Anchoring in Coral & Floating your Chain

[Montanan]

Originally Posted by MathiasW

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.

The chain with a float attached will not stretch out any further than the same length of rode without floats. Floats will not aid in avoiding coral once the rode is pulled taught. The floats will be pulled down. There is only modest cantinery in the rode under harsh loads. The floats will have little effect under storm conditions; they may add a little bit of spring, being rather similar to having placed a kelt on the rode which kelt has to be pulled upon to raise the chain rode is straightened under tension; the floats have to be pulled downward when the rode is straightened under tension. The issue with a kelt is it yet another object that can drag on the bottom if it is set too far down the rode.

[MathiasW]

Sure, if you use the same length of chain, you are right. But I would have thought one needs / or should use more chain when doing this type of anchoring... Otherwise, the pulling angle at the anchor will be much worse than when doing straight anchoring.

You would never want the chain to go more or less straight, anyway. It may look like it does, but at least in deeper water a catenary will often still develop.

And regarding the anchor buoys - it is a trade off, isn't it. If the chain and buoys already constitute a navigational hazard, then adding an anchor buoy may actually be beneficial in reducing this hazard.

[NevilleCat]

I seem to remember reading somewhere in an article about sailing southern Chile that the author (maybe Skip Novak? maybe not) sometimes used to set up his anchor like a mooring with a big mooring float attached. In light conditions the boat would simply range around the mooring buoy and in the 60kn bullets when the load came on it would try to pull the buoy underwater so acted with a similar effect as a snubber.
Wish I had the article as i can't quite get the detail of how it was set up but it made sense.

[MathiasW]

NevilleCat,

Yes, that is based on the same mechanism!

Further on the swinging radius: I think one needs to compare like with like. So, my requirement is that the pulling angle at the anchor is the same in both cases, so A) when using standard anchoring, and B) when using buoys to float the chain.

Whether this pulling angle is horizontal or not, does not matter. Just the same.

Then, in case A), the chain will run as a simple cosh curve towards the surface. Done! In case B), it will start out in exactly the same way and direction, but when the first buoy is reached, there will be a downward kink in the chain, letting the chain continue at a larger angle with respect to the vertical compared to case A). At each buoy, this process will get repeated. In the end, all these kinks will mean that it requires more chain to reach the water surface and the point at which it does so will be farther away from the anchor than in case A).

Hence, the swinging circle will be larger when floating buoys are used. One can opt to compensate for that by accepting a worse pulling angle at the anchor, but in the absence of that, the above analysis holds.

[chouliha]

Originally Posted by MathiasW

NevilleCat,

Yes, that is based on the same mechanism!

Further on the swinging radius: I think one needs to compare like with like. So, my requirement is that the pulling angle at the anchor is the same in both cases, so A) when using standard anchoring, and B) when using buoys to float the chain.

Whether this pulling angle is horizontal or not, does not matter. Just the same.

Then, in case A), the chain will run as a simple cosh curve towards the surface. Done! In case B), it will start out in exactly the same way and direction, but when the first buoy is reached, there will be a downward kink in the chain, letting the chain continue at a larger angle with respect to the vertical compared to case A). At each buoy, this process will get repeated. In the end, all these kinks will mean that it requires more chain to reach the water surface and the point at which it does so will be farther away from the anchor than in case A).

Hence, the swinging circle will be larger when floating buoys are used. One can opt to compensate for that by accepting a worse pulling angle at the anchor, but in the absence of that, the above analysis holds.

Not sure why the swinging radius would be greater or more scope needed when using floats. We never added more scope due to having floats. We anchored and based on depth and weather we added enough scope to give us a comfortable amount i.e 4:1. Then added floats.

[MathiasW]

Originally Posted by chouliha

Not sure why the swinging radius would be greater or more scope needed when using floats. We never added more scope due to having floats. We anchored and based on depth and weather we added enough scope to give us a comfortable amount i.e 4:1. Then added floats.

ok, I can very well believe you that you did not increase the chain length when you had floats out, but the above reasoning very clearly points to this leading to a pulling angle at the anchor that is larger than with conventional anchoring.

Apparently, you never had problems with this and all was fine, even with that larger pulling angle, but definitely you had a larger pulling angle. The geometry / catenary equations won't allow it in any other way.

In any case, it is good to hear that it is not needed to use much more chain. That had been my biggest worry after the analysis...

[GordMay]

You might also be interested in the “Mooring Buoy Planning Guide”, prepared by the Project AWARE Foundation, and PADI International Resort Association (PIRA)
➥ https://www.coris.noaa.gov/activitie...ing_buoy_g.pdf



“Floating your chain”, a very good description on how to anchor in coral, written by Cain & April on SV “Spirit of Argo”
➥ https://www.spiritofargo.com/2019/08...-what-is-that/
➥ https://www.jacarandajourney.com/floatingyourchain

[CaptainRivet]

Originally Posted by GordMay

You might also be interested in the “Mooring Buoy Planning Guide”, prepared by the Project AWARE Foundation, and PADI International Resort Association (PIRA)
➥ https://www.coris.noaa.gov/activitie...ing_buoy_g.pdf



