Whisker Pole length has nothing to do with "J" deminsion. Don't confuse the Whisker Pole with the Spinnaker Pole. They are not the same. They are not made the same, are used on completly difference types of sails, they are not carried the same, and are not trimmed the same. Whisker Pole length should be measured to the foot of the largest headsail carried or rated. Whisker Poles are adjustable to allow lengthening of the pole to accomodate the foot length of each headsail in the boats inventory (up to the largest). Since the luff of the headsail is fixed to the headstay, the whisker pole is also adjustable to allow the pole to be adjusted in/out to carry the poled headsail to the proper wind angle. Spinnaker Pole length is fixed and generally measured to the "J" deminsion established by the boat designer.
