Photos of Anchors Setting

[Group9]

Originally Posted by lancelot9898

Appreciate all your efforts norlex in posting the pictures. I think the photos themselves are more instructive than many of the anchor tests done by the manufacturers. I have a friend who claims that he used a Danforth anchor during a hurricane and it dug in through the mud several feet such that it could not be retrieved. Instead of attaching the chain or rope directly to the Danforth , he used a 5 or 6 foot cable. He called it a cheese slicer which allowed the anchor to penetrate deeply into the mud. Such an anchor would be very dependent on the bottom composition and I don't think it would be very suitable for most anchorages, but thought it might be a good ideal for specific locations and conditions. My 2 cents.

I anchored a 25D Cape Dory in Hurricane Elena with three Danforth anchors in deep mud, a 22 pounder set in the direction I anticipated the most wind to come from. Afterwards, we tried to get it up all day and finally just gave up and cut the chain and let it go.

On another occassion, I helped anchor a friends Hunter 31 in Hurricane Ike in deep mud, again using three Danforths and again putting a Danforth 22 in the direction I anticipated the wind to come from. We got that anchor up, but it was two hours of using the buoyancy of a 22 foot center console by moving four people to the front, snugging the chain down and then moving every one to the back, over and over again, to finally inch the thing loose. When it finally came up, it had a huge ball of clay and mud on it.

[noelex 77]

A nice sand anchorage. Yeah.......back in clear water . 5:1 in 6.8 m

We dropped just on dusk, so this photo was taken the next morning. You can see the Mantus has set almost immediately. This anchor sets incredibly quickly.

These photos are from the tender, but the loose weed which has collected in the depressions makes the contours clearer. The fluke is completely buried with only a tiny amount of the shank visible. There is almost no heaping up of sand.

The only criticism is that there is a slight list. You can see from the marks in the sand that the force while setting changed about 30 degrees when our boat rotated to port due to the prop walk in the light wind.

[JPA Cate]

So, did the chain unwind itself?
or have you developed a trick for making it do so?
Once the anchor is clear of the bottom, have you tried going backwards to encourage the unwinding?

Other possible tricks to help it unwind?

Thanks, Noelex.

Ann

[noelex 77]

Originally Posted by Ann T. Cate

So, did the chain unwind itself?
or have you developed a trick for making it do so?

Once the anchor is off the bottom it will spin around and unwind the chain.

The problem is retrieving the chain to short enough scope where you can break the anchor out. As you retrieve more chain, the twists are compressed into the remaining part of the chain.

If it jams, letting some chain out seems to encourage the twists further along the chain towards the anchor and a bit more chain can be retrieved. However, the chain can only accept so many twists per unit length and at some stage no more chain will go through the gypsy.

I have only had a serious problem twice and even then I was just able after a lot of mucking about to retrieve enough chain to pull the anchor out, but it was close.

The only real option I can see with a more severe twist is to let out all the chain undo the bitter end of the chain and rotate it the opposite way.

[Tayana42]

One possible option if conditions allow us to break out the anchor using a long snubber brought back to a primary winch. Then in deeper water lower the twisted chain and anchor so it can untwist itself. I've only done this once in fairly calm conditions.


S/V B'Shert

[cwyckham]

I have the occasional problem with twisted chain as well. One way around it if it "bunches up" as noelex describes, is to attach a chain hook as far forward on the chain as you can reach, take the tension off the chain, pull the chain up off the gypsy and untwist the section that is slack, passing the twist down into the chain locker, then place the chain back on the gypsy.


This doesn't fix the problem in the long term, but it gets the anchor off the bottom and most of the twist out (that which is still there when you break free the anchor).


You'll then want to properly untwist the chain at a later date.

[noelex 77]

Thanks Tayana and Cwyckham. They sound like great solutions.

It is a rare problem, as the boat has to spin around in the same direction quite a number of times to cause this. However, I can see it being an issue for anchorages with reversing current, especially if they are shallow (this means the twists are compressed into a shorter distance).

It has been suggested that these twists could upset the anchor by twisting it out of the seabed. I don't believe this is likely. With a normal amount of scope the twists are spread out over a long length of chain and the torque is minimal.

When the anchor is retrieved and the twists get compressed to last bit of chain, the torque becomes quite considerable, but if anything this just helps break the anchor out.

Once the anchor breaks free of the bottom it spins around with some considerable speed. It also makes a bit of a weird noise and vibration, especially as the links that have been twisted horizontal jump back into place. In the clear water here I can see what is going on, but in murkier water you might wonder what was happening if you had not experienced this before. Possessed anchor springs to mind .

It sounds, and feels, like the anchor is banging against rocks on the bottom.

[JPA Cate]

Originally Posted by noelex 77

Thanks Tayana and Cwyckham. They sound like great solutions.

