Anchoring in Coral & Floating your Chain

[chouliha]

We have recently uploaded an article by SV Spirit of Argo with some additional suggestions by us that maybe of interest to the group.

I am sure we will get bashed as this method doesn't work, not enough holding power, chain should be on the bottom, etc etc. But I will tell you we have used this method in excess of 400 nights at anchor in various atolls in the Tuamotus French Polynesia and it does work. Not only have we sat out some drafty conditions (in excess of 45 knots) but we feel its the only way to safely protect the coral.

The most important thing to take away from this discussion is how can we as a sailing community protect coral when anchoring?

At the bottom of the French Polynesia list is the article "Floating your chain in Coral"

https://www.jacarandajourney.com/other-good-stuff

Safe anchoring

Chuck
Jacaranda

[MathiasW]

Originally Posted by chouliha

We have recently uploaded an article by SV Spirit of Argo with some additional suggestions by us that maybe of interest to the group.

I am sure we will get bashed as this method doesn't work, not enough holding power, chain should be on the bottom, etc etc. But I will tell you we have used this method in excess of 400 nights at anchor in various atolls in the Tuamotus French Polynesia and it does work. Not only have we sat out some drafty conditions (in excess of 45 knots) but we feel its the only way to safely protect the coral.

The most important thing to take away from this discussion is how can we as a sailing community protect coral when anchoring?

At the bottom of the French Polynesia list is the article "Floating your chain in Coral"

https://www.jacarandajourney.com/other-good-stuff

Safe anchoring

Chuck
Jacaranda

Thank you for sharing this in this community! I was recently made aware of this technique by April from SV Spirit of Argo, and out of curiosity did a mathematical modelling of this technique, which you can find on my web page towards the end:

https://trimaran-san.de/die-kettenku...atiker-ankert/

At first I did not believe it would work, but the model clearly says why it does (as long as enough chain is available). I am curious to get feedback from those with practical experience whether my assumptions in this model make sense or not.

Cheers

Mathias

[chouliha]

Hi Mathias

I read your document with interest a few weeks before I posted this note and found it very interesting.

I would like to add a few comments in addition to what we added to SV Spirit of Argos write up posted on our website. Have you read our notes?

1. Depending on the depth we are anchored for example 45’ the first 2 floats are not even close to the surface. The weight of our 3/8” BBB chain pulls the floats below the surface. One reason is that we use the hard pearl floats rather than our fenders which we found get compressed flat and the floats do not. I am not sure that your analysis takes this chain weight /depth of float into consideration. With the pearl floats way below the surface it changes the angle of the chain.

2. In our multiple nights(350-400) of using this method to anchor in the Tuamotus we had a few drafty conditions with considerable fetch and it has always worked well. Often when the wind switches in an uncharted lagoon we just couldn’t move. It happens at night or it’s cloudy or the sun is in our eyes. So fetch is almost always involved in windy conditions. In one lagoon its 30 miles to the other end. With that said what we found was using the floats softened the movement of the boat almost like a spring Different than if we did not use the floats. Using only chain with a snubber we noticed that when stretching back and the chain stretched tight the boat had a different movement.

It was always interesting to be in the clear water and watch what happens as the boat surges back the movement of the boat tries to drag the pearl floats down. Opposite if the boat was only on chain trying to lift it.

We have sat out 40-45 kts in 60’ of water using 4 floats on 235’ chain with no issues or dragging. In this case we could only see the float closest to the boat in lulls.

3. Take the example that the wind and fetch is strong enough to stretch the chain out bar tight. In either case(floats or no floats) the angle of the chain is the same. The floats under these conditions offer no lift at all as the chain is stretched out tight. They would all be dragged below the surface.

Would we use this method when there was no coral below us - of course not as it takes some extra effort when anchoring. But this is the only way to save the coral from complete destruction.

Others have said “Oh we just move to a sandy area”. That is NOT possible in many places in the Tuamotus as often there is coral everywhere.

We encourage our fellow sailors to use this method in any area that has coral or even sea grass that you want to protect.

[fxykty]

That’s awesome, thanks very much. Great suggestion to use floats rather than fenders, and noting that fenders OK closer to the boat in deeper water where they’re expected to stay on top.

Absolutely right that we cruisers are responsible for preventing coral destruction where we anchor. Another tip is to pick up a mooring if available - often they’re there to prevent anchor and chain damage to coral. If no mooring available (where there are moorings) consider moving to another location rather than anchoring nearby.

[bobnlesley]

Originally Posted by chouliha

...hard pearl floats rather than our fenders...using the floats softened the movement of the boat almost like a spring...as the boat surges back the movement of the boat tries to drag the pearl floats down. Opposite if the boat was only on chain trying to lift it....the wind and fetch is strong enough to stretch the chain out bar tight. In either case(floats or no floats) the angle of the chain is the same...

Much as we found using them in the Tuamotus and a few times in the Society Islands and Fiji too; the floats are not infallible though, we did once get badly snagged on coral anyway and on a couple of occasions in 'fluky' winds, the chain wrapped/tangled around the floats themselves; the easiest way to sort the latter problem was to cut the float ropes close to the chain.

The one trick/tip I would add is to fasten the float-rope to the chain using easily released clips rather than tying it, we had something like these:
https://uk.rs-online.com/web/p/safet...E&gclsrc=aw.ds

[MathiasW]

Originally Posted by chouliha

Hi Mathias

I read your document with interest a few weeks before I posted this note and found it very interesting.

I would like to add a few comments in addition to what we added to SV Spirit of Argos write up posted on our website. Have you read our notes?

1. Depending on the depth we are anchored for example 45’ the first 2 floats are not even close to the surface. The weight of our 3/8” BBB chain pulls the floats below the surface. One reason is that we use the hard pearl floats rather than our fenders which we found get compressed flat and the floats do not. I am not sure that your analysis takes this chain weight /depth of float into consideration. With the pearl floats way below the surface it changes the angle of the chain.

2. In our multiple nights(350-400) of using this method to anchor in the Tuamotus we had a few drafty conditions with considerable fetch and it has always worked well. Often when the wind switches in an uncharted lagoon we just couldn’t move. It happens at night or it’s cloudy or the sun is in our eyes. So fetch is almost always involved in windy conditions. In one lagoon its 30 miles to the other end. With that said what we found was using the floats softened the movement of the boat almost like a spring Different than if we did not use the floats. Using only chain with a snubber we noticed that when stretching back and the chain stretched tight the boat had a different movement.

It was always interesting to be in the clear water and watch what happens as the boat surges back the movement of the boat tries to drag the pearl floats down. Opposite if the boat was only on chain trying to lift it.

We have sat out 40-45 kts in 60’ of water using 4 floats on 235’ chain with no issues or dragging. In this case we could only see the float closest to the boat in lulls.

3. Take the example that the wind and fetch is strong enough to stretch the chain out bar tight. In either case(floats or no floats) the angle of the chain is the same. The floats under these conditions offer no lift at all as the chain is stretched out tight. They would all be dragged below the surface.

Would we use this method when there was no coral below us - of course not as it takes some extra effort when anchoring. But this is the only way to save the coral from complete destruction.

Others have said “Oh we just move to a sandy area”. That is NOT possible in many places in the Tuamotus as often there is coral everywhere.

We encourage our fellow sailors to use this method in any area that has coral or even sea grass that you want to protect.

Hi Chouliha,

Thanks for this feedback, and yes, I did read you additional comments. Interesting that you allow the first couple of floats to go under water. For sure, this helps the angle at the anchor. I hinted at this possibility somewhere in my description on my web page, but without giving any quantitative analysis. I guess, if you allow the first floats to sink, then you must compensate for that at the floats closer to the bow, as otherwise the entire line would sink. So, overall, all the floats together must still support the entire chain.

Floats offer buoyancy and this is potential energy, so yes, I can believe that it is acting like a huge nice spring and will be very different from chain+snubber alone. Compared to the latter scenario, the floating chain will require a longer chain, but if that chain is available, it will work very well.

In any case, it will reduce the effect of strong surges on the anchor load and that alone is already most useful.

You state that fenders compress when under water? Why is that? I would have thought if I inflate them with more air, this should not be an issue?

Cheers

Mathias

[chouliha]

As the fenders are pulled under the water by the weight of the chain they are being compressed by the pressure at that particular depth. We have seen fenders completely flattened like a pancake at depths of 40'. Also the valves on the fenders are not made to hold air at extreme pressure. That is why its great to collect the pearl floats as they are thick hard plastic and made to support strings of pearl oysters which can be very heavy.

We use the formula of the first float being placed at 1.5xs the water depth. Then the second float depends on the water depth but often 30-35' along the chain from the first float. Third float is similar. If we are anchored deeper than 50+ feet we may put the floats closer together.

So the floats do not support the entire chain as there is some chain laying on the bottom. Using the 1 1/2 times the depth if we were in 30' of water the first float would be attached at 45' This usually left 20'+ chain on the bottom as the first float would be pulled under by the weight of the chain.

Bobnlesley's comments are totally correct. If you do not spot the initial drop of your anchor in a sandy patch with enough area you may snag a bommie. Often the water in the lagoons are not super clear and we have found using a fishfinder will give us a pretty good indication of bottom type and where the bommies are located. We installed a cheap Garmin 150 and stuck the transducer to the hull with silicone. We found it a great addition to the boat

The use of clips (which we mentioned in our added tips) is very helpful and speeds up setting the floats and retrieving them. Older snap shackles, caribeeners or even old sail hanks all work well

In over a year of using this method we have had 2-3 times when there was no wind and we were anchored shallow that the boat drifting around caused the floats to tangle. Usually a quick push on the boat with the dinghy cleared them.

Chuck
Jacaranda

[MathiasW]

Originally Posted by chouliha

As the fenders are pulled under the water by the weight of the chain they are being compressed by the pressure at that particular depth. We have seen fenders completely flattened like a pancake at depths of 40'. Also the valves on the fenders are not made to hold air at extreme pressure. That is why its great to collect the pearl floats as they are thick hard plastic and made to support strings of pearl oysters which can be very heavy.

Hmm, interesting. But I guess yes, when you think about it, in 12 metres depth, the pressure is much higher than a normal fender would be operated at...

[Montanan]

Originally Posted by MathiasW

Hi Chouliha,

Thanks for this feedback, and yes, I did read you additional comments. Interesting that you allow the first couple of floats to go under water. For sure, this helps the angle at the anchor. I hinted at this possibility somewhere in my description on my web page, but without giving any quantitative analysis. I guess, if you allow the first floats to sink, then you must compensate for that at the floats closer to the bow, as otherwise the entire line would sink. So, overall, all the floats together must still support the entire chain.

Floats offer buoyancy and this is potential energy, so yes, I can believe that it is acting like a huge nice spring and will be very different from chain+snubber alone. Compared to the latter scenario, the floating chain will require a longer chain, but if that chain is available, it will work very well.

In any case, it will reduce the effect of strong surges on the anchor load and that alone is already most useful.

You state that fenders compress when under water? Why is that? I would have thought if I inflate them with more air, this should not be an issue?

Cheers

Mathias

Pressure on the submerged device increases dramatically with depth. A strong hard shell will not crush and thus will retain its volume of water displacement whereas a soft shell will compress and have reduced volume displacement thereby reduced lift capabilities. Yes increasing the internal pressure significantly will enable the device to not compress as much in volume as a less pressurized device, but an over pressurized device will also be stretched outward when raised towards the surface and it is difficult to maintain a seal when the device is under high pressure. One often see fenders that have compressed after having been cycled repeatedly under hard loads as a boat rubs against a hard object such that the fender has little benefit.

A hard shell float is much more robust for use below the surface and is why they are commonly used in eco-friendly moorings to raise the chain rode of a mooring so as to never let it touch the bottom, thereby avoiding degrading the flora and fauna as a boat rotates on its mooring.

