For the benefit of readers I would like to say a few words, as there are so many variables as well as 'beliefs' around the size & weights & designs of anchors and chain needed when anchoring, and some beliefs could bring 'grief' to the 'uninitiated,' due to being unaware of the 'power' within forces of nature.
Most anchors will perform successfully under light or moderate conditions. The focus of our decision making should be: "How 'does' or 'will' this anchor perform in a 'blow' or heavy weather?" I speak on the capacity of anchors to 'penetrate' and hold their position, and I also release my new anchor design that goes back to the 'original' style as given by God to man.
~ Holding capacity ~
Many people use 'minimal' chain/rope combinations that in my opinion are 'unsafe' when in 'dire' straights, and also there are but a 'few' who really 'test' their anchor, as they assume that it will function properly when needed. The reality is, that all anchors 'marketed' today have their 'shortcomings,' - - - hence these pages are freely given to assist the 'uninitiated' in making their choice.
A small craft sitting in still wind, no waves, and no tidal flow, needs only a 'rock' attached to a line to ensure it stays stationary when a 'fish' is caught. However, once you have wind and waves and tidal or river flow, it is a different matter.
The other 'factors' being the vessel weight & size and 'windage' area that is 'pressed' by the wind and wave force. * The need for an anchor is to ensure that the craft remains stationary in the 'spot' you wish to anchor it. For if it does not, then it may be destroyed on the 'rocks' or it may be swept 'offshore' where it could 'founder' in heavy seas.
Note: force. *- The 'windage' area of a craft can be 'pressed' by wind with a pressure exceeding 10 lbs per square foot. At a wind speed of 60 mph, there is a load imposed on the anchor of a vessel of 15' beam x 10' high of 504 N = 10.5 x 150 = 1575 lbs - - - AND, the further 'lift' and drag induced by current and wave effect will impose an additional greater force added to that.
One needs to 'visualise' the 'how & why' an anchor holds itself in the seabed. For 'anchoring' a 'line' to an immovable object like a 'jetty' is one thing, but tying it to a 'moveable' object like an anchor is another.
I have no doubt that most small anchors with e.g. "Only 6' of chain" on a short 3 : 1 scope as 'advised' by some, could or would drag in winds over 20 knots or 'gusting' if the water was of any 'depth.' A 'long' length of chain is needed especially in deep water to ensure safe anchoring.
I wish to say that during my coastal 'voyages' I have been shown that many anchor types 'drag,' either due to them failing to 'dig' deep enough or from a faulty design, or a 'deadly'* combination of both, as well as high winds and other 'wave' or tidal factors. Many a 'tall' ship has also foundered due to having the wrong anchor system aboard when the decision to 'anchor' was made.
Note: 'deadly'* - Is when the anchor fails to 'hold' the craft and both it and its occupants suffer the consequence that may be fatal.
For an 'anchor' to anchor itself, its fluke has to slide downwards until the force 'loading it' has reached a point whereby it no longer has the capacity to drag it any deeper and, - - - it then 'holds' this position or, - - -
The fluke has penetrated fully to the point that its surface area loading is such that the vessel is unable to pull it 'horizontally' through the seabed, - - - being a position whereby the 'ground' between the anchor 'face' and the water above is strong enough to 'resist' being dragged through or 'broken out' of the ground by the load 'pull' of the anchored vessel.
If you have a well designed and structurally strong anchor it will remain intact under load stress, if not, it will distort and you may no longer be 'at anchor.' The principal attributes of an anchor is that it must be strong, as well as having a quick and 'self-setting' capability and, - - - the 'capacity' to 'hold' the size of vessel it is attached to under 'uncertain' conditions.
This you only get to know when you are either 'tried & tested,' or you have the capacity to 'scientifically' calculate the needs of the implement reference your requirement of it to dig deep and anchor itself.
It is the catenary 'curve' of the anchor 'rode' that keeps the pull against the anchor in a horizontal position. This aids the anchor to remain 'set' in the ground and thus hold its position.
~ The 'catenary' curve ~
The catenary curve is the 'sag' caused in a 'chain' that is 'stretched' between two fixed points. The longer the chain length, the greater becomes the sag length and 'depth' for any given loading placed upon the 'vessel' being anchored. You may be anchored in only 20' of water, but if you have 120' of chain then the catenary 'sag' may become 100' long in heavy wind or current situations, leaving a 20' length lying horizontally on the seabed.
This is the CORRECT and SAFE anchor deployment.
Using 3 to 6 times more rode line than the depth of water, and also all chain or plenty of chain. This ensures that the anchor remains 'set' and does not 'break out' when wind and waves are strong, as 'pull' on the anchor remains horizontal. The 'H' factor above is the amount of chain remaining on the seabed at all times even when a great load is imposed, for only this horizontal section is what stops the anchor being lifted UP and OUT of the ground.
In 'nil' wind or tide or wave situations, a chain would 'lie' or 'drop' straight down to the seabed, and as long as there was some 'slack' in the pile of chain resting on the seabed, the vessel would take up this slack without 'disturbing' the anchor if a wave was created by a passing craft.
However when there is wind and waves or current the vessel is exerting a 'pull' against the chain. It is at this point (when a 'drag' load is imposed) that the chain between the ground and the vessel becomes 'curved' due to the pull exerted by the craft, and this curve decreases as the load is increased.
The time can come when the chain is 'loaded' to a point whereby some or all or most of it is 'lifted' off the seabed, and the anchor then takes up the full load, be it vertically or horizontally, or a combination of both if the rode is too short.
If the wind strength increases greatly, the catenary curve is reduced or even 'nullified' if there is not enough 'chain' weight and length or 'scope' of rode being used. This could result in your anchor 'dragging,' or its line 'snubbing' that results in the anchor being 'jerked' out of the ground.
This is the WRONG and UNSAFE deployment.
short a rode scope (length,) and either not enough or no chain
being used = no catenary action.
If you have only a 'little' length of chain, and are relying more on rope, then you have 'no' catenary curve but you do have 'stretching' of the rope. In strong wind and wave action there would be a tendency for the rope to be stretched to its limit and thus be 'taut,' and thus there would be no slack or 'curve' in the line, and the pull on the anchor would become 'upwards' and, - - -
It would probably be 'torn out' of the ground or dragged through it and, - - - you could also sustain damage to the bow of your craft due to 'jerking' when it is stretched to its limit. Either way, the end result would be the 'disaster' that could have been avoided with a little foreknowledge.
It is important to keep the 'pull' on the anchor in a horizontal position, and to do this one must have enough length and weight of chain for the size of your vessel. And to keep an effective catenary you must deploy enough length chain or rope and chain for the water depth and wind - tide - wave conditions and, - - -
In extreme conditions, if your chain length is inadequate, then shackle a series of heavy weights onto the rope rode. Starting about 15 metres from the anchor and then every 10 metres or so. This can be done using 'shark clips' to clip four or more 'sets' of 10 lb. weights onto the rode as you let it out. This will act as a catenary multiplier.
The catenary curve also permits the rode to 'lengthen' slightly during the passage of waves, and this reduces the 'jerking' tendency to both the anchor as well as the bow of the craft, and lessens the 'strain' on the anchor rode and the craft 'attachment' point.
Note: catenary 'curve'* - Is the 'depth' of 'sag' in the line that arises from its length and weight combination. The longer and 'heavier' the rode chain, the deeper the sag and the 'better' holding capacity of the anchor, as the 'pull' remains horizontal as wind and wave and 'tidal' flow action increase.
The catenary curve 'factor' takes 'up' the stress impact of passing waves, and reduces or 'nullifies' to a great degree the 'load' placed upon the anchor and the vessel at that moment.
Note: catenary 'curve' - When towing another vessel offshore you pass your line to it and your line is then attached to its anchor that is run out with a certain amount of chain. (30% of line length approx) This way both vessels are not subjected to jerking as the catenary effect of the towed vessel's chain allows a stress free tow. Allow enough combined length of 2.5 or more wave distances between vessels.
~ The 'lift & drag' considerations ~
There are two separate 'efforts' operating that are trying to dislodge and anchor from its 'set' position. The greatest one is that of lift, being the upward force that lifts it upward due to the 'flotation' capacity of the vessel it is tied to.
In the 'lift' consideration, one needs to realise that a boat or 'ship' is a floating object that has a far greater capacity to lift than the anchor has to 'drag down.' For example, in a small 30' fishing vessel one may only be using a 10-15 kg anchor, and the 'flotation' or capacity of a 'boat' to 'lift' a sunken object off the bottom of the sea is in relation to its 'spare' buoyancy.
