What Is Scope?
The length of chain paid out when anchoring - more often than not, this figure decides whether the anchor holds rather than the anchor itself.
Scope is the length of chain (or rope) you pay out when anchoring. It sounds simple, but whether the anchor holds is often decided more by this number than by the anchor itself. The aim is to keep the pull on the anchor as far as possible horizontally: the catenary formed by the weight of the chain softens the snatch load and helps the anchor bite into the seabed.
Scope ratio is the length of chain paid out in relation to water depth. When working out the depth, you need to add not just the waterline but also the height from the bow roller to the water. The table below shows how the ratio should increase as the weather freshens, and how that works out in metres of chain in a 10-metre bay.
Scope ratio table
Condition | Scope ratio | Chain at 10 m depth | Notes |
|---|---|---|---|
Calm, daytime, short stop | 3:1 | ~30 m | Fine if you are only sitting by the bow; not one to rely on |
Normal overnight anchoring | 5:1 | ~50 m | Standard practice for most bays |
Strong wind (6-7 Beaufort) | 7:1 | ~70 m | Increases the swing circle, so keep clear of your neighbours |
Storm forecast (8+) | 8-10:1 | 80-100 m | If possible, move and head for shelter |
The Göcek way
The classic setup in the Göcek bays is stern-to ashore. In that arrangement the scope calculation still applies, but tension balance matters more than swing: enough chain is paid out to the bow anchor, while the stern is secured with two lines to separate points. The bays are deep (8-15 m is common), so trying to stern in on too little scope is the main reason for dragging.
Mark your chain: without knowing how many metres you have paid out, there is no scope calculation; a colour mark every 10 metres is enough.
Load test: once the anchor is down, put the engine astern and see that it holds, then shut the engine off.
Swing circle: every extra metre you let out increases the circle you will draw when the wind shifts; plan your spacing from the next boat accordingly.