Safe Boat Operations – Anchoring – Anatomy of an Anchoring System
It is important to be familiar with several common terms as they relate to the anchoring system:
Anchor: A device designed to engage the bottom of a waterway and through its resistance to drag maintain a vessel within a given radius.
Ground Tackle: A general term for the anchor, anchor rodes, fittings, etc., used for securing a vessel at anchor.
Rode: The line connecting an anchor with a vessel.
Scope: The ratio of the length of the anchor rode to the vertical distance from the bow chocks to the bottom (depth plus height of bow chocks above water).
There are different types of anchors with specific advantages of each type. The type of anchor and size (weight) of anchor a boat uses depends upon the size of the boat. It is advisable for each boat to carry at least two anchors.
- A working or service anchor should have the holding power equal to approximately 6% of the boat’s displacement.
- A storm anchor should be at least 150-200% as effective as the service anchor.
The complete anchor system consists of the anchor, the rode, and the various fittings connecting the rode to the anchor. The rode is the line from the boat to the anchor and is usually made up of a length of line plus a short length of chain. Large vessels may use an all-chain rode. Each element of the system must be connected to its neighbor in a strong and dependable manner. The most commonly used line for rode is nylon. The line may be either cable laid or braided, and must be free of cuts and abrasions. Foot or fathom markers may be placed in the line to aid in paying out the proper amount of anchor rode.
Chain added with the rode has several advantages:
- Lowers the angle of pull (the chain tends to lie on the bottom).
- Helps to prevent chafing of the line on a rocky bottom.
- Sand does not stick to the chain.
- Mud is easily washed off (without the chain, nylon gets very dirty in mud).
There are various methods for securing the rode to the anchor ring. With fiber line, the preferred practice is to place an eye splice with thimble and swivel at the end of the line. If the thimble does not allow the swivel to be attached before the splice, a shackle is used to attach the swivel to the thimble. Then shackles are used to attach the swivel to one end of the chain and the other end of the chain to the anchor’s shank.
Source: americanboating.org Mariners Learning System, By Captain Bob Figular