Plastic Classic Forum

My boat has a state-of-the-art (circa 1968) roller-furling boom.

The previous owner told me that it had a vang that clamped onto the boom, but that was removable for when you wanted to rotate the boom. I never did find that device among all the stuff he passed along with the boat, but I know what it looks like, because an acquaintance of mine has one.

The vang for a roller boom attaches to the boom using two curved pieces of flat stainless steel with a lip that wraps around the top of the boom. Tightening the vang pulls those metal pieces tight around the boom and they clamp on tightly.

Any ideas where I might find one of those?

Or - since I plan on abandoning the roller-reefing capability anyhow and just use slab reefing - maybe I should just install a vang fitting on the boom and do it that way?

Most roller furling booms that I have seen used a claw with a couple of plastic rollers. If you are going to go with slab reefing I would either attach a soft vang with a standard boom bail or install a rigid vang such as the Garhauer and do away with the topping lift at the same time. Good luck

We used one of those vang straps on our old CAL 21. Actually still used it after converting to slab reefing too. Ours was made by Nic-Fico if I recall. Not sure if they are still made, I don't remember where we bought the first one (might have been at a BOAT/US Store), but do recall buying a second one at James Bliss Marine when they had a big warehouse sale just after E&B bought them out in around 1987. Guess that info won't help much in your finding one? I'd scour Craigs-List, eBay, and any area Marine Consignment shops. We did have trouble getting the strap to lock in place (perhaps our boom was too small in section?) so had to attach a couple of little aluminum pieces to the boom to stop the stainless-steel plates from sliding forward towards the gooseneck.

Please excuse a dumb question. Do you mean Vang or preventer? A vang allows tacking and holds the boom down; a preventer prevents a jybe.

I've got a former roller reefing boom, the crank is still in the lazarette. But the boom's been rigged with a pair of rope clutches and a winch for slab reefing the leech. I also now have a Vang but its angle is so poor and the purchase so limited and light, that it's pretty useless. Vangs on FD or Finns are often 16:1; they mean business! When I need a Vang (Sue's exceedingly wary of sailing downwind, and I don't like it much when sailing by the lee to keep the genny filled when wing-on-wing), I usually have an unreefed main and pass a preventer between the boltrope and the boom.

I think you could make a Vang readily enough. All you'd need to do is to make a jaw big and roller-ey enough to allow the boom to rotate and the sail to build up within the jaw. Then you have to keep the jaw from moving forward when the Vang is tightened. This would be easy with a pennant from the jaw to the rotating bit, the bail, that your mainsheet hangs from. You could arrange this pennant to allow the jaw and the Vang to stow forward near the mast to keep its annoyance level to a minimum when not desired.

I think that if you want the Vang to be useful downwind, really what it's all about on boats whose spars don't flex enough to flatten the main, then you could do with a preventer run from the mainsheet's bail down through a block on your genny's track and the line run to a winch.

I mean vang. I want to be able to better control the shape of the sail and apply tension mid-boom, if need be.

I plan on not using the roller feature of the boom and convert to traditional slab reefing. I had a new sail custom made earlier this year, with two sets of reefing points in. I have yet to sail the boat with the new sail (or any other sail, for that matter), since she's been on the hard all year.

I guess I'm not entirely clear on your description of the preventer - the main sheet is all the way at the far aft end of the boom. It goes to a traveler mounted across the stern end of the cockpit, behind the tiller.

You can see it here:



Could you point to any good resource that describes or depicts a preventer setup in more detail?

Thanks!

ILikeRust wrote: Could you point to any good resource that describes or depicts a preventer setup in more detail?

A preventer is any line of pulley system that is temporarily attached to a secure fitting outboard on the deck or toerail to keep the boom out. They are mostly used down wind to keep the boom from gybing and to help keep it flatter. I don't like them. Should you veer to leeward enough to gybe you now have your main backwinded and no fast way to release it. I think this is looking for trouble. I prefer to tack down wind anyway. It is faster and a more comfortable ride.

Sorry, I wasn't clear enough.

I understand what a preventer is and what it does. I was looking for something depicting the arrangement described above.

Tack downwind? You mean come about every time? I.e., do a 270-degree turn?

Well, you'll have an easy time of adding a Vang since the boom won't be rotating with your new slab reefing. Add a bale to the boom and to the mast at the partners. Hang as beefy and multiply parted tackle as you care to between the bales and lead the tail aft to a cleat on the cabin top. Or go whole hog and buy the internally extending/retracting rigid Vang that Earlylight suggests.

Hirilonde is, as usual, right about rigging a preventer for going downwind. You do have to pay attention and the wind had better not be so flukey as to backwind the main. It's a mess on a bigger boat like ours. Hirilonde is also right about tacking down wind as faster and more comfortable for some/most boats. Tacking down wind means jybing every so often and sailing at say 15-20 degrees closer to the wind than dead down wind. The sail begins to act as an airfoil instead of a barn door. The boat goes faster and the extra distance is made up by the extra speed. On our boat, the genny isn't a useful sail until the boat is 30 or so degrees off dead down wind so I tend to sail wing and wing. Wing and wing requires a preventer, sailing about 5 degrees by the lee, and probably a whisker pole on the genny. Rigging a preventer is easy; tie a line around the boom which can be done anywhere if the sail is not rolled, or to the mainsheet mounting at the end of the boom. Then run the other end of the line through a block on the track and cleat it off. When you wish to jybe, uncleat the preventer, pull it out of the block, and throw the end to the windward side. After you jybe, run it through the new leeward block and cleat it.

Small planing boats and catamarans profit amazingly by tacking down wind. They absolutely scream as they sail about 45 degrees off dead down wind and the extra distance is traveled very much faster. The hotter the boat the wider they sail: counter intuitive, but true.

