Anchor Drag Marker

[GOBKJA]

I'm a novice so this may seem like a silly question. I understand anchor dragging is a concern. What if you attached something heavy to a line and a float, and dropped that where you drop your anchor? Of course you'd allow for tide fluctuation but it would stay afloat within the area you originally dropped the anchor. Could that give you a rough indication if your anchor was dragging? Of course you may swing and have to take that into consideration in judging but I imagine a drastic change would be obvious.

Has anyone tried this before or know something obvious I'm missing that would make this a silly idea?

[Gallivanters]

I'm certainly no expert, but...

Your idea would probably work... and it'll be easy to retreive when you raise your anchor... provided you haven't dragged.

We always make note of a few transit lines ashore by lining-up a light pole, building or any un-movable object with a distant mountain peak or something which gives us a quick reference when we wonder if we're holding.

But lately - I've learned the best method for me is to zoom in close on our chartplotter and place an anchor mark on the spot where our track line reverses on the screen. This way I can see exactly how we've been swinging on the hook over time. When currents & winds remain steady our anchor track lines add-up to a smile shape... which makes me smile in return, because I know we're securely anchored and holding fast. In areas of tidal & wind swings the track resembles a big blob... with the anchor symbol in about the middle. When the wind really pipes-up and we drag - our track line begins to drag to leward of the track mark and is immediately recognisable that we're dragging... and without even needing to see my transit references to make sure.

Recently, while in Tahiti, a series of 60 knot squalls blasted the achhorage and several boats were on the bricks due to poor holding. We were dragging with everyone else. It was a blinding rain that went on through the night and I couldn't see our shore references... or an anchor marker if we'd had one. But our chartplotter made it clearly evident that we were dragging AND it made it clearly evident that we were holding once we moved and re-set the hook out in the middle of the channel. Our little cockpit chartplotter provided all the warning and reassurance at a glance. If you don't have a chartplotter, I imagine a hand held GPS could also be used in a similar way.

Again - I'm no expert... but the chartplotter works best for me as an anchor marker and I no longer have to "wonder" if we're dragging, or not. It serves as a stress relief for me... and that (in my opinion) is what cruising under sail is all about... Stress Relief.

To Life!

Kirk

[atavist]

Gobkja: That's called a trip line... traditionally it's used to help trip your anchor if it is fouled but since it has a float on it could be used for the same purpose... I've used a trip line a lot and for me it wasn't a good indicator or whether or not I drug, since it's relationship to the boat stays the same for the most part... if there are other things to reference it too (other boats, other bouys, land) you can use those as references in themselves just as easily as the float on your trip line in relation to them... however that's just me and I can see where it may be nice to have an anchor reference as well in certain circumstances... it certainly won't hurt to have it...

[JeanneP]

Dropping a float near your anchor is not a bad idea for daytime, but it won't help you in a bad storm or dark night. Unless you had reflective tape on the float, how would you know that you had dragged away from it?

It's these nighttime dramas that encourage the use of chart plotters. We don't have a chart plotter for our flybridge, so we are under a bit of a handicap during late night storms and such. Then we navigate by compass and depth sounder and listen very hard and look squinty-eyed real hard, too.

A few years ago we were anchored in Point Judith, RI, in the outer harbor, when a pretty violent electrical storm blew through. We were feeling a bit too smug as we sat inside watching our position from the entrance lights. Then a large sailboat started dragging anchor and we watched it drag right past us and head for the breakwater rocks. (Point Judith outer harbor is a man-made harbor constructed of a rock breakwater forming a "C" around the inner harbor entrance, with two entrances from the sea, one on the North side of the breakwater, the other on the South side. The odds are you'll drag into the rocks, not onto the sand). We turned around and saw that the water was getting thin, and realized that we had started to drag back with the sailboat. I'd say that we got our engine going and the anchor up with very little time to spare before we would have hit the rocks. It was a pitch black night, an early bolt of lightning had knocked out the lights in the town so we didn't even have the glow to orient ourselves. Constant vigilence and a lot of luck kept us off the rocks that night.

