Anchoring

[William_H]

Here anchoring at Rottnest Island involves the use of a fisherman anchor if anchoring in weed or a Danforth in sand. The bottom is quite clear to see from deck.
Lower the anchor as the boat drifts backwards slowly to ensure chain then rope are laid out on the bottom. Tidy up the boat and get the swimmers on. Then with mask and snorkel it is overboard to dive and check/admire the anchor doing it's thing. Well in the sand anyway. If there are any problems just realign the anchor and push into the sand a bit.
Back on board have lunch or whatever before going ashore. Make sure we are back on board before the wind comes up. That's when you start checking for drag.
Wind always comes up strong about 2AM from the east (lower tide) when you anchored on a South Wester. (higher tide). Yuck! olewill

 

[Bertramdriver]

If it doesn't work you just go round and do it again, same as picking up a mooring under sail. No biggie.

There is a scary thread on newbie anchoring on the MB forum at the moment, where they seem to be engaged in a who-uses-the-most-chain bidding war. Last time I looked it was 7x depth but I expect it has gone up by now. Mind you, seeing the anchors MB manufacturers fit (stainless teaspoons) that may not be so daft.

Sorry to rain on your parade but four things you ought to appreciate about anchoring mid to large mobo's
1 size for size a mobo weighs around 30 to 40% more than a sailing yacht
2 the engines on a mobo generate massively more torque than the usual SY moped engine.
3 the slab sides and higher freeboard of a mobo means than the wind has a greater influence on the movement on the boat
4 on a properly set up mobo the crew are handling heavier tackle and are more machine reliant

What this translates into is more ploughed harbours, boats 'squirming' around once the hook bites. Ie not tracking back in a straight line. And guess work about when the hook hits the bottom

Having operated both yachts and mobo's with 30 rears experience, it's much much easier to anchor a 40' SY than a mid size mobo.

 

[JumbleDuck]

Sorry to rain on your parade but four things you ought to appreciate about anchoring mid to large mobo's
1 size for size a mobo weighs around 30 to 40% more than a sailing yacht
2 the engines on a mobo generate massively more torque than the usual SY moped engine.
3 the slab sides and higher freeboard of a mobo means than the wind has a greater influence on the movement on the boat
4 on a properly set up mobo the crew are handling heavier tackle and are more machine reliant

Not quite sure what that had to do with post, but thanks, anyway. Sounds as if motorboats need big anchors, but I can't see why they would need to use such absurd lengths of chain.

 

[Bertramdriver]

Not quite sure what that had to do with post, but thanks, anyway. Sounds as if motorboats need big anchors, but I can't see why they would need to use such absurd lengths of chain.

Lots of research on the relationship between chain and anchor on holding done by the Royal Navy after the 1st WW.
Conclusion was that it was the weight of chain across the sea bed that held the boat... Not the anchor (check internet).
I carry an extra 30m of 10mm chain which I shackle above the hinge of my CQR if I'm worried about holding. Easier to handle than a second (tandem) anchor but seems to work fine when dropped before my anchor is laid.

 

[Storyline]

Lots of research on the relationship between chain and anchor on holding done by the Royal Navy after the 1st WW.
Conclusion was that it was the weight of chain across the sea bed that held the boat... Not the anchor (check internet).
I carry an extra 30m of 10mm chain which I shackle above the hinge of my CQR if I'm worried about holding. Easier to handle than a second (tandem) anchor but seems to work fine when dropped before my anchor is laid.

The part about the chain holding rather than the anchor is now outdated thinking (see various recent anchor threads & earlier in this thread) but your idea of attaching a length of loose chain to the anchor is not something I have seen discussed. However would be interested in reading what the anchor gurus think of it. Do not think it would really be of any benefit as if the anchor started to drag it would just drag the chain along with it - not really the same as having a chum just ahead of the anchor.

