Making an anchor

In "Haul Out", I showed the float assembly for my haul-out. That float has been anchored with a temporary anchor (a "killick") for too long. I wanted a heavy anchor that couldn't be easily dragged or lifted from it's final resting place. A boat anchor wouldn't do; it would be too light or too expensive, and a heavy anchor would be very difficult to get up to the cottage to install. So, I made my own anchor from stuff I had around the cottage.

The anchor consists of a short, wide block of concrete with an eye-bolt emerging from the top. The eye-bolt connects, within the concrete, to a length of chain, in order to resist the upward pull of the mooring float. A wide washer fastened to the end of the eye-bolt provides a minor additional resistance.

I prototyped out the eye-bolt assembly, prior to constructing the anchor. It consisted of

  • 1 6" eyebolt,
  • 1 length of galvanized anchor chain,
  • one washer, and
  • four nuts.

I selected a Rubbermade tub as the form for the concrete. I would fill it half-way up the sides with the concrete mix, embedding the eye-bolt in the concrete through a hole in the bottom of the tub.

First, I slit a cross in the bottom of the tub, at the dimple in the centre, and inserted the eye-bolt through this hole, with the eye outside of the tub. I next affixed a nut to the eye-bolt on the inside of the tub, near (but not at) the bottom. I used a hammer and small anvil to squash the nut on the bolt, ensuring that it would not turn and loosen.

Next, I placed one link of the chain over the eye-bolt, and affixed it in place with another nut. This nut was also squashed to the bolt, ensuring that it would not loosen.

Finally, I sandwiched the washer between two more nuts, placed on the end of the eye-bolt and again squashed for tightness. I then dug a shallow groove in the dirt, and placed the tub, face up, over it. This allowed the eye-bolt to extend vertically in the tub.

For the anchor itself, I mixed a bag of concrete mix, and poured it into the tub. I fished the ends of the chain off the bottom of the tub, and embedded them in the concrete. I also smoothed over the top of the concrete; this will become the bottom of the anchor when I invert the tub and remove the set concrete.

After letting the concrete set for 24 hours, I inverted it, widened the slit through which the eye-bolt had been inserted, and removed the entire concrete anchor. The anchor needs additional time to cure before I can place it in the water.