Build Your Own Cradle
16 June 2012
Build Your Own Cradle
By Jim Hawkins and David Dickenson
A version of this document was published in Good Old Boat, July/Aug., 2006.
Ellie Adams and I, on Meta Fog, were trapped by fog in Burgeo, Newfoundland. Dave and Fran Dickenson were trapped because the engine on Saskatchewan, their beautiful cold-molded, wood/epoxy composite boat Dave built in their backyard in England, had blown up. Somehow they had arranged a tow to Burgeo where the Province maintains a marine center with a travel-lift. While we were alternately having fun and being bored in the fog, they were busy preparing the boat to stay the winter on the hard right there.
Since the marine centers are designed to support the fishing fleet, they make no provision for blocking sailboats. This meant Dave had to build a cradle! I shuddered at the thought that I might have to do the same thing some day to deal with an emergency of my own. Dave told me he is a shipwright who, when he is not out cruising, maintains a fleet of wooden shrimpers in Chesapeake Bay. Confronted with my own ignorance, I thought, “Here is an expert. I am going to take a lesson”. I watched Dave in action, took notes, and photos. Later, I contacted Dave and we prepared these instructions together, me the writer and Dave the shipwright. Three guesses who really knows what he is doing!
The cradle described will work for a boat with a full keel or one long enough to support the boat on blocks. The weight of the boat provides an anchorage point for the hull supports which, all tied together, resist forces trying to tip the boat. For a boat that would remain unattended for months, a cradle is superior to screw stands as wind generated vibration can sink screw stands into soft ground loosening them from the hull. A cradle with its boat-load just sinks as a unit into the ground.
Of course, an emergency of the sort Dave and Fran faced is not the only reason to build your own cradle. Buying a steel one might set you back a couple thousand dollars. The cradle described here cost Dave a few hundred dollars and is just as effective.
First, you need three large beams, the larger the better, but try for eight inches square or larger depending on the weight of the boat. (Or laminate them out of three or four 2”x 10”s per beam stood on edge.) They can be a little longer than the beam of the boat itself, but must not be shorter. Cut notches at the ends of the beams as shown. Mark the center of the beams.
Place the beams on the ground, notches up. Place a one inch thick spacer on each beam astride the center line. Haul the boat over the beams. Lower it onto the beams adjusting them so as to get the boat exactly on the center lines. Later the lift can raise the boat just enough to remove the spacers so that the weight of the boat descending that final inch can spring the cradle into tension. The boat will stay in the slings a few hours while building the cradle. So work out the timing with the lift operator.
Through-bolt 2”x 4” lateral supports to the beams so that the ends of the supports clear the turn of the bilge and touch the hull at about the water line. Place one on each side of each beam on both sides of the hull.
Note: If bolts of proper length are not available, use threaded rod cut to length. Place washers between all nuts and wood. The project requires a hand saw, hammer, ¾” wrench, and a drill capable of pushing a long 9/16” bit through soft wood.
Cut one end of each of six 4”x 4” or 6”x 6” “compression struts” shaped to fit the notches previously cut into the ends of the beams. Cut each strut to length such that each pair of lateral supports AND its strut (with the lower end of the strut lodged in the notch at the end of the beam) all come to rest at the same point on the hull. The struts must stand at least vertical, better still lean in towards the hull.
Bolt the upper ends of each pair of supports and its strut together tightening the ends of the supports to the strut. Mount 12”square pads and cover them with rug material. Place the supports and struts in position with the pads against the hull and the lower end of the strut lodged in the notch on the beam.
Now remove the spacers and lower the entire weight of the boat onto the cradle. This puts the entire structure into compression and makes the notches in the beam ends work for a living. The lift can now be removed if necessary, but preferably kept in place until you have bolted cross braces on the struts to mitigate fore-and-aft lean. And there you have it.
Now all Dave had to do after de-commissioning the boat was build a frame on deck, cover with tarps and fish net, all properly tied down. Oh, and then there was the small detail of the blown engine. Well, you get the idea. Let’s you and me hope we never, ever have to face such an ordeal.
(As of this writing, the engine has been repaired and Dave and Fran are making plans to re-install it and continue their Newfoundland cruise.)