 

[Bertramdriver]

The part about the chain holding rather than the anchor is now outdated thinking (see various recent anchor threads & earlier in this thread) but your idea of attaching a length of loose chain to the anchor is not something I have seen discussed. However would be interested in reading what the anchor gurus think of it. Do not think it would really be of any benefit as if the anchor started to drag it would just drag the chain along with it - not really the same as having a chum just ahead of the anchor.

Weight of second anchor 20 kilos, weight of 10 mm chain 40 kilos. The bottom drag exerted by 40 kilos of chain becomes a significant multiplier to the lead anchor and less effort to manage.

Would be influenced more by current thinking if the research on anchors was done by anyone other than anchor manufacturers ( I used to own a R&D company)

 

[Daydream believer]

All this talk of ploughing up the sea bed has raised some concern
There is a lot of eelgrass in Studland Bay where the seahorses hang out
Do you think someone ought to look into the effect this has
Perhaps we should ban anchoring there incase a sea horse gets killed
After all yachties are wealthy - they own boats - so can afford to park elsewhere - say a marina
Just wondering!!

 

[ghostlymoron]

Lots of research on the relationship between chain and anchor on holding done by the Royal Navy after the 1st WW.
Conclusion was that it was the weight of chain across the sea bed that held the boat... Not the anchor (check internet).
I carry an extra 30m of 10mm chain which I shackle above the hinge of my CQR if I'm worried about holding. Easier to handle than a second (tandem) anchor but seems to work fine when dropped before my anchor is laid.

Try pulling a 10kg length of chain across your back lawn and then replace the chain with a 10kg anchor (danforth in my case) on a rope. The chain will drag the anchor digs in. Even more so on a sandy bottom.

 

[vyv_cox]

Try pulling a 10kg length of chain across your back lawn and then replace the chain with a 10kg anchor (danforth in my case) on a rope. The chain will drag the anchor digs in. Even more so on a sandy bottom.

I have reported my chain dragging efforts previously, debunking another of the 'anchor does nothing, it's all in the chain' enthusiasts. Two years ago I dragged all 60 metres of my 8 mm chain along the yard at Leros. It wasn't far and it wasn't easy but I am distinctly on the elderly side, never very muscular and the weight of my chain is 81 kg. It wouldn't take a lot of wind on a boat to generate that.

Noelex has been showing us very effectively in the past couple of days that chain without an anchor, or with one lying on its back, is almost totally ineffective when it comes to anchoring. I don' know what the Navy did to arrive at their findings but it might be worth repeating in light of hundreds of findings to the contrary.

 

[charles_reed]

Lots of research on the relationship between chain and anchor on holding done by the Royal Navy after the 1st WW.
Conclusion was that it was the weight of chain across the sea bed that held the boat... Not the anchor (check internet).
I carry an extra 30m of 10mm chain which I shackle above the hinge of my CQR if I'm worried about holding. Easier to handle than a second (tandem) anchor but seems to work fine when dropped before my anchor is laid.

Research nearly 100 years old and with stockless anchors - wise up, times have changed, anchors have changed, anchoring models have been developed which more faithfully reproduce the real thing.
What you're describing is a kellet - great if you're superman and can handle it. And definitely improves the setting angle.
So you're right about a weight on the immediate rode/shank intersection improving setting.
But to confuse that with chain doing the anchoring job shows a lack of intellectual rigour.
Perhaps this will elucidate
http://alain.fraysse.free.fr/sail/rode/anchor/anchor.htm
You'll need to read more than the first 3-4 pages

 

[GHA]

I don' know what the Navy did to arrive at their findings but it might be worth repeating in light of hundreds of findings to the contrary.

There was a thread a while ago with a paper linked, what it pointed to was actually that as boats get that big they can't have as proportionally as big anchors as we can, so the friction of the chain starts being significant. And they all drag when it gets windy .
Chain friction might help at lower wind speeds to stop the boat sheering about quite so much but when it really pipes up it's off the sea floor anyway.

