Dragging whilst on anchor

[Bandit]

My Delta is on all chain, check the depth , judge the wind and tide rise/fall and tidal flow as well as wind direction, let out the desired amount of chain and in the desired direction run dead slow astern on one or other engine pick a suitable transit and wait until the anchor bites.

If not set on the transit lift, clear anchor of any weed and re-lay he anchor.

My boat on one engine or slipped in out of gear stern runs at minimal speed.

The weight of chain is the secret and feeling a good "set" o the anchor, there again we have significant tidal flows where we are that is the risk.

If I cant feel the "set" of the anchor and judge it on a transit, I will re-lay or go elsewhere.

 

[RupertW]

My Delta is on all chain, check the depth , judge the wind and tide rise/fall and tidal flow as well as wind direction, let out the desired amount of chain and in the desired direction run dead slow astern on one or other engine pick a suitable transit and wait until the anchor bites.

If not set on the transit lift, clear anchor of any weed and re-lay he anchor.

My boat on one engine or slipped in out of gear stern runs at minimal speed.

The weight of chain is the secret and feeling a good "set" o the anchor, there again we have significant tidal flows where we are that is the risk.

If I cant feel the "set" of the anchor and judge it on a transit, I will re-lay or go elsewhere.

The weight of the chain is utterly irrelevant as the maths of the catenery effect shows as the chain will almost straighten in moderate wind/tide. However the rest of the set advice you give makes sense to me with the possible addition of making sure that once you feel the anchor properly set you put up the reverse thrust until you think you have put the same force on as the highest gust/tide pull that you are forecast to encounter.

You are not testing the anchor when reversing but are testing that the seabed/anchor combination works for your boat for that forcast.

 

[KINGFISHER 9]

I’m sorry but I can’t agree. My Delta now sits on the basement floor by the dryer, apart from there the only place I think it could belong is being towed by a tractor. It’s a plough! It’s made for digging in shallow then breaking the surface, like a.....plough. A spade type anchor digs in, like a spade. I now have a Rocna

Does it fit n the bow OK or have you had to make alterations?

 

[Zing]

Uhh apologies, got a 10kg delta 6mm chain on 8m power boat.
Set at high tide, checked by reversing, in soft mud 30m chain out, now in 1m water.
After 4 hours of 20 knots of wind, no chop to speak of, I have dragged 50 m. Tide has dropped 3m.

It’s on a bow roller, it needs to self stow. Fortress 45’ highly rated, but will it self stow ?

Or ya all know better ?!

I have a Rocna and a Fortress. The Rocna is really great for general use. For soft mud as you describe it is no good (Your Delta will be worse).That is when the Fortress gets used. It is massively better at soft mud and sand. It doesn’t go on the bow roller as I don’t use it much, but it probably would. Many boats fit one there. It is so light you can lift it out of a locker. I have a size 55 and can manage it fine.

 

[jrudge]

The weight of the chain is utterly irrelevant as the maths of the catenery effect shows as the chain will almost straighten in moderate wind/tide. However the rest of the set advice you give makes sense to me with the possible addition of making sure that once you feel the anchor properly set you put up the reverse thrust until you think you have put the same force on as the highest gust/tide pull that you are forecast to encounter.

You are not testing the anchor when reversing but are testing that the seabed/anchor combination works for your boat for that forcast.

Very black and white!

There are many on here who have upgraded to 12mm chain ( I am not one of them ) who report good results.

This is logical as the weight will require more pull until the angle is such the anchor comes unstuck. If not then we would all use cheap rope instead of expensive chain which we dont!

JFM - I would love to drop more than 3 times scope, but in Mallorca ( surprised SOF is much different) any more would lead to me hitting someone!

 

[NBs]

I had 40 'feet about 14000kg boat and delta 25kg + 10mm chain, there was never a problem anchor grip. I also use the Fortress FX23 6,7kg + 16mm lead fiber rope for my anchor tether when I bow towards Bert / rock and when the Fortress has settled, then its grip is incredible, I have not used this anchor boat free to rotate because it is easier to use the delta as windlans.

If a soft mud, the chain collects a tedious amount of mud in the wrist thick, but I have effective water pressure to help wash the problem out. Fortress is also a nasty way to bring a big sample of mud / clay up from the bottom and it will do a little extra work, but vs a very sleepy night it is a small grief.

Delta also digs well with vegetation through, Fortress a little tricky if vegetation is on the bottom.

NBs

 

[MapisM]

I never do that thing where you run engines in reverse to "set" the anchor. I don't see the need for it.

Nice to hear that I'm not alone in having never done that.
With one noticeable exception, just for the records: when anchoring with stern lines ashore.

