Anchoring 101
There’s more to anchoring than throwing a heavy piece of metal over the bow and settling down for the night! In this article we’ll cover the basics of anchoring.
An anchor consists of two parts: the anchor itself and the rode. The rode is the line that attaches the anchor to the boat. To be effective an anchor must have good holding power and the rode must be able to withstand strains that are put on it. These strains originate from three sources: water, wind, and wave action.
For any model anchor, a heavier version always has more holding power than a lighter one. A boat’s main anchor should have at least one pound of weight for every foot of boat, i.e. a 36’ boat should have at least a 36 lbs anchor.
The rode for any anchor setup should consist of both chain and rope (nylon rope is the best material due to its strength and elasticity). Generally you want approximately 1 foot of chain for every 6 feet of rope. The chain serves two purposes. First, it keeps the nylon rode from wearing away from rubbing on the bottom of the sea-floor as the boat swings. Second, because the chain is heavy, it holds the rode to the bottom so the pull on the anchor is horizontal. With these facts in mind, the basic setup for a a 28’ foot boat have a 28 lbs anchor with 28’ of 5/16” chain attached to 168’ of 3/8” nylon rope.
Scope
One of the most important things beginner boaters overlook when anchoring is the scope needed. Scope refers to the ratio of the length of rode let out to the depth of the water. If, for example, 100 feet of rode is let out in 20 feet of water, there is a scope of 5 to 1. When anchoring, you want at least five feet of rode let out for every one foot of depth in your anchoring location. Optimally, you should have a seven to one scope.
Selecting an Anchor
The three most popular types of anchors are claw (Bruce style) anchors, plow anchors (CQR anchors), and Danforth anchors. All three of these anchors (along with most other types of anchors) perform well in muddy and sandy bottoms. The plow and Bruce anchor perform especially well in rock, coral, and weedy bottoms; the Danforth does not perform well in these conditions. You should have a secondary anchor on board at all times in case your lose your main anchor.
Selecting an Anchorage and Anchoring
There are books for almost all ocean cruising grounds in North America detailing the best anchorages in the area (in terms of protection, facilities, etc.). These books are usually pricey ($50+) but you will find they are one of the best investments you can make.
When selecting an anchorage you want to look for a few things (aside from a recommendation from the book’s author). First, you want to make sure the anchorage is protected from all wind directions and that the water depth is enough. Remember, if you’re in ocean waters there’s an often overlooked variable called tides! A 20 foot bay at high tide could easily be a waterless mud garden at low-tide. Next, look for evidence of a bottom that may be foul with stumps, boulders, weeds, etc. The shoreline is usually a good place to look for this evidence. Finally, make sure there is enough swinging room for your boat. In a bay 25 feet deep, you’ll have at least 125 feet of rode out so the amount of room needed will be significant.
Now that you’re actually ready to anchor, drive your boat into the direction of the wind or current to the desired anchoring location. Put the engine in neutral and slowly drop the anchor until it reaches the bottom. Put the engine slowly in reverse and let out the necessary rode (with a scope of at least 5:1). If the rode hasn’t been secured to a Samson post or another strong cleat already, do it now. When you feel the anchor has set, stop the engine and take two bearings and make sure the anchor is not dragging (i.e. the boat is moving away from your bearings). It can take a couple of tries to get the anchor to set properly so don’t be disheartened if you fail after the first try.
