Wednesday, November 28, 2012

Building a yacht mooring

There are plenty of resources on the internet to help sort out the specific design criteria of the mooring system, the real problem is how to cost effectively place the mooring.    In a area with a sufficient tidal range the possibility exists to building the mooring at low water and use lift bags at high water to float the mooring into position.  In areas without a sufficient tidal range the task of moving a 4200 lbs mooring block might require the very expensive services of a crane mounted barge.

On possible approach is to build a crude boat integral to the mooring and then scuttle the boat at the desired location.  One such design would consist of plywood formwork/boat 4' wide x 6' long x 4' tall with a 14" reinforced concrete slab poured in the bottom.  If concrete weighs 150 pounds per cubic foot and sea water 64 pounds per cubic foot then it's pretty simple math to determine that the 4200lbs of concrete will displace 67 cubic feet of sea water while the 4'x6'x4' box would displace 96 cubic feet of water.  So a properly reinforce the plywood box/boat would easily float the mooring with a reserve buoyancy of 30 cubic feet or 1900 lbs resulting in 15" of freeboard.  

Design critera