what size is your main sheet? go one size smaller or so
Capta has it exactly right.I have always run a preventer from the end of the boom, outside everything, to a convenient point farthest forward on the boat, which usually ends up being the bow chock. This is completely independent of a vang.
I think you've got it exactly right, that's definitely the way to go... I'm amazed at how many boats I deliver, that have no proper preventer setup in place, and one has to cobble together something using a dockline, or whatever...I'm not trying to answer for the OP, but when I read his idea, a little light bulb actually went off in my head...I hate rigging a preventer for the simple reason that you either have to bring the boom inboard to tie it off on the boom, or hang out over the lifelines.
If you had a permanently rigged line that was just shorter (say 3/4 length?) the boom, you could get the sail out where you want it, then unclip the inboard end of the preventer, and hook it to the stretchy, adjustable nylon line. Seems like it might make the whole process a bit safer in rolly seas.
I'm sure those of you who cruise extensively would have other solutions for this problem, but for a guy who races weekly, and only cruises occasionally, this would be an improvement over anything I've got set up.
Glad you liked it, morganscloud is a wealth of information, some extremely knowledgeable and experienced people contributing there... I have as much respect for John and Phyllis as anyone in the world of cruising, it's amazing what they have done...Hey guys;
Thanks for the link to the John Harries site.
I just spent 40 minutes over there and almost forgot that I was reading something here!
Jim's recommendation of 3/8 sounds about right to me... The high aspect main on my 30-footer is considerably smaller than yours, I'm using 8mm dynamic climbing rope of a Kernmantle construction for the connection to the low stretch portion that lives on the boom, and it seems about right, to me...What I want to know is sizing the nylon preventer line. I don't want to put a big line on that won't stretch at all for the loads it will encounter but I don't want some wimpy line that will fail if by some chance I have a full on flying gybe in heavy air. Probably the best answer I've received was to go one size down from my mainsheet.
I am curious as to how the brake works in rolling seas. I have traditional preventers. They are used in light winds and beam seas when the boom tends to wiggle back and forth. The wind isn't shifting so much as the roll of the boat causes the boom to swing. I would not think that a boom brake would be optimal in these circumstances but I might be wrong.Depending on the angle from end of the boom to the bow attachment point, it may be necessary to use no-stretch line like Amsteel. Line with even a small amount of stretch on a narrow hull, creating an acute angle in the line, will allow the boom to swing back over and create a real problem. My decision to go with a ladder type brake was based on two things: 1. My narrow hull and the geometry of a typical preventer as described above and 2. the idea that the purpose of a preventer is exactly that-to prevent a disastrous unintentional jibe that can do damage to people and gear. The brake does that. I fabricated a LONG plate for the boom attachment which distributes the stress over a long section of the boom. The setting of the ladder provides plenty of drag to slow down any jibe but not enough to break lines, pull out deck attachments, or create VERY DANGEROUS projectiles. If the boom swings across at a slow rate, it is not going to hurt anyone, if a fitting snaps from the enormous forces created as the end of a boom submerges, not only will the boom then be free but the boom AND MAST may well come down. Creating the possibility of these kinds of forces IMO, makes a boom-end preventer a dangerous item.