[saxon]

It's an interesting thought GOBKJA, you are suggesting a weight, line and marker separate from your anchor I understand. I see your reasoning but I think the marker bouy would need to be fairly substantial to be easily seen, especially if you accept that most but not all anchor dragging occurs in bad weather, when because of rain or increased wave height it would be quite difficult to keep track of a small marker. You could of course use a bigger marker but I'm guessing you would probably need a bigger heavier weight to anchor it in position in case that too dragged in bad weather.

I do partly what Gallivanters does, I take compass bearings on features ashore like a tall building, a radio/television mast or something similar and also try to line up transits of similar things. I don't have any electronic navigation equipment like a chart plotter but that sounds like a good idea too. Just as a point of interest. The great majority of European sailors use chain almost exclusively on their main anchors, so it's fairly rare to see anyone anchoring with rope alone. Like a lot of people I have rope too but that's on the inboard end of my 80 metre main 8 mm anchor cable. One benefit of chain is that once you get accustomed to the sound, you can usually hear if you're dragging. Even when it's howling with wind, if I stand in the fore cabin and listen where the chain comes down into the locker I can hear the rumble as it drags, you soon get to tell the difference between that sound and the chain simply moving on the seabed as the boat swings.

That might sound like a bit of a yarn, but most cruising folk will say the same.

But who knows? I'm not a cruising Guru anyway, you may well have thought of a new anchoring technique.

[atavist]

Originally Posted by saxon

One benefit of chain is that once you get accustomed to the sound, you can usually hear if you're dragging. Even when it's howling with wind, if I stand in the fore cabin and listen where the chain comes down into the locker I can hear the rumble as it drags, you soon get to tell the difference between that sound and the chain simply moving on the seabed as the boat swings.

dead on... that's the best drag indicator I have as well... I use all chain on my primary and have drug it several times in bad blows (200ft of 3/8bbb in 20ft of water once even)... on bad nights, if there's no risk of other boats dragging into me, I usually keep watch laying in the v-berth asleep... as soon as she starts the drag the sound wakes me up... this is the reason i don't use a snubber... it takes the rattle out of the chain when she drags... that and I really just don't see the point, I just cleat the chain off with two round turns and it's never slipped and is off the windlass but leave me my drag indicator.

these days I've gotten in the habit of always anchoring with 2 anchors bahamian style... if one drags it quickly turns into a Y (Fork) and stops the dragging.... if a real blow is coming I set a third anchor mid way on my secondary (which is primarily rhode) to keep the effort horrizontal... I've never drug 2 anchors, not even in sustained 80+ knot winds with a lot of fetch... .....

On that note, it's my experience that fetch (or the big seas they cause) is the primary reason for dragging anchor, once a big wave knocks the bow off and the wind gets it pinned that's where your anchor breaks loose... if you've got a nice flat anchorage the wind can do what she likes for the most part and if your boat doesn't hunt the wind the forces on your anchor shouldn't be enough to break her loose.... I recommend to anyone witha fin keeled boat to always set a bahamian mooring... I've seen a lot of fin keeled boats go aground in moderate winds because they ran over their own anchor tripping it then blowing aground (I think every boat I've seen do this was using a danforth style anchor, of which I'm personally not a fan... the claw is my favorite unless it's a really weedy bottom, then I use a CQR)

[GOBKJA]

Great, we bought a chart plotter so I'll definitely use that. Thanks. The only time we ever anchored (on a charter boat years ago) we had heavy wind and visibility was horrible and my husband was up and down like the Assyrian Empire worrying if we were dragging. Didn't get a wink of sleep. The next morning we tried to lift the anchor to move on and couldn't budge. It had been wrapped around a brommie the whole time; we weren't going anywhere. After a sleepless night we sat 'till 3 in the afternoon waiting for a returning dive boat to come help us untangle it. I think we're better prepared now with a chartplotter and a hooker.

[saxon]

Sleepless nights at anchor..welcome to the club!

About three years ago I was anchored off one of the Greek Cyclades Islands in the Aegean Sea. Weather was settled and I did my usual checks before turning in. Anchor light working, line up my markers ashore, the lit dome of the Orthodox Church with that tall building etc: then crashed out in my bunk.

