Anchoring Fundamentals: Terms and Techniques
Anchoring a boat is easy, everyone knows that. Why, you just drift up to the best spot in the harbor or cove, grab the "hook" and, in the spirit of Jesse Ventura, throw that thing overboard. Splash! The anchor will do the rest. Sounds pretty easy, but it ain’t necessarily so. Performing a secure hookup with the bottom requires boating knowledge and an awareness of you equipment and how it holds you in place.
To begin with, there are a few terms to know about your anchoring system and the anchoring procedure. These apply to small "lunch hooks" as well as large anchors. Here they are:
Anchor: device designed to penetrate or grab the bottom of a waterway and hold the vessel within a certain radius.
Chain: usually part of anchor rode, connecting anchor to line using shackles, but sometimes the entire rode
Rode: Line or chain, either alone or in combination, connecting the anchor to the vessel.
Shackle: a metal C- or U-shaped ring closed by a threaded pin, used to connect chain to anchor and chain to line.
Ground Tackle: term for the anchor, anchor rode and related fittings
Mooring bitt or cleat: the post or cleat attached to forward deck around which anchor rode is fastened
Windlass: mechanical device on foredeck used to haul and control anchor rode, electrically, hydraulically or manually driven
Bitter end: the very tail-end of the anchor rode made fast to the boat
Chocks: open faced fittings on boat deck outer edge that control anchor rode as it leads over the bow into the
water. Also control location of dock lines.
Scope: the ratio of the length of the anchor rode being used (as measured from the height of the bow chocks to the anchor)
to the depth of the water plus height of anchor chocks above water. Example: 70’ rode in 6’ water + 4’ height to chocks = 7:1 scope
Swing: the movement of the boat around the radius allowed by the ground tackle
Breaking out: the unsetting of the anchor by pulling upward on the rode when directly above it
There are many different kinds of anchors, each having variations in design to handle different conditions. The all-in-one anchor doesn’t exist yet, but some come closer than others. For a detailed look at the different types of anchors, go to our companion article "Anchoring Fundamentals: The Anchor".
A successful anchoring job requires advance planning. It begins with having ground tackle that fits the size of your boat, and possibly having more than one anchor on board. A light anchor, sometimes called a "lunch hook" is adequate for short stays in a protected anchorage where the boat will not be left unattended, while a heavier "working anchor" is necessary for longer stays, changing weather conditions and leaving the boat. On larger boats a third, or "storm anchor" is often necessary for tough conditions.
An anchor is no good to you if it’s not ready to be used, and that applies the minute you leave the dock, mooring or trailer until you return. Not only is an anchor useful for staying in one place at your destination, it’s also an emergency device should you lose power or steering on your boat. So first and foremost, make your anchor ready to use. Have it properly assembled, stow it properly so it is handy but won’t get loose (tie off the bitter end so you won’t lose the whole system), and know how much rode you have.
When you’re traveling to your anchoring destination take time in advance to study the chart or other information to determine how deep the water will be when you get there, what kind of bottom exists, and what the local weather and current conditions will be. Discuss your plan with your crew. Once you’ve arrived, confirm your information and assess how much room you have not only from land or ledge, but also other vessels. Notice how other vessels are laying on their anchors or moorings. Be alert to not setting your ground tackle over that of another boat.
Setting the anchor once you’ve determined your spot is relatively straightforward. Move slowly upwind or up-current to your location and then, if under power (some sailors like the challenge of doing it all under sail), back the boat down slightly and let the anchor overboard. Good communication is important if you have a crew to help, with words or hand signals agreed to in advance. The anchor person must be watchful for any snags or kinks in the rode which will impede its free flow overboard, and be especially careful not to get caught in the line. Standing with one foot inside a coiled line is a big "no-no"! Throwing the anchor is not recommended given the possibility of fouling the rode or getting caught up in it.
The amount of line to send overboard, or the scope (see definition above), is determined by the depth of the water and by the holding conditions of the bottom. As a general rule, a scope of 7:1 is regarded as adequate in most conditions. If you need to reduce the swing radius due to other boats or obstacles, shortening the scope to 5:1 is possible, but only if the weather or current conditions will allow it to be done safely. If you have the room and the conditions are rough (windy and lots of current) extending the scope to 10:1 may be necessary. The amount of scope can also vary with the type of anchor you are using. Use your own experience and judgement to determine how much line to pay out. Marking your anchor rode in predetermined increments takes the guesswork out of setting the scope. Note that if you happen to use all chain for your rode, then a shorter scope of between 3:1 to 5:1 maybe adequate. The overall goal with your scope is to provide an adequate low angle of pull against the anchor to help it set—and hold.
Setting the anchor means making sure it is fast to the bottom and not caught temporarily on weeds or other moveable objects. Continue backing down your boat until the rode becomes taut and, using landmarks ashore, you can see that no further movement is occurring. A good technique for the anchor person is to rest a hand on the rode and feel for the anchor skipping across the bottom; also feel for a strong tension in the line that indicates the anchor is holding. Double check the fastening of the rode around the bitt or cleat, taking a full turn around the base of the deck fitting before securing it. If you use a windlass do not depend on the brake to carry the anchor load—always secure the rode around a post or cleat. Again, make sure the bitter end is also tied off.
Once you’ve successfully hooked up to the bottom you can relax—but not completely. While you are anchored you still need to remain vigilant that the boat is staying where you put it. Make a point to monitor your boat’s position against your landmarks, other boats or even using your GPS if it’s really accurate. If you see that your anchor is dragging you have several options. If room allows you can increase the scope, back down the boat to try to dig the anchor in more firmly, or, move to a location with better holding bottom.
That’s anchoring in a nutshell. There is more to learn about issues like fouling, guarding against wind or current shifts, tide changes, anchoring at night, anchoring stern first to wharves, and rafting with other boats, and we’ll look at those in later articles. An excellent source for information about anchoring can be found in the boating "bible" Chapman’s Piloting and Seamanship.
As someone once said, "It ain’t rocket surgery". With some study and practice anchoring safely and securely will be a source of great satisfaction and—peace of mind.