Hi, with a sail luff 509-513 and a 490 mast what setting on my mast base should i use. It goes out to 30.

Also to what measurement should i be pulling the sail down to. Would it be the base of the pulley on my sail that is my measuring point or something else.

Finally what is the ideal distance from sail pulley to mast base when downhaul is pulled to correct setting.

Thanks.

Guy Cribb said to get the 2nd batten down from the top or 1/3 way down roughly so it sits straight out from the mast ( not under or over) and use that as a a basic setting.So set your extension so it can put enough downhaul on till you get that result then get a waterproof marker pen and write on the extension..i.e - 8.5m so you can find it quickly next time.

Looking at that extension, the first number is 5cm yes?
You will never get the sail pulled down to zero - the closest you will get no matter how good you are, is about to 3cm as you can't get pully to pulley contact.

Lots of extensions have this, so people are always under downhauled.

For my Chinook I add 4cm to every sail's measurement and it is perfect.

You need to set extension at 26cm at least in order to acheive the 513 measuremnt.