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Education program submitted by |
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page 1 Ocean 'Para' sea anchor The parachute anchor is a deep sea 'surface' anchor used in situations where the sea is too deep to use the ground anchor. It is sometimes called a ‘sea anchor.’ It is a parachute that travels very slowly through the water as it is 'pulled' by the boat that is itself being subjected to wind and wave forces driving it downwind. In survival situations or when one is in a small vessel and in need of rest due to being in very rough sea conditions the Para anchor is ones only means of security. Also when winds are high one cannot 'run' before the wind in many craft as they would be overpowered or 'broach' and capsize or be thrust beneath the water. The only safe alternative is to anchor yourself with the Para and face the oncoming waves. Tasmanian squid fishermen with 70' fishing vessels use 100' Para anchors to stay 'steady and comfortable and safe' whilst fishing in rough weather in Bass straight.
Let it be understood that huge and treacherous waves are generated by the power of the wind. Using the "Noah 'easy rider' technique" there are no massive shock loads.
If you are offshore and need to 'hold' your position facing wind and waves without using a ground anchor, then you need to use a 'Para' or 'parachute' anchor. This is the safest way of holding your craft safe when offshore. This also halts the vessel from being blown downwind. It enables you to remain relatively stationary affected only by the current drift, and thus you may 'rest' or simply allow the weather 'front' to pass you by as you 'sit' in safety without being in danger of 'broaching' or capsizing. The Para-anchor also permits you to 'drift' fish in comfort with the craft 'bow' held facing the wind. Be it for 'squid' fishing or bottom fishing or other. The principle purpose of this ‘Para’ anchor is to place the vessel and its occupants in a safe and secure environment and this is accomplished by using an underwater parachute that keeps the vessel facing into wind and waves. The secondary purpose of the Para is to slow the ‘drift’ of the vessel downwind where it could come to grief on the shore or on a reef. To do this the ‘chute’ area must be large enough to offer a good resistance against the wind and wave pressure exerted against the vessel, thus slowing the movement of the vessel through the water as much as possible. For the parachute to remain ‘open’ and offering a resistance to forward movement it has to be moving through the water. The larger the ‘chute’ the more resistance it offers to the water and the slower the Para and vessel will move downwind. The higher the wind speed the greater the pressure against the frontal area of the vessel, and the more forceful the wave action against its hull. The larger the Para is in relation to the vessel size, the greater will be the strain imposed upon the whole system, for there will be less ‘give’ or movement by the Para in the water and thus the rode and vessel will have a greater strain imposed upon them in certain conditions. This will be greatest when the rode is all nylon and there is no chain being used to give a positive tension and ‘catenary’ shock absorbing affect to waves thrusting against the vessel as wind speeds increase. When using no chain, all the 'shock' being absorbed by the stretching of the nylon, but in severe conditions this is not desirable as the nylon can be damaged and break and sudden loads to an 'over tightened' line cause severe stresses and jerking to vessel and occupants. If a smaller size Para is used in relation to vessel size this may reduce sudden load a little as there will be more downwind flow movement of the Para through the water. However general downwind drift becomes faster. If the Para is used correctly with a ‘set’ nylon rode length (20 to 50 metres) * and used in conjunction with 30 to 100 metres of anchor chain as given in the Noah's 'easy rider' technique, then there will be no jerking or sudden loading placed upon the Para or vessel or rode, as the ‘catenary’ curve or ‘slack’ of the chain absorbs this load. Note: (20 to 50 metres) * - small Paras under 11'diameter may use 20 metre nylon rode and Paras of larger size would use 50 metre length. Note: rope - 3 strand nylon rodes can unwind if the Para swivel jams, and this will create a big problem in difficult conditions, and it is better to use a braided rope that neither stretches nor 'unwinds.' When using the 'Easy Rider' technique the 'shock' loading is taken up by the chain and the rope is not required to stretch.
