Called 'continuous support tape'
http://www.sailrite.com/FAQ?search=conversionIf the sail has piston hanks already installed just remove the hanks, the grommets, and the fabric sleeve + rope thats already there at the luff. Then simply apply the new 'luff tape' with a *strong* sewing machine ... its usually best to reinstall new D-rings mounted to strong webbing (instead of grommets at the very top and at the bottom of the luff). The 'new' luff should be a 'system': D-rings to luff tape to D-rings so you can still apply a lot of stress/load to the luff with the halyard. You can apply just the luff tape only but this wont be as quite as 'strong' as a new luff tape AND new sail attachments to the furler 'swivels'. Be careful, as all 'continuous support tapes are very precisely made: and, fit ONLY the furler that its designed to fit. There are many many many geometries of furler gooves and you will need to get the EXACT continuous support tape that EXACTLY fits YOUR furler --- usually specified by exact furler model number and YEAR of production of the Furler. If you dont have a 'strong' sewing machine it will be difficult to sew through the webbing with a 'home' sewing machine, usually sewing through such webbing will require a 'sailmakers' sewing machine. Only ONE 'luff tape' is applied to the sail. That second groove is so that you can raise an additional sail on the same foil, either for aggressive downwind sailing with two jibs flying simultaneously ..... OR simply when changing sails when underway - you raise the next sail in the other groove on the 'windward side' of the previous sail while that other sail is still flying; when the new sail is 'up' you tack/gybe and pull the previous sail down from the windward side of the new sail - the newly raised sail will help prevent the previous sail from going overboard. Such a maneuver can be done without losing any speed of the boat while performing this maneuver - called a 'peel'. http://www.sailrite.com/FAQ?search=conversion ... and then look in the 'instructions' or 'projects' section of the website for a precise method to apply the continuous support tape to your sail.