pt 2

Anchors and Ground Tackle

Part 1 of Anchors & Anchoring  looked at all the various anchor types anchor makers and how to choose the anchor which is best suited for you and your boat or vessel.

Part 2 looks at the rest of the ground tackle the Anchoring Gear, & Anchor Equipment  that attaches your boat to the anchor.

Article overview and quick links

This article is divided into 2 parts;

A   Ground tackle the parts.

B   Factors involve in setting your Anchor and ground tackle

Then Other information; Sources of anchoring techniques, Reading

Ground Tackle Parts

Ground tackle refers to all the parts of an anchor package between the boat and includes the anchor. If you use only line the ground tackle may be referred to as simply the anchor line.

Parts of an anchors "ground tackle"

All chain Ground Tackle

All chain is popular on large boats, heavy displacement boats, large power boats and Mega Yachts. The two benefits of chain are weight and chafe. Weight keeps the chain on the seabed which keeps the angle of the anchors shank close to parallel with the bottom.

If this angle gets too great then the anchor can break free. With the chain on the seabed, it is subject to chafe, and chain can withstand chafe much more than rode, rope or warp.

The down side to all chain is again weight, and also the lack of stretch. Chain is heavy and 200m of 10mm diameter chain is going to weight 560 kg, which means 20M will weigh 56kg. Stowing this up forward in a boats vastly increases the chance of pitching in waves. The chain also takes up more space.

The second issue with all chain is lack of stretch. This manifest itself in 2 ways. First in a swell and wind the boat is moving around over the anchor. As the boat gets further away, the ground tackle will load up and pull the boat back to the middle. This loading up will transfer to the boat and the crew will feel the jarring. Crew may even fall down because of this shock loading. Here it is necessary to have an anchor snubber to dampen the load.

The second result from lack of stretch with all chain is again anchoring in a swell. Here the load from the vessel is transferred through the chain and the forces transferred to the anchor, possibly braking it free. Again using a snubber with dampen the load.

Chain comes in 3 types. To learn about these types of chain follow this link

All rode Ground Tackle

For smaller boats having an all rope, anchor line, warp or rode is more popular. It is lighter, can be thrown, takes up less space and stretches. The down side is chafe.

Unlike chain rope stretches and this results in a smoother ride at anchor. When the boat swings at anchor and loads up the line, the load is dissipated by the stretch in the line. Unlike with Chain the load is not transferred to the anchor, and so the anchor is not effected.

Twisted three-strand nylon rode, has good stretch properties, it also sinks. For the rode a nylon line is very strong and with the 3 strand construction has lots of stretch

Polypropylene has good stretch floats but has poor shelf life in the sun.

Three-strand line can absorb shock and the constant tugging associated with anchoring much better than braided line.

Nylon Three-Strand line is the leading choice for use as an anchoring line. Lines generally come in a "soft" or "medium" lie. Soft lines are generally softer and loosely woven, than medium or hard lines for anchoring, as they are more prone to unraveling and chafing. Medium and hard lines are best to handle chafe. Lines that have been treated with a wax-like coating are available, and can help the line resist water/salt absorption.

Chain Rode combinations

Since all chain or all rode have their pros and cons a combination chain and rode is most popular. Here the chains weight and chafe characteristics prove their worth on the seabed. The rode proves its woth with the stretch, so dampening any shock loads from the boat swinging around. Also the rode takes up less space. 

So how much chain should we use. In the next section we look at how much anchor rode ground tackle you will need. This is calculated on scope. Scope is the ratio of water depth to line put out. This ratio is somewhere between 3:1 and in extreme cases 10:1.

How much chain to rope

some rules of thumb say one ft of chain per foot of boat length. Another says one lb of chain for every pound of anchor.

Chain to Rode length calculation

Earl Hinz, a former aeronautical engineer and inveterate Pacific Ocean sailor, in his work The Complete Book of Anchoring and Mooring, says the chain lead should weigh at least as much as the anchor whose weight it is supplementing.

From his experience, he has determined that the length of the chain lead has nothing to do with the depth of the water or the length of the boat. He suggests using the following formula to help you determine the minimum
length of chain lead you will need:

Minimum              Anchor weight in lbs.          
length of     =     x Anchor materials factor               
chain lead         Unit weight of chain,                   
                                     lbs./ft.

