When not to use the boom vang?

[Kings Gambit]

If you read Peter Nielsen (September 2017 Sail p. 56) you find: "On boats equipped with mainsheet travellers, the vang is not used when going to windward because the mainsheet applies sufficient tension to the mainsail leech..." He goes on to say, however, that when sailing to windward in the absence of a traveller: "... it [vang] must be used to keep the leech tensioned when the mainsail is eased in gusts." It's hard to imagine how the vang on my boat (Rodkicker) could do much more to affect sail trim going to weather with the traveler raised to windward, the mainsheet properly sheeted, and the mainsail leech lines properly tensioned. Are we saying that easing the vang in that trim configuration and point of sail will ease the heeling force on a 38-ft boat?

It appears by Neilsen's article that the vang and the traveller have related functions. When there is no traveller, one eases the mainsheet in gusts and the vang controls leech tension; when there is a traveller it is eased in gusts and the mainsheet controls leech tension; consequently, there is no important role for the vang in that configuration sailing to weather--i.e., when there is a mainsheet traveller.

 

[Scott T-Bird]

Sometimes, I find that my soft vang doesn't give me enough mechanical advantage to get as flat as I like, so I just pull down the back of the boom by hand while a crewmate tightens the vang.

There you have it ... this highlights how inefficient the set-up of a vang really is. A simple, hand applied force at the end of the boom does the trick, where tugging on a line that is working against you doesn't really fill the purpose.

 

[Kings Gambit]

See this from the Cal-20 Racing guide published by Ulman sails (emphasis mine).

Upwind Mainsail Trim Mainsheet & Boom Vang

The mainsheet and boom vang are the primary sail controls on the Cal 20 since the boat does not have a traveler. In most conditions, trim the mainsail so the top telltale is slightly stalled. If you feel slow, need acceleration, or the wind is very light, ease the sheet to keep the telltale flying. In light air, do not use any boom vang tension. As the wind increases, tighten the vang to control the leech. When it is windy enough to heel the boat 15 degrees or more, use enough boom vang tension and ease the mainsheet to keep the boat flatter than 15 degrees of heel.

 

[dziedzicmj]

As boat size (mainsail area) increases the soft vang becomes less & less efficient

How is it possible that a soft vang is less or more efficient than the rigid one? The only difference is that the rigid vang not only pulls the boom down (in exactly the same way as a soft vang does), but also pushes it up (which a soft vang cannot do). But we are talking about a situation where the sail is filled with air, so the question of pushing the boom up does not apply (as the sail pulls the boom already).

Additionally, if you really want to raise the boom and have no rigid vang, you more than likely have a topping lift that could be used for the same effect.

 

[Don Guillette]

For your original question: Ease the vang to de-power as you said. I don't understand why you said a rigid vang can depower more than a soft vang. If anything the opposite is true.
No, it's not the opposite. With a soft vang, the boom is sitting almost horizontal or lower and is held in that position by the mainsail so, as I stated, the only way it can pull is down to take out the twist the sailmaker built into the sail. When a rigid vang is installed the boom is set at 10* above horizontal so in addition to the built in twist you're getting a bit more twist to play with.

Here's how I could used the Garhauer ridig vang on my C30 in a cruising situation closehauled in say 8 knots of wind. I've got the sail leech as flat as possible with the vang cranked down tight to harness all the power I can get. Say the wind started to pick up a couple of knots -- I've got a couple of options. I could drop the traveler a bit to keep the boat on it's feet. I like using the traveler because it's use doesn't effect the set of the sail. I could also ease the vang and spill power off the top of the sail. That works to a point and then I have to take other actions to keep the boat on it's feet. With a masthead rig, I also have to deal with the jib, which is the engine of the boat. In any event, there are many ways to use all the sail trim controls on a boat and a sailor should fool around with them to find out what works for them. If a sailor doesn't think a particular sail trim control works for them then he shouldn't use it. For example, Garhauer gave me one of their fanciest backstay adjuster. I never used it - it looked trick, like fancy hubcaps!!

I wish I could explain things more scientifically instead of the simple way I explain stuff which many times makes it hard for me to explain a point. That's where other folks like Scott, Joe from San Diego, jackdaw, Stu J and others can chime in to help me out. It doesn't matter whether they agree with me or not. If they don't agree they explain where I'm off base. The whole idea of this forum is to get to the exact truth concerning sail trim. To me, that's the problem with some of the other sites here - with some of the opinions expressed, I have no idea what in the hell they're talking about.

 

[Head Sail]

Use the rigid vang to bring the boom down or raise the boom up. Pretty simple. Use as desired under sail for the desired affect. As dziedzicmj said, it eliminates the need for a topping lift which frees up a sheave on the masthead.

 

[Ross S]

Gotcha about the rigid vang giving more twist to play with. In light winds, when I need more twist, I simulate the effect with my topping lift.

I've thought about getting a Boomkicker or Garhauer rigid vang, but have not been able to justify it to myself.

 

[Don Guillette]

Ross; I don't think a rigid vang is justified on a boat less than 27'.
Regarding sailing in light winds -- next time you're in that situation try sailing with the sail as flat as possible with zero twist & belly. Here's why -- the light winds have a tough time getting around even a flat sail. When you induce belly or twist, in my opinion, you're just making the situation worse. Try the flat sail the next time and see if it works for you.

