Yawing at anchor and dragging

[noelex]

i.e. the first mark includes the height from the bow to the waterline.

You can of course use any formulae you want to estimate how much chain to deploy, but if you want to calculate your scope you need to use the correct definition for scope.

This is:
Scope = The amount of chain deployed / (The depth of water where the anchor is dropped + The bow roller height, or the height where the snubber is attached)

Some also incorporate the rise of water due to the tide. This will give you a figure for the minimum scope you will experience at high tide.

Displacing just the first mark to "include the height from the bow to the waterline" or using the "metres of chain in the water" will not result in correct scope calculation.

 

[trapper guy]

A para anchor is a type of sea anchor. And possibly of use in a seaworthy yacht (with no large windows) mid Atlantic - but not a lot of relevance to the OP anchoring in a small bay

thats interesting, as the RNLI guy was speaking of its use in an anchoring situation, to avoid all the rolly i was experiencing prior to his arrival.

 

[ctva]

As Noelex and Dogone have said above, it is very simple, water depth+now roller height+tide rise.

I a perplexed as to how so many seem to have complex and not what is considered best practice, methods. Having been involved in training for the last 40 odd years the accepted method has not changed since before my time despite improvements in anchors.

In the specific situation of the op, scope in very shallow water (or very deep water) requires an adaption of the usual 3/4/5:1 and is well documented.

Popcorn is deployed…

 

[ctva]

Xxx

 

[Greg2]

Displacing just the first mark to "include the height from the bow to the waterline" or using the "metres of chain in the water" will not result in correct scope calculation.

I didn’t say it did - it just tells me how much chain is out measured from the waterline i.e. an easy reference. How much needs to go out is a different matter of course.
.

 

[westernman]

Yesterday we were in the Lerin Islands for the day and stayed the night. Wind was forecast to be very light, if any at all. However, at about 9.30pm it became very windy. I don't really know how strong, but it was enough for the wind to keep picking up one of our paddleboards that was floating behind the boat.

For the next couple of hours I kept watch on our position as we were quite close to shore, and for some reason we were yawing a lot. This seemed to induce creeping in the anchor that had been set all day, and we were getting uncomfortably close to a neighbour, so at midnight I moved the boat.

I have never experienced this type of yawing, which did seem quite violent at times, and I'm wondering what caused it and if there was anything I could have done to prevent it. Was it just the type of wind event? Could the other paddleboard which was tied to the rails on deck towards the bow, act like a sail?

FYI, 33kg Rocna anchor, 4m water, 17m of chain out, plus anchor seemed well set when we lifted it to relocate, although we had clearly crept about 20m or so

Yes definitely does not help.
If possible attach close to the stern.

Also, sometimes, adding an additional snubber to a side cleat to place the centre of pull of the anchor slightly off to one side can sometimes help.

Of course more chain out the better, but the reality is, in the med in most places you don't have the luxury to do this.

 

[dunedin]

thats interesting, as the RNLI guy was speaking of its use in an anchoring situation, to avoid all the rolly i was experiencing prior to his arrival.

You and/or your RNLI person is very confused - para anchor for oceans, and boat needs to be moving to work - Para-Anchors Para-Anchor Yacht Drogue (Vessels upto 50ft) | Force 4 Chandlery

For reducing rolling (a) anchor somewhere else (b) use a second anchor or side rope on main anchor cable to change angle to the waves or (c) attempt a "flopper stopper" on the boom.
(Assuming not in the size or budget for ship stabilisers)

 

[Hurricane]

Ok ‘need’ wasn’t the best word. We only need drink, food and shelter. What I meant to say was the only measurement we need when anchoring is bow to seabed and bow to anchor. I suggest those that use other measurements are probably working with muddled logic. I can’t see the point in knowing Hurricane’s chain in water numbers either. Maybe he can explain.

So by example: Say you anchor in 3m of water and want a scope of 4 then you want 12m of chain. Going off the measurement from the water you will have that 12m at the first chain mark with a 2m bow height. What you actually have though is a scope of 2.4. (12m/5m). That’s not safe anchoring.

I think everyone is overthinking it.
One big benefit of having the chain painted like that isn't anything to do with the actual anchor and holding etc.
If you are single handed, when you see the last painted chain section come up over the roller, you know that the anchor is breaking the surface.
Useful information for a number of reasons.

 

[trapper guy]

I think everyone is overthinking it.
One big benefit of having the chain painted like that isn't anything to do with the actual anchor and holding etc.
If you are single handed, when you see the last painted chain section come up over the roller, you know that the anchor is breaking the surface.
Useful information for a number of reasons.

ive got my chain and rope marked with bands of insulating tape, 1,2,3 and 4 bands, at 5mt intervals.
i based this on the 5/1 for all rope anchoring, even though my chain is 30m and the rope 25m.
when the 4 bands appear, i know ive got 20m left to go.
so if i was anchoring in 1m (in theory, not practice) i would lay out to the first marker of 5m, plus 'one for the pot' to account for bow height over water, so far ive had no problems.

 

[Dogone]

I think everyone is overthinking it.
One big benefit of having the chain painted like that isn't anything to do with the actual anchor and holding etc.
If you are single handed, when you see the last painted chain section come up over the roller, you know that the anchor is breaking the surface.
Useful information for a number of reasons.

Painting the chain is one thing and if you can see the paint it’s a good idea. I can’t and have to rely on the clatter of the anchor. It’s the counting chain out from the water that makes no sense to me.

 

[jcwads]

Well done on handling it like you did Mark. It must have been quite scary. A Princess 75 with crew bailed the Lerins and came back to port that night because it was so nasty. Their captain is really experienced and even he said it wasn’t good at all. The weather has been so random with these events. Last week a tornado ripped up a sail on a sailing yacht 35 miles off shore from Antibes. It was violent out there. Then you had the tragic events in Sicily this
morning and Formentera recently too…..

 

[Hooligan]

Yesterday we were in the Lerin Islands for the day and stayed the night. Wind was forecast to be very light, if any at all. However, at about 9.30pm it became very windy. I don't really know how strong, but it was enough for the wind to keep picking up one of our paddleboards that was floating behind the boat.

For the next couple of hours I kept watch on our position as we were quite close to shore, and for some reason we were yawing a lot. This seemed to induce creeping in the anchor that had been set all day, and we were getting uncomfortably close to a neighbour, so at midnight I moved the boat.

I have never experienced this type of yawing, which did seem quite violent at times, and I'm wondering what caused it and if there was anything I could have done to prevent it. Was it just the type of wind event? Could the other paddleboard which was tied to the rails on deck towards the bow, act like a sail?

FYI, 33kg Rocna anchor, 4m water, 17m of chain out, plus anchor seemed well set when we lifted it to relocate, although we had clearly crept about 20m or so

Not enough chain out. I would never put less than 20 out in 5 m or under. The problem is that others put so little out in general which means your swing arc becomes an issue. I usually take the view in those situations that risking dragging to fit in to their swing arcs makes no sense so I usually find somewhere else.

 

[markc]

Not enough chain out. I would never put less than 20 out in 5 m or under. The problem is that others put so little out in general which means your swing arc becomes an issue. I usually take the view in those situations that risking dragging to fit in to their swing arcs makes no sense so I usually find somewhere else.

Problem with the Lerin Islands is that even if you do find enough space to 'swing' when you arrive in the morning, you'll be surrounded by lunchtime. It's not ideal, obviously.