Therefore this craft may have as much as 16 cu metres of 'airspace' under its deck, and this would give it a 16,0000 kg lifting capacity when sitting directly above a sunken object. Now you see the need for not anchoring directly above the anchor, for any small wave passing would lift the craft and dislodge the anchor.
The other force is the combined drag action imposed by wind and waves and current against the vessel that 'tends' to drag it along the seabed.
This 'dragging' action may also occur when the 'lift & drag' are joined, as in the situation where there is either too short a 'scope' or length of line, as well as too little chain. This results in no catenary action, and a combined drag and lift is placed upon the anchor that just drags along the seabed.
The purpose of having the vessel as far away from the anchor as 'practical' is firstly to reduce the 'lift' factor to zero, and secondly to ensure the drag 'factor' remains solely that, a horizontal drag along the seabed. For only in this manner can the anchor fluke remain embedded fully, and thus permit the anchor to do its work without having any 'lift' factor added to the drag.
To ensure that no 'lift' factor enters the process due to wave or wind or current pulling the 'line' taught in a straight line down to the anchor, one needs the long length of chain, so as to ensure that there is a catenary 'curve' in the line under all weather conditions. For only this curve ensures that the last few metres of chain before the anchor do remain on the seabed.
Understand the LIFT & DRAG effect on your anchor in every situation it is deployed.
~ Setting the anchor ~
Always ensure that there will be enough water under the vessel once the tide has run out, and if you know it will 'bottom' then ensure there are no obstructions under it that will damage the hull and, always ensure that there is enough line out to accommodate the height of the high tide in that area.
In order to 'set' the anchor in a satisfactory manner it must first be deployed by running it out in a steady manner whilst the vessel is moving 'backwards' or 'forwards' in the direction away from the required anchored position.
There is no point in just dropping it down with chain that might get entangled in the fluke. Let it down steadily, and as it 'sits' itself down you are keeping the vessel moving away so that the 'line' has no excess slack in it.
To enable the anchor fluke to be able to 'dig' downwards when the pull from the boat is 'upwards,' there is the need for the 'angle of pull' to be as little as possible, and this is accomplished by ensuring there is enough 'chain' or line rode run out to ensure that the anchor 'shank' is subjected to a horizontal pull, rather than an upwards one towards the sea surface.
I repeat, this 'ground' penetration is accomplished by having little or no upwards 'angled' pull on the actual anchor line and, - - - this is accomplished by knowing the approximate the water depth and multiplying it by a factor of 6 or more, and then letting out that amount of line whilst moving away from the deployed anchor before putting any 'strain' on the anchor, thus permitting quick and easier and deeper penetration of the flukes.
This way, one is ensuring that when one does 'lock' the end of the line, and the load of the vessel is placed upon the anchor using 'power' from the motor or sail, that it is being pulled horizontally across the seabed and not 'upwards,' thus the anchor is given the maximum opportunity of digging-in and holding.
Once the chain or combination rode has been 'laid' out, it is important to apply a 'slow' approx. half a 'knot' speed 'rearwards' to permit the anchor to bury itself deeply. Once it has so done, it will bring the vessel to a halt even when more power is applied.
Also, even if you have to anchor in a confined space and thus can only use a 3 to 1 'scope,' it is wisest to initially let out a length six times the water depth, and after 'reversing' to 'dig' it in deeply, you then 'retrieve' half the line length.
This 'operation' ensures that you have buried the anchor deeply, and it will have the 'opportunity of doing its 'job' even though on a short scope. For if an anchor is merely laid out on a short 3 to 1 scope the 'upwards' angle is approx. 20 degrees, then it cannot set properly.
Some anchors are designed and advertised as 'easy break out' when retrieved. This in fact means that the anchor is one that does not 'set' itself deeply in the first instance, and for these types it is imperative to have a good catenary effect, so as to keep any 'pull' horizontal or dragging occurs easily.
It is good practice to mark your chain with paint every 10 metres, and do the same with any rope by using a coloured cloth 'strip' inserted in the braid. This will give you an easy reference as to how much 'line' has been 'paid out' during anchoring. ( 1 strip for 10 metre mark - 2 strips for 20 metre mark etc.)
Always 'check' that the anchor chain or rode is firmly secured to the vessel prior to deployment.