 

[Ross S]

Ross; I don't think a rigid vang is justified on a boat less than 27'.
Regarding sailing in light winds -- next time you're in that situation try sailing with the sail as flat as possible with zero twist & belly. Here's why -- the light winds have a tough time getting around even a flat sail. When you induce belly or twist, in my opinion, you're just making the situation worse. Try the flat sail the next time and see if it works for you.

Agreed. The sail goes where the telltales tell me!

Next time I'm bobbing around in the very light stuff, I'll give it a shot.

 

[LeeandRick]

I guess on a boat with a stiff mast all of the above may be true with a vang but don't tell a dingy sailor this. The quickest way to de-power the mainsail upwind is to tighten the vang. I learned this from Julian Bethwaite sailing 18s and there other designs. Flame suit on, but think about your response before hitting the button. Yes I know the OP has a Cal 21.

 

[Ross S]

I guess on a boat with a stiff mast all of the above may be true with a vang but don't tell a dingy sailor this. The quickest way to de-power the mainsail upwind is to tighten the vang. I learned this from Julian Bethwaite sailing 18s and there other designs. Flame suit on, but think about your response before hitting the button. Yes I know the OP has a Cal 21.

On a dinghy the vang bends the mast significantly, thus flattening the maintain and depowering the rig.

The effect is similar to using an adjustable backstay on a larger, fractionally rigged boat.

 

[JRacer]

Yes, to a lesser degree, it did the same on the J24. But backstay and upper/lower shroud tension was more relevant to mast bend on that rig.

 

[Jackdaw]

On a keelboat, upwind is vang off, if:
The boat has a decent traveler,
You are not vang sheeting in bigger breeze

This is because the traveler is controlling AOA and the sheet controls twist. Having the vang on might limit the mainsheet’s ability to twist off, essentially starting to vang sheet.

If you are racing, this is doubly important, because 1) having the vang on can prevent the boat from ducking quickly, and 2) big ease of the main at the windward mark with the vang on is a great way to snap your boom.

 

[JRacer]

Yep!

 

[Scott T-Bird]

On a keelboat, upwind is vang off, ... because 1) having the vang on can prevent the boat from ducking quickly, and 2) big ease of the main at the windward mark with the vang on is a great way to snap your boom.

Well that pretty much answers the question raised in the original post! But are these issues really a concern for the typical sailor? I can't imagine a situation where my boom would snap because the vang was left on.

 

[Jackdaw]

Well that pretty much answers the question raised in the original post! But are these issues really a concern for the typical sailor? I can't imagine a situation where my boom would snap because the vang was left on.

They sure can, they just happen a lot more to racers.

The first can happen anytime you have a late port/starboard situation, either on port you see the other boat late or or starboard you have to take action. Ducking is almost always the best choice, but that can be impossible if the main is not fully eased.

The second can happen any time you turn quickly from beating to a deep reach or run in breeze. When not racing this can happen at the top of an island or at a government mark when you make a big direction change.

But the point is still the same. Vang off when going upwind.

 

[Scott T-Bird]

I guess on a boat with a stiff mast all of the above may be true with a vang but don't tell a dingy sailor this. The quickest way to de-power the mainsail upwind is to tighten the vang. I learned this from Julian Bethwaite sailing 18s and there other designs. Flame suit on, but think about your response before hitting the button. Yes I know the OP has a Cal 21.

Well, it is funny that you mention this. The mast bend is what opens the leech and depowers the sail. I used to do this with my windsurfing rig, except that I did it with the downhaul line. With the typical mast of a keel boat, we tighten the vang to close the leech, not open it. So it begs the question, on a racing dinghy, is the purpose of the vang to bend the mast and open the leech, or is it to draw the boom down and close the leech? I'm confused, because it seems like conflicting reactions. This is part of the reason why the geometry of the vang just seems (to me anyway ) like a very inefficient means of sail trim/control.

 

[LeeandRick]

With the typical mast of a keel boat, we tighten the vang to close the leech, not open it. So it begs the question, on a racing dinghy, is the purpose of the vang to bend the mast and open the leech, or is it to draw the boom down and close the leech? I'm confused, because it seems like conflicting reactions. This is part of the reason why the geometry of the vang just seems (to me anyway ) like a very inefficient means of sail trim/control.

On the dinghies I've raced the vang with just enough tension controls the leech tension as with all sailboats. When you over tension, it will bend the mast and hook the leech to windward and the leech tension will bend the top of the mast. ( head stay about 3/4 up the mast carbon mast top). This flattens the sail to board straight. For entertainment think about what a reverse vang does to sail shape. I'm with you on the efficiency of a vang. You could install a curved track on the cabin and pull straight down. Or better yet buy a trimaran with an arcing traveler that covers the full range of the boom and no vang required. When I see these travelers I wonder how the car is controlled on such a large arc. All of this traveler talk made me decide to breakdown and add one to the O'Day next week.

 

[Jackdaw]

I'm with you on the efficiency of a vang. You could install a curved track on the cabin and pull straight down.

Interesting you should say that... one of the very first boats with a 'vang' (the Olympic-class STAR) uses a curved track for the vang.

 

[walt]

Great thread, Ive enjoyed reading this, lots of folks giving advice whos opinions are very respected!!! FYI, Ive learned a bunch from Rick (LeeandRick) about vangs etc sailing at Lake Havasu during the winter (where we are headed in about a month). Rick, adding a traveler.. Im somewhat headed the "other way" now thinking about adding a 140 watt solar panel and an isotherm cooling system to my home made ice chest.. Must be getting old as sustainable cold beer on those boat trips is whats getting to be more important. Anyhow, back to vangs and travelers and going fast!!!!