I've put them on my 18ft boat.
I was having problems with my new main when singlehanded. About £10 worth of line and some rolling hitches sorted it. Don't pay£70 for a "kit".
I was wondering how lake sailor did it, if you use a conventtonal sail cover I thought you could slide it between the lazy jacks and close under the boom, they do not seem to be attached to the boom? I was avoiding a lazy jack/sail bag system to avoid costs and other factors?
This is how I designed mine. Add more slits for more lines obviously.
Another way is to drop the lines and run them along the boom when you fit the cover, but you end up in the same situation with the sail falling off the boom as you release the lines...
Ooops. Back again. My boom has roller reefing so I just loop the lines under and back up to the diagonals from spreaders to boom end. I used rolling hitches so that I could fine-tune the position of the loops to catch the battens (which are not full length). The sail cover is just a regular sailcoat with a foot to cover the stack of sliders in the mast groove and those plastic luggage clips underneath the boom to hold it on.
After covering the sail I raise the gooseneck to reduce the height of the slider stack and clip on the topping lift so the lazyjack loops hang loose.
(crap picture,sorry)
I use a conventional sail cover with lazy jacks, I only have two lines on each side though which is not really enough. I rigged more but we found our sail got caught.
I feed the sail cover through between the lines and tie up under the boom as you say.
It does seem a bit overkill. But when you are trying to put the sail away single-handed and it's blown up to a 5 it just makes it so much easier. It depends very much on how your boat is set out. As mine is small I have to leap up and down the cabin roof all the time as my lines are all at the mast. So having something to catch the sail before it falls all over the place is very handy.
My lazyjacks cost me all of a fiver and took me at least 3 hours to set up - a couple of hours on one day for the first try then a couple of half-hour sessions to adjust. I use cheap polyprop line - one hank of 6mm should be enough for your boat and some plastic hooks where you see blocks on the posh sets, but LakeSailor's setup doesn't even need them!
I have roller reefing, so I have a taut line under the boom and attach my jacks to that rather than leaving them haging loose. I have an ordinary sail cover and just slacken off the LJs so they'll fit under it when I want to put it on. The sail doesn't fall off the mast 'cos I've got Stemar's patent sail tie system holding it on.
This is a double length of bungee along the underside of the mast, whipped together at suitable intervals and with a hook between each whipping on on one length. To fit, pull one piece around each side of the boom to the top and use the hook to hold them.
My main has two little stainless rings sewn into the sail either side, by the bolt rope for the boom track.... the lazy jacks tie to these.... it acheives exactly the same, but means no rope below the boom.... just slacken them off, and the whole lot goes into the main sail cover....
I have slab reefing on the boom/mast, so I may be able to find an appropriately placed attachment for the lazyjacks on the underside of the boom. I'll have a look as soon as I can. Cheers.