope is the ratio of line connecting your boat to the anchor with respect to the depth of the water. If you have 10 feet of line and 10 feet of water, you will have 10:10 or 1:1 scope.
If you have 20 feet of line and 10 feet of water, you will have 20:10 or 2:1 scope.
if you have 30 feet of line and 10 feet of water, you will have 30:10 or 3:1 scope.

You get the picture. 

Now, as your scope goes increasing, the angle from the anchor's shank to the sea floor goes decreasing! Anchors are hooks and they are designed to hook into the sea floor when they are slid along the sea floor at an angle. When you pull straight up on them, it is because you are trying to pull them out of the bottom so that you can continue sailing. Therefore, anchors are also designed to be easily retrieved and will pull out if they are pulled upwards. 

With a 1:1 scope, the anchor is dangling vertically, and obviously won't hold the boat to the bottom very well.  with a 10:1 scope (so 100 feet of line for 10 feet of water), an anchor will hold with 100% of its rated holding capacity. So, when you are sold an anchor and told that it will hold the weight of your boat pulling on it, this is only when you have enough scope out, and the scope they calculated it with is 10:1. This means that if you really need your anchor to hold well, you need to let out enough anchor line to give it the needed scope.

Home

When you live on land and travel, you always feel that you have a home to come back to. No matter how far away you travel, you know where you will return to when the journey ends. When you liveaboard, this changes a little, as your home is floating and is easily moved from one place to another. While a boat in a slip is a permanent as a leaf on a shore, you will feel like this small patch of water that your boat floats in is home! 

We lived aboard for 5 years before we set off cruising. In that time, we would sail for a day, weekend, or even month, but we always returned to our slip in Fells Point, in downtown Baltimore. When we decided to make the leap from liveaboards to cruisers, we had to make a strange decision, we had to end our slip lease. 

The marina I lived in did annual slip leases starting in January, and our cast off date was in July, so it felt rather odd to sign a lease that would end in a few months with no plans on extending it. When we sailed out of the marina, we knew we were giving up our wonderful slip in the heart of our favorite neighborhood as we voyage far and away. 

This was such an odd feeling, as I knew that now I had no "home" to return to. Every moment we sailed forward, we were sailing away from a place that we had called home for so many years. We had to dissociate that patch of water as home and instead recapture that sentiment towards the entire boat.  

Home is where the anchor drops! As we ventured off, we still felt like we were off on a weekend sail. We were sailing through waters that we have been in almost every weekend of the year. This meant that we knew how the winds worked, and where the currents are strongest, as well as where to anchor to enjoy the best sunsets! After a few days, we got a bit restless, as we felt it was odd that we were still sailing away and not returning to our old slip. It took a little strength to subdue that thought, and it faded quickly, as did our knowledge of the date and time.

We soon transitioned from city dwellers who know what day, date, and time everything around them was happening, to cruisers who get up when the sun rises and drop anchor when the sun sets. 

As we ventured south in the Chesapeake Bay, we felt like if we were seeing things for the first time, but this was not true. Two years ago, we did a month long trip where we sailed down the bay and offshore to Kitty Hawk, NC. On that trip, we were in a rush to get as far south as fast as we could. This time we are at a much more relaxed pace, enjoying the sights and scenery and drifting along without any time constraints. 

While we felt it was new territory for us, we had the comfort in our mind that we had in fact sailed these waters once before. This feeling lasted for only so long, then we passed this point and continued onward! 

The day we finally passed Kitty Hawk was magical. It felt like if we were birds that just flew out of a cage. Every moment was now further from home than we had ever been, even though home was always with us. Every town we anchored in would bring the same questions: Have you done this before? Is this the farthest you have ever sailed? 

Practice makes perfect, and being asked these questions over and over makes you better at answering them. "Nope, everyday is the furthest we have ever been!" Is our answer of choice. 

The memories of our slip and neighborhood have been fading as we have found new favorite places to relax and explore. I guess this is what you do when you feel disconnected from your "home." When we were in the bay, we knew that we could always turn towards Baltimore and reach our old port in under four days. Now, we are hundreds of miles away and returning to Baltimore would take much more than a few days! This sensation of being so far away that it would be hopelessly pointless to feel homesick helps you find new "comforts of home" wherever you are. 

Every town we make landfall in, we make friends, explore the town, and find ways to make this place our new home! 

Choosing a Chain Rode

When it comes to selecting an anchor rode for your cruising yacht, you will be faced with a multitude of choices. To begin, we will separate two main groups of options: Dock candy (which has no practical use) and real ground tackle. 

Dock candy is anything stainless steel. This can be in the form of a polished stainless steel anchor, or even worse, polished stainless steel chain! Stainless steel polishes to a beautiful mirror finish that makes the bow of your boat glisten in the sun, therefore, it should be thought of as Dock Candy and nothing more. 

