Build the Perfect Swimming Dock Anchor

This weekend I and my son will be towing out the 'new' swimming dock and anchoring it for the summer.  In preparation, I created four anchors last weekend.

Here is how I did it:
I used an anchor design that I saw (and really liked) many years ago that used a old card tire.  Basically you fill the tire with concrete and embedded an eye bolt to attach to your anchor rope or chain.

1) Cover one side of the tire with a piece of scrap plywood.  I used 1/4 inch plywood and used four deck screws to secure it to inside of the tire.

2) Drill a hole in the middle of the plywood you just installed and using two nuts and two washers (one set of washers and nuts on either side of the plywood) secure an 8-inch eye-bolt to the plywood so that it will be held in the concrete once it fills the tire.

3) Fill the tire with standard concrete, let it cure for a few days before you throw the anchor in the Lake.

For each anchor you will need:
  • A car or truck tire
  • Scrap peice of plywood cut into a circle approximately 17-inch in diameter (yours might be different depending on the size of the tire)
  • An 8-inch eye-bolt (use 3/8- or 1/2-inch bolt), two washers and two nuts
  • Four bags of pre-mixed concrete (each about 66 lbs/30kg) - this will also vary with the size of tire.
  • Four 1 to 1.5-inch deck screws
  • A source of water
You will need - substitues at your descretion:
  • Jig saw to cut the plywood into a circle
  • Drill and a bit to match the size of the eye-bolt
  • two wrenches to tighten the nuts on the eye-bolt
  • Wheelbarrow in which to mix the concrete with the water
  • Shovel
The parts...
Assembled but before concrete...

Why I like this Design:
  • The anchor is heavy -- almost 300 pounds (135 kg)
  • It is easy to move on land - just roll it 
  • No sharp edges
  • I have been wondering what to do with the old tires and scrap plywood - I am a certified pack-rat!