A very basic anchoring question - sorry!

[Achillesheel]

I have only ever anchored for an hour or so, for lunch etc but would love to be brave enough to anchor overnight.

So I come in to the anchorage at e.g. high tide, drop the hook (doesn't matter what type, lets assume its effective) in 7m, and let out 35m (5 times depth) of our rope warp.The tide drops by 4m, leaving us with 3m of depth which is fine for my 1.2m draft.

But by then I have warp of more than ten times depth, so do I need to adjust the amount of warp, or do I simply ensure that I have enough swinging room to accommodate vast amounts of rope along the sea bed? Or a combination of the two?

 

[rib]

the 3/4/5/6/7 times depths are only guide lines if you have the room get it all out and sleep well,its no good sitting in the anchor locker.if you use warp be aware of your sea bed stoney/rock can chew thru warp,

 

[dt4134]

You normally wouldn't adjust it. Of course there's always the rare exception where you don't have enough swinging room and the tidal range is biggish.

The more likely mistake is anchoring nearer low tide and not allowing for the height of tide at HW. But sounds like you're thinking about it enough to avoid that.

 

[Pleiades]

Anchoring

Have never shortened my anchor cable - more often not I put more cable out the harder the wind blows and the less brave I get. In the same vein I have never wished I had a lighter anchor when the wind has picked up.
Trouble with shortening your cable in an anchorage with other vessels would be that no one else would shorten theirs so rather than all stay nicely apart you would close up on someone. Rather one should ensure that even at low water and at full length of cable you will have enough sea room not to clout the rocks or hit the bottom. For example - in anchorage below a goof in judging where to hook and how much to veer might easily put you on some pointy scenery at low water.

Robin
Pleiades of Birdham
MXWQ5

 

[CPD]

As said, you are in far greater danger of doing it wrong the other way ie anchoring at low and not throwing out sufficient to cope with the rise in height. last year I started to use a floating ball tied to the anchor so i could see where it was relative to the boat. I found it strangely reassuring !. (A bit of strig tied to the anchor goes through a small block under the ball and hen a weight is tied to the other end to cope with the rise/fall in the same way as the anchor for the boat, but clearly not critical).

 

[Sybarite]

I have only ever anchored for an hour or so, for lunch etc but would love to be brave enough to anchor overnight.

So I come in to the anchorage at e.g. high tide, drop the hook (doesn't matter what type, lets assume its effective) in 7m, and let out 35m (5 times depth) of our rope warp.The tide drops by 4m, leaving us with 3m of depth which is fine for my 1.2m draft.

But by then I have warp of more than ten times depth, so do I need to adjust the amount of warp, or do I simply ensure that I have enough swinging room to accommodate vast amounts of rope along the sea bed? Or a combination of the two?

Where you need to be careful is if you anchor on an offshore wind and then there is a 180° wind shift. That would put you 70m closer to the shore. At low tide would you then have enough depth? It's useful to check your soundings and to make sure that there are no rocks within the radius of your swing.

 

[ChattingLil]

and be prepared not to sleep a wink the first time you do it!

 

[Poignard]

Where you need to be careful is if you anchor on an offshore wind and then there is a 180° wind shift. That would put you 70m closer to the shore. At low tide would you then have enough depth? It's useful to check your soundings and to make sure that there are no rocks within the radius of your swing.

That's true but if the wind comes onshore wouldn't you be awake anyway - worrying about whether it's time to clear out? I know I would!

 

[mjcoon]

and be prepared not to sleep a wink the first time you do it!

No-one's mentioned using an alarm on either depth sounder or GPS. Is that because they don't engender trust and reassurance?

Mike.

 

[wazza]

No-one's mentioned using an alarm on either depth sounder or GPS. Is that because they don't engender trust and reassurance?

Mike.

We always set the alarm on the plotter, then you KNOW you haven't dragged and you don't need to assume either way.. pre plotter/gps I was always concerned and "thought" we'd dragged.. MUCH better now
But chain is the key and not warp..

 

[sigma38dave]

The only comment I would add not previously mentioned, with mainly warp (our set up) you let out more scope to alter the angle of pull on the anchor to keep it horizontal, this is great until slack water when the boat spins around.

Without the weight of chain usually going straight down off the anchor roller, the warp can get caught around the keel/rudder. This can be a real PITA!

I am considering making an 'anchor chum' to lower down the warp to hopefully help with the angle of pull and the slack water problems.

I wouldn't worry to much though, try in settled conditions first, you will experience a real sense of freedom moorings and marinas don't have.

