To select an anchor, one should base the best choice on three points: Price, Weight, and Efficiency
A high quality model type is your best insurance and, like your insurance, it seems expensive only before the accident occurs. When the weather deteriorates and your boat drags towards the rocks, it is too late to regret the amount of dollars saved on the purchase price. If your boat is tossed on the shore, then the cost may well be thousands of dollars. Security and sleep filled nights at anchor are priceless.
The weight of your mooring has almost no relation to the holding power. Holding is related to:
The stability of your anchor
Its surface area
The shape of the holding surface
All recent tests have proved that aluminum anchors have the same holding as steel anchors of the same size (Practical Sailor, Bateaux, Voiles magazine.)
However, weight is very important for the PENETRATION of the metal tip. If you choose a light (i.e. aluminum) anchor, then favor stable models, those with a penetrating angle like a chisel and those with a heavily weighted tip.
Efficiency is a function of both penetration and holding.
To ensure good holding, it must first penetrate regardless of the sea bottom type, as quickly and deeply as possible. Once set, it must not break free regardless of weather conditions. This is a function of anchor stability and the shape and size of the holding surface.
Penetration is related to two factors:
1. Penetrating angle: I will explain the working angle of four classical tools:
Spreader: - a tool is forming an angle with the material in front of it of less than 70 degrees.
Scraper: - a tool forming an angle with the material close to 90 degrees
Chisel: - a tool forming an angle with the material in front of it of about 120 degrees
Razor: - a tool forming an angle with the material in front of it of more than 150°
- Out of these four tools, only the "chisel" has been conceived for penetration. Ask a Carpenter!
- The penetrating edge has to be as sharp as possible...
2. Pressure on the tool: More the pressure, easier will be the penetration... This is obvious.
Look at the percentage weight on the tip of some classical models: (from Practical Boat Owner, page 80 n° 391 - July 1999)
Having both the right penetrating 'chisel like' angle and the heaviest tip will have the maximum chance of penetrating, even in difficult sea bottoms such as hard sand, coral and weed…
Holding is related to three factors:
Holding surface area
- Stability: Generally speaking, ALL HINGED ANCHORS are unstable (Plow anchors, fluke anchors…) under strong pulls, they corkscrew and break free.
- Stable anchors of the new generation could slightly drag under strong wind gusts, but they keep a constant high holding and they will not break free suddenly... (Very SAFE behavior)
- Holding surface: Try to pull one square meter of steel on the bottom, this is quite easy.. Now bury this plate of steel in the bottom and try again. Holding has nearly no relation with the weight, but is related to:
- The surface area perpendicular with the direction of the pull.
The Shape of this surface
a "wing" shape has an "holding" coefficient of 0.1
a "chevron" shape has an "holding" coefficient of 0.5
a "flat" shape has an "holding" coefficient of 1.1
a "concave" shape has an "holding" coefficient of 1.7
Or in other words, a surface with a "Chevron" shape must be more than three times the area of a surface with a concave shape to have the same holding.
This may seem simple, but in addition:
A good anchor must hold regardless of wind and /or current change of direction.
lt should not have the possibility to become tangled with the rope.
lt should not require any specific anchoring technique.
lt should fit snugly on a the bow roller
Used with an electric windlass, it should be self launching and self retrieving.
lt should be very strong
If you assess all models, and can find one that has all the characteristics mentioned here, then you can be sure you have made the best choice.