Reference image below of Eco Friendly Mooring ECM. Note the common use of floats for keeping the rode off the bottom and / or the use of elastic rode which is kept under tension by the main surface located mooring float.

The use of floats in fixed mooring can be replicated for temporary anchor use in coral fields and rocky fields as well, which scheme of use is just an extension of a well proven method of managing fixed anchor rodes. All very common and in more and more locations the mandated system by law; for obvious reasons, it eliminates all the barren circles imposed by traditional, non-eco friendly anchoring and mooring.

Meaning that such floats should be used ALL the time, not just when trying to avoid wrapping around a coral head or rock.

It is simple to tether an easily removable float from a chain rode as one plays the rode out and to untether as one retrieves such. It being more difficult to attach to a rope rode and a rope rode will end up floating at the surface and can become a navigational hazard whereas floats on chain are intended to just raise the rode from the bottom not to float to the surface.

[MathiasW]

Hi Montanan,

Yes, I agree with your reasoning!

One point, though: If one uses a made-up float construction with one's own anchor and not a mooring brick, one will have to use enough chain in the first leg, in order that the anchor is not pulled at a vertical angle. And then there are the additional hops of chain between buoys. This results in more chain that needs to be used, and consequently, I would think that the swinging radius is larger than normal anchoring. So, it might not be so popular in crowded anchorages...

[Montanan]

Originally Posted by MathiasW

Hi Montanan,

Yes, I agree with your reasoning!

One point, though: If one uses a made-up float construction with one's own anchor and not a mooring brick, one will have to use enough chain in the first leg, in order that the anchor is not pulled at a vertical angle. And then there are the additional hops of chain between buoys. This results in more chain that needs to be used, and consequently, I would think that the swinging radius is larger than normal anchoring. So, it might not be so popular in crowded anchorages...

Your reasoning is correct you don't want to have enough floatation that the chain is pulled harshly up, just enough to carry much of the weight off the bottom. You don't need to deploy more scope with floats. When the boat is not being backed away from the point of anchor by the pulling forces of wind or tide then the boat will tend to move back towards the anchor point similarly as it does when the tension of the rode is slackened and the chain rode drops to the bottom surface. Without tension on the rode you will end up with a series of slack loops laying lower than each of the series of small floats. The bottom of each chain loop between the floats can reach down and lie on the bottom [and can tangle with the underwater object that you are trying to avoid wrapping around]. You should not need more swing radius with floats than is derived when your rode is put under full tension without floats. Actually when using floats, you will tend to not be set as far away from your anchor when there is not tension applied to the rode because your rode will try to form a series of gentle loops rising where there is a float, kind of like a series of UUUUU, instead of lying like the customary chain rode as depicted crudely here: _____/. You will tend to ride a shorter turning radius with floats because the slack chain is taken in by each U. Edit: One could leave a short length of chain from the anchor to provide for horizontal set, say ten or fifteen feet then implement the loops of U shaped series of floats and chain so as to have it lie like this ___/UUUUU. The point being to minimize the contact with the bottom.

And if your chain rode does loop down and touches the bottom it will do so in only a limited length of touching the surface and with less damaging force of weight and drag. The distance between floats is established depending on the depth of the water. One can calculate the displacement weight of the float and the displacement weight of the chain and strike a balance so as to keep the chain below the water's surface but still minimizing the contact to the ground surface. If there is a tall coral head then one has to put much more floatation so as to raise the chain above the coral for that section of the rode and that chain and its floats are navigational hazards but then so is a tall coral head. Boomies is a term I am common with as to referring to the coral heads. If there are a lot of them in the swing radius then there is need for a lot of floats to keep clear as one can't form a drop loop between floats that will reach low enough to make entanglement. Best to just avoid such entangling fields. Find a clear sandy bottom.

One needs to strike a balance between keeping much of the rode off the bottom but also away from the surface. Minimizing damaging and entangling as little as possible with the ground / coral / rocks / grass but not riding at the surface to be a navigational entanglement.

