Anchor Safety
Anchor Equipment
A boats primary ground tackle consist of an anchor, chain, shackles and line, all of which must be sized according to the weight of the vessel and the weather conditions such as wind, current and surge.
There should be 6 to 12 inches of (galvanized) chain per foot of boat running from the anchor to the anchor line. This is required to keep the end of the anchor pointed down by the weight of the chain to help it dig in by reducing the angle that the line is causing by running back up to the boat. Anchor Chain should be 3/16" galvanized on medium sized boats of 20 to 30 feet.
The anchor line and chain should be 4 to 7 (4:1 to 7:1) times the depth of the water you are anchoring in, this is called "scope". The more chain you have the less scope you need. So if you go with 12 inches of chain per foot of boat you could get away with 3:1 scope in a calm anchorage (as long as you are staying on the boat to keep an eye on it). The scope also depends on how much force will be applied to the anchor due to wind, current and swell. The line should be 7/16" nylon on medium sized boats of 20 to 30 feet. The purpose of nylon is to let it stretch a little to act as a shock absorber and not yank the anchor lose or make it uncomfortable in the boat with the sudden jerking.
A Danforth style anchor should weigh about 1/2 pound per foot of waterline on medium sized boats of 20 to 30 feet. On boats larger the 30 feet use about 1 pound per foot of boat length at waterline.
Setting and Retrieving Anchors
Start by heading into the wind or current whichever is stronger to the point where you want the final resting place of the vessel to be and check to make sure that there are no obstacles in the way of the swing due to tide and wind changes. Also make sure there are no other boats that will swing into to your boat. Once the position is determined to be a safe anchoring spot continue moving forward the length of the pre-determined scope that will be used.
Make sure the boat has no forward motion and then lower the anchor slowly to the bottom. Once the anchor hits bottom move the boat back slowly while letting out line so the anchor chain does not pile up on top of the anchor. Having the anchor facing the right direction and the chain laying in a straight line ensures the anchor will set properly.
Keeping a small amount of tension on the anchor line while letting more line out helps to keep the bow pointed toward the anchor, to much tension will cause the anchor to drag.
After you let about half of the anchor line out, bump the anchor a few times by gently tugging on the anchor line to basically hammer the anchor into the bottom. Remember the anchor does not just lie on the bottom, it digs in like a wedge. Continue backing down and letting anchor line out while bumping the anchor every so often until you get your full scope out.
Once the full scope of anchor line is out secure the line to the bow cleat, do not try to hold onto the anchor line and stop the boat, it could be stronger then you. Once the anchor line is secured grab the line and feel if is set or dragging, if it is dragging you will feel the bumping as it passes over the sea floor, you will want to feel steady tension on the anchor line to know it is set. Reverse the engine and make the anchor drive deeper into the seabed, this is a good way to test the holding power, if the anchor breaks lose, pull it up and start over.
Grass and hard mud will make it harder to set but once set will hold real good and might be hard to get back up. Best way is to drive up on it taking the line on board until it is straight down and cleat it off and continue to drive over it to twist it up breaking it free. Once loose stop and pull it up, do not continue to drive forward and allow the line to become entangled with the prop.
