Boating Safety – Anchoring: Part 5 of 16
Most boaters in our area have at least one story of an anchored boat that got away; I know I have a few. In most cases we are on the beach or in a situation where the incident is noticed before any real serious problems occur. Sometimes we come back from the Gulf side of the beach to find our shore anchored boat has drifted across the Intracoastal Waterway and we are in for a long swim. In others we have broken loose during the Blue Angel weekend and are in for a possible collision with another vessel. No matter whether the situation is minor or major they can all be avoided by becoming more knowledgeable about anchoring and aware of where you are anchoring. The four most important parts of safe anchoring are knowing what type of equipment you have, knowing what type of bottom there is, how deep you are, and the wind conditions.
The Equipment – ground tackle
The first piece of equipment we will discuss is the anchor itself. There are two basic types of anchors used by coastal boaters; the Danforth (or Fluke), and the CQR (or Plow) anchor.
The Danforth is the most common and provides a good hold in sand and mud. It is said to be the best to use in mud conditions because the design forces the flukes through the mud to the harder sandy bottom beneath. Because our area is predominantly sand or mud most captains use this type. IT IS NOTED HERE that Danforth’s DO NOT hold well in grasses. Because of the damage that anchors can do to grassbeds, and their high importance to the productivity of marine life, we recommend that you not anchor in any of our seagrass beds. The CQR (plow) is typically used on larger boats. It is said to hold well in most types of bottom including rock.
The line and/or chain used to hold the anchor to the boat is known as the RODE. Traditionally the rode was made of fibrous manila. Today synthetic nylon is better and preferred. The advantages if nylon include its resistance to rot and its elasticity. A taut line can pull an anchor if the seas begin to build. Elastic nylon will stretch allowing for the pitch of the swells to swing the bow without freeing the anchor. Nylon has been found to be 15-25% more elastic than traditional manila, Dacron, or polypropylene lines. This elasticity also allows the captain to purchase smaller diameter line without losing holding power.
Not all captains use chain on their rode but many prefer it. The chain allows the first few feet of rode to lie horizontal on the bottom so that the shank is not pulled vertical while the anchor is trying to set. One rule of thumb used is 1 inch of chain for each inch of waterline. Chapman’s Piloting indicates that no more than 6 ft. of chain is needed to do the job. The length and diameter of both the nylon line and chain required per vessel size can be found at: http://www.theensign.org/uspscompass/compassarchive/compassv5n11/v5n11_anchor.htm
Attaching the rode to the anchor can be done using several methods. Many captains will purchase braided nylon with a thimble already attached to one end. A shackle can be added to this and attached to the chain, which is then attached to the anchor via another shackle. Twisting swivels are sometimes used to avoid fouling or twisting of the line. Others will attach the line directly to the anchor using a bowline.
Selecting an Anchorage
When selecting an anchorage for the day or for the evening there are several variables the captain should consider.
One, the wind – the lower the wind, the lower the chance your anchor will pull. In our area during the summer mornings can be quite calm but by mid-day the afternoon sea-breeze picks up. These winds are out of the south and the north side of the island is a good location. The FETCH is the area over water is which the wind blows. The larger the fetch, the larger the seas, the greater chance of your anchor breaking loose… try to reduce your fetch when selecting an anchorage. You should also note that when overnighting on the boat the winds will switch out of the north around midnight. If you are anchored close to Santa Rosa Island with a large area (fetch) of Pensacola Bay to your north, you may encounter higher seas after you have gone to bed and awaken to find you have dragged or broke loose.
Two, the bottom – as mentioned earlier the harder the bottom the better the hold. Sometimes in quiet coves the water current is reduced significantly and mud can build. You will want to make sure anchor has ventured through the mud and set in the hard sand below.
Three, your approach. It is best to approach an anchorage head into the wind at slow speed. Once you have reached the point you wish to anchor place in neutral and allow the wind to back the boat down and which point you can let the anchor go slowly making sure it is digging in as you pay out line. Sometimes using the motor to back down may be needed. There is no need to “throw” your anchor; you will increase the chance of fouling if you do.
Four, swing. By this we mean as the wind shifts you boat will “swing” on anchor. Based on how much rode you paid out you may find yourself colliding with a day marker, an oyster reef, or another boat. Be courteous on the water and be sure you allow enough swing room so that you do not force another anchored vessel before you to have to alter locations. This is something to remember also when anchoring overnight in a small cove. The sea-breeze that is holding your boat over deep water during the day will become a land-breeze that will put your boat on the beach overnight.
Five, SCOPE… this is VERY important and one of the more common reasons for anchors breaking free. SCOPE is the amount of rode you pay out while anchoring. It is measured as a ratio of line to depth. The MINIMUM scope is 5:1 and the U.S. Power Squadron recommends a scope of 7:1. Here is how it works… Let’s say you are heading over for the Blue Angel show in July. You arrive to a location that you like in 5 feet of water. Your minimum scope would then be 25 feet of rode and you would prefer to be at 35 ft. (if swing allows). If you are anchoring on a wreck in 35 feet of water then you minimum scope (5:1) would be 175’ of rode but if you can (7:1) 245’ would be better.
Six, setting. Some captains will hold the line somewhat taut while paying out. Others will allow it to drop and pay out for several feet before pulling taut and setting. Still others will tie off at the acceptable scope and slowly backing down. Some like to periodically give short tugs as it slowly pays out to force the anchor into position. Here it is the captains’ preference. They know their boat better than anyone and know which method will work best.
Seven, making fast… most captains will simply “cleat off” the free end of the anchor rode to a cleat or bitt and feed the line through a chock.
In some situations it may take the captain and the crew to actually set the anchor. In this case it is recommended that when the captain gives a command, the crew verbally respond this same command. This allows the captain to know that the crew has heard and understands the command. This is especially important on windy days where voices are hard to recognize. Another plan could be to come up with a set of hand signals that they captain and crew both know and understand.
With good equipment and knowledge safe anchoring is easily done. If you have any questions concerning this topic or others in this series you can contact Escambia County Sea Grant Agent Rick O’Connor at firstname.lastname@example.org