Although there is no law requiring you to have an anchor on your boat, all safe boaters will carry at least one. If you run out of gas, for example, or are otherwise disabled, you won't want your boat drifting out to sea, or into shallow water, while waiting for help.
You may even want two anchors of different sizes or types. If you just want to hold your boat in place while you go swimming, for example, a smaller anchor will do. If you need to hold your position during a storm, though, you'd need to use a heavier anchor.
Types of Anchors
The type of anchor you need depends on the bottom, not the boat. The size of the anchor depends on the boat. There are three basic types of anchors:
Patent or Fluke Anchor. Choose this anchor if you nearly always anchor in sand.The most popular of this type of anchor is a Danforth® anchor.
Advantages: Lightweight, with
good holding power. Stows flat.
Disadvantages: Won't penetrate thick weeds or hard bottoms.
Plow Anchor. Use a plow anchor if you will be anchoring in areas with thick weeds, mud or rocks. If the anchor is carried on a bow roller, be sure it is always lashed or pinned in place when not in use.
Advantages: Holds well on
almost any type of bottom conditions.
Disadvantages: Heavy and difficult to stow unless you have a bow pulpit and roller.
Kedge Anchor. Use a kedge anchor in heavy grass, weeds, or rocks where one arm (called a fluke) can penetrate a crevice. The weight of the boat provides most of the holding power, so the bigger the boat, the better this type of anchor will work.
Disadvantages: Not good in mud or loose sand. Fluke can get tangled in the line.
Mushroom Anchor. Use this anchor if you are setting a permanent mooring buoy.
Advantages: Sinks down into
the mud or sand and, if left long enough, will have tremendous holding
power. Most permanent moorings use a large mushroom anchor.
Disadvantages: Hard to pull back up after sinking into the ground.
Size of Anchor
Once you decide on the type of anchor, you need to select the correct size, which is based on the length and above-water profile of your boat. Check the chart provided by the anchor manufacturers for the proper size.
Size of Rode
The line connecting the anchor to your boat is called a rode. While a
complete chain rode provides the best holding power, it is very
difficult to handle without a power winch. If a line is used instead
of a chain, the best lines for anchors are nylon rope, either laid or
braided, because they are resistant to rotting and have a reasonable
stretch, which helps accommodate shock loads due to waves. Even a rode
made from line must have a lead of anchor chain to keep your line from
chafing on rocks or shells that might be on the sea floor. The chain
will also make the pull on the rode near the anchor more horizontal,
which will reduce the risk of the anchor dragging excessively.
The anchor won't function properly unless the rode is the correct length. The length depends on three factors:
- Depth of the water.
- Distance from the waterline to the bow of your boat.
- Weather and sea conditions.
To figure out how long the rode should be, measure the depth of the water from the bow of your boat. Multiply that number by 7 if the weather is good and the water is calm. For example, if the depth is 20 feet and the weather is good:
20 feet x 7 = 140 feet
For this example, you would need to let out 140 feet of rode.
If the winds are gale force or if the current is extremely strong, you may need to multiply the depth by up to 15. So for the above example, if you multiplied by 15, you would need 300 feet of rode.
Calculate the diameter of the rode the same way you calculated the diameter for the docking lines. For example, if your boat is 30 feet long, you will need a rode that is at least 1/2 inch in diameter.
If you mark your rode every 10 or 25 feet, it will be easier to know when you've let out the correct length of rode.
Just like all the other lines on your boat, inspect the rode for knots and signs of wear. Inspect the chain for corrosion; make certain all treaded shackles are wired to prevent loosening. If you don't take care of your rode, you run the risk of not only losing your anchor but also having your boat drift into an area you don't want it to go.
