The majority of boats at the club ( other than dinghies) are 20ft to 25ft open deck keelboats, with our shallow waters, the keel depth of the classes is around 3ft. So that crane attaches to the boats keel bolts , with a frame, or wire /cable lifting adaptor. I built Blue Moon's keel bolt setup with Eye nuts on top and a specific adapter for BMWhat a thoroughly British way of moving a yacht.
It only has to lift a couple of inches, the trailer is pulled out, the crane pushed to the dyke edge, and the boat lowered in. Normally the water level is about 18 inches below the quay heading height, though on that day we had a lower tide, so the water level was about an extra 6inches down and Blue Moon and the other boats being launched that day ran aground being moved up the dyke.
The cranes users annual meeting is this weekend, we are going to increase the fees to £75 per year, due to increased insurance and annual survey costs. Unlimited lifting is permitted, so many lift for a scrub down mid summer.