Preventer comments
About three decades ago I did some crewing on a local C&C 30. The owner had double preventers rigged with no conventional vang, per se.
There were two part tackles from somewhere on the mid portion of the boom up to the rail on each side of the mast. From there the tail of each went aft to a cam cleat on the aft corners of the cabin.
He bouy raced with this set-up and also did distance racing. He was both a really nice skipper and a regular winner.
(I will always remember his advice to the crew when another boat was threatening us from behind - chute up on a tight off wind leg - "Don't worry and just keep adjusting the sails square to the wind no matter which way I point the boat..." As I recall the other boat never did get to take us up. And then as soon as things calmed down on the course again, his good natured wife would hand up more fresh sandwiches from the galley!)
So many times in racing and cruising, your chosen course has enough restrictions that you need to spend time running dead down wind or even a little by the lee when the wind vector varies. (This keeps the crew alert...)
With the preventers you no longer have to deal with an unplanned gybe, and when you do decide to gybe you can use the windward preventer tackle to modulate the speed of the boom coming across.
I have also seen this double preventer scheme used on blue water cruisers quite a bit, where wave action can slew the boat around unpredictably and cause a gybe that would not happen in smooth waters.
For local cruising or racing I would not add this layer of running riggind complexity, but for an offshore trip I might reconsider...
:nerd:
Best,
Loren