Hi-
My first post here, and first I'd like to thank ya'll for a most civilized and educational forum .
I'm in the process of re-furbing my first beach cat, a 1985 AMF Trac 16.
I had mostly intended to just watch and learn, but I saw this thread, and thought I might actually contribute something, as we have something like 20+ years in making small boat sails with zipper reefing.
I apologize in advance if this is long-winded, but I'm just trying to be clear .
A zipper reef could probably be installed on many, if not most, full batten sails.
We've put them in sails up to about 100 sq ft, but I'm sure it could work in larger ones as well.
The thing is, that it can't work with a bolt-rope luff - The sail has to be converted to slugs - One per batten.
The reef is set up, somewhere in the lower mid section of the sail, where the luff and leech are mostly parallel.
It can only work from any 2 adjacent parallel battens, with the zipper on the facing edges of the 2 batten pockets - the 2 batten pockets zip together.
OR - It can work by putting the (tape reinforced) zipper in the 2 spaces between 3 adjacent battens, with the reef spanning the middle batten.
Either the battens also need to parallel, or the zipper itself must be installed separately, perpendicular to the luff.
Does this sound clear? If you think about the geometry involved, it makes sense.
The poster that said the zipper needed to be supported by web straps was absolutely correct,
But not exactly the way he thinks.
Once the zipper is zipped together, imagine the fold of slack cloth resulting now,
hanging down alongside the the next lower section of the sail -
THIS is where the straps need to be.
The sail cloth forms a continuous, unbroken line, from above the upper half of the zipper, down to the bottom of the cloth fold.
If you put webbing straps, with side-release buckles, at luff and leech, at the bottom of the fold, and fasten them to the sail section below, THEY will take all the strain, and NOT the zipper.
Assuming of course, that they're adjusted to do so.
The nice thing about a reef like this, is that it can reduce sail area, while still preserving decent shape.
And no big bunch of cloth at the bottom.
And since it comes out of the mid section of the sail, no boom is involved, or needed, really.
Now, I'm only relaying the mechanics of the reef itself, the whole subject of mast bend, compression. or downhaul tension, is another subject entirely - YMMV
Thanks again, and I hope you're still awake , after all this
Tom