 

[vyv_cox]

There was a thread a while ago with a paper linked, what it pointed to was actually that as boats get that big they can't have as proportionally as big anchors as we can, so the friction of the chain starts being significant. And they all drag when it gets windy .
Chain friction might help at lower wind speeds to stop the boat sheering about quite so much but when it really pipes up it's off the sea floor anyway.

I was giving a talk on anchoring a couple of years ago and a man in the audience made a similar point. It turned out he was ex RN deck officer on an aircraft carrier. He told me they always dragged, in almost any wind. A man was stationed somewhere on deck to watch their position and once they had dragged far enough he would notify the bridge to steam back up again. A never-ending process apparently.

I have swum on my anchor in 30 - 40 knots of wind with a scope of well over 10:1 and watched all the chain lifting off the bottom for probably 50% of the time. I had a Delta then and it didn't move, nice sandy bottom.

 

[JumbleDuck]

Lots of research on the relationship between chain and anchor on holding done by the Royal Navy after the 1st WW.
Conclusion was that it was the weight of chain across the sea bed that held the boat... Not the anchor (check internet).

I don't believe it. It's dead easy to pull 30m of chain along the ground and it's damn near impossible to pull any embedded anchor. If it really is the dhain doing the work, why does anyone both with an anchor? How, for that matter, does any anchor ever dig in if the chain is taking all the horizontal forces?

 

[oldbilbo]

There's a timely 'news report' here from Belfast Lough/RNLI....

http://www.motorboatsmonthly.co.uk/news/537139/bangor-lifeboat-called-out-as-anchored-boat-drifts-toward-rocks

....and I don't recall anything about anchoring techniques, or even best practices such as anchor bearings and/or how to determine if one is dragging, in the RYA Syllabus. Nevertheless, I introduced some of that in my Shorebased sessions 'cos of the importance.

IMHO effective anchoring is far more than a convenience 'knowhow', and is an essential safety skill which no competent skipper should be without.

 

[ghostlymoron]

Anchoring is definitely in the dayskipper syllabus although not under sail.

 

[vyv_cox]

Anchoring is definitely in the dayskipper syllabus although not under sail.

Anchoring advice on the RYA website seems to have been written in about 1950 although it says it was updated in 2013. Latest anchor covered is Delta. No advice about chain other than vague stuff about scope. Nothing on other topics such as windlass, shackles, swivels, kedges, snubbers. No NG anchors, aluminium alternatives.

 

[BobnLesley]

....and I don't recall anything about anchoring techniques... in the RYA Syllabus...

IMHO effective anchoring is far more than a convenience 'knowhow', and is an essential safety skill which no competent skipper should be without.

When we learnt to sail, or at least do the RYA day/coastal skipper courses back in the late 90s (the real 'learning' came once we cast off on our own) there was a bit in the shorebased courses, but the instructor who taught us the practical course claimed that the RYA practical course syllabus did not include any requirement for him to teach anchoring. He added it in, as like you, he considered it 'a important skill for the safety and protection of you and everyone else.'

 

[JumbleDuck]

Anchoring advice on the RYA website seems to have been written in about 1950 although it says it was updated in 2013. Latest anchor covered is Delta. No advice about chain other than vague stuff about scope. Nothing on other topics such as windlass, shackles, swivels, kedges, snubbers. No NG anchors, aluminium alternatives.

Do they still punt that terrible "so many times the square root of the depth" idea?

 

[ghostlymoron]

I thought it was 1:4 for chain and more for chain/warp. I employ as much as i can without swinging into something in windy conditions. A cross channel ferry skipper told me 'use the lot, it doesn't do any good in the chain locker'.

 

[vyv_cox]

Do they still punt that terrible "so many times the square root of the depth" idea?

No, 4:1 for chain, 6:1 for rope. That's it. And they tell us that 5 - 10 metres of chain on a rope rode 'acts as a cushion, helping to reduce the action of the boat pulling the anchor free'.