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This article was taken from the Boat US online course at www.boatus.com
here
Anchoring
Good anchoring skills are essential for every boater. Just as important as understanding the equipment you'll need, is mastering how to use it.
Although not required by Federal Law, it is recommended you carry one anchor of sufficient size and strength to hold your boat for an extended period, like overnight. It is also recommended that you carry a "lunch hook", a small, lightweight anchor to use for short periods of anchoring during good weather. If you're doing extended cruising, where you may not be able to reach a berth in a safe harbor, consider purchasing a storm anchor, which can hold your boat in winds of 40 knots or more.
The general name for all of the equipment you need to anchor your boat is "ground tackle". This includes an anchor, chain, line and connecting elements. The anchor line, including chain, is called the rode. Anchors have several parts, as seen in the illustration below.
Types of Anchors
There are several types of anchors. You should choose a style based on the bottom characteristics in the areas you will anchor most often. Then, choose a size based on the size and weight of your boat.
Lightweight or "Danforth" Type
- Lightweight type anchor with two long pivoting flukes; designed to reduce clogging with mud and grass; range from 2.5 to nearly 200 lbs.
- Commonly used on small recreational boats. Best in hard sand or mud.
- Soft mud, which can ball up around the flukes; or on rocky bottoms where the flukes cannot penetrate, Also not recommended for grassy bottoms.
- Pivoting flukes bury the anchor and part of the line.
Plow Anchor
- Deep burying flukes stay in place. Has either a fixed or pivoting shank.
- Sand and mud; commonly used on larger recreational boats.
- Rocky bottoms, weeds and grass.
- Lands on its side, then when pulled, buries itself.
Bruce
- Unique shape allows a 360 degree turn without breaking out.
- Mud, sand and rocks.
- A burying type, it will right itself no matter how it lands on the bottom.
Kedge or "Hook"
- A more traditional style anchor with arks, flukes and stock.
- Heavy grass, weeds, rocky bottoms or hard sand where one arm can penetrate a crevice.
- Mud or loose sand.
- Not a burying anchor, one arm digs into bottom and one lies exposed.
Grapnel
- Very inexpensive, not much holding power.
- Recovering items on the bottom, wreck or reef anchoring.
- Anchoring recreational vessels; more commonly used to anchor commercial fishing vessels.
- Drag back and forth, or grapple, to recover items on the bottom.
Navy or Stockless
- Chunky device used on larger ships.
- Mud or sand.
- Rocky bottoms, shale or grass.
- Relies on great weight. Suitable only for "lunch hooks" in recreational boats.
Lines...
The best all around line for anchoring is nylon in three-strand twist. Three-strand line can absorb shock and the constant tugging associated with anchoring much better than braided line. Chain is also widely used, especially in anchorages that are primarily rock or coral. A length of chain should be used between the anchor and a longer length of line. The chain will add weight to set your anchor without making it too heavy to lift manually, while serving to exert a horizontal pull on the anchor to set it.
Before leaving the dock, determine how much anchor line, or rode, you will need. It is recommended that you use a scope of 7:1, meaning that for every foot of water depth, you should use 7 feet of rode. For example, to anchor in 10 feet of water, you would throw out 70 feet of line. Measure the scope as the ratio of the length of the anchor rode to the height of the bow above the bottom.
Scope = Length / Distance
If you're using a lightweight anchor on a small boat in good weather conditions, a shorter scope of 5:1 is sufficient and safe. A prudent boater always has extra line and chain on hand, just in case!
It's Time to Set the Anchor
- Never anchor a small boat by the stern! Your engine, and the bulk of the boat's weight rest here. Stern anchoring is likely to result in swamping and flooding.
- Check your chart for bottom characteristics and to determine that you are anchoring in a safe and allowable place.
- If there are rocks, shoals, reefs or other boats to consider, give them all as wide a berth as possible, keeping in mind a possible swing of 360 degrees about the anchor with wind shifts or current changes.
- Secure the bitter end of the anchor line to a bow cleat.
- Make sure the line is ready to run free once tossed overboard.
- Head into the wind or current.
- Reduce speed and reverse the engine.
- When the boat starts to make a slight sternway through the water, lower -- do not throw -- the anchor.
- Tug the anchor line to see how firmly it's set, and then readjust the rode at the bow cleat if necessary.
Even if anchoring only in designated anchoring areas, it is always prudent to have the appropriate signal such as an all-around white light on to notify other boats that you are anchored at night. During the day you must display a ball shape which is sized according to the size of your boat.
Staying Put
It's a good idea to take two immediate bearings. Select two items, one off each beam, that form a natural range and watch for any changes in their relationship. You can check these later to determine if you're boat is swinging as expected or if you're dragging anchor.
WATCH OUT!!! Common Anchoring Mistakes...
- Letting the anchor go with out securing the line to the boat.
- Letting the anchor go with your foot wrapped in the anchor line.
- Poor communication between the captain and person on the foredeck.