Vang Tension

Stu Jackson · Jun 24, 2009

Vang parts

It'd help if you explained the tackle and purchase you have on your vang. It's always easier to vang when the mainsheet is tight. That brings the boom down anyway. When running it's easy to use the vang even with the mainsheet out. Not being able to Pop it when reaching is strange, you should be able to get it out of its cam cleat relatively easily. I've never used a winch on a vang in over 30 years - C22, C25 and C34.

Don Guillette · Jun 25, 2009

Josh: Have you though about a Garhauer Rigid Vang?

The primary use for the vang is to control twist. Its secondary function is one of the controls for draft position. When you ease the boom out, without a vang, the boom wants to rise and you don't want that to happen. There is only so far that you pull the boom down and that is once the sail becomes flat that is as far as you can go. You really don't have to exert a lot of force on the soft vang for that to happen.

Next time your out, with the boom centered, grab the end of the boom and pull down on it and you'll see what I'm talking about. Also push up on the boom and watch the top of the sail open up or twist off.

4:1 should be plenty but you'd really like the Garhauer rigid Vang.

tsmwebb · Jun 25, 2009

joshw5144 said:
Hi All,
I have been playing with the boom vang ...I tighten as much as possible before easing the boom out. Is it possible to get it tight enough this way or should I look at lenthening the line to reach a winch? When I tighten it the main is centered with me under it so I cannot really see the effect it has. Also if I try to ease it while reaching it is near impossible. So basically, is a vang without winch power kind of useless? Or is putting a vang on a winch ridiculous because if I need that much power something is wrong?

4:1 is not a lot of purchase -- 8:1 would be better and you could do that with only one more block. Putting it on a winch isn't unheard of but you can damage your sail or even break your boom if you really haul on the vang. It is not good that you can't release the vang while under load. Not being able to release the vang in overpowered conditions can result in uncontrolled rounding up.

For cruising in most conditions 4:1 should be adequate and safe. If you are on a reach it may be quicker and easier to dump the main by easing the sheet or rounding up so you can get more vang on rather than attempting to grind out all the twist with your sheet.

Do you know if you have too much or too little vang tension? It really helps to have leach telltails on the main. You'll be mostly concerned with the top one or two tails. If you have too much vang the the top tails will stall when the lower tails are flying and if you have too little the top tails will flow earlier than the lower tails. As Don notes there is also some effect on draft and section shape. Absent telltails, if the top batten is parallel or a little to leeward of the boom then your vang tension is about right. I've attached a cartoon in the hopes that my art will be clearer than my prose.

--Tom.

Dick Westwood · Jul 1, 2009

another vote for the Garhauer rigid

Love mine!!!

Being rigid, it also works like a boomkicker - ie no need for a topping lift.

Geoff K · Jul 19, 2009

Why rigid?

Does the rigid vang add anything to sail trim or is its only advantage to replace the topping lift? I have a Garhauer rigid vang, new this year. It is my first experience with a vang of any type. I've not learned how to use a vang yet.

I miss my topping lift. The vang spring no where near able to hold my weight and when using the boom for support while moving around the cockpit the boom is a very unstable support. It's gets a bit treacherous when securing the lowered main in rough seas. Now the boom not only goes back and forth, but up and down as well. When tightening the main to prevent the boom from swinging at dock it will hold tight enough only if the vang spring is completely compressed. This makes the boom low enough to be in the way and knock noggins. (So far not hard enough to knock some sense into this one.) The boat is a Pearson 323 which has a low boom anyway.

I think I'll reinstall a topping lift. I don't think I like my vang. But I'm new at this. Perhaps you folks can clue me in to what I should and should not expect of the rigid vang.

Geoff

Alan · Jul 19, 2009

Geoff,
First let me say you need to buy Don Guillette's 'Sail Trim' guide from the Chandlery on this site. It will explain in some detail how and why a vang is a necessary sail control.
Solid vangs do eliminate the need for a topping lift, among other things. Your vang should be completely un-tensioned when the main is stowed. Use the main halyard to relieve the vang of any load and the main sheet to counter the halyard. I also use a removable three part tackle as a third loading point which holds the boom completely rigid.
As for the vang as a sail control, it controls twist and draft location in the main. On a reach or run the vang becomes the primary sheet control of the main leaving the main sheet for controlling angle of attack. Solid vangs are generally much more powerful than ordinary rope vangs which makes adjustments much easier.

tsmwebb · Jul 19, 2009

Geoff K said:
...
I miss my topping lift. The vang spring no where near able to hold my weight and when using the boom for support while moving around the cockpit the boom is a very unstable support. ...

When the main is down you can use the main halyard as a topping lift. It supports the boom and keeps the halyard from slapping on the mast.

--Tom.

Geoff K · Jul 20, 2009

Why more powerful?

Thanks. That clears up a lot. The halyard as a topping lift is obvious, but I hadn't seen the obvious.

Why would a rigid vang be more powerful? The downward force is still a block and tackle system. The upward force is a spring? Is the upward force ever needed for sail control?

Geoff

Alan · Jul 20, 2009

Geoff,

Most rope vangs are usually 3 or 4 to 1. My rigid vang is 8 to 1. You could build a rope vang with this same power. But the removal of the useless topping lift is an advantage gained with a solid vang also.
The topping lift is not a sail control though some skippers think they need it to induce twist in the leech in light air. In very light air twisting off the leech is detrimental to sailing performance. In very light conditions a flat main keeps the flow attached to the sail far better than a twisted off main.

tsmwebb · Jul 20, 2009

Geoff K said:
...
Why would a rigid vang be more powerful? The downward force is still a block and tackle system. The upward force is a spring? Is the upward force ever needed for sail control?
...

You're correct, the solid vang isn't any more powerful than a soft vang with the same purchase.

The upward force from the spring can be useful for sail shaping if you are sailing in very light wind or have a very heavy boom. At some point as the wind drops the weight of the boom will pull down on the leach closing it too much. You'll see the upper telltails stalling while the lowers are working. The first thing is to move the traveler to windward so the sheet loads aren't closing the leach but in really light winds that may not solve the problem. In that case the spring can push the boom up so that you get proper twist.

--Tom.

tsmwebb · Jul 20, 2009

Alan said:
...
The topping lift is not a sail control though some skippers think they need it to induce twist in the leech in light air. In very light air twisting off the leech is detrimental to sailing performance. In very light conditions a flat main keeps the flow attached to the sail far better than a twisted off main.

IMO, this isn't a "one size fits all" kind of thing. Particularly in light airs there can be dramatic differences in the apparent wind speed and angle between the top and bottom of the mast. But sometimes not so much. Twist needs to be adjusted so that the the angle of attack of the sail is correct at every height for the conditions one is experiencing. On some boats in some conditions the weight of the boom alone pulls to much twist out of the sail. Since we can't see the wind the best way to understand how much twist you need in any given situation is to have a complete set of telltails.

Section depth is a different issue and you're right that in very light air you need flatter sections to keep the flow attached. But, too much leach tension isn't going to help you with that...

--Tom.

Geoff K · Jul 20, 2009

Thanks

I guess I'll keep the vang. I have Guillette's book and chart on my wish list.

Thanks much for the help you've given.

Geoff

Vang Tension

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