Suggestions on anchorage in bay
This post is also available in: Italiano (Italian)
A boat anchorage requires careful analysis of two crucial variables: the anchor and the most suitable place for mooring.
The choice of the anchor depends on several aspects such as:
- Shape of the roller and space available on deck;
- Type of vessel;
- Navigation programme;
- Reliability and models.
The tables supplied by the anchor manufacturers are usually a good reference but they are a mere indication that might differ from the final choice: if the anchor recommended didn’t adapt to the roller of the boat, you’d better choose another model.
I recommend to make a carton template reproducing the anchor broad measures in order to calculate the room available on deck and to check that, while dropping the anchor, it doesn’t impact against the stem, which can be coated with a stainless steel plate for protection.
Weight and shape are no doubt the two key elements when choosing an anchor.
As for weight, nowadays boaters tend to adopt anchors slightly heavier than what indicated in reference tables unless space is an issue. A higher weight is ideal for fast and safe anchorage, often when the scope of the cable is short.
The last generation of anchors has greatly developed shape, gripping power, hold and retrieval during tripping. For instance C.Q.R. anchors provide the best shape to dig into the seabed but are not ideal for rocky ones, which preferably require a grapnel anchor.
When the boat has tall and rounded bulwarks it tends to move a lot when at anchorage therefore larger size and higher weight are recommended: check the windlass pull is correctly dimensioned on the windlass handbook.
Weight and shape are two crucial elements when choosing an anchor but the scope of the cable is one of the most variable ones: for small vessels the easiest solution is a textile line made of several strands and possibly some metres of chain for connection to the anchor.
When considering the chain, in addition to its diameter you need to know the type of steel (stainless or galvanized) and its strength, often indicated in grades that can be:
- 30 (kg/sq. mm);
- 40 (kg/ sq. mm);
- 70 (kg/ sq. mm).
The first two grades are more widely used while the diameter of a chain made of the last high-strength steel grade can be as much as 2 mm smaller.
When choosing a chain the windlass gypsy is an aspect to be taken into account as well as the space available in the locker. In principle, a 10/12-m long vessel will have an 8-mm chain, a 12/15-m long boat will have a 10-mm chain and a 16/17-m long one will have a 12-mm chain or a 10-mm one if made of grade 70 steel (70 kg/sq. mm).
As for length, the scope of the cable used is 5 to 8 times as much as the draft therefore when mooring at 12-m draft you’ll need about 50/60 metres of chain, for a 14-m draft the chain shall be 70-m long, and when anchoring at 16-m draft you will need 100 metres of chain. When space doesn’t permit, use a length of line to extend the cable.
Another major aspect is the anchor-chain connector, either a traditional system with a safe and simple shackle or swivelling connectors that allow for easy anchor retrieval up to the roller. There are special joints on the market whose eccentricity prevents time waste when retrieving the anchor and the chain doesn’t haul in correctly.
Moreover the joints must be oversized in order to stand all onboard loads and move along with the chain and the anchor shank. Ultimately it is crucial to always remember to release the anchor pull from the roller and the windlass by means of a hook and lines on their respective cleats, both at anchor and during navigation, to prevent stressing the windlass gearbox unnecessarily.
The bay is also part of the choice and it mainly depends on its shape and the type of shelter it offers.
An open bay usually offers limited shelter and from a single wind direction while the waves come from several directions, for example going around the cape and making the boat roll. Fiord-like bays are usually better: the longer the bay, the less waves and wind creep into it.
The depth of the bay shall also be checked: one where a lot of cable is required is suitable for a daily stop with low wind while the best bay for anchorage has variable draft from 5 to 10 metres. Protection from the wind is not as crucial as protection from the waves since this latter involve higher stress for the anchorage.
The seabed is another limit to consider when choosing a bay for anchorage: a sandy or muddy seabed is better than one with seaweeds because this latter might be rocky, which makes it difficult to hold and trip the anchor. The pilot book and the nautical charts are very useful since they supply details on the different kinds of seabed.
Within the shelter of a bay the yachtsman in particular looks for protection from forecast or prevailing winds therefore an enclosed bay will be ideal. Hills and trees will also offer protection in comparison with anchorage in front of a beach.
A central position is to be preferred and that takes into account a possible change of wind direction because should the boat rotate, that would still be space and depth enough.
Ultimately it is good practice to:
- Anchor in an outer position if the bay is crammed;
- Anchor near boats of similar length that will most probably have the same scope of the cable;
- Always arrange the day signal and the mooring light;
- Check the weather forecasts;
- Arrange an anchor, seabed, position or app alarm.
Autore del libro “Lavori a Bordo” e conduttore del serial Tv “Lavori in barca”.
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