Anchor materials factor =       1 for steel and 1.6 for aluminum
                                 

For example: If you have a 7-lb. Fortress aluminum anchor with a 1/2 inch twisted three-strand nylon rode, you would need to use at least 11.2 lbs of 5/16 inch proof coil chain, which weighs 1.15 lbs per foot. Therefore, you will need at least 9 ft 8 inches of boat anchor chain.

Other parts of a ground tackle system

Anchor rode chain Splice

How to make your own Splice by animated knots.

This splice by animated knots lets you see the splice step by step.

You can use an eye splice and shackle but this will not work with a chain rode Windlass.

Anchor Swivel

A swivel allows the anchor to settle on the seabed and the anchor chain or line to align to pull horizontally.

Many swivels operate in one plane only. This swivel can articulate as well as swivel.

Chain Snubber  A snubber is designed to provide shock absorbing capability into the system. Chain does not have any give and so loads give the boat and crew a jarring feeling which can make life onboard uncomfortable

A Chain snubber is basically some twisted three-strand nylon attached to a hook. The line is tied on the boat and the hook hooked to the chain.

The increase the stretch you can lead the line down the boat and tie it off on an aft cleat. A longer line means more stretch.

The image left is of Shockles

Boat Anchor retrieval system

Anchor can be hard to get to dig in, but when they do they can be hard to get out. Retrieval systems help breaking the anchor free of the bottom. The AnchorLift is one example of an anchor retrieval system.

Roll Stabilizers

When lying at anchor boats tend to roll. Roll stabilizers or Rocker Stoppers combat this.

Davis Rocker Stoppers  help dampen the rocking motion of boats at anchor. Simply tie Rocker Stoppers approximately 44 cm (18") apart, making a string of them, with a 5-10 pound weight attached at the bottom of the string.

If a rocker stopper is not enough try a stabilizing fin which is a mechanical fin controlled by software. Use on larger boats, the software changes the angle of the fin to appose the roll motion. Some stabilizers for anchored boats are called Zero speed stabilizers.

Size of the anchor ground tackle

What chain diameter do I need and what line size do I need. These diagrams from the ABYC will help you decide.

This Chart from part 1, gives you an anchor horizontal loads at various wind speeds.

For our 30 ft boat the horizontal load is 700 lbs for a Working Anchor which is rated at 30 knots.

Below you will se that for this boat 7/16 inch line is recommended and 5/16 inch chain.

Chain Types   

types of Boat Anchor Chain

excerpt from good old boat via sailnet

Proof coil chain is made of low-carbon steel. It usually will have "G3" cast into each link. Its name comes from subjecting the chain to tensile loads (its proof load) until it breaks.. Anchor chains working load rating is usually 50 percent of the proof load. Proof coil is usually the least expensive chain, since it has fewer links per foot. Proof coil will not work with a windlass.

BBB chain (known as triple-B) is also a Grade-30 low-carbon steel. It can be identified by the "3B" cast into each link. It has been the chain of choice for boaters for years since its added weight creates more of a catenary and its shorter links have less chance to deform.

High Test (HT) boat chain is made from high-carbon steel that has been heat-treated to increase its strength. The heat treating gives HT chain a higher strength-to-weight ratio than other chain. "G43" or "G4" are cast into the links. With slightly longer links than BBB chain, many windlass manufacturers specify HT chain as the most compatible with their winches.

COATINGS

All these chains are galvanized. Some anchor chain can be purchased with a thin polymer coating. Vinyl coatings are also used. which makes the chain thicker, but gives more protection.

Stainless-steel anchor chain is also available. This is 316 stainless and is stronger than the steel, galvanized counterparts, but not as strong as high-carbon HT galvanized chain. It is also considerably more expensive than any of the galvanized chains. It does, however, prevent rust stains.

Part B

Factors involved in setting an anchor and ground tackle

Scope in ground tackle.

to Sailnet and good Old Boat for the image and link

All anchors are designed to dig in when pulled horizontally. If pulled vertically they break free, otherwise we would not get them back.

Scope is the ratio of depth to line paid out.

Short scope (3:1) limits your swing in a crowded anchor, but is harder to get a good hold on the bottom.