 

[MapisM]

I would love to drop more than 3 times scope, but in Mallorca ( surprised SOF is much different) any more would lead to me hitting someone!

Yup, with no or very little wind, just letting out enough chain to have the anchor sitting on the bottom can be enough.
Occasionally, I do that also with zero boats around, just to stay closer to the shore than a higher scope would have allowed.
I'd never dare overnighting with less than 5x, though.

 

[Deleted User YDKXO]

yeh, coming to that long term conclusion too, its all v gloopy round here, most of the time it sets ok

I just want to say that generally I have had good experience with a 60kg Delta in any kind of seabed which offers resistance like clay, gravel, firm sand. For me it certainly performed better than a Bruce particularly in weedy condirions in which the Delta seems better able to cut through the weed to the seabed below. However I have had 3 experiences which spooked me with the 60kg Delta. In all 3 cases the anchor appeared to set well initially in a sandy seabed but then started to drag later after a few hours at anchor. I'm no expert on anchoring but I think the sand on those bays was rather soft and sugary which seemed to offer less resistance to the anchor pulling through it. The Delta is plough anchor and that seems to be exactly what it did. On the final occasion it dragged, it happened overnight and fortunately we dragged away from the shore and there were no other boats in the immediate vicinity. Remember this was a 60kg Delta with 12mm chain on a 40t boat so overkill by many boat manufacturers standards.

After that experience I decided to try another anchor and eventually settled on a 55kg Rocna after much research. That was fitted 3yrs ago and hand on heart it has never given me a moments concern. It has always set almost instantly and never dragged. I'm not saying its the best anchor out there but I do tend to believe that the modern generation of anchors like Rocna, Ultra, Manson Supreme and Spade are better than the traditional types like Bruce, Delta and CQR

Yes I concur with jfm. It is also vital to put enough chain. Not only does the catenary effect of the chain help to keep the pulling force on the anchor as near to horizontal as possible but I believe that the friction of the chain with the sea bed also assists the anchor to resist dragging. I will use the traditional 3x scope for a lunchtime stop but if I'm leaving the boat unattended or sleeping overnight at anchor I always try to put out at least 5x. On the subject of chain, for the reasons I've just set out, one of the things I always do when I buy a new (to me) boat is change the chain for the max size the windlass can handle. For me the combination of a big f*** off anchor that I trust and a load of heavy chain on the seabed leads to a restful night's kip

 

[Deleted User YDKXO]

The weight of the chain is utterly irrelevant as the maths of the catenery effect shows as the chain will almost straighten in moderate wind/tide.

I have been in the Med for 15yrs now and (because of the bearable water temp) I have made a point of snorkelling out many times to observe how the anchor and chain behave in windy conditions and I have yet to see the final third or so of chain before the anchor lift off the seabed despite the chain being bar tight at the bow of the boat. The chain moves slightly side to side on the seabed as the boat shears but, as I say, I have never seen it lift off the seabed and thus apply an upward force on the anchor. IMHO if you have enough chain on board (120m in my case) and its as heavy as your windlass can handle and you put enough of it on the sea bed, the catenary effect is going to keep the final bit of chain on the seabed in anything short of a gale

 

[Portofino]

I have been in the Med for 15yrs now and (because of the bearable water temp) I have made a point of snorkelling out many times to observe how the anchor and chain behave in windy conditions and I have yet to see the final third or so of chain before the anchor lift off the seabed despite the chain being bar tight at the bow of the boat. The chain moves slightly side to side on the seabed as the boat shears but, as I say, I have never seen it lift off the seabed and thus apply an upward force on the anchor. IMHO if you have enough chain on board (120m in my case) and its as heavy as your windlass can handle and you put enough of it on the sea bed, the catenary effect is going to keep the final bit of chain on the seabed in anything short of a gale

I agree it will only go bar effect if you have not let enough out for the depth .
We Med boaters do have the luxury of snorkelling around and in a busy place seeing everyone’s else set up .
Like JFM says we just drop it wait ( chain counter and depth display) for it to touch the bottom and gently reverse as its payed out .No need for any gigging in .
It gets windy too and again we can observe the effect if you have enough out it just lifts a longer piece .
So for me I,am happy with the OEM and quite grateful as I suspect it would be a real PITA as the Bruce seems fitted to a pocket .
Just thinking of Rupert W,s “ chain L is irrelevant..... “ picture the scene - Sydney harbour you drop the hook under adjacent to the opera house , 8 mm and then reverse all the way back up the Atlantic and stop outside Penzance.
There’s no way that’s gonna get bar tight , anchor drag - so L of chain out vs depth plays a part .
Q is it’s it relevant ? .From what I’ve seen it seems so in a liesure boat.

