What size and type of anchor do you need?
To fully answer the what size and type would require a book and even then not everyone would agree on the conclusions. What size and type of an anchor is a question bar fights have been known to be made of.
The bottom line is that all anchors will fail in some conditions many cruisers carry multiple types and sizes of anchors so they are ready for different conditions.
Every boater is encouraged to check the size and type of anchor and rode for their boat at least once to help insure they have the proper anchor and rode for their intended use. Every boater should understand the limits of each anchor they have on board. The manufactures literature as well as various catalog sheets and tests by publications such as Practical Sailor, Chapman Piloting, Seamanship & Small Boat Handling as well as the manufactures of your anchor line.
Extreme caution should be exercised when setting and retrieving the anchor to prevent damage to the boat and injury to the crew. Do not stand in the byte of the rode and getting caught in the rode and drug overboard. Also be careful of the windlass as it is easy to get caught in it’s teeth, also guard fingers against getting caught in or pinched by the chain.
Bottom Characteristics and Holding Power
| Type | Description |
|---|---|
| Firm sand | Excellent holding power and is consistent |
| Clay | Excellent holding quality if quite dense, but sufficiently pliable to allow good anchor engagement. |
| Mud | Varies greatly from sticky, which holds well to soft or silt that is of questionable holding power. |
| Loose sand | Fair, if the anchor engages deeply. |
| Rock and coral | Less desirable for holding an anchor unless the anchor becomes hooked in a crevice. |
| Grass | Often prevents the anchor from digging into the bottom, and so provides very questionable holding for most anchors. |
| Cables and wrecks | If the anchor hooks on them, high holding power but the anchor might not be able to be retrieved. |
A chart can help show the type of bottom to expect. Also ask other boaters that have anchored in the same area what their experience has been and any cautions they have for that area.
Improving Holding Power
A Sentinel or Kellet can be added to the anchor line. This is additional weight added on the rode to lower the angle the rode has to the anchor and the bottom. Commercial Sentinel’s can be purchased, additional weight is attached to the Sentinel and then it is clipped over the anchor rode and lowered down the anchor line. The Sentinel has a line attached to it so the position on the anchor line can be controlled and the Sentinel can be retrieved. In an emergency most any weight can be added in a similar method if care is taken with the method of attaching the weight to the anchor rode.
Another method is to carry an additional boat length of “substantial chain” with extra weight at one end (Chapman Piloting says 25 lbs. But does not address boat or anchor size). The additional length of chain is added between the original chain and nylon rode with the additional weight at the attachment point with the nylon rode. Remember to wire the shackle pins so they will not unscrew.
Additional weight can also be added by itself at the end of the chain and start of the nylon section of the rode.
Anchor Types
Danforth: Very popular, Lightweight, high holding power to weight, developed to pull landing craft off beaches in World War II. Most effective in clay, sand or mud. The flukes will tend to skip or sail on rocky or weedy bottoms. Caution: Not all “Danforth” anchors are created equal. Many manufactures have made subtle changes to the design, some work better than others or the construction is better.
Fortress: Danforth style but made of aluminum so it is lighter, they are also designed to be disassembled for easier storage. The fluke angle can be changed to match the bottom characteristics. Best in softer bottoms.
Plow or CQR: Has a hinge to reduce the tendency of the anchor to pop out when the boat swings and changes the direction of pull. Effective on a wide variety of bottoms. Holding power is reduced if the hing is jammed with debris. Breaks out easily if the pull is vertical.
Delta: Similar to the CQR but it does not have a hinge. Weighted so pointed flukes can dig in easier. Good holding power and resets well.
Bruce: Originally developed for offshore oil platforms. Designed to right itself on bottom and dig in quickly, good resetting ability.
Anchor Rode
The entire anchor rode should be fully inspected on a regular basis as well as each time the anchor is used.
The bitter end of the anchor rode should be attached securely to the boat. Many boaters use a short section of nylon line at the bitter end of an all chain rode to reduce the shock load if the chain freewheels to the bitter end.
The anchor rode should be properly sized, The rode is usually all chain or a combination of chain and nylon line. Too large of nylon line can be as bad as too small, if the line is too large for the boat it will transmit shock to the anchor and tend to pull it out of the bottom. When looking as manufactures recommendations, remember that each boat is a unique combination of length, width, height and weight and these factors need to be balanced against each other.
Twisted Nylon: Stretches under load to absorb shock. Three strand stretches the most, can be harder to coil in the chain / rode locker. Working stretch limits are in the 15% to 25% depending or manufacture. Should be stored out of direct sunlight.
Double Braided Nylon: Less stretch than twisted nylon. No tendency to twist. Easier to feed into the rope locker and lays easier. Smother than twisted so should have better resistance to chafe. About 14% working stretch.
Braided / Brait / Mega Braid: 8 to 12 strand single braided construction. Easy to coil or flake. No tendency to twist. Working stretch about 10% to 14%.
All Chain: Very resistant to chafing. Good shock absorbing as long as adequate scope is let out. The weight of the chain makes a large sag in the chain that cushions shocks well. If there is not enough scope the chain can become “bar tight” however and transmit a large amount of shock to the boat and anchor. Heavier than a mixed nylon / chain rode, the weight can be an issue in some boats. Favorite of many serious cruisers. Adding a nylon “snuber” is a good idea to take the load off the windlass and prevent the windlass from slipping or being damaged.
A trip line can be attached to the anchor to help retrieve the anchor if the anchor becomes stuck, the trip line can also mark where an anchor is to warn other boaters where anchors are set. Caution should be exercised to prevent the trip line from wrapping around the keel.
Anchoring Your Boat – Guidelines from a power boat cruiser.
FILE:AnchorNotes 8/06/2010
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