You have to measure it.
Open your marketing brochure and read the "J" dimension (sorry, cant seem to open the specs for a C-42 on the www.Catalinayachts.com site). That is the distance between the front of the mast and the tack of the headstay. Multiply that by 1.4. That gives you the "140% LP dimension for your genoa. Lay your Genoa out on the ground. Measure from the furthest point of the clew towards the luff of your sail. Swing your tape up and down the luff, reading where the tape meets the iinside edge of the cord making up your luff tape. The SHORTEST measurement that you read is your LP. Divide this by "J" to get your "%LP". If your maximum is 140%, your measurement must be less than that. To measure the mainsail, again, take the sail off teh boat. Fold the head down to the tack. Measure along the fold between the luff and the leach. This is your 50% measurement. Leave the sail folded. Take the head and bring it back to the 50% fold along the luff. Measure at the new fold. This is your 75% measurement. Have fun. Steve C-320 "Alchemist"
