Rig dimensions primarily used by sailmakers to know how to size a sail.
"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 band.
"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.
"I" is measured along the front of mast from the genoa 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.
"JSP" is the length of the spinnaker pole or the distance from the forward end of the bowsprit (fully extended) to the front face of the mast.
"ISP" is measured from the highest spinnaker halyard to the deck.
"PY" and "EY" are, respectively the luff length and foot length of the mizzen of a yawl or ketch measured in the same way as for the mainsail.
"IY" is the measurement from the staysail halyard to the deck.
"JY" is the measurement from the staysail stay to the front face of the mast.
"LP" is the shortest distance between the clew and the luff of the genoa.
If you need to know the I J P or E of  your yacht or rigging diameter of wires which is useful if you are fitting a furling gear or changing your standing rigging send me an email, I have records of most boats.
Sailmakers guide to I J P and E
The following formulas will give you approximately areas for:
Mainsail = (P x E) / 2 (add 10% for racing mainsail 155% Genoa = (( J x I ) / 2) x 1.65

135% Genoa = (( J x I ) / 2) x 1.44

100% Jib = ( I x J ) / 2

Racing Symmetrical Spinnaker = 1.8 x J x I

Racing Asymmetrical Spinnaker = 1.8 x J x I

Cruising Asymmetrical Spinnaker = 1.65 x J x I
Spinnaker Poles
Whisker Poles

1. What is a Whisker Pole?

Whisker Poles are used to "wing-out" the jib when sailing downwind. They extend between the mast and jib sheet at the clew to hold the jib out on the opposite side of the main in clean air, producing a greater degree of control and efficiency than you could possibly achieve without a whisker pole. Sailors who have attempted downwind sailing without a whisker pole can appreciate the value of being able to stabilize the jib, enabling the sail to work more efficiently.

2. Advantages of Using a Whisker Pole.

A whisker pole allows you to control the shape and position of the jib on a downwind run, exposing it to air that is undisturbed by the main sail, thus producing a very noticeable increase in efficiency and boat speed. Sailing wing-on-wing is much easier than handling a spinnaker and takes less people to handle equipment.
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