I awoke a couple of hours later, sat up and casually glanced out of the port to see the town lights going by...

I probably hold the world record for tumbling out on deck, panic stricken and wild eyed to see one of the big inter-island ferries going by. Well I don't care what people say, when you're half a sleep those rows of wretched lights in her ports and windows certainly look like the town is moving..

After a couple of years you and hubby will be sleeping like babies, anchored in half a gale without a worry.

[Coyote]

Originally Posted by saxon

I probably hold the world record for tumbling out on deck, panic stricken and wild eyed to see one of the big inter-island ferries going by.

When in doubt, sleep with your boots on. Well, with something on, anyway.

[CaptainHeidi]

Yeah, my touchscreen Garmin chartplotter does that and I can set some parameters and have an alarm sound if we are dragging.

Heidi

sv Fyfe & Drum

[Seafarer]

Danforth (Fluke, in general terms) style anchors are excellent anchors when you can set them to hold in the direction of the highest expected winds.

What I mean by that is this: If you'll be anchoring for extended periods of time, with the boat moving all about, they are much more likely to drag than most other anchors. They don't seem to like turning in the bottom as well. However, they hold excellently in one direction and therefore make great storm anchors.

That being said, my boat came with only one anchor- a Danforth. It held without dragging for 7 months in a large but protected bay with hard sand bottom. It held through many storms, and with my all-chain rode (with a ton of scope, I think I had around 200' out in 7' of water) I never had to worry about rope chafing through.

Recently, however, it has dragged on me twice in the muddy river where I am now, when the wind was blowing from the West where there is the least protection. I moved it over to my mostly-rope rode (which of course worries me even with the chafing gear in place) which is long enough that I still exceed 10:1 scope and ordered a Rocna (Scoop, in general terms) that recently arrived. I'm putting that on the chain with a new swivel and expect to sleep better at night.

2006 West Marine test results:



"Max before releasing" is the force the anchor withstood before moving (i.e. the effective holding power) and is the critical indicator of performance. The lack of the "Max pull" measurement for any given anchor is bad, as it implies the anchor pulled free rather than remaining embedded.

Check them out: http://www.rocna.com/

I was interested to find that their anchors are rated at 60knots, where I already knew that most manufacturers only rate their anchors at 20 knots. (I'll be damned, but I can't find where I read that right now.) According to their chart, at 35' and 7 metric tons I should be using a 15kg Rocna. I went two sizes larger and got the 25kg model.

[Seafarer]

Aha! I found where they say the anchors are rated to 50 knots (not 60 like I wrote earlier):

http://www.rocna.com/kb/Rocna_sizing_recommendations

The relevant part is copy-and-pasted below:

Our sizing is conservative, intended to provide an anchor adequate for use in all conditions most boaters would ever endure. We base our calculations on 50 knots wind, associated surge, and soft moderate holding bottoms into which it is assumed the anchor has set. Adequate scope is assumed. This is far in excess of most manufacturers.

Windage and resulting forces is judged based on typical vessel profiles according to LOA and displacement.

Note that tidal flow generally does not generate a hugely significant amount of force and in most areas can be all but disregarded. On a typical 10m (33') yacht, it takes a 6 knot current to generate about as much force as a 20 knot breeze on the same boat.

Naturally there are many variables involved, and in many situations an adequately sized Rocna will easily handle far worse winds than 50 knots. There are others where even a Rocna will not hold well. However, our aim is to consider a realistic poor case scenario as the basis for our recommendations.

[Aquaria]

Originally Posted by GOBKJA

I'm a novice so this may seem like a silly question. I understand anchor dragging is a concern. What if you attached something heavy to a line and a float, and dropped that where you drop your anchor? Of course you'd allow for tide fluctuation but it would stay afloat within the area you originally dropped the anchor. Could that give you a rough indication if your anchor was dragging? Of course you may swing and have to take that into consideration in judging but I imagine a drastic change would be obvious.

Has anyone tried this before or know something obvious I'm missing that would make this a silly idea?

