Anchoring – Can you Dig It?
Probably one of the most unnerving things a sailor may have to do is anchor in a busy anchorage, especially overnight. Ironically, this is a key skill for being a competent sailor and even some small dinghy classes like the Buccaneer 18 class require an anchor for class legal racing. Here are the basic concepts required to anchor safely and effectively.
Anchor selection – There are many types of anchors. Most common are the Danforth, Plow, and Bruce anchors. For your most common anchorage, what is the right anchor for the sea bottoms you will most often encounter?
Anchor Rode – The anchor rode is how the anchor is attached to the boat. Almost always it is some combination of chain and rope, with a length of chain being attached directly to the anchor and the line extending off of that.
Scope – The idea that for every foot directly below the point you attach the anchor (so the depth of the water plus freeboard, or the height of the deck above the water) you must pay out a corresponding length of line that is “X” times more than that. So if your depth plus freeboard is 10 feet, and you want a scope of 7:1, you must pay out 70 feet of anchor rode.
Why do you have to use so much rode? The anchor works by digging into and burying itself in the sea bottom. It can only do that pulling (mostly) horizontally. If you just send the anchor straight down, with a tight anchor rode, it won’t hold. But if you let enough rode out so that it drags across the bottom and the anchor can dig into the ground, now you can safely go to sleep and know you’ll be right where you left yourself in the morning.
Here is an example scope problem for you.