Stainless steel suffers from two main problems, work hardening and crevice corrosion. The cyclical loading of the anchor rode will lead to work hardening which will make the metal brittle and break. Crevice corrosion will cause your precious anchor or chain to simply fail catastrophically and with little warning.  

If weakness and brittleness were not enough of a reason to ward away from stainless steel ground tackle, there is one other reason: Cost! 

For example, 5/16 BBB galvanized chain costs $6.19 per foot. The same chain in stainless steel costs $29.99. This makes the price of a 300 foot rode skyrocket from $1,857 to $8,997. That is a $7,140 price jump for some shiny chain! Anchors are the same scenario, with a 65 pound Mantus Anchor made of galvanized steel costing $619.99, while the stainless steel version costs $1,479.99! An $860 price jump. 

The same ground tackle setup would cost $2,476.99 in galvanized steel or $10,476.99!  

Needless to say, the only reason you would buy a more expensive but less reliable ground tackle is because it is shiny and looks pretty while you walk past it on the pier. 

So, now that we have ruled out stainless steel options, we can look at the real options for ground tackle, which are the three main grades of galvanized steel chain.  

The bottom, but old standard is BBB, also referred to as Grade 3 or Grade 30. This chain is the weakest and heaviest of the chains, but when it was first introduced, it was rather revolutionary. It is made of regular low carbon steel and can be safely re-galvanized over its lifetime. The chain derives its strength from simply making each link rediculously thick and hefty. 

The next tier is the first HT chain, referred to as Grade 4, Grade 40, or Grade 43. This chain is heat treated, giving it more strength for the same size, allowing you to use a smaller chain and still have the required strength. 

The top tier is the next level of HT chain, referred to as Grade 7 or Grade 70. This chain is heat treated through a strenuous process which makes it very strong for its weight and then allows you to use an even smaller link for the same strength requirement. Being how the heat treatment process is so crucial to its strength, re-galvanizing the chain can reduce its strength as the heat of the process can damage the links ever so slightly. 

While all this information is fun to have, it isn't very useful without a way to draw it into the real world. Luckily, the world of chain anchor rodes has a very real application, the bow of your yacht! 

For our examples, we will be looking at rodes of the standard cruising length of 300 feet. 

If we need a rode that can withstand 4,000 pounds, the our options would be as follows: 

300 feet of 1/2 BBB 

Weight: 840 pounds
Strength: 4,500 pounds
Cost: $2,460 ($1,731*)
Safety Factor: 4x

300 feet of  3/8 G4

Weight: 450 pounds
Strength: 5,400 pounds
Cost: $1,917 ($1,536*)
Safety Factor: 3x

300 feet of 5/16 G7

Weight: 300
Strength: 4,700 pounds
Cost: $1,947 ($1,170*)
Safety Factor:  3x

*When you buy items from marine chandlers in large quantities, they will usually give you a discount. This should be your target number to aim for in your negotiation. If you can get it down lower, great, but at least try to get it to this level. 

As you can see, BBB chain is considered to be an inexpensive chain, but the links need to be very large to support the load, and you end up purchasing a very large and heavy chain that costs a lot of money. As you move up to Grade 4, you can see that you are able to go down a link size. The same occurs as you move up to Grade 7. While the chain is more expensive per foot in the same link size as you move up in grade, the increased strength lets you go down a link size and save on the smaller chain.  It should be noted though that the higher grade chains use a smaller safety factor than BBB does, but these chains are still very strong by comparison.

Not only do you save on money, but you also save on weight!  

The switch from 1/2 BBB to 5/16 G7 saves 540 pounds of weight in anchor rode and also saves around $530 in the process as well! 

When choosing an anchor rode, don't be put off by the higher cost per foot of the higher grade chains because you might actually find that you are able to save money and weight by going with the fancier galvanized chain! 

Grade 7 and 70 Chain

Grade 7 and Grade 70 chain are the eventual evolution of Grade 4, 40, and 43 chain. The chain is subjected to a more profound heat treatment which produces a very strong and yet very light chain link. The links of the chain are formed from low carbon steel wire, and the size of the link is actually referring to the size of the wire that was used. For example, 5/16 G7 was formed from a 5/16" wire, while 1/2 G7 was formed from a 1/2" wire.

Common dimensions for G7 chain are 5/16", 3/8", and 1/2". Larger and smaller links are available, but these are the three sizes that you will encounter in most marine chandlery stores.

5/16 G7 has a working strength of 4,700 pounds; and a breaking strength of 14,100 pounds.
3/8 G7 has a working strength of 6,600 pounds; and a breaking strength of 19,800 pounds.
1/2 G7 has a working strength of 11,300 pounds; and a breaking strength of 33,900 pounds.

