Moorings are usually designed for 2:1 scope
, or less if in protected areas. Several sources talk about one "maximum water
depth" of heavy chain and one of lighter chain. Thus the heavy chain sits on the bottom most of the time and lifting it in heavy weather
provides some shock absorption. If things get nasty enough, youíre dependent completely on the mooring anchor.
Lots of people use concrete for mooring anchors. Itís cheap
. But it loses about half its effective weight in water
. So, in very general terms, if the design tables indicate 1000# deadweight anchor, you can get away with a 600# mushroom anchor, or a 2000# concrete block. Four 500# concrete blocks are not equivalent and the hardware
to tie them together creates more failure points. Like any parallel connected system, the load will never be quite evenly distributed. So the weaker link breaks first, putting increased strain on the rest, and so on until youíre drifting.
One canít "trust" moorings unless you dive to inspect them completely AND have lab tests of the bottom characteristics. Even after all that, the insurance
companies are unhappy with the lack of certainty.
And then something can just break.
Whenever youíre on a mooring, make sure your anchor is quickly and easily deployable.