Vang Sheeting

[ozskipper]

A lot depends on the rig. Using the vang in heavy winds on a fractional, pushes the lower part of the mast forward and assists in flattening the main in stronger winds. Strong winds, tight lines. Light winds, light lines.
Play your vang around the course By Dave Dellenbaugh

If youre really worried about it though, spread the load points out. I prefer webbing ( like seat belts) as they spread the load over a greater surface area. This will only work with a loose footed main as the webbing needs to wrap around the boom itself.

Having said all that, in 35 years of racing and cruising I have never broken a boom due to a cranked on vang.

[cwyckham]

Originally Posted by svTOTEM

cwychham - Booms should be engineered to take vang loads without problem: some will flex and others not. Excessive flex can mean poor engineering or that a vang was added later and the boom wasn't designed for it.

There are 2 concerns using a vang: 1) not easing in higher winds can lead to excessive heel, knockdown, and losing steerage (because main sail forces overpower the rudder, especially when well heeled and the upper rudder may be out of the water). 2) boom hitting the water, usually when broaching will often enough lead to a broken boom.

If the vang is on tight and your heeling 20 degree or more, it's time to ease it a bit unless there is a skilled vang trimmer. I rarely let the vang off altogether because excessive twist plasters the upper main against the rigging, causing chafe. At that heel it's probably time to reef and then trim with moderate vang -fast, less heel, less load, less chafe.

Thank you, Jamie. That is exactly how I understand it and how I use the vang. I've broached racing large keelboats a few times and we always blew the vang first. When we started getting on the edge, we'd drop somebody off the rail to have their hand on the vang clutch.

As far as the video goes, the main was unreefed in 25G32 knot winds on a small race boat with a spindly boom. They had the main plastered on the shrouds. I'm not sure that the main could have spilled much wind with an eased vang, it would have just wrapped around the spreaders more and maybe broken battens. Seems to me the crew error wasn't using too much vang, it was not reefing.

[FecklessDolphin]

Originally Posted by svTOTEM

FecklessDolphin - The context of Dave Dellenbaugh's article is small boat racing, and has nothing to do with cruising boats. Most cruising boats have 1-1/2" to 3" of prebend, no backstay adjuster, and a stiff mast section so that vang tension has no affect on the mast; and so is irrelevant to how a vang works on cruising boats.

Given that my experience is on small boats with bendy masts I stand corrected but also wonder if this explanation would then suggest that the answer to the OP is that there is not a role for vang sheeting on a cruising boat. If the main does not become more full when releasing the mainsheet while close-hauled without vang on, then just sheet out in a puff, right?

[savoir]

You could ease the traveler to leeward.

[MarkSF]

The boom snapping thing seems to be a problem particular to the J105. I found this at J105.org :

"There have been a few broken booms. These breaks always occur just aft of the vang
attachment fitting. The triangle formed by the tight vang, boom, and mast, makes the
front half of the boom very rigid. When the boom is tacked or jibed a shock load is
applied and the subsequent force is all concentrated on this point.
This problem seems most prevalent when there are large swings of the boom such as
down wind jibes or beam reach tacks like those we normally do before the start. The big
swing coupled with quick motions makes for big stress on the boom.
The best fix is to ease the vang before the start and at the windward mark. When this is
done the main sail is allowed to act as a shock absorber and the point of maximum stress
is moved aft to the main sheet attachment points. We are not aware of any booms that
have broken back there."

Has anyone heard of a vang breaking the boom on a well-built cruising boat under reasonable conditions? Because I can't find any examples on Google. And as another poster pointed out, if you can't use the vang on a beam to broad reach, what's the point of having it at all?

No-one with any seamanship would have allowed the boom to bend like it was in that video before the break.

[svTOTEM]

FecklessDolphine - Correct. In my view, vang sheeting offers nothing on a cruising boat. Start with traveller down (if you have one) as Savior said, and then go to eased sheet if need to depower more.

[roverhi]

Vangs are needed anytime the boom is out to the point that the traveller/mainsheet does not allow enough down force to properly flatten the sail. Letting the boom rise to bag out the sail and dump air is only a temporary move to reduce healing moment till you can reef or the momentary increase in wind velocity passes. If you aren't using the vang when it's needed, you have a poor setting main that has uneeded healing force and reduced driving force. See so many cruising boats with poorly trimmed mains when on a reach or run that a little vang tension would cure. Like, though couldn't fit, the rigid vangs that keep tension on the boom all the time unless loosened for sailing in light air.