 

[noelex]

The tide dropping will effect your swinging room very little. A 4m drop in tide will only increase the swinging distance by a few meters.
Before you drop your anchor you need to be sure you have a safe swinging distance from rocks and shallow ground, usually over 360 degrees and all tide levels, unless you are absolutely certain the wind cannot change.
Rope rode is OK on the bottom if its mud or sand, but not if rock or coral. So for many anchorages you do not need to make any adjustment, but if there is the possibility of the rope contacting something sharp it needs to shortened to chain (and you need enough chain to still anchor in the depth).
If you shorten the rode you need to consider if you will hit other boats sitting with more scope as many will have all chain rode and make no adjustment for low tide. A boat lying on rope and chain will swing differently to a boat on all chain anyway and this combined with very different scope can present problems for boats anchored close.

 

[jimi]

Have you got any chain at all or is it all warp? You could try and dig the anchor in with a bit of reverse to make sure its set properly?

 

[noelex]

We always set the alarm on the plotter, then you KNOW you haven't dragged and you don't need to assume either way..

I always set a GPS anchor alarm as well. Good insurance.
Transits are better to tell if you are moving backwards as you can pick even a very small amount of movement, but the GPS alarm is always watching.

 

[Achillesheel]

Wow! I posted this last night and went to bed, and now I have two pages of replies! Thanks guys!

We have 10m of chain, and 50m of warp. The boat is an Achilles 24.

Where we sail, the bottom is usually sand/mud, and we do always use reverse to set the anchor properly.

We don't have a plotter, but the handheld GPS has an anchor alarm, so we'll use that.

I will definitely pop my anchoring cherry next season!

 

[jimi]

with that set up you have no issues anchoring up to c10 m of water at HW where I'd calc as follows:

use divisor of 3 for chain 10/3 =3.3
multiplier for warp =5 so (10-3.3)*5= 35m warp

so all the chain + 35 m of warp


for 7M at hw

use divisor of 3 for chain 10/3 =3.3
multiplier for warp =5 so (7-3.3)*5= 20m warp

so all the chain + 20 m of warp.

 

[capnsensible]

Wow! I posted this last night and went to bed, and now I have two pages of replies! Thanks guys!

We have 10m of chain, and 50m of warp. The boat is an Achilles 24.

Where we sail, the bottom is usually sand/mud, and we do always use reverse to set the anchor properly.

We don't have a plotter, but the handheld GPS has an anchor alarm, so we'll use that.

I will definitely pop my anchoring cherry next season!

Try transits on the beam, there is always something! Dont even need GPS.

 

[onesea]

Wow! I posted this last night and went to bed, and now I have two pages of replies! Thanks guys!

We have 10m of chain, and 50m of warp. The boat is an Achilles 24.

Where we sail, the bottom is usually sand/mud, and we do always use reverse to set the anchor properly.

We don't have a plotter, but the handheld GPS has an anchor alarm, so we'll use that.

I will definitely pop my anchoring cherry next season!

If anchoring in creek / beach I always try anchoring as shallow as prudent. It saves agro of putting so much rope out for HW your shallow ish drafted less chance of big neighbors.

Personally I do not dig the anchor in to hard, as I figure it best to let it set its self.. My thinking being when the tide turns it might not then but when current/ wind is strong and it is less likely to dig back in again

Anchoring is not an exact science, even the best calculated anchoring can go wrong.

You just have to sleep in the knowledge that if it all goes wrong you might have to react quick no matter what precautions you take (sleep in something to preserve your modesty).

If your not sleeping well stick your head up if you are in doubt you will sleep better afterwards... Transits are exerlent, for this any fixed light, head out of hatch check GPS is not wrong back to sleep...

Given the concerns and precautions you are taking also check for other boats if you pop your head up, they are probably more likely to be dragging than you

 

[prv]

pre plotter/gps I was always concerned and "thought" we'd dragged..

I turn the GPS off along with the radio and instruments as soon as we're anchored. But I do pick a couple of transits, and if they're not utterly unmistakably obvious I do a little sketch. Above the chart table there's a pad of little slips of paper and a clip (like a tiny clipboard clip), for navigational jottings, marina loo codes, etc. Little transit sketches are a fairly common use for it, and save wondering at 2am whether the pile was supposed to be lined up with the left or right end of the building (or whatever).

(To be clear, I'd only expect to be looking at transits at 2am if I'd got up anyway for a pee or whatever. Under normal conditions I sleep perfectly well at anchor.)

Pete

 

[ChrisE]

At the risk of stating the bleeding obvious it might be wise to make your first night at anchor one with a settled, light wind forecast.

Like others I sleep well at anchor but if the wind gets up or changes direction I get a bit twitchy.