The 'common and 'old' way of using the sea anchor
In this manner of securing the vessel, the parachute is attached with a long nylon line to the boat, and much has been written by people about the best way to go about it, for when using a 'Para' anchor with a lengthy line there will be a lot of 'stretching' as the craft surges away from it when a wave 'lifts' the boat out of the 'trough' and into the full force of the wind. This stretch will 'relax' as the wave passes, and the craft will 'surge' down the back of the wave towards the Para and 'swing' a little sideways. This may be 'lessened' by using the correct length of rope in relation to wave to wave distance and some recommend using a 'bridle.' The bridle keeps the craft at an angle to the wind and 'hopefully' lessens the intensity of the movement. But if the nylon reaches the 'end' of its capacity to stretch there may be a very bad 'jerking' of the vessel. The above image does not show the 'trip' line that is used to retrieve the Para anchor. The trip line is attached to the rear of the Para to a float so that the trip line can be reached and the Para can be hauled in backwards once the main line has been bought aboard, and some people run this line all the way to the vessel . One of the most crucial factors to be considered when deploying a Para-anchor with an all nylon rode is the length of the rope in relation to the distance between waves tops due to the actual energy movement within the wave and, - - - the other crucial factor now given by me is the use of the 'catenary effect' of chain that is given further down the page, - - - being the use of your own anchor chain as being half or more the length of the 'total' rode length, as this will add a huge safety factor and give you what I call "Noah's 'easy rider' Para anchor technique." In the image below I give a little example of how or 'why' the nylon rode stretches and slackens if it is not of the correct length/ratio to wave distances apart. I use the example of a log that is not blown along by the wind as it is mainly submerged, thus it shows how the submerged parachute also moves as the wave energy passes around it with each wave.
It shows that a 'log' floating in the water remains relatively stationary in its prior to and after the wave has passed position 'A' above the ground, but as the wave approaches the log it is 'sucked' towards the wave front (position 'B') and, is then thrust back to its original position 'A' as the wave passes by. This is because the energy within a wave is of a revolving nature as it moves through the water. It is the energy travelling through the water that is elevating and lowering individual sections of the water as it (the energy) travels through the ocean. The water mass is relatively stationary but is lifted and lowered as the energy flows though it. Only when the wave 'breaks' does it the water fall forwards. What this means is that the vessel is anchored with a powerful parachute that is apparently stationary, but is in fact also subjected to the passing wave energy 'rotation,' thus it is very necessary for the back and forth 'surge' to be operating upon the Para and the vessel in unison especially if there is no chain being used to give a catenary effect. If the parachute is positioned 20' or more beneath the wave action then the affects of rotational energy are less on the Para. There is a false belief by some Para users and suppliers of an ‘all nylon rode‘ that: “The longer the rode, the less the strain on the boat and the parachute sea anchor due to the ‘stretchiness’ of nylon.” This is incorrect because in many instances it is the very fact that nylon has the capacity to stretch to its limit of stretch that it can impose adverse loads through ‘jerking’ movements in the first place. The problem in using an ‘all nylon rode’ is that there is no catenary action, thus the only protection against ‘jerking’ is the capacity of nylon to stretch. However, once it has stretched to its limit there is no protection, and in some instances severe damage can result to the Para canopy, the rode itself, the vessel, and the occupants. Note: in some instances – refer to the article on page 3 below. For when anchored to a ‘Parachute’ sea anchor it is similar to being anchored to the sea bed, in that one is anchored to an immoveable object that itself does not ‘give’ if it of a correct size for the vessel and, - - - As you know, if you were anchored to the sea bed using only ‘rope’ with no chain to give your vessel the benefit of the ‘catenary affect,’ as the wind and wave power increased your vessel would jerk so violently through wave and wind action that it would cause severe stresses to the nylon, the vessel and, it would be difficult for the occupants to survive without injury as they are jerked violently as each wave passes. Note: Catenary effect – To understand this most important aspect of any anchoring technique go to The Catenary curve. Note: At all times any 'section' of the rode must be strong enough to handle the great loads imposed by greater than force 12 winds, for when they are encountered the usual nylon or chain 'ground' tackle used to anchor your vessel to the sea bed may not be strong enough when used with a powerful parachute anchor and have the added stresses imposed through 'jerking' violently because you have no chain in the line and no catenary affect. Note: force 12 winds – To understand this go to Beaufort wind scale.