[MathiasW]

Hmm, I need to wrap my head around this. As I have not yet tried this for real, I just do not know and take your experience for it. But my model seems to suggest the swinging circle would be larger.

In any case, it seems prudent to have an anchor buoy out that marks the position of the anchor. I had not thought about the navigational hazard for others when the chain is half sunk, but you are right, of course.

[Montanan]

Originally Posted by MathiasW

Hmm, I need to wrap my head around this. As I have not yet tried this for real, I just do not know and take your experience for it. But my model seems to suggest the swinging circle would be larger.

In any case, it seems prudent to have an anchor buoy out that marks the position of the anchor. I had not thought about the navigational hazard for others when the chain is half sunk, but you are right, of course.

Prepare to duck. Responses surely to be invoked with the subject of marker buoys.

Marker buoys [and / or anchor retrieval lines that allow one to pull the anchor from its backwards direction if it has become stuck] certainly serve their purpose but boy oh boy oh buoy do they become navigational hazards, but they are also anchoring hazards as if an adjacent boats swing is inclusive of where the marker is vertically rising above its anchor then the rode of the adjacent swing boat will be entangled with the marker buoys rode and the swinging boats rode will pull the anchor vertically up and the boat that is attached to such anchor will be off to the races dragging and / or pulling on the adjacent swinging boats rode.

The swing radius can only be as long as the rode that is let out and placed under tension. If the rode is caused to be shortened when it is in slack condition by forming gentle loops between floats then it will have a shorter swing radius when it is not under tension.

[Montanan]

The point of keeping the rode off the bottom is to avoid entanglement with hard items [coral or rock, or logs, or wrecks] and to avoid damage to the bottom dwellers [plants and animals]. When one is anchoring in shallow areas with eel grass the anchor or mooring chain will form cleared crop circles. Avoid anchoring in grass fields, it is similar say to driving across a pristine boggy marsh, the damage is very traumatic and quite long lasting. There be a wonderful ecosystem even in the clear sandy bottoms.

So loved my marine biology classes during high school and the time spent off campus on boats, tide pools, marshes, mudflats, beaches, and snorkeling, or staying at marine laboratories and aquariums. Not many boaters collect the mud that comes up with their anchors, to investigate and ascertain what all is in the bottom sample. Most just hose it off and don't ever consider what disruption they just invoked and to what their actions imposed harm.

One needs to be securely set in a position but try to be gentle with the surroundings; tread lightly. Be clear who the intruding visitor is in the situation. When one drops anchor and rode, it lands on living things. We have the capacity and responsibility to be good stewards of our planet.

Images of eel grass damage due to anchoring and mooring.

[MathiasW]

Originally Posted by Montanan

Prepare to duck. Responses surely to be invoked with the subject of marker buoys.

Marker buoys [and / or anchor retrieval lines that allow one to pull the anchor from its backwards direction if it has become stuck] certainly serve their purpose but boy oh boy oh buoy do they become navigational hazards, but they are also anchoring hazards as if an adjacent boats swing is inclusive of where the marker is vertically rising above its anchor then the rode of the adjacent swing boat will be entangled with the marker buoys rode and the swinging boats rode will pull the anchor vertically up and the boat that is attached to such anchor will be off to the races dragging and / or pulling on the adjacent swinging boats rode.

The swing radius can only be as long as the rode that is let out and placed under tension. If the rode is caused to be shortened when it is in slack condition by forming gentle loops between floats then it will have a shorter swing radius when it is not under tension.

Yes, certainly, there are pros and cons for such a marker buoy. I do not often use it, not at all. But if I do, it has a light at night. It can only be used if the anchorage is not crowded at all and when its main purpose is to indicate to new arrivals what the situation is.

As to the swinging radius, sure, as long as it is doing UUUU, the swinging radius may be rather small. But once there is a storm and the buoys are all under water, I am sure the swinging radius is larger than for conventional anchoring. It is a compromise, after all, and something has to yield. I am sure it is the swinging radius under storm conditions.