Yachting Monthly magazine had a good article on furling main systems a couple of months ago - you might want to have a look at it.

Agree with CptCook on the importance of not furling a baggy sail. Also important to look at the furling system at the mast. There will be a preferred tack for rolling up. Most are designed to be furled on starboard tack to minimise the friction and chafe. While it is certainly possible to furl on either tack, the system will be happier with one or the other. Both of these two points will make furling and the next unfurl easier.

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