“Floating your chain”, a very good description on how to anchor in coral, written by Cain & April on SV “Spirit of Argo”
➥ https://www.spiritofargo.com/2019/08...-what-is-that/
➥ https://www.jacarandajourney.com/floatingyourchain

I stumbled upon this on Instagram and know found the thread here…interesting also from skip Novak…

For this setup also an additional weight shackled into the chain where it still lies on the floor will improve holding power even more, making the first 7-10m of chain very heavy.
I have and use a 15kg weight (11cm diameter cylinder filled with lead, in German it’s called Reitgewicht) which I shackle in the chain 7-10m after the Anker when I have a chain to depth ratio of 3.1 or less or stormy conditions. It helps the chain stays longer aground and even if fully stretched it still improves the angle of the Anker chain to the ground and Acts like a spring too. Really noticeable with and without the weight. It’s like having a 14mm chain the first 10m and then a 10mm one for the rest. The cylinder fits over the Anker roller which is necessary because the Anker is recessed between the bows on the Lavezzi and like this I can shackle it in a deploy and retrieve it from the Anker locker on deck.

It’s normally ment for reducing the swing radius in a crowded Anker bay but still give you more holding power.
My weight is oversized, coming from my old 13t longkeeler ketch and know used on a 8,5t cat, 10mm g4 chain is on the heavy and slightly oversized side too.

[downunder]

The diagram is not realistic for the Great Barrier Reef (GBR).

The coral heads are often up at and near to the surface. Floating a chain would be a pain in the neck.

Anchoring is a matter of picking the spot similar to avoiding other vessels.

Always a chance of contacting coral heads that's why all chain.

[chouliha]

Originally Posted by downunder

The diagram is not realistic for the Great Barrier Reef (GBR).

The coral heads are often up at and near to the surface. Floating a chain would be a pain in the neck.

Anchoring is a matter of picking the spot similar to avoiding other vessels.

Always a chance of contacting coral heads that's why all chain.

Just curious what you do when you are in a spot that has lots of bommies and very little swinging room and no other place to go?

The point of my original note is many lagoons at least in French Polynesia, Fiji, etc. have bommies almost everywhere. Some of the bommies come up close to the surface.

Yes chain is a must agreed.

[Montanan]

Originally Posted by chouliha

Just curious what you do when you are in a spot that has lots of bommies and very little swinging room and no other place to go?

The point of my original note is many lagoons at least in French Polynesia, Fiji, etc. have bommies almost everywhere. Some of the bommies come up close to the surface.

Yes chain is a must agreed.

The boomies that rise to nearer the surface are like landmines. They will KaBoom against the rode that swings in an arc, thereby complete changing the vessel's swing radius, or in the worst case cause the vessel to be pulled into contact with another boomie.

One is overthinking and over complicating the situation by trying to float over a Boomie.

Anchor elsewhere or anticipate your rode to wrap around and damage a boomie and to become problematic.

Best solution is to deploy fore and aft anchors to fix your boat with two rodes so as to not swing and thus to not let a rode come into contact with a boomie, or the vessel to make contact with a boomie.

Keep the boat in taught line between the two anchors and away from Boomies. Then chain is not a must because there is no potential for chafe.

Protect The Lagoon and the Boomies Within; Do No Harm; Leave No Trace. You are the Visitor, Accord Nature Its Prioritization Over Your Anchoring Desires.

[fxykty]

Originally Posted by Montanan

The boomies that rise to nearer the surface are like landmines. They will KaBoom against the rode that swings in an arc, thereby complete changing the vessel's swing radius, or in the worst case cause the vessel to be pulled into contact with another boomie.

One is overthinking and over complicating the situation by trying to float over a Boomie.

Anchor elsewhere or anticipate your rode to wrap around and damage a boomie and to become problematic.

Best solution is to deploy fore and aft anchors to fix your boat with two rodes so as to not swing and thus to not let a rode come into contact with a boomie, or the vessel to make contact with a boomie.

Keep the boat in taught line between the two anchors and away from Boomies. Then chain is not a must because there is no potential for chafe.

Protect The Lagoon and the Boomies Within; Do No Harm; Leave No Trace. You are the Visitor, Accord Nature Its Prioritization Over Your Anchoring Desires.

This.

Not only potential damage to the coral, but why would you ever anchor where there are surface or near surface bommies between you and your anchor? Any sort of swinging or wind change would put you on them with your boat.

Floating your chain is to keep it off of deep coral that is within your swing circle.

As Montanan describes, if you are in a tight spot between surface level bommies, anchor fore and aft inline with primary wind and/or current so that you can’t swing onto any coral. Do remember how quickly loads on your gear increase if the wind or current comes from the side.

[AiniA]

Originally Posted by chouliha

Just curious what you do when you are in a spot that has lots of bommies and very little swinging room and no other place to go?

The point of my original note is many lagoons at least in French Polynesia, Fiji, etc. have bommies almost everywhere. Some of the bommies come up close to the surface.

Yes chain is a must agreed.

We only ran into this problem once in four years RTW and that was in Indonesia where finding somewhere to anchor is complicated by the fact that the bottom falls off so quickly from volcanic islands. We didn't have a problem at all in FP.