The interesting thing to note is that the breaking strength is 3x greater than the working load, giving this type of chain a significant safety margin. When the chain is manufactured, it is then subjected to a rigorous test of strength, followed by a close inspection of each individual link. 

Aside from strength, the next important factor to consider is the weight of the chain, as this directly affects the holding power of your anchor that is desperately trying to hold onto the bottom!

5/16 G7 weighs 1.0 pounds per foot.
3/8 G7 weighs 1.45 pounds per foot.
1/2 G7 weighs 2.7 pounds per foot.

A standard recommended length for an all chain rode on a cruising yacht is 300 feet. This will give you the ability to anchor in 25 feet of water with a 5 foot freeboard and still maintain 10:1 scope for storm condition anchoring. The weight at these particular sizes are as follows:

5/16 G7 would weigh 300 pounds.
3/8 G7 would weigh 435 pounds.
1/2 G7 would weigh 810 pounds.

This weight will help cause the chain to sag and pull towards the bottom, creating a catenary curve. The curve will make the chain fall vertically from the bow, but curve away from the boat as it runs. The chain will lay on the sea floor because of its weight and cause the load on the anchor to be parallel to the sea floor. This will help the anchor set, and hold, as all the load will be sideways and not upwards.

Modern light displacement boats are very sensitive to how much weight is added and extremely sensitive to where the weight is added, as it will drastically affect the trim and handeling of the yacht. The high strength to weight ratio allows you to carry a chain that is strong enough to hold your yacht during a blow but not weigh your boat down excessively.

When looking at G7 chain, an important feature to evaluate is Strength to Weight Ratio. 

5/16 G7 is 4,700:1 = 4,700:1 working load, and 14,100:1 breaking load.
3/8 G7 is 4,552:1 working load, and 13,655:1 breaking load.
1/2 G7 is 4,185:1 working load, and 12,556:1 breaking load.

Lastly, you need to evaluate strength to cost ratio, as this will directly affect your wallet;

5/16 G7 costs $6.49 per foot
3/8 G7 costs $10.99 per foot
1/2 G7 costs $6.75* per foot (not galvanized)

If you look at the pounds that can be held (of working load) per dollar, it starts to look like this:

5/16 G7 724.2 pounds per dollar
3/8 G7 600 pounds per dollar
1/2 G7 1,674 pounds per dollar (not galvanized)

As you can see, the weight, cost, and strength of the chain all increase with size, but your money goes farther at holding your yacht as the size of the link increases. These numbers are all well and good, but how do they relate to your actual setup? Lets look at what the actual values would be of actual 300 foot rodes.

300 feet of 5/16 G7

Weight: 300 pounds
Cost: $1,947
Working Load: 4,700 pounds
Breaking Load: 14,100 pounds
Safety Margin: 3x
Bulk Discount Cost*: $1,170
Savings: $777

300 feet of 3/8 G7

Weight: 435 pounds
Cost: $3,297
Working Load: 6,600 pounds
Breaking Load: 19,800 pounds
Safety Margin: 3x
Bulk Discount Cost*: $1,935
Savings: $1,362

300 feet of 1/2 G7 (Not Galvanized)

Weight: 810 pounds
Cost: $2,025
Working Load: 11,300 pounds
Breaking Load: 33,900 pounds
Safety Margin: 3x
Bulk Discount Cost*: $1,359
Savings: $666

When you buy large quantities of an item, most chandlery stores will give you a discount. Being how you are not buying 300 individual feet of chain, but instead a 300 foot length, this is a rough estimate of how much you should expect to pay if you can negotiate the price down, and thus the amount of money that you would save by negotiating.

Grade 4, 40, and 43 Chain

For a very long time, BBB was considered to be the epitome of perfection when it came to anchor rode. BBB is very strong, galvanized to protect against corrosion, and produced in a calibrated method that allowed it to run smoothly through a windlass. With advances in metallurgy though, BBB became a relic of the past as stronger and lighter heat treated chains came to the market. 

HT is commonly used to denote this class of chain, but there is some discussion as to what the "HT" actually stands for. HT chain is made out of high tensile strength links which are also heat treated. Lastly, the chain tests higher than BBB, leading to people also referring to it as high test chain. Luckily, all of these terms start with H and T, but sadly, it leads to people referring to the same thing under many names: High Test, High Tensile, Heat Treated. 

