anchor scope !

[lewi]

at the weekend during a chat about over nighting,
the topic of how much rope would one use in fresh water
the same or less than in salt, my point of view was to use
the same as its about setting the hook at the right angle to
give best hold, the chap who used less argued the point that
in fresh there is no tidal effect so no need for as much rope,
he was not prepared to except the effect of wind / undertow
etc,
i was just wondering if anyone else has given this any thought,

 

[hlb]

Your question is imposible to answer, it's a bit like saying, how hard to put the handbrake on. You will only ever know, if you start moveing.

But chain is much better on the ground than in the anchor locker!!

 

[Richard10002]

Cant see why there would be a difference. The Mediterranean is mostly not affected by tides, but the recommendations for scope dont change, and the wind can be just as strong.

Equally, on a freshwater inland lake, the wind may be more fluky, thus tugging the boat in all directions over a short period of time.

Let him do what he likes..... and hope he doesnt anchor upwind of you

 

[nonitoo]

Cant see why there would be a difference. The Mediterranean is mostly not affected by tides, but the recommendations for scope dont change, and the wind can be just as strong.

Equally, on a freshwater inland lake, the wind may be more fluky, thus tugging the boat in all directions over a short period of time.

Let him do what he likes..... and hope he doesnt anchor upwind of you

I agree that there is no correct answer here.

My early years were spent on the west coast of Scotland where all chain was the rule of the day.

Nowadays living down in the south I use a combi chain and warp but have an old 14lb butchers weight that I shackle to the chain/rope joint in really dodgy weather.

It helps keep the chain on the ground, reduces the wind snatch, and the keeps the pull on the anchor as horizontal as possible.

But getting back to the OP, I wouldn't have thought that tidal range would make much difference to the scope used.

Tom

 

[Deleted User YDKXO]

He may have a point in that he is correct that in freshwater anchorages, there are less likely to be currents and changes in depth putting a strain on the anchor so, in theory, he could use less anchor rope/chain. He may also be concerned about the boat swinging on a longer rope in a tight anchorage. The rules of thumb (ie 3 x max depth for chain, 5 x max depth for rope) are for guidance only and a skipper has to consider various factors before deciding on the length of rope/chain he is going to use. For example, if the boat has a heavy anchor, he knows the holding is good and the weather is settled, maybe he could safely use a rope length shorter than recommended. On the other hand, if the boat had a light anchor, the holding was unknown and the weather forecast unsettled, then he would be prudent to use longer than recommended. It's always going to be an individual decision taken with the factors relevant at that particular time and place. Personally, I sleep better with a long length of chain laid out, whatever the circumstances, but maybe I'm just paranoid

 

[blueglass]

better out than in, as they say. For a good night's sleep I run out as much chain as is possible without risk of swinging into anything. Fresh or salt water wouldn't change that.

 

[MedMilo]

The only thing worth adding is that the 3/4/5 x depth formula generally assumes the measurement being taken from the anchor roller. Bear in mind that the depth gauge is measured from the transducer which is normally off-set to calculate the depth from the bottom of the props, say 1m below the transducer plus a safety margin of 50cms or so. Consequently to get the measurement from the anchor roller to the sea bed one needs to calculate the following;
- Depth gauge reading, say, 3m
- Add 1.5m to get from bottom of the safety margin to the transducer
- Add, say, 1m to get from the transducer level to the water level
- Add, say, 1.5m to get from the water level to the anchor roller level

So....if the depth gauge is reading 3m one ought to add another 4m to get to a total distance of 7m from the anchor roller to the sea-bed. THEN multiply 7m x 3/4/5 depending on the conditions.

Of course, you only have to calculate your 'add-on' (4m on my boat) once and then alway just add it to the depth gauge reading.

 

[Richard10002]

The only thing worth adding is that the 3/4/5 x depth formula generally assumes the measurement being taken from the anchor roller. Bear in mind that the depth gauge is measured from the transducer which is normally off-set to calculate the depth from the bottom of the props, say 1m below the transducer plus a safety margin of 50cms or so.

My depth meter read the depth from the water line, so I knew the depth of the water. Another meter to the bow roller, and multiply by whatever seems right for the conditions.

If you know your draft, you dont need any of these confusing safety margins- you might be able to calculate them by instinct, but what about crew.

 

[MedMilo]

I prefer my depth gauge to instantly tell me how much depth I've got below the props without having to subtract my draft from the depth reading (as Richard 100002 prefers to do). When anchoring don't find it that confusing to simply add 4m to my depth reading and multiply it by 3/4/5 etc depending on conditions. Guess it's a personal thing!

 

[Richard10002]

We all do what we do, and as long as we know what we're doing, that's fine.

My draft is, (was), 1.5m so, if the depth reads 2m, I know I have 0.5m below the keel, and I can compare easily with the chart.