If you choose the combination of chain and line, the chain is used between the line and the anchor, and it should be at least half the diameter of the line that it is attached to, for example, a 1/2-inch line would be attached to a 1/4-inch chain. As stated earlier, one advantage to using a chain is that, because is sinks into the sand, it keeps your rope from chafing on rocks or shells that might be on the sea floor. The second advantage is that it holds the rode to the bottom, which makes the pull on the anchor more horizontal and reduces the risk of your anchor dragging. The disadvantage is that it is heavy to carry and lift out of the water when you are pulling up your anchor to store.
Generally, for the chain with line combination, you should have 1 foot of chain for every 1 foot of boat. However, because of the weight and available storage, that might not be possible. Ten to fifteen feet of anchor chain should be sufficient.
Using the Anchor
Even lighter-weight anchors can cause damage to you and your boat if you are not careful. The following tips will help save your boat, as well as fingers and feet:
- Keep your anchor handy and ready to use.
- Do not place the primary anchor off the stern. Having your primary anchor off the stern presents a serious swamping hazard. Doing so places your stern into the current or wind, which could allow waves to splash over the transom or allow the current to pull your boat under.
- Be sure you are far enough away from any other anchored boats before dropping your anchor.Remember that your boat (and others anchored near you) could swing 360° in changing wind conditions. Also take into consideration that the rode lengths of other boats may be different from yours, depending on the size of the other boats and the type of rode (chain swings far less that line in light winds). Verify you have ample swing room to all other vessels (as well as obstructions, channels and shallow water) should the wind direction change to any other direction.
- Check your charts or use a lookout to determine the best place to anchor. If you have a GPS, check the water depth. You should also check the tide tables if you are planning to stay for an extended time. Avoid areas with a strong current, if possible. If your GPS has a mooring drift alert, use it.
- Approach your anchor spot from downwind or down current (whatever is dominant) and stop when you are over your chosen spot.
- Wait until your boat has come to a complete stop before putting the anchor in the water.
- Be sure nothing is on top of the anchor or rode, including anyone's feet.
- Be sure one end of the rode is tied to the anchor and the other end is attached securely to the boat.
- Do not throw the anchor overboard. Instead, carefully lower the anchor over the bow of the boat, using a hand-over-hand motion to let the rode out. Using gloves will save your hands from rope abrasion.
- Back the boat away, downwind, from the anchor. Let out 7-15 times as much anchor line as the depth of the water
- Let out the correct length of rode and tie off the line around a bow cleat. Sit there for a few minutes to allow the boat to swing into proper position for the wind and current. Pick a stationary target nearby and slowly back-down (reverse) on the anchor rode. After the rode tightens, aft motion should stop, indicating the anchor is set. If the anchor continues to drag on the bottom, try letting out more rode or going to a different location.
- Use a tripping line if you anchor in rocky areas. The simplest way to use a tripping line is to deploy a second line tied off to the opposite end of the anchor and attach it to a small float. This second line need only be longer than the depth of the water and be capable of carrying a load of several hundred pounds. If the anchor becomes lodged into a crevice or rock formation, loosen the anchor rode, and pull on this tripping line to allow the anchor to be backed out of the jammed position.
- Make certain that your boat is not drifting. If you are drifting, you need to reset your anchor, or let out more rode, or both. If you have a GPS on board, set the anchor drift alarm.
When you are ready to pull up the anchor, follow these steps:
- Move your boat toward the anchor.
- Begin to pull the rode into the boat as the boat gets closer to the anchor.
- Pull the anchor straight up vertically once you are directly above the anchor. If the anchor cannot be loosened and the rode is vertical, tie the rode off onto a cleat and slowly back off (reverse) on the anchor rode to release the anchor. You may have to perform a series of reverse-forward motions to unseat the anchor. If a tripping line has been deployed, slacken the rode and use the tripping line to remove the anchor.
- Haul the anchor out of the water using the rode once the anchor is free. Keep the rode away from the prop, keel or rudder.
If the anchor cannot be freed from the bottom, the last resort is to cut the rode. Do not send someone under the water to retrieve it.