When my boat arrived in Australia it was fitted with slab reefing which proved too hard and long for just myself to pack away (reelfing was not a problem) so before I even got the boat home from Sydney my wife had ordered a new Leisurefurl boom from NZ. The main thing for furling booms is the main sail
must be built for a furling boom. After consulting with Norths Sail I was told that it was not worth trying to modify my new FCL main sail to suit a furling boom. There are a number if things with a furling main that are different to a standard main, luff tape, soft batton ends, batton angle in sail, depth of the sail, foot of the sail, just to name a few. The good thing is the area of the sail is full size and good shape, unlike an in mast sail. As the new boom weighs 250kg it also ment we had to fit a new bigger vang strut as this is what you use to set the critical boom angle when furling, not the boom topper. In any boat you mark the vang rope at the correct position. (marking the vaNg rope is more accurate as the vang usually has at least 4 to 1 purchase, so if you are a little off the rope mark it will not make as much difference) and then take up the boom topper to prevent any boom up down movement. Some one above said you are to release the vang, this is a big no no As the boom must be held from going up or down (the boom angle is critical to 1 deg.). Main sheet is eased. When furling or reefing you also need the hold a little tension on the main halyard. The tension you hold will also very the furl, this tension is something you learn after a while.
With a boom furling main sail you do not have an adjustable out haul, so you set the foot up with the amount of sag you would normally run with off the breeze. When you go to windward and you want to flatten the foot you simply furf the boom about a half turn as a proper furling main is attached to the boom mandrel at each end of the foot as well as the centre point of the foot, by doing this it pulls the drive from the centre of the sail.
Reefing is also simple, it is just a matter of furling the mainsail down to a batton position. Generally the boom angle is not so critical when reelfing as you do not require to roll the entire sail in, but you will have to rehoist the main and set the boom angle prior to furling the main away. As you do not have any form of out haul on a roll furled sail, the trick is to furl the sail so as the batton is aligned with the under side of the mandrill, this way the batton works as an out haul. With a proper furling main the sail looks just perfect at any reef point and no foam needed. The photo below is the main with a single reef. You can see the batton that creates the out haul.
I can see where an old badly set up furling boom and main could be a total pain, but a well set up system is brilliant. Unfortunately it is one of those things you can not do by halves.
In our case it was a hard decision to throw out a brand new main sail, main sail slider system, Selden boom and Selden kicker and fork out another $60,000.00. It could have been done a little cheaper but I opted for a Norths 3DL one piece moulded carbon cruising main. These sails are basically the same as a race main but have taffiter stuck to each side. Was it all worth it? You bet it was!!! Because of the furling boom I can see myself and my wife sailing the boat for a lot more years to come until we are both silly old farts, making a nuisance of ourselves and warring our kids as to our where adouts. Deb thinks I am already a silly old fart.
PS. if any body wants a cheap brand new boom, main sail and kicker for a 50 to 60 foot boat, let me know.