~ Multiple Anchors ~
There are times when you may wish to use two anchors. If you need to anchor safely when there is expected very bad weather and your craft could be in danger due to your present 'Bower' * or 'main' anchor being less than efficient, then you may also deploy a second anchor about 70 metres away from the first.
Note: 'Bower' * - The main anchor kept stored in the 'bow' of the vessel.
As the wind builds, some vessels have the tendency to sail back and forth across a 'single' anchor as a result of the wind working on the hull and rigging. Using two anchors in a 45 degree spread will assist to steady her head and she will be better 'equipped' to lie weather cocked head to wind.
Have a separate rode for each, with the two anchors bisecting the axis of the wind at 90 degrees. This means that your craft once anchored and facing into the wind, will have each anchor approx. 35 metres either side of the wind path. If you believe that the wind will be 'veering' on way of the other later, then set the anchors at an 'angle' to the present wind. (The one that will be nearest to the future predicted wind direction is 'set' nearer to the boat, and its rode lengthened when the wind veers that way).
Mooring 2 - You may be anchored in a tidal inlet, and not wish your craft to have the opportunity to swing to its full scope in the opposite direction at each tide change, and you may wish it to not be 'swung' towards the bank by any wind gusts. You also may wish to ensure that the anchor does not become dislodged when the tide turns and swings the vessel around, thus putting a 'strain' on the anchor from the opposite direction to which it was 'set.'.
Thus you may deploy two anchors that you 'set' in line with the tidal flow, and lay them down a certain distance apart that you so choose. This way you set them facing towards each other, and there is never any chance of the chain 'snagging' the shank, nor is there any possibility of either anchor becoming disengaged.
If you are anchoring in only two to four metres of water during tide changes, anchors may be set approximately 30 metres apart etc. This way the craft will be positioned centrally between these two points, and only be able to swing around and face the tide without being able to be moved 'sideways' by wind, and its travel up or down stream during the tide changes is restricted between the two anchors. This 'technique' may also be used as a safe 'mooring' facility in non tidal applications.
Mooring 3 - If you need to 'moor' your craft in a manner that keeps it stationary, thus not affected by wind or tides, then you might need to consider a 'three point' mooring. This is accomplished by using three anchors or three concrete blocks situated in a triangle.
Take a chain or chain & rope up from each anchor and attach them to a floating buoy. Your boat will then always maintain a very close 'circle' of position. This is useful when your mooring is close to a bank or underwater obstacles, or when at low tide the craft needs be kept within certain limits of anchoring.
It is also a good anchoring practice to have a buoyed 'trip line' line attached to the 'crown' of your anchor. This not only 'marks' the position of the anchor, but may also be used to retrieve the anchor in the event that you have to 'slip' it free for any reason or, retrieve it 'backwards' if it is stuck.
This line can vary from 8 mm to 16 mm, and needs only be as long as the 'general' depth of water you anchor in. In case of greater depth then just add a little more before deploying the anchor. Divers can follow the anchor line downwards, and rise up to a 'meeting' place at the 'buoy' later.
For diving in open water or where there is current can be dangerous, and it is good practice for 'learners' to 'hang about' the anchor area, in the foreknowledge that they will always be 'swept' towards the vessel if the tide or wind changes.
Also, if you are anchored with your anchor 'marked,' then others will not so easily drop theirs across your 'line,' and neither will you 'sit' down on it in the shallows.
Another consideration for some is to use a small drum winch on your vessel. This could be manually operated similar to the trailer style winch that draws a boat onto a trailer. You could use 100 metres or more of multi-strand 8 mm stainless steel wire rope that has a 'working' strength of some 3000 kg. This gives a far better catenary effect than any rope, and it could be shackled to a length of chain attached to the anchor.
It could be fitted to the bow or stern of the vessel, and used to anchor and retrieve from the rear of the craft if needed. 100 metres weighs about 26 kg, and 100 metres of 10 mm weighs approx. 40 kg and has a strength of approx. 5000 kg load.
~ Notes ~
Note: 'reversing'* - It may be easier in some craft to 'launch' an anchor over the rear, and sail or motor away from it travelling 'slowly' with the wind, and once enough 'line' is out then it takes up the slack and the craft will swing around into wind as the anchor 'digs' in and holds. The 'rode' would of course be 'set' from the bow of the craft.