The chain is further classified by the manufacturers into various groups that also all mean the same thing. The manufacturers refer to this chain as Grade 4, Grade 40, and Grade 43. The important thing to look for on the chain is a 4 stamped onto the link. BBB chain links will have BBB or 3B or G3 or G30 on it, while HT chain will have G4 or G40 or G43 stamped onto the side of the link. Basically, if you see a 3, you have regular chain, if you see a 4, you have HT chain (43 is just there to confuse you, but it has a 4 so it is HT). 

The links of the chain are formed from low carbon steel wire, and the size of the link is actually referring to the size of the wire that was used. For example, 5/16 HT was formed from a 5/16" wire, while 1/2 HT was formed from a 1/2" wire.

Common dimensions for HT chain are 5/16", 3/8", and 1/2". Larger and smaller links are available, but these are the three sizes that you will encounter in most marine chandlery stores.

5/16 G4 has a working strength of 3,900 pounds; and a breaking strength of 11,700 pounds.
3/8 G4 has a working strength of 5,400 pounds; and a breaking strength of 16,200 pounds.
1/2 G4 has a working strength of 9,200 pounds; and a breaking strength of 27,600 pounds.

The interesting thing to note is that the breaking strength is 3x grater than the working load, giving this type of chain a significant safety margin, but still a smaller margin of safety when compared to BBB. When the chain is manufactured, it is then subjected to a rigorous test of strength, followed by a close inspection of each individual link. This strict quality control gives you the confidence that your chain will hold up well when you depend on it the most!

Aside from strength, the next important factor to consider is the weight of the chain, as this directly affects the holding power of your anchor that is desperately trying to hold onto the bottom!

5/16 G4 weighs 1.1 pounds per foot.
3/8 G4 weighs 1.5 pounds per foot.
1/2 G4 weighs 2.5 pounds per foot.

A standard recommended length for an all chain rode on a cruising yacht is 300 feet. This will give you the ability to anchor in 25 feet of water with a 5 foot freeboard and still maintain 10:1 scope for storm condition anchoring. The weight at these particular sizes are as follows:

5/16 G4 would weigh 330 pounds.
3/8 G4 would weigh 450 pounds.
1/2 G4 would weigh 750 pounds.

This weight will help cause the chain to sag and pull towards the bottom, creating a catenary curve. The curve will make the chain fall vertically from the bow, but curve away from the boat as it runs. The chain will lay on the sea floor because of its weight and cause the load on the anchor to be parallel to the sea floor. This will help the anchor set, and hold, as all the load will be sideways and not upwards.

Modern light displacement boats are very sensitive to how much weight is added and extremely sensitive to where the weight is added, as it will drastically affect the trim and handeling of the yacht. This is what made HT chain virtually replace BBB chain, the same strength could be had in a much lighter link which saves on the weight of the entire ground tackle. This weight savings could add up to hundreds of pounds located at the tip of the bow on larger cruising yachts.

When looking at G4 chain, an important feature to evaluate is Strength to Weight Ratio. 

5/16 G4 is 3,900:1.1 = 3,545:1 working load, and 10,636:1 breaking load.
3/8 G4 is 3,600:1 working load, and 10,800:1 breaking load.
1/2 G4 is 3,680:1 working load, and 11,040:1 breaking load.

Lastly, you need to evaluate strength to cost ratio, as this will directly affect your wallet;

5/16 G4 costs $5.59 per foot
3/8 G4 costs $6.39 per foot
1/2 G4 costs $10.99 per foot

If you look at the pounds that can be held (of working load) per dollar, it starts to look like this:

5/16 G4 697.7 pounds per dollar
3/8 G4 845 pounds per dollar
1/2 G4 837.1 pounds per dollar

As you can see, the weight, cost, and strength of the chain all increase with size, but your money goes farther at holding your yacht as the size of the link increases. These numbers are all well and good, but how do they relate to your actual setup? Lets look at what the actual values would be of actual 300 foot rodes.

300 feet of 5/16 G4

Weight: 330 pounds
Cost: $1,677
Working Load: 3,900 pounds
Breaking Load: 11,600 pounds
Safety Margin: 3x
Bulk Discount Cost*: $1,146
Savings: $531

300 feet of 3/8 G4

Weight: 450 pounds
Cost: $1,917
Working Load: 5,400 pounds
Breaking Load: 16,200 pounds
Safety Margin: 3x
Bulk Discount Cost*: $1,536
Savings: $381

300 feet of 1/2 G4

Weight: 750 pounds
Cost: $3,297
Working Load: 9,200 pounds
Breaking Load: 27,600 pounds
Safety Margin: 3x
Bulk Discount Cost*: $2,010
Savings: $1,287

When you buy large quantities of an item, most chandlery stores will give you a discount. Being how you are not buying 300 individual feet of chain, but instead a 300 foot length, this is a rough estimate of how much you should expect to pay if you can negotiate the price down, and thus the amount of money that you would save by negotiating.