Longer scope increases the holding power of the anchor, but you will need more space and the likely hood of sailing around the anchor increases. The above image is 5:1 scope 100 ft in 20 ft water depth.

Problems with long scope

Long scope helps getting an anchor to dig in as the anchor line is more likely to pull horizontally. The problem with lying to a long scope is that you need lots of space which you might not get in a crowded anchorage.

Secondly you will find out about anchor sailing. This basically means that the wind will blow you side ways and when the anchor line goes taught you are pulled back. The momentum built up sends the boat to the other side. So you are essentiality sailing around the anchor which gets uncomfortable and the anchor line goes taught slack and taught again.

So how do you prevent this. One way is the put up an anchor sail, another is to hand a large bucket ( check this link) from the bow. This acts to dampen the swing as the bow has to tug on the bucket dragging it through the water.

Bahamian anchor method is another method we will be looking at in part 3. This involves setting two anchors.

How do you measure scope length

mark the chain

Imtra have these markers you can press between the links at measured points like very 10ft or 3 meters. A different color for 20ft and 30ft will let you know how much scope you have let out.

Mark the line with magic marker or slip some leather strips in between the strands.

Chain rode counter

Auto Anchor Remote chain counter telling you how much chain or line you have let out. The counter will work for either chain and rope/chain Rhodes. AA150 is Freeman K. Pittman award winner 2006.

Anchor data

This counting device can replace your anchor roller or be placed behind it. Designed for boats in the 25-45 ft range and rope dia 8-20mm and chain 6-10mm. £250 ex vat. The LED display on top of the unit counts the anchor rope or chain from the last reading or from zero if reset. The LED is solar powered so does not need wiring.

How to get the features of a short scope but with a long line.

Anchor kellets, angels   sentinels

These are weights that are added to the anchor line or chain with a large shackle or loop which allows the weight to slide along the chain. The weight is lowered down the chain (see below). The effect is to lower the angle of the chain at the anchor bringing it closer to horizontal.

Sources of anchoring techniques

Sailnet 

"to have and to hold" sponsored by "Good Old Boat" The basic rules of anchoring -- and staying put. by Don Launer.

A technical look at Ground Tackle

sailonline the charter company's instruction on anchoring

Sailing issues, a free and personal website providing unique information on marine navigation and sailing holidays in Greece and Turkey.    lessons on anchoring

When dropping anchor make sure the coast is clear

Other reading

The Complete Book of Anchoring and Mooring

This book has been cited in a few sites like www.boatsafe.com and other respected organizations.

Contents

Chapter One: Introduction

Part I: The Technology of Ground Tackle

Chapter Two: Loads at Anchor
Chapter Three: Deck Gear for Anchors
Chapter Four: Anchor Windlass
Chapter Five: Anchor Rhodes
Chapter Six: Anchor Options
Chapter Seven: Anchor and Rode Selection

Part II: The Art of Anchoring

Chapter Eight: Human Factors in Anchoring
Chapter Nine: Technique of Anchoring
Chapter Ten: Anchoring Tricks
Chapter Eleven: Rights and Responsibilities
Chapter Twelve: Storm Anchoring

Part III: The Mechanics of Mooring

Chapter Thirteen: Permanent Moorings

The Complete anchoring handbook

A modern, authoritative anchoring guide for sailors and powerboaters A boat swinging safely at anchor can be a relaxing conclusion to a great day of boating or an essential emergency measure, while failure to anchor properly can be frustrating, inconvenient, or downright dangerous. The Complete Anchoring Handbook is your path to mastering this indispensable seamanship skill. Based on original engineering analysis--and with contributions from such international anchoring experts as Alain Fraysse and Chuck Hawley--The Complete Anchoring Handbook emphasizes the proven best gear and methods for anchoring safely in any situation with any boat, sail or power. Here's everything you need to know, from the basics to the most advanced techniques

US Sailing Bareboat Cruising

One selection form this manual covers Anchoring Techniques
24. Select an anchorage and demonstrate appropriate helmsman and crew coordination and the skills necessary to anchor with two anchors under power using one of the following methods: bow and stern, two anchors off the bow at 60° , or two anchors off the bow at 180° (Bahamian Moor).
25. Pick up a mooring.
26. Demonstrate appropriate helmsman and crew coordination and the skills necessary to recover your anchor under power.