CHAIN

Some think there may be a connection between this unit of measurement and the anchor chain, but this is false. The chain is a surveyor's measuring tool, equal to 66 feet (Gunther's chain). The actual chain used by surveyors (before the advent of modern optical measuring tools) was comprised of 100 metal rods, each 8-inches long, connected with rings. One chain is equal to four rods. Ten chains equals one furlong, and ten square chains equals an acre. These are all land measurements and have nothing to do with the sea. From Wikipedia

LOFTING

The original plans for a boat are drawn to scale by the marine architect. With pencil and paper, he is able to refine the lines so that they run smoothly from frame to frame. He can emphasize the elements of speed, stability and buoyancy that he is trying to achieve with his concept for a new design.

When the time comes for construction to begin, those line drawings are recreated at full size, often on the floor of the workshop. That process is called "lofting". Usually there is a degree of art involved in boatbuilding, since nothing is made square. The reference points are marked on each station using careful measurements, and then those points are connected using sweeping curves drawn with the help of flexible battens.

When the lofting is complete, the boatbuilder can begin cutting and shaping each piece, using the lofting drawings for his reference.

ELECTROLYSIS

Sea water is salty, the result of river waters carrying salts out of the rocks of the earth during endless millennia, and washing those chemicals down to the oceans. The salt makes ocean water more buoyant, so that a person or a ship actually floats higher in salt water than in fresh water. The salt content also makes sea water a fairly good electrolyte, meaning that the liquid can more easily conduct electricity. The underwater parts of boats and ships often expose different metals to that electrolyte creating a kind of battery. One metal, such as the bronze of the propeller may lose electrons through the water to the stainless steel drive shaft. Over time this will cause pitting of the propeller, weakness and eventually failure. That devastating process is called "electrolysis".