The wrong way when using only nylon is shown here
In the above image the distance between the vessel and the Para is about 60% more than one wave distance or 40% less than two wave length distances. The Para is surging forwards with the elevating body of water as the energy flows past the 'B' position of the Para anchor and thrusting it back to its initial point 'A' and, - - - At the same time the vessel is sliding down the back of the preceding wave and the body of water it is floating on is surging 'backwards' towards the next wave and its 'B' position. Thus the boat and Para are coming towards each other, and this slackens the rope and the vessel is also able to 'slew' to one side as the 'line' loses some of its tension.
In image 2 above, the wave of energy that moved the Para in the direction of the vessel has changed its rotating direction, and the 'water' in which the Para is situated is surging 'backwards' towards the next wave away from the vessel and 'tightening' the slack and, - - - at the same moment the vessel has been elevated by an approaching wave and is surging away from the Para due to both wind action as it comes up out of the trough as well as the forwards movement of the wave. This is a very bad situation, for the parachute anchor is similar to being anchored to an immoveable object, and the slack is taken up fast as both ends are 'yanked' apart and there is a tremendous 'snatch' and jerk and, - - - the vessel can be damaged as can the line and Para anchor and it also can cause injury to the occupants. This jerking can go on wave after wave, and the effects of the stretching and jerking of the nylon is that it is being twisted and untwisted continually and it causes great stress to the rode and attachments. This effect becomes more noticeable as wind speed increases, and if you have no chain then the longer the rope used the less 'snatch' effect. The better only rope rode is shown here
If you are using nylon rope and with no chain being used then try and deploy correct rode length so that both energy rotational movements takes place at the same time, - - - so that when the vessel is on the crest of a wave and surging with the energy 'roll' the Para is also surging on the crest of a wave, both moving in unison and there is much less added stress on everything. In the image below as the wave passes, and the vessel is being 'sucked' back towards the next elevating wave front, then it is happening to the Para anchor at the same moment. This keeps the 'line' taught and there is less jerking and the vessel keeps itself facing in the correct direction more easily.
If you wish to have out more than one wave 'distance' length of line or more then do so. If you have to deploy the Para in the dark and cannot establish any wave 'distance' then simply put out all the nylon rode you have.
The correct Noah's 'easy rider' technique is shown here Due to the 'elasticity' of rope and the fact that the pressure on the vessel must decrease and increase as waves pass by and windage effects alter, the 'easy rider' Para anchoring technique should be seen as no different to normal anchoring as it uses the catenary affect of a long chain length that is supported by floatation at both ends, the boat at one end and a float at the other. As the chain is supported by a float it does not cause the Para to sink downwards and, this ensures that the pull on the Para remains constant and horizontal at a predetermined depth, a depth that is 'set' by you depending on the Para diameter and the depth you wish to have it 'running' beneath the waves.
The benefits of this are obvious, not only can one use much shorter Para nylon rode length of 40 metres, (example) but one can then simply attach it to the main anchor chain with a 3 way connector and adjust the chain length needed accordingly. This also not only maintains a constant 'static' pressure on the Para and its nylon rope but the vessel as well and, - - - the catenary affect of the chain then ensures that there is never any sudden jerk that could damage the Para, line, vessel, or occupants and, - - - The vessel will lie 'steady' to the wind and, - - - if the 'sync' changes due to wave distances increasing or decreasing it will not be a problem, for the catenary effect of the chain ensures adequate absorption of distance movement in the horizontal plane. The chain is the 'shock absorber' and the Para and the nylon rode remain under a constant positive load with no 'wave by wave' stress.
This image shows the chain catenary effect in action as the chain is tightened due to the vessel being thrust away from the Para as the wave thrusts against the vessel and it also meets the full force of the wind as it rises to the top of the wave. Using your anchor chain as being an integral part of your rode line ensures that the nylon section and the chain is under 'tension' at all times when the Para or vessel surge from wave action and, - - - there is no 'slack' at any time and thus no 'jerking' of the vessel which 'rides' as smoothly as if it were anchored to the sea bed with an 'ample' chain length catenary affect.
