Anchoring "fun"

Cardo

Cardo

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In a plastic tub!
www.yacht-tinkerbell.co.uk
We've had a bit of a busy day messing around with our anchoring. It's pretty blowy, so we ended up scuppering our destination plans and tucked into a sheltered harbour in hopes that the weather will be calmer tomorrow!

However, we've just finished anchoring for the 3rd time. I'm a bit confused as to why we've had to re-anchor this third time. Maybe someone could shed some light?

The bay we're in has "good holding" according to Heikell, although it deepens quickly as you move away from the edges. Due to the quick drop off in depth, free anchoring isn't really an option. The first couple of times, we dropped the hook and took a line ashore, ending up beam on to the wind. The anchor appeared to have set and the line ashore was pretty tight. As the afternoon wore on, we noticed we were getting closer and closer to the downwind rocky shore. It was clear we were pulling back on the anchor and swinging down on the shore line. Maybe because we hadn't pulled the chain taught and the breeze was pulling the slack?
I decided to re-anchor but this time put out more chain, and then when at the right position, applied quite a lot of reverse to make sure the anchor was well and truly in, which it appeared to be. Tightened up the line ashore and settled down again. Alas, as the afternoon carried on, and the odd gust (20ish knots?) hit us from the side, we discovered we were again getting blown closer to the downwind rocks. I had plenty of chain out, so pulled some in to tighten it up again, but the same result occurred a while later.

We've ended up trying out a different method. We've dropped the hook in the shallow stuff near the beachy bit directly upwind and dropped back into the deeper stuff. We've then put out our kedge anchor downwind in case the wind changes overnight so we don't end up on the beach, or worse, the rocks. Anchor alarm is on, too, just in case!

Our anchor has been pretty solid, so far. Once it's in, it's in. The only time we've had issues was when we anchored in a bay with really thick weed and reported poor holding, where when the wind picked up we ripped out a huge patch of weed. But that's not the case here, the anchor came up clean both times.

We've anchored with a line ashore plenty of times, and sometimes with a decent crosswind, and not had this issue before.

So, from those of you with thousands of nights' worth of anchoring experience... (or who just happen to know!) What's going on?

Signed
Baffled of Anchoring
 
Baffled of Anchoring, Mrs Trellis will be along shortly

Where was this - Heinkel is not always right.
What Anchor
How much chain out and depth.

Cannot help without this info.

Sounds like your technique is not wrong, but always be wary of anchoring blowing off shore if the bottom slopes off very steeply - hence your good reason for a line ashore.

When going stern too, I usually try to put out in excess of 50 meters even if its quite shallow.
 
if there is any vibration in the warp then a phenomenon known as liquifaction may be taking place. Especially if the holding is clean homogeneous sand. Try sliding a chum down the warp to absorb any vibrations form e.g. current or wind to alter the resonant frequency of the warp. It also puts the end of the warp closer to the ground so the catenary angle is less.
 
Beam on to the wind is always tricky. The load on the anchor is magnified by a big factor, three, four??? The more chain you can get out the better, let friction on the bottom do some of the work. Any pilot guide cannot be accurate, it might be good holding over there but not here. If you can't see the bottom it's a lottery. I will always go stern into the wind if possible, ideally with shore lines tied to trees. Especially with deep water further out. If you have to be beam on, try putting the kedge out to windward, attached somewhere forward.
 
It does sound like you have a mismatch between the bottom type and the anchor. Perhaps there is a big plate of rock down there just below the sand, or the sand is coral sand and very light and your anchor ploughs?

If there is a big drop-off, why not put the anchor down the drop off so it has to climb out? I've used this technique on numerous occasions ...... when many other folks try and anchor in the shallowest spot, only to drag deeper resulting in too short a scope.
 
The second time I had put out 45m chain, starting in 12m but quickly rising to 9m. I usually aim for x4 the depth (though when going stern to I've nearly always put out a lot more than that, out of chance, rather than planned), but I hadn't thought about the extra effect the wind on the beam would have, as opposed to free anchoring where you tend to line up with it. Anchor is an original Bruce, 9kg I think. Bottom, as it turns out, is mud.

I'm guessing the wind on the beam was simply causing enough pull to cause the anchor to drag through the mud. Never had that before! Will ensure I put out plenty more chain in future.

Our last technique worked a treat, though. Lined up with the wind, the anchor didn't move an inch. The kedge anchor ensured we stayed put when the breeze turned in the early hours.
 
Assuming that the depths you mention are the actual depths of water rather than the depth under the keel, and you have a 1.5m height of bow, that gives you a scope of 3.3x. Anchors generally need 7x + for maximum holding, although 5x is generally accepted as providing near maximum holding.

A 15 kg killick would have helped with the short scope ... but at 3.3 x you are asking a lot from your anchor.

You probably suffered from poor ground conditions (soft mud), short scope, and beam winds.
 
for a 105, isn't a 9kg Bruce a bit near the top end of its useful range ?

Not a crit, just a feeling that you might have found a bigger one would hold.
 
Cardo said:
The second time I had put out 45m chain, starting in 12m but quickly rising to 9m. I usually aim for x4 the depth (though when going stern to I've nearly always put out a lot more than that, out of chance, rather than planned), but I hadn't thought about the extra effect the wind on the beam would have, as opposed to free anchoring where you tend to line up with it. Anchor is an original Bruce, 9kg I think. Bottom, as it turns out, is mud.

I'm guessing the wind on the beam was simply causing enough pull to cause the anchor to drag through the mud. Never had that before! Will ensure I put out plenty more chain in future.

Our last technique worked a treat, though. Lined up with the wind, the anchor didn't move an inch. The kedge anchor ensured we stayed put when the breeze turned in the early hours.
Click to expand...

Cardo, you have answered your own post. Too light an anchor, Bruce will slowly drag in mud especially if its on the small side, and also rather too little chain.

As a matter of interest, where was it
 
Chris_Robb said:
Cardo, you have answered your own post. Too light an anchor, Bruce will slowly drag in mud especially if its on the small side, and also rather too little chain.

As a matter of interest, where was it
Click to expand...

There is soft mud and soft mud, but if its really slimy and deep mud then you need something like a Danforth or Fortress. I'm not sure that adding more chain would make much difference to the performance of the Bruce in very soft mud - but there is not much use in the chain sitting in your anchor locker - untried. I do not think moving up one size of Bruce would make much difference and going much bigger than one size then might put unreasonable demands on your ability to lift it - Go Fortress!

The idea that one anchor will handle every seabed is an illusion put about by anchor makers. Most anchors that survive on the market for more than a few years do well in specific areas and are adequate in others - but most have an achilles heel (weed being a universal problem except for Fishermen or Marsh). Do not feel bad you have found a limit for a Bruce - at least you know now and can do something about it.

Finally not all Bruce copies work the same way as the original Bruce.

Jonathan
 
TradewindSailor said:
Assuming that the depths you mention are the actual depths of water rather than the depth under the keel, and you have a 1.5m height of bow, that gives you a scope of 3.3x. Anchors generally need 7x + for maximum holding, although 5x is generally accepted as providing near maximum holding.

A 15 kg killick would have helped with the short scope ... but at 3.3 x you are asking a lot from your anchor.

You probably suffered from poor ground conditions (soft mud), short scope, and beam winds.
Click to expand...
3.3x would imply the depth remained at 12m the entire time. The depths shallowed to 9m, so surely the chain would've been lying along the sloping bottom? I hadn't thought about height of the bow roller above water level, I will take that into account in the future.

sarabande said:
for a 105, isn't a 9kg Bruce a bit near the top end of its useful range ?

Not a crit, just a feeling that you might have found a bigger one would hold.
Click to expand...
Apologies, it appears my memory isn't what it used to be. The anchor is a 15kg Bruce.

Chris_Robb said:
Cardo, you have answered your own post. Too light an anchor, Bruce will slowly drag in mud especially if its on the small side, and also rather too little chain.

As a matter of interest, where was it
Click to expand...
This was Ormos Vidhavis in the Gulf of Corinth. Not a planned stop, but the westerly swell was sh*te and we decided to tuck away and wait it out.
 
Cardo said:
3.3x would imply the depth remained at 12m the entire time. The depths shallowed to 9m, so surely the chain would've been lying along the sloping bottom? I hadn't thought about height of the bow roller above water level, I will take that into account in the future.


Apologies, it appears my memory isn't what it used to be. The anchor is a 15kg Bruce.


This was Ormos Vidhavis in the Gulf of Corinth. Not a planned stop, but the westerly swell was sh*te and we decided to tuck away and wait it out.
Click to expand...

I don't know that bay.

Good sailing for the rest of the season - looks like there is going to be a wet autumn perhaps! Off to Leros tomorrow morning for the autumn cruise - hopefully with no dragging anchors!
 
vyv_cox said:
Where are you heading, Chris? We are homing in on you, currently at Paros. Weird weather, have had three days of almost flat calm at Mykonos!
Click to expand...

Mykonos - flat calm...

We will be launching from Pathane on Wednesday, stocking up on wednesday night in Lakki and I suspect with a calm loving crew we will head north rather than south - just in case the meltemi sets in. I suspect they will be ecstatic if we have to motor for 2 weeks - out of water Sept 24th.

Will be on email -especially now O2 has now gone unlimited MB per day on my deal. Hope we can meet up - but I would really like to get down to Astipalia if I can persuade them to go. It is good anchoring and swimming?
 
Last edited:
> I usually aim for x4 the depth

Ah the myth of four times depth some say five. The key to anchoring is to obviously set the anchor but use the weight of the catenary to hold the boat and think of the anchor as back up if the wind gets up. 5 meters should be 10 x depth, 10 metres 7 x depth. 20 metres 5 x depth and 30 metres 3 x depth.
 
KellysEye said:
Ah the myth of four times depth some say five. The key to anchoring is to obviously set the anchor but use the weight of the catenary to hold the boat and think of the anchor as back up if the wind gets up. 5 meters should be 10 x depth, 10 metres 7 x depth. 20 metres 5 x depth and 30 metres 3 x depth.
Click to expand...

I do wish you would stop posting this nonsense. You must know by now that you are the only person on the forums, perhaps in the world, to hold these views. 50 metres of chain in 5 metres of water? Bonkers.
 
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