This may assist when setting two anchors, by sailing across the wind as you deploy the first one over the stern, and then you swing into wind after having travelled 70 metres and drop the second one as you begin to drift backwards. Only take up the 'slack' once you have let out an equal and full rode length on both lines.
Note: My 'advice'* to 'offshore' boating beginners of craft of 35' is to have two anchors, one for 'calm' seas and quiet bays in the 25-35 lb. range, having either all chain, 100' of 8 mm chain attached to 150' of 12 mm rope and, - - - another 'heavier' anchor of 45 lb. range for use when the need arises due to life threatening or adverse weather conditions.
This article is to get your mind thinking of your needs that depend on your vessel weight, size, and boating weather and other conditions. Carrying a spare 'heavy' chain section and some shackles is good practice, it can be used to 'weigh down' your present system.
Note: Chain storage. As it is not desirable to store heavy weights in the front of a small boat due to it 'nose diving' in a following sea, it is best to have the chain 'locker' as far back as you can. You may store one anchor at the stern of the vessel.
Note: - If your vessel has a tendency to 'broach' when running before the wind in large seas, or if you require safer steerage when entering a 'bar way,' then you could use a Para 'drogue' that is deployed over the rear of the vessel, and it will assist in slowing it so that you do not 'surf' and capsize. It can be set to one side and thus it steers the vessel to port or starboard as it runs before the wind.
It is always * best and safest to exit or enter any narrow harbour 'channel,' or cross a sand bar entrance when the tide has already 'turned' and is flooding in, as this lessens the wave size over the sand bar considerably, and when the tide is running out at 3 to 7 knots against an 'opposing' wind there can 'arise' large and dangerous waves. Some may be high standing 'pressure' waves that form in a certain 'spot' that make it dangerous to 'climb over.' If you intend to 'enter' a port or depart through 'such' conditions it is advisable to first 'reconsider,' and if you are determined to 'go' then say a 'prayer.'
Note: always *- If you are in a large vessel (ship etc) that needs 'steerage' to negotiate bends in the channel then you might need to enter at high slack tide so that you do not have any excess speed (over the ground) caused by the flood tide that could make maneuvering difficult. you could also enter the 'estuary' on the upper 'half' time of the outgoing tide as the out flowing tide would enable you to more easily maintain steerage at low forward speed, (over the ground) and wave size would not be an issue of safety.
Note: quality* - Is an anchor made by the principle manufacturer to the 'exacting' standards set by the designer. Having visited 'a' boating warehouse I noted that many of the anchors for sale of many designs were of a 'sub standard' design & construction compared to their original, and thus not only 'cheap' to purchase, but also all in my opinion unsafe.
Any person who has had the opportunity to test an 'after market' plough design anchor compared to the original will know the difference and, - - - the problem is, that some manufacturers are 'copying' copies, thus they 'stray' even further from the 'truth.' Copies of copies leads to 'chaos,' as 'biblical' translators know only too well.
Note: Concave v/s Convex. As the 'resistance' to forwards movement through a substance be it air or water etc is greatest when the 'concave' face is presented to the direction of movement. Example: A parachute slowly descending to earth with its concave side facing its direction of movement and thus 'resisting' the pull of gravity and, - - -
As the 'resistance' to forwards movement is least when the 'convex' face is presented to the direction of movement, it follows that flukes having their concave face towards the direction of 'pull' will give the greatest 'resistance' to being dragged.
If you are 'camping' on an 'offshore' island such as 'Northwest' Island on the Queensland coast, then be aware that very high winds can arise that might be 'blowing' in an offshore direction that could cause an improperly deployed anchor to be dragged into deep water. If this occurs then your 'ship' will be blown away and you will be stranded.
You always need to ensure that your vessel will not be blown away whilst you are on the beach or scuba diving or snorkelling on an offshore reef. Anchors that 'drag' are a very 'common' cause of 'suffering' and loss. Make sure that you are conversant with rope and chain and 'catenary' factors as well as the 'correct weight' anchor requirement of your size vessel.
When anchoring offshore and leaving your vessel, then ensure that you have the correct anchor/chain combination and length of scope, and you also may decide to set two anchors from the bow so that it matters not from which direction the wind blows, you are safely anchored.
When scuba diving it is best to follow the chain down against the wind and 'current' as you dive, so that when you return you do not have to swim back to the vessel against wind or tide. Always leave a long length or rope trailing from the vessel when diving offshore so that you can haul yourself back if you surface far behind it.