Boom Vang

BCC Forum
1

Just looking at some old threads on Boom vangs. I note that some are using them as preventers and also as vangs. The difference seems to be where the vang/preventer is attached to the boom. The vang more forward than the preventer.

Do some folks have both, or is the base of the boom starting to look like a ball of yarn. The other issue is if only one is used for both purposes then it will have to be moved periodically. Which may be a hassle.

One last point is boom chafe on the aft shroud, any tips for preventing this?

2

I use a vang/preventer attached to the boom slightly forward of the dodger. This position keeps it clear of the Cherub dinghy when it is stowed on the cabin top. I find that as a vang it works very well. As a preventer it is effective as well except when sailing on a very deep reach or downwind. Then the preventer becomes vertical to the bulwark and does not allow you to get the boom extended as much as you would like. That’s when I would rig a traditional preventer from the end of the boom to the bow. I don’t ever recall having the boom contact the aft shroud however to prevent that from happening you could just keep the mainsheet trimmed to keep it a bit aft of the shroud. BTW I have setup two block and tackle vangs, one for each side.

Ron Thompson
Ho’okahiko 97

3

Itchen has a hefty snap shackle at both ends of the vang tackle. This gives
us a lot of flexibility in deciding where to secure it (especially the lower
end) when converting from vang to preventer. The usual boom attachment is
too close to the mast for ideal use as a preventer but works alright in
light to moderate conditions. I’d prefer an attachment much farther from the
mast going downwind in heavy air with attendant risk of a wave tripping the
boom and breaking something, and am interested in how others have dealt with
this issue. I think I would prefer a broken sacrificial “weak link” to a
bent boom! As for the vang, the typical four or five part tackle mounted
rather close to the mast is not powerful enough to do all that much in heavy
air unless led back to a winch. It is ok under some conditions but compared
to what one expects to see on racing craft it is pretty puny. That’s one of
the advantages of a BCC, not so many strings to pull trying to get that last
tenth of a knot, and more time to relax and enjoy the ride! On balance I
think a working preventer is essential and the vang may be a luxury?

Boom chafe? Time to put some leather chafing gear on Itchen’s boom; good
idea.
Scott

On Mon, Nov 8, 2010 at 18:04, BCC Forums bccforums@samlmorse.com wrote:

4

Stewart,
As always, there’s lots of ways to skin the cat. Because we stowed our 7’ Fatty Knees on the cabin top, there wasn’t room for a vang running from the mast to the boom. We tried a 4:1 tackle from the boom about 1/3 of the way out, down to the bulwarks. At first we tried to make do with one tackle, moving it from side to side. That was a hassle that we fixed by having a tackle on each side. We made the mistake of using blocks on the bulwarks end that had cam cleats attached. In light winds we could flick the line out of the cam from the cockpit, but at 15-20k, we had to go up to the block and jerk down on the line to free it. So, we changed the bottom blocks and put the cam cleats on the forward edge of the cockpit coamings. This has worked great for many years.

I preferred to avoid drilling through the boom to attach a bail, and instead used a dacron webbing strap with D-rings on each side, that wrapped around the boom, passing under the foot of the sail. The tackles attached to the D-rings with a snap shackle for easy removal when launching the dinghy.

When we’re off the wind, I pull the boom down with the tackle, from the cockpit. This isn’t as effective as a jibe preventer as a line from the end of the boom up to the bow, but it does stop the boom from slamming across to the leward rigging. In the case of the rare uncontrolled jibe, the sail backs but the boom doesn’t swing much past fore and aft.

In addition to flattening the mainsail and reducing sail twist, the stabilized boom reduces chafe on the sail. On the recommendation of our sailmaker (Shatthauer), I put sail mending tape on the seams where they met the rigging. After some use, you can see where the rigging leaves marks the sail. Of course each reef had it’s own set of tape.

When we’re running downwind on a broad reach, I let the boom all the way out, and it’s prevented from contacting the aft lower stay by the figure 8 knot in the mainsheet.