.View attachment 74722
Bruce .

 

[Bandit]

The weight of the chain is utterly irrelevant as the maths of the catenery effect shows as the chain will almost straighten in moderate wind/tide. However the rest of the set advice you give makes sense to me with the possible addition of making sure that once you feel the anchor properly set you put up the reverse thrust until you think you have put the same force on as the highest gust/tide pull that you are forecast to encounter.

You are not testing the anchor when reversing but are testing that the seabed/anchor combination works for your boat for that forcast.

In most conditions the weight of an all chain anchor rode will mean that the pull on the anchor is horizontal along the sea bed.

Where I am its far too cold for me to snorkel in a pair of budgie smugglers to check the anchor, however the seawater is clear enough to see it and when it buries into the sand.

With all chain in moderate conditions the pull on the anchor will be horizontal along the sea bed and not a straight line to your bow roller.

When the anchor sets to my satisfaction at idle on one engine, that's it. The anchor will be buried and subsequent movement of the boat at anchor will bed the anchor further.

The important thing is that you don't pick up a load of loose seaweed as that will need clearing for the anchor to set and bed in properly.

 

[jrudge]

I agree it will only go bar effect if you have not let enough out for the depth .
We Med boaters do have the luxury of snorkelling around and in a busy place seeing everyone’s else set up .
Like JFM says we just drop it wait ( chain counter and depth display) for it to touch the bottom and gently reverse as its payed out .No need for any gigging in .
It gets windy too and again we can observe the effect if you have enough out it just lifts a longer piece .
So for me I,am happy with the OEM and quite grateful as I suspect it would be a real PITA as the Bruce seems fitted to a pocket .
Just thinking of Rupert W,s “ chain L is irrelevant..... “ picture the scene - Sydney harbour you drop the hook under adjacent to the opera house , 8 mm and then reverse all the way back up the Atlantic and stop outside Penzance.
There’s no way that’s gonna get bar tight , anchor drag - so L of chain out vs depth plays a part .
Q is it’s it relevant ? .From what I’ve seen it seems so in a liesure boat.

.View attachment 74722
Bruce .

Theft must be a problem. All of those boats have had their rails nicked!

 

[petem]

Theft must be a problem. All of those boats have had their rails nicked!

That pic must show every one they ever built .

 

[MapisM]

IMHO if you have enough chain on board (120m in my case) and its as heavy as your windlass can handle and you put enough of it on the sea bed, the catenary effect is going to keep the final bit of chain on the seabed in anything short of a gale

+1.
I can't be bothered to look for some catenary calculator and do the math, but I strongly suspect that the force required to perfectly straighten 100m of 12mm chain is beyond even gale force winds.
In fact, I believe that this would still be true also with much lighter chains.

 

[MapisM]

picture the scene - Sydney harbour you drop the hook under adjacent to the opera house , 8 mm and then reverse all the way back up the Atlantic and stop outside Penzance.

Blimey PF, some pretty radical geological transformation must have taken place since the last time I've been down under.
Do tell, how far does the Atlantic stretches nowadays...?

 

[Deleted User YDKXO]

+1.
I can't be bothered to look for some catenary calculator and do the math, but I strongly suspect that the force required to perfectly straighten 100m of 12mm chain is beyond even gale force winds.
In fact, I believe that this would still be true also with much lighter chains.

100m of 12mm chain weighs 325kg according to Google and as you say its going to need one hell of a pull to straighten that

 

[Zing]

+1.
I can't be bothered to look for some catenary calculator and do the math, but I strongly suspect that the force required to perfectly straighten 100m of 12mm chain is beyond even gale force winds.
In fact, I believe that this would still be true also with much lighter chains.

When I looked at this once I found that the chain would snap before it got straight. That said I have observed that the chain is to all intents and purposes straight in a good blow. That’s when your anchor holding will be tested, so I can’t see a lot of point in catenary and therefore in a heavy chain. It will help a lot when the wind is not strong of course, but who needs help then?

 

[Bandit]

There is a story of a British battleship in an atoll in WW1 which laid out its anchor and chain as a typhoon was approaching, after the typhoon they sent down a diver to see how well the admiralty style anchor was bedded and were surprised to find it was sitting vertically on the seabed and it was the weight of chain that had held the ship.

 

[MapisM]

When I looked at this once that the chain would snap before it got straight.

I'm not surprised at all to hear that.
And I also see your point that it doesn't take a bar tight chain to leave only the anchor holding, though I always experienced the same as Deleted User - i.e., a relevant chunk of chain never lifted from the seabed.
OTOH, also the pulling angle is bound to make a big difference on the anchor holding power, and in this respect a heavy chain can only mean a more horizontal pull, aotbe.