...long ago I read about a similar idea: Throw something heavy tied to a line close to the anchor, give as much line as you have chain out, but then keep the end of the line in the cockpit and tie it to an (empty) bottle or even to your great toe. Advantage: you even can go to sleep and if the bottle falls or if the line is pulling you off the bunk *you are adrift. I tried it once with the bottle. The night was terrible, the bottle falling down every few minutes. Since then I'm back to just noticing sinificant changes in noise ("listening" to the anchor chain works!) and the movement of the boat. And nowadays using the gps anchor alarm set the way the situation demands makes it even more easy.

Uwe

SY Aquaria

[Tonearm]

Originally Posted by GOBKJA

I'm a novice so this may seem like a silly question. I understand anchor dragging is a concern. What if you attached something heavy to a line and a float, and dropped that where you drop your anchor? Of course you'd allow for tide fluctuation but it would stay afloat within the area you originally dropped the anchor. Could that give you a rough indication if your anchor was dragging? Of course you may swing and have to take that into consideration in judging but I imagine a drastic change would be obvious.

Has anyone tried this before or know something obvious I'm missing that would make this a silly idea?

Not silly. If there is tension on your anchor rode/chain lift it about 6" from deck if it is dragging you will feel the anchor

dragging. If there is not tension, anchor rode chain, you will not feel the drag. No tension you may be sailing within your

anchoring circle. You cannot drag on anchor without tension or feeling the pull on the rode/chain.

[Louiesails]

We use the anchor alarm on our chartplotter every time we anchor, and if the water is shallow or items to hit are close, make the alarm setting a very low distance. Deeper water or fewer things to worry about, bigger distance. We also set our B&G depth alarm for the high and low alarms that represent what we think will be 'normal' for the spot, and it has a loud enough alarm that sleeping though it is not an issue. Occasionally a fish or squid under the boat will set it off, but being sure things are OK makes getting to sleep again easy.

We take a compass bearing of what heading is 'safe' for leaving the anchorage, just in case a zero or near zero (squall or other event) visibility event and the desire or requirement of leaving the anchorage comes up. Having the heading grease penciled on the binnacle cover makes orientation at oh dark hundred when not as sharp as normal an easier for safe departures.

The last item we use a lot is a laser range finder. My honey bought it at a golf store, it has a infared crosshair, and since most anchorage dragging, or other boats too close are the bigger issue over actually dragging onto the beach. Knowing the range has closed from 99 yards to 71 yards in 15 minutes means 'time to go' and this is more effective than using the radar on very low ranges.

Those are the items that work for us over a very long time period, and we also anchor the furthest out if possible, or away from everyone else, but there is the apparently magnetic effect of 'big boat anchored over there' attracts boats, but being anchored in over 80' usually limits that somewhat.

[Allan]

GOBKJA

Your method is a good one and one i have used before

I remember a night spent 100nm off shore surrounded by reef

This was before the days of GPS (just showing my age)

A 40 knot blow came up during the night

This was a 112 ft vessel anchored in a lagoon and surrounded by reef with no landmarks, gps or radar

Sent the crew out in the dory to drop an anchor with a line and buoy attached near where the anchor should be

Set an anchor watch for the rest of the night

We were still in the same spot next morning but without the marker we would not have known if we were dragging

So yes a good idea

Allan

[redbopeep]

We have to keep a computer on in order to use the chartplotter w/gps, therefore our anchor watch consists of:

1. taking bearings on fixed objects far and near (at least 3 bearings, in different directions at least covering a 90 degree arc hopefully more, on objects suitable varying distances away depending on the size of the anchorage and the swing we expect to have) and keeping track of those through the day or night. If the objects are too far away, it won't do you any good since you won't notice the change as you drag. Too close and you'll be frantic for no reason.

2. set the hi and low depth alarm for appropriate range.

more recently--

3. turn on the "tracking" feature the little Maemo Mapper chart plotter (freeware) which resides on our Nokia N810 (an organizer similar to a Palm with features similar to an IPhone w/o the phone but with a gps). This is the "back up" chart plotter which takes no energy. No alarm on it, but you can see your track and know if you're still where you think you are.

When it's stormy, even if the computer and chart plotter are available, I must say I'm more comfortable if I'm taking bearings and keeping watch in that manner. I do like the idea of the range-finder from the golf store, too