It is a rare problem, as the boat has to spin around in the same direction quite a number of times to cause this. However, I can see it being an issue for anchorages with reversing current, especially if they are shallow (this means the twists are compressed into a shorter distance).

It has been suggested that these twists could upset the anchor by twisting it out of the seabed. I don't believe this is likely. With a normal amount of scope the twists are spread out over a long length of chain and the torque is minimal.

When the anchor is retrieved and the twists get compressed to last bit of chain, the torque becomes quite considerable, but if anything this just helps break the anchor out.

Once the anchor breaks free of the bottom it spins around with some considerable speed. It also makes a bit of a weird noise and vibration, especially as the links that have been twisted horizontal jump back into place. In the clear water here I can see what is going on, but in murkier water you might wonder what was happening if you had not experienced this before. Possessed anchor springs to mind .

It sounds, and feels, like the anchor is banging against rocks on the bottom.

Ah, not for the Davy Jones believers amongst us!

Actually, thanks for the warning!

[chouliha]

Originally Posted by noelex 77

Once the anchor is off the bottom it will spin around and unwind the chain.



The problem is retrieving the chain to short enough scope where you can break the anchor out. As you retrieve more chain, the twists are compressed into the remaining part of the chain.



If it jams, letting some chain out seems to encourage the twists further along the chain towards the anchor and a bit more chain can be retrieved. However, the chain can only accept so many twists per unit length and at some stage no more chain will go through the gypsy.



I have only had a serious problem twice and even then I was just able after a lot of mucking about to retrieve enough chain to pull the anchor out, but it was close.



The only real option I can see with a more severe twist is to let out all the chain undo the bitter end of the chain and rotate it the opposite way.

Many years ago when we first installed the bow roller we used a rubber roller. Probably something I found in the local Sale bin at the neighbor marine store(means cheap haha) that was used for trailers. What we found out is the chain started getting these terrible twists in the so in a short period of time could not get it over the windlass. I finally broke down and had a bronze one made out of an old 4" prop shaft. That resolved about 99% of the twist. Every 3-4 years we still get twists in the chain but just let it down in very deep water stopping just before it hits bottom and then crank it back in (whew thankfully with a electric windlass)

Chuck


Sent from my iPad using Cruisers Sailing Forum

[noelex 77]

The wind has picked up slightly to the mid to high 30's. Not much of a challenge for the big Mantus, but enough to apply more force to the anchor than I can achieve using the engine alone while setting, so I expected the anchor to settle a little deeper.

I let out a bit more chain so the scope is now a bit over 7:1.

The conditions were not great for photography, in fact even operating our tender is marginal especially when I am trying to look through the bathyscope rather than keeping an eye on the waves. There was a bit of a lull in the wind and I managed to get these photos. It might have been drier to go swimming .

Anyway, you can see the Mantus has buried a bit deeper. It has done this with no heaping up. The very top of the shank that was just visible after setting has disappeared. In fact the roll bar is 1/3 to 1/2 buried (it is a bit hard to tell exactly from the surface) so the fluke is quite a long way down.

You can still see the original setting mark and the anchor has only moved back a few inches while burying deeper. It is remarkable the steepness of the angle that excellent anchors bury. The less movement backward, the less chance of the anchor hitting some debris, rock, or weed, although this is not a significant concern at this deserted spot as the bottom at this anchorage is very clean and uniform.

[noelex 77]

The last anchorage was mud. Despite some considerable effort, I never found the anchor. So that was the first anchorage I have missed showing an underwater photo of the Mantus since the thread began.

I could just make out the bottom with the bathyscope, but we had some reasonable wind (35-40 knots) so I suspect the anchor was completely buried. As I never found the underwater float I cannot be sure.

I did take this photo of the anchor coming to the surface. The Mantus sheds most of the bottom material as it is raised. The Rocna retained a lot more.

Some would hail this as a major improvement. The shedding of the bottom material as the anchor is raised is promoted as a selling point for the convex anchors. Personally, I liked the bottom sample the Rocna provided. It is good to see what the substrate was like, particuarly a couple of feet under.

Anyway, here is photo of the Mantus breaking the surface at this particular anchorage. Not using a swivel means the anchor often turns a few times on the way up and this probably throws off any material. In the hard sand it usually comes up completely clean.

[noelex 77]

Dropping the anchor.

I guess this counts as an underwater photo - just

There are two ways of dropping the anchor.

1. Slowly lowering the anchor. This is usually done using the "power down" feature of the windlass. I often dangle the anchor just above the bottom. If you can see the bottom this makes it easy to hit a very precise spot. Usually this is unnecessary, but some anchorages have only small patches of sand in amongst lots of weed or rock. It is surprisingly hard to hit a small target. It takes coordination between the helm and foredeck and is a skill worth practicing before it is actually needed.