As you can see from the above image, once the wind has dropped to below 15 kts and there is only little pressure against the vessel, then the weight of the chain draws the vessel towards the float but there is always a positive 'tension' of the entire chain/nylon combination between the Para and the vessel when there is any wind force. In nil wind conditions the bow of the vessel would be touching the float holding the other end of the anchor chain, and the Para anchor would be suspended below the trip line float. If you 'sat' in this position until the wind picked up, then the vessel would move slowly away from the main buoy, and the lower end of the catenary 'curve' of the chain would be rising upwards towards the sea surface as wind speed increased. But at all times the vessel would be able to rise and fall with no jerking, as it is not connected to the Para in a direct line. When you deploy the Para rode of nylon and chain, you simply ensure that there is enough chain 'out' to ensure a catenary effect in maximum wind conditions, so that there was no jerking of the vessel as each wave swell passed by. The buoy 'float' holding up the chain-nylon connector has to be large enough to easily 'support' half the weight of the chain length and not be dragged under. Thus if you are to be using up to 100 mtrs of 13 mm chain weighing max 330 kgs, the connector float buoy (or buoys) would be adequate if it could support 200 kgs. If using up to 30 metres of 8 mm chain weighing max 50 kgs, the connector float buoy would be adequate if it could support 35 kgs. If you have a 30' boat or larger that has no anchor winch, then when using a long length of chain extended due to dangerous conditions, you may find it difficult to 'pick up' the chain by hand once the wind has dropped due to its hanging weight. To avoid this situation it is best when deploying the chain to place two or more float lines clipped onto the chain between the principle 3 way connector and the boat. This reduces the chain weight that you have to lift up on board, as there is less weight of chain between floats.
If you are using a Para to keep the head of the vessel into wind on a fishing trip in moderate winds you also may use a much smaller Para that is less than half the diameter of the 'storm' one, and you could use a much shorter nylon rode of approx 12 metres that you attach to your anchor line in a similar fashion. ( You decide)
Trip line Para retrieval The 'trip' line for easy retrieval of the Para anchor has a few options. 1 - If you are using an all nylon rode with no chain, the trip can be a rope that extends from the rear of your Para all the way to the vessel, and it is deployed and retrieved in conjunction with the Para. This line has to be at all times longer than the length of the rode as it must take into account the length of the Para itself and any 'stretch' taking place, for if it is too short it will 'trip' the Para. I am not in favour of this 'style' trip line as it can get entangled in the Para, and the vessel propeller, and it has to be managed together with the main rode as you deploy and retrieve. It does have the advantage over (2) below in that you can trip the Para direct from the vessel prior to hauling in the Para and rode. Every trip line should have a 'float' attached to it that floats above the Para. The distance to the float from the Para connection would be about double the Para diameter. This ensures that the Para cannot sink when you wish to retrieve it, and you may also retrieve the Para by seizing the float. 2 - If you are using an all nylon rode with no chain, the trip can be a 10 metre or more line that extends from the rear of your Para to a float only. This way you first retrieve the main rope rode and, as you bring your vessel up to the trip line float that will be 'blown' towards you, you seize it and you haul in the Para backwards. The problems that can arise in this is the difficulty of having the Para still 'effective' as you bring your vessel near to it prior to reaching the trip float, for the wave action against a vessel attached to a fixed object could cause problems at such close proximity as the Para stops the bow from rising up. 3 - If you are using a nylon - chain rode combination as given in the Noah's 'easy rider' technique then I suggest this manner of trip line and retrieval. In the 'Noah' easy rider' combination system there will be an 10 mm 'trip' line extending from the rear of the Para up to a small float (5 to 20 metres above) and then onwards to the main anchor chain connector float and, it will be 'clipped' onto a 'ring' situated at the base of this float or to the top of the float if it has a 'handle.' This will ensure that the entire 'floating' trip line positions itself above and away from the nylon rode and the connector during normal operations. As this trip line does not go back to the vessel it does not matter how much chain you use. Once you have decided on the length of your nylon rode section between Para and 3 way chain connector then you know the length of the trip line. This will differ due to boat size, a small 20' vessel might use a short 20 metre nylon rode and a larger vessel may use a 50 metre nylon rode. Example - if the nylon rode is to be 40 metres, then add the full length of the Para and its shrouds, plus distance to Para float, plus 40. Thus the overall trip line system length might be 70 metres or so. The 3 way connector
The 4"x 3"connector may vary in thickness from 4 mm up to 16 mm depending on rode strength needed.