We’ve never been racers and so I admit that this setup may not be the last word for anyone interested in sailing the boat at its fastest. We did break our boom near NZ when a 35-40k front hit us. We were running downwind under the Aries with the seas on our quarter, discussing heaving-to at 2AM, when a BIG sea hit us on our beam and tossed us into the trough on our beam ends. The boom and it’s fully reefed sail were submerged, at about 7k! The boom broke about in the middle. No big surprise. Some folks put a rubber strap between the boom and the tackle–maybe a good idea, although I doubt if it would have saved our boom. After 29 yrs and about 55k miles, we’ve only broken one boom. Yeah, we should have been hove-to.
Dan BCC 59

5

Excellent and thank you, got good stuff going here. Some of this is of course as usual, resolving forces. Then the next thing is simply the convenience of operation and that always gets interesting when the wind gets up. I have purchased the parts for a preventer which I did not have over the summer. However I rather quickly saw the need for either a preventer or a vang or indeed both. Maybe a rubber strap would be useful not just at the vang bail but also at the back end of the boom where the preventer would attach also.

Obviously when one considers where the vang is attached to on the bulwark the mechanical advantage must be much less than the preventer which would go from the end of the boom to the bow. This may be better in that it might prevent a boom fracture. Lots to consider. Of course the simpler we can keep things the better!

6

Stewart,

I use two tackles, one to port and one to starboard. They act as prevent and vang, and are made off to stainless rings that are heavily seized to the lowest toggle on either aft chainplate. The seizing is a weak link on purpose; I’d rather my preventer come lose than have a bent boom or something else. That said, it’s prettty damn strong, and has withstood accidental gybes (not by me…of course :slight_smile:

Photo attached.

~Aaron

IMG_3278.JPG

IMG00372-20101016-1520.jpg

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We have talked about an elastic connector to attach either the vang or the preventer to the boom to try and eliminate fracture of the boom issues, what are folks using for this.

8

Stewart,

I think the best thing for what you’re talking about is some form of nylon strop. It can be done all sorts of ways, but the key is getting it to be very stretchy.

For this I took a 5’ long piece of 3/4" 3-strand nylon and spliced an eye into an end, then made a whipping at the end of the splice. Then I untwisted the line back to the whipping and braided (rather than twisted) the three strands back together, finishing by making an eye splice into the braid at the other end.

If in conditions that justify it, I’ll pilgrims hitch the braided eye to the boom’s bail, then clip the two vangs to the twisted eye. It’s a LOT stronger than any bungy, and this lizard-style thing stretches about 40% and is about 30" long. The braid induces a lot of recoil in the line.

I have made a bunch of these things for use around the boat, but with only one eye. They’re especially good sucks up and holds on itself. Good for positioning a genoa car, or moving a halyard or sheet from a winch, etc. I also use them for sail gaskets - tuck the bitter end through the eye and make a single slippery hitch - works great!

Cheers,
Aaron

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Aloha BCC Sailors,

Boy o boy, do I love a BCC as she knows how to she. Ask Brion Toss if you want to know about a boom vang and a traveler and the preventor. He says he loves the BCC best of all. Me too.

In selling 58 BCCs, we’ve seen exactly one with a vang. To my mind the boom is so long and the mainsail so big that the normal style vang will be challenged. The BCC has no traveler save for the “natural” traveler afforded by the double end mainsheet. She is brilliant in design. Ask Brion Toss.

To flatten the sail when going hard to weather a block and tackle to the bulwark amidship can is useful and can add some degrees to windward, which does what you want the vang to do.

And finally, regarding the preventer…the only good way to do this is from boom end to and thru the bow chock and back to the cockpit. You have ultimate control and can let go from the cockpit in emergency. The boom can raise if it needs to. It is safe and effective. We have done it this way on every BBC and have transferred the practice to every boat we sail. It works and is safe. Stretchy line is good!

Mahalo,
Kate