While this might not a learning experience for you old salts, a parent-sailor taught me something I should have known years ago.
It’s called “scope”. Think of the scope rule as “The greater the scope, the greater the holding power of an anchor.” While perhaps not entirely accurate, it’s a good rule.
Scope is the length of the anchor line divided by its depth. 5 to 1 is good; 7 to 1 is better. 1 to 1 is horrible.
When we started our club, some dad who had no idea of scope, built the usual “lots of concrete in a box” type anchor. It weighed so much, we just pushed it off the edge of our dock and it sunk straight down below the dock. Any wind and wave action would pick up the anchor (despite its 60 lbs) and the dock would blow into the shore. For years it failed. We just added more weight and it would fail less often, but be hard as heck to move as the water receded in our lake.
A father and sailor came along and took our smallest anchor (maybe 8-10 lbs) and challenged me that he could have it hold far better than the 60+ lb anchor we used. He took maybe 100 feet of rope for maybe 12 feet of depth and deposited the anchor some 90 feet from the end of the dock. Dang thing held against gale force winds. He showed me another trick. Extend a line out from the first anchor about 20 feet to a second anchor and it will hold even better.
Because the anchor line is so close to the surface near the dock, we took a simple 5lb weight with a hole in the center from our weight set. We tied a 5 ft rope on that and connect the other end to the dock. Through the hold-in-the-center of the weight, we run the anchor line so that the weight pulls the anchor line down to a greater depth near the dock….just so a skeg won’t catch on it.
Last night we had the remnants of the Midwest storm that produced so many tornadoes in Illinois……..50 mph winds for us…..and I know the docks didn’t move…..don’t have to worry anymore with the proper scope.