The correct retrieval and deployment when using chain/rope combination To deploy the Para system Be it a large or small vessel you may wish to deploy the Para from the side of the vessel on the rear deck so as to be sheltered and less likely to fall in heavy seas. In this case it is best to (in good weather conditions) have already disconnected the anchor and dragged 20 - 30 metres of chain around the side of the vessel, and secured it on the rear deck ready to be deployed by hand release. It can be tied with rope that can be released on deployment. Make sure the Para and nylon rode are joined to the 3 way connector securely and the trip line is clipped to the main float and, that all line and chain is under the railing so that it does not 'catch' when deployed. With the vessel pointing into wind but slightly off to one side, throw the trip line float overboard to the windward side (so your vessel does not get blown over it) and then release the Para into the water, and as you 'reverse' or float away you feed out the main nylon rode section after ensuring that the Para has opened. The trip line is also fed out. When the nylon rode section has about 5 or more metres left to go out then throw the 3 way connector and float overboard, and the float and rode will float away and this act will start to drag out the 'free' end of the chain that will spill overboard and, - - - as soon as you have done this you 'cut' the lashing holding the tied section of the chain that kept it tight from the winch end and the outboard chain will also slip into the water. It is important to have the chain running out before the Para is fully affective so as to avoid any 'snatching' taking place. You may then go forward and release more chain if needed or you may have already stowed it all on the rear deck so that you do not have to venture forwards after deployment. To retrieve the Para system You motor towards the main chain float and bring the chain on board. As soon as you reach the 3 way connector and main float you disengage the float trip clip and clip it around the bow rail of the vessel. You then unshackle the chain from the connector and let the 3 way connector and nylon rode drop back into the water as you back off downwind. Thus leaving the nylon rode and the connector and main 'float' to float away and you are 'free' from the Para influence and well away from any lines. As you back away drifting downwind the Para trip line will 'trip' and empty the Para. You may then simply haul the Para and the nylon rode aboard quite easily without any danger. I add that it is best to practice launch and retrieve and use of your Para anchor in fair weather conditions. This web page is to assist you in coming to your own personally informed decisions as you take personal responsibility for your own actions at all times.
Note: The Para may be deployed over the bow or side or stern of the vessel depending on your choice and sea conditions and safety factors. The Para may be retrieved over the bow or side or stern of the vessel depending on your choice and sea conditions and safety factors. Note: When using the Para as a fishing aid in moderate wind conditions you may only need to use a much shorter (half length) nylon rode, and to also only use the nylon or also let out 5 to 10 metres of chain and, you can use a half diameter size Para. Example: If your main survival Para anchor is 10’ diameter then you can use a 5’ diameter one, saving your larger and more expensive one for when it is needed. Note: The 3 way connector float line needs to be between 3 and 20 metres long depending on Para diameter and the depth that you want your Para to position itself beneath the sea. For the weight of the chain will ensure that the 3 way connector link between nylon and chain is traveling at that specific depth below the surface, thus the Para will also travel at the same required depth. Note: - The Para 'trip' line length between the Para rear and the Para trip line float must be about 30% longer than the distance between the 3 way connector and its main float. So if your connector float line was 15 metres long then make the trip line Para to its float about 20 metres long, this permits the Para to sink down to the correct depth of travel. Note: Always 'clip' the trip line clip directly to the ‘handle’ on top of the main chain float or, to the ‘eye’ bolt ring at the base of the main float. This is done for easy retrieval. Note: Even small 5 - 6 metre length boats with outboards need to carry a small 3'to 5' parachute, for if offshore and there is a motor breakdown the winds swings the front of the boat away downwind and the 'laden' transom faces the chop and it may easily be swamped and sink. It is important to deploy a small Para as soon as the motor stops and put out a few metres of rope as this will keep the boat facing the wind. This also steadies the craft whilst repairs are being made and ensure that it remains in a safe and stable state. Note: Most suppliers of parachute sea anchors are presently advertising the use of 'all nylon rode,' as they are unaware of the Noah 'easy rider' technique, so you will need to advise them of the 'reduced' length of nylon you will be requiring to use in conjunction with your anchor chain.
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