2. Let the anchor drop from the surface. This is usually done by freeing the clutch.

When I first purchased the Rocna, I used technique one above, but Jedi suggested on a Cruising Forum thread that using technique two broke up the substrate and helped the anchor to set. I started using technique two unless the anchor needed to hit a very precise spot. It is hard to measure any difference, but as the anchor lands it kicks up a strangely satisfying mushroom cloud of bottom material .

The Rocna dropped straight down very rapidly like a stone. The Mantus is different. It "flies" in an upright position. If the anchorage is deep enough, it will fly forward then back in a pendulum like action.

This has the advantage that on all the occasions I have been able to see the bottom, I have observed the Mantus landing in an upright position. The other bonus is that the Mantus has always landed facing the same direction as the bow is pointing. This puts the anchor on the seabed in the ideal orientation to set.

I therefore feel with the Mantus is especially worth using technique two where possible. It is also helpful if the boat is pointing in the direction that the anchor is going to set. However the "flying" property means the anchor can land several meters away from the drop point.

Splashdown:




In this photo from the bow you can just make out the Mantus on the seabed. You can see it has landed upright and in line with the bow.

[kas_1611]

We normally use option 1 with the controlled drop on the windlass to give better control of exactly how much chain we let out. As we use the 2x, 3x, 4x scope setting technique we find this easier.

However, given what has been said about the free fall technique potentially breaking the surface on impact maybe it is worth figuring out how to do this with our windlass to help the Delta dig in quicker and deeper.

Keiron

[Alan Mighty]

Originally Posted by noelex 77

2. Let the anchor drop from the surface. This is usually done by freeing the clutch.

When I first purchased the Rocna, I used technique one above, but Jedi suggested on a Cruising Forum thread that using technique two broke up the substrate and helped the anchor to set. I started using technique two unless the anchor needed to hit a very precise spot. It is hard to measure any difference, but as the anchor lands it kicks up a strangely satisfying mushroom cloud of bottom material .

The Rocna dropped straight down very rapidly like a stone. The Mantus is different. It "flies" in an upright position. If the anchorage is deep enough, it will fly forward then back in a pendulum like action.

This has the advantage that on all the occasions I have been able to see the bottom, I have observed the Mantus landing in an upright position. The other bonus is that the Mantus has always landed facing the same direction as the bow is pointing. This puts the anchor on the seabed in the ideal orientation to set.

I therefore feel with the Mantus is especially worth using technique two where possible. It is also helpful if the boat is pointing in the direction that the anchor is going to set. However the "flying" property means the anchor can land several meters away from the drop point.

Dinkum?!?


1. What's your speed of rode handling, in metres/sec, with the clutch free? That should be not too hard to derive, given that if you can watch the anchor all the way to impact with the bottom you can count seconds and you have estimates of the fall distance, including from marks on your anchor rode


2. What's your speed of rode handling when using the anchor windlass to power handle the rode?


3. If dropping with the clutch free, how do you ensure an unimpeded fall of the anchor - to attain maximum fall velocity - and also ensure that no chain falls on the anchor (which might increase danger of fouling the anchor)?


4. Are such NGA designs as the Rocna and Mantus immune to being fouled by chain piling on them?


The high density of water, 1027 kg/metre cubed, means that a heavier object with the same drag coefficient and the same frontal area will have a higher terminal velocity than a lighter one. So big might be better if a free fall did make for better anchoring.


I tried calculating terminal velocities for Led Myne's 15 kg Rocna. Depending on its attitude (fluke horizontal versus fluke vertical - the frontal area makes a big difference) I calculated a range of possible velocities from 1.6 m/sec to 17 m/sec. Led Myne's anchor windlass handles rode at 17 metres/minute (0.3 m/sec, 56 feet/minute or 0.9 feet/sec).


For a model calculation of terminal velocity of an object (a 7 kg shot put, in the example given) falling in water, see: How long will a falling object take to reach the bottom of the deepest ocean?


That model derived velocities of 4 - 5 metres/sec for a spherical 7 kg shot put. That's 14 - 18 km/hr, 9 - 11 mph, 8 - 10 knots.


Known unknowns include (i) what impact velocity is necessary to disturb the substrate to advantage anchoring; and (ii) whether disturbing the substrate is ever an advantage to a drag embedment anchor.


Al

[onestepcsy37]

FWIW, I also use method 2 with my 45lb manson supreme and concur with your findings. But when it hits bottom I stop the chain and then slowly pay it out as the boat drifts backwards. When I get about 7 to 1 I stop the chain again and secure it. When I'm satisfied it's holding I set the nylon snubber, which usually requires letting out more chain.

Not a problem when you are anchoring in 10 to 15 foot depths.