Some folks find jybing worrisome since things are all a flutter and the boom tends to come whipping across the cockpit. When it's really too windy, hardening up and tacking, then bearing off makes things seem less exciting. This is the 270 degree tack you mentioned and it's called waring ship. Jybing merely requires thought and practice. Do it fast enough and the main comes wailing across only to flop against a cushion of air on the new side, rather than threaten to tear the rig out and scare the crew. Do it more slowly by hauling the main to center before jybing.

Quetzalsailor wrote:Hirilonde is also right about tacking down wind as faster and more comfortable for some/most boats. Tacking down wind means jybing every so often and sailing at say 15-20 degrees closer to the wind than dead down wind.

Ah, ok, I see - rather than trying to run dead downwind, wing-and-wing, or risking sailing by the lee. I hadn't realized the distinction we were making here.

Anyhow, yes, this is what I believe as well. I've done the wing-n-wing thing - it's more awkward to try to keep the genny inflated (mebbe should try to pole it out or something) and the boat does rock around alot, which can be nausea-inducing. And then you've got to watch for the crash gybe. I suppose that is the situation in which you really want a preventer, whereas if you're sailing as you describe, keeping the wind off the aft quarter, you don't really need the preventer and just do an easy gybe now and then.

I have found my boat actually is easy to gybe. The main sheet being all the way back at the tail end of the boom gives more control and leverage. Additionally, the previous owner re-rigged the main with all new hardware, so it's got something like 6:1 purchase, which makes it exceedingly easy to sheet in. So when gybing, I start hauling in the sheet as I am pushing the tiller over, and pull the main back closer to center. Then as the wind crosses the transom, there is no big crash or flutter, because the main is already midship. Then I can let the main sheet run out through the cam cleat as the wind hits it from the other side. I have found I can do it pretty smoothly, if I time it right. Of course, I haven't yet tried doing it in a really stiff breeze.

Thanks all!

I don't want to stray too far from the original post, but I want to offer a different perspective on using a preventer. We have used one quite often to control the boom in sloppy seas and light air when we're off the wind. I think a preventer is a valuable piece of equipment to have onboard and ready to rig. We went so far as to install a line that stays attached to the boom through a shackle at the boom's end. We attach the line to a handy-billy secured to a padeye mounted at the bow to draw the boom tight against the mainsheet. This arrangement is quick to deploy and adjust. It's also been a handy way to sheet the drifter through a snatch block on the end of the boom to keep it drawing well. There have been more than a few times when the seas have been so sloppy and the air so light that even a broad reach wouldn't keep the boom from slatting around. (I might add that for our Cape Dory 36, quartering seas are miserable; sailing DDW is a whole lot more comfortable since the waves simply lift her stern and slide under her without all the rolling and yawing).

That said, I wouldn't be inclined to use a preventer to keep a mainsail firmly plastered against the shrouds while sailing downwind. There's just too much chafe in that situation, and there are more effective sails for that kind of sailing. In light air, something like a drifter or genoa poled out is likely to be more effective and a lot easier to control. In heavy wind, a small jib or prevented staysail (if you have a cutter) works well.

Anyway, I think options are good, and the preventer has been an effective method for us.

David's point is important. A boom fully eased for my taste is such that the sail brushes only lightly against the shrouds. Our main is so full that that means the boom is only out about 60 degrees.

Bill wrote -

The vang for a roller boom attaches to the boom using two curved pieces of flat stainless steel with a lip that wraps around the top of the boom. Tightening the vang pulls those metal pieces tight around the boom and they clamp on tightly.

Any ideas where I might find one of those?

Or - since I plan on abandoning the roller-reefing capability anyhow and just use slab reefing - maybe I should just install a vang fitting on the boom and do it that way?

Bill - if you are still looking for the boom vang cheek plates (not sure the proper term) I still have my old ones. I have since converted into slab reefing and installed a boom hanger for the vang to attach to. PM me if you are interested. They are your for the shipping cost from SF Bay Area.

I don't use a preventer when going down wind in light to moderate conditions. Instead I move the boom vang attachment point from the base of the mast to the toe rail. Gybing in this configuration could be a bit of pain though...

So last weekend I was up on the boat and digging in the lazarette for some lines. I really need to empty it out completely and organize what's in there a little better.

And what did I discover, way down deep in the nether recesses of the lazarette?

The original boom vang, with the cheek plates, or whatever you call them, for clamping onto the roller-furling boom, and all hardware - fiddle with cam cleat, blocks, etc. Just need to clip it on and it's ready to go. I might replace the old weatherbeaten line.

I could swear I dug all the way down in that lazarette a while back, looking for it. Oh well, in any case, turns out I have what I need after all.

bill t. wrote

> Could you point to any good resource that describes or depicts a
> preventer setup in more detail?

our setup is permanently rigged, from a boom-point 1/2 beam aft the
gooseneck, to blocks shackled to lifeline stantion bases just outboard
of the upper shroud, then aft outside the combing to turning blocks
shackled to the sternrail, thence forward to the secondary winches.

this is setup whenever the boom is outboard the traveler ends, about
30-35 degrees. The passage main is battenless, with chafe patches, it
has survived around the world.

as to backwinding, well, having the preventer at such times is the
whole point--I'd much rather slack the preventer (on the winch) than
have a goosewing gybe. My last such gybe, in the Agulhas current,
knocked off the companionway slider, and would have destroyed the port
side compass if not for a protective metal tripod.

Just for the record, the device in question is a "reefing claw".

After using roller reefing on my O'Day Daysailer for a few years, I converted to jiffy reefing and have never looked back. Two of us can set a reef in a good blow in about 20 seconds. With the Old roller reefing, it took a minute or more wrestling with the whole thing while sails are furiously flapping.

Hank