Vang Tension?

[Glenn AUS 719]

The mystery of vang tension when sailing down wind poses some questions I hope people may be able to answer.
What is the determining factors that define how much tension you create on the leech with your vang. Are there certain pointers that people look for or is it time on water and trying different tensions when sailing against others. As a new sailor to OK's this is a bit of a mystery and some help would be gratefully appreciated.

[Deleted]

My 2c worth: no mystery, just look at your telltales. You want to set the vang so that they break evenly top to bottom (I take it this is on the reaches).

When it gets really windy (like survival stuff), vang off a bit on the reaches so that the power comes in and out a bit smoother and you can still steer through the waves.

[Village Idiot]

If you pull the vang on quite firmly and begin to ease it, it will reach a point (quite quickly) when the upper leach relaxes enough and the upper luff can be seen to sag fw behind the mast. In other words. If you look at the head of the sail as you ease vang downwind you will see the effective sail plan of the head shrink before your eyes as the sail lurches fw behind the mast.

I try to use as little vang as possible without this happening. You don't want to put unecessary load on the leach/mast but you still want the leach to stand up and provide some resistance against the wind.

This all depends on wind strength and angle sailed but is my own general rule.

[Deleted]

For what it's worth I try to do this.
On the runs I try to set the vang up with just enough tension that the top batten area of the leech opens and closes by itself especially in the light/ moderate. it kind of self pumps if you get it right. In breeze then firm enough to be controllable. Max vang is probably in around 15/18knts. after that it is eased again back from max. 35knts has around the same as 10knts.
On the reaches I tend to use a bit more than most people as with the carbon sticks the idea is to keep the power going into the boat. The masts are stiffer sideways and so here is less lag between puff and speed. I pull it on until the power seems to go and the boat gets dead. then I ease it until it comes alive again but try to keep it quite firm. It is important with this to keep the board well up as well otherwise it doesn't work.
I also constantly adjust the vang. more than a lot of people. you can't set and forget as it changes with each puff. Again on the reaches I use less when it is windy to keep the boom out of the water. On tight reaches I try to get it quite tight but with very little board down. if you sail with a lot of board down then less vang is better to stop the boat tripping over.

[Glenn AUS 719]

Thanks very much guys, I now have more than enough to practice and play around with out on the water. It all makes sense and it will now be just time on the water to develop the feel.