I, J, P and E are dimensions used in measuring the rigging and sail area.
I is measured along the front of mast from the jib halyard to the main deck. The main
deck is where the deck would be if there were no deckhouse.
J is the base of the foretriangle measured along the deck from the headstay pin to
the front of the mast.
P is the luff length of the mainsail, measured along the aft face of the mast from
the top of the boom to the highest point that the mainsail can be hoisted or black
E is the foot length of the mainsail, measured along the boom from the aft face of
the mast to the outermost point on the boom to which the main can be pulled or to
the black band.
The following formulas will give you approximately areas for: