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  #21  
Old 01-30-2014
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Re: Is a Vang Really Useful on a mid to Large Boat?

Quote:
Originally Posted by jackdale View Post
I am with Rich, Jeff, Bob, Jon and Ron.
Me too. You don't have to come from solely a racing background to like vangs, especially at jibe time.

And on a dead run without one, you'll have the boom cocked up and the top of the main on an angle that would like to be on a broad reach on the opposite tack. And it will try to get you there, too. Let your attention wander and get a little by the lee, and that little "topsail" will start heeling you to windward, toward what we in dinghies used to call the "death roll" or the "burnout". And that heel to windward will immerse your port side more, and move your Center of Effort to the "wrong" side of the Center of lateral resistance. Presto! you've now got a much bigger case of lee helm you may not be able to cure, and crew (if not clicked in) losing their grip and tumbling to leeward, and a crash jibe at about the same time.
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Re: Is a Vang Really Useful on a mid to Large Boat?

Quote:
Originally Posted by Alex W View Post

The traveler position hasn't made a gross change in sail twist as you travel across the range on the boats that I've sailed on. On my Pearson 28-2 it closes twist slightly at the extreme ends of the range, but typically by the time I'm there I've also switched to using the vang to control leech twist. I have little experience on boats over 30' and perhaps the geometry there does make a bigger difference.
On small monohulls strait travelers are fine, since the distance from the gooseneck to the traveler doesn't change much as the sail is eased. On larger monohulls you start to see the advent of travelers bent to match the arc described by the end of the boom. On large multihulls this gets carried to the extreme, since the traveler can be much longer until you get to maxi tri's like Banque Populaire that have added arches to mount the traveler on (the aft curved beam below).

Note that on BP they don't use a vang, but then the boat is so fast it is never deeper than a reach anyway.
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Re: Is a Vang Really Useful on a mid to Large Boat?

Quote:
Originally Posted by Stumble View Post

Note that on BP they don't use a vang, but then the boat is so fast it is never deeper than a reach anyway.
..and boom end is never outside traveler limits...
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  #24  
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Re: Is a Vang Really Useful on a mid to Large Boat?

again every boat is different...learn and know your boat and it will thank you in return by keeping you safe

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Re: Is a Vang Really Useful on a mid to Large Boat?

Thanks for the posts guys. The last few are especially are very well considered. Jeff_H in particular was the tipping point toward my decision. I've decided to keep the vang because I was never especially thrilled with getting rid of it for the reasons so well put by Jeff, Rich, and Alex. The change that I will make will be twofold:

1. Change the geometry as Jeff suggests. I plan to do some measurements, then work out the trig and verify if the reduction in moment arm is offset by the improved angle. If the numbers support the change, I will rig a temporary attachment point more forward on the boom. But I suspect that Jeff is right.

2. I won't try to apply vang when going up wind. The mainsheet will do that for me. But when off the wind, I will rely on it more.

I will still rig a preventer downwind (for now). I've found that accidental gybes in air up to the mid 30s, result in only a few inches lateral boom movement if the preventer is vertical prior to the gybe and snubbed such that there is no slack. If there is slack, then the loads mount dangerously. I saw those loads that firsthand when we blew a Catalina 30 gooseneck apart on an accidental gybe in 20 knots. So I do respect Jeff's caution and will carefully reevaluate the practice over time.

Thanks guys... good stuff.
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Re: Is a Vang Really Useful on a mid to Large Boat?

With respect, Christian, with the possible exception of the big multis and winged sails, I think any standard rigged boat will benefit from a vang. Hell, I even put a fixed strop vang on my then-6-yr-old son's little sailing dinghy...

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Re: Is a Vang Really Useful on a mid to Large Boat?

Great thread.

Quote:
Originally Posted by Alex W View Post
The vang isn't that useful close hauled. Your mainsheet has more downward force on the boom.
I don't agree. In big air you can dump the mainsheet without having the mainsail power up. Of course you can drop the traveler in a puff also, but that may be either harder to reach or take too long to think of. As seas build you'll want the sail flat even as you ease it out as the angle of close-hauled changes.

Quote:
Originally Posted by JonEisberg View Post
An effective preventer needs to be led from the end of the boom to a point well forward of the mast, in my opinion, and when it's led back to the cockpit, it's an arrangement easily adjusted on any point of sail off the wind...
Exactly. I've run the numbers a bunch of times and there is no substitute on any boat I've sailed for a preventer that runs from the boom end to the bow and back to the cockpit or stern quarter.

Quote:
Originally Posted by Jeff_H View Post
The preferred method of rigging a preventer is to take it forward to a turning block and then back to a quick release in the cockpit. The line should be stretchy enough to absorb an impact should the boom hit the water, but no so stretchy that it will allow the boom to reach within 30-40 degrees of the centerline of the boat.
I strongly disagree with having a stretchy preventer. The loads increase dramatically over a system that holds the boom as steady as possible. You have to look past static loads to dynamic ones.

Quote:
Originally Posted by nolatom View Post
Let your attention wander and get a little by the lee, and that little "topsail" will start heeling you to windward, toward what we in dinghies used to call the "death roll" or the "burnout". And that heel to windward will immerse your port side more, and move your Center of Effort to the "wrong" side of the Center of lateral resistance. Presto! you've now got a much bigger case of lee helm you may not be able to cure, and crew (if not clicked in) losing their grip and tumbling to leeward, and a crash jibe at about the same time.
To quote one of my favorite movies "the big boats get the glory but the small boats make the sailor." I'll take a dinghy sailor on board a delivery in a second. I can teach systems pretty fast. You can't teach the kind of understanding nolatom describes on your way out an inlet.

Quote:
Originally Posted by Sabreman View Post
I've found that accidental gybes in air up to the mid 30s, result in only a few inches lateral boom movement if the preventer is vertical prior to the gybe and snubbed such that there is no slack.
You'll have to help me understand what you describe. You want the preventer as near perpendicular to the boom as you can. Perfect isn't attainable of course but it is much more horizontal than perpendicular, and much more longitudinal than transverse.
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  #28  
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Re: Is a Vang Really Useful on a mid to Large Boat?

Quote:
Originally Posted by Sabreman View Post
Should I ditch the vang and stay with the preventer? This discussion is not about rigid vangs, it's about whether any vang can effectively shape a mid-size main with mid-boom sheeting.
Disclaimer: I didn't read 3 pages of replies.

Short answer: YES

Long answer: You need to move the attachment point on the boom towards the gooseneck. Try to keep the angle of the purchase to around 45*, that will be the most efficient angle. 8:1 might do it, but a 16:1 would probably be better for that size boat. Can you get a better photo? Email it to me and I'll take a closer look.
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Re: Is a Vang Really Useful on a mid to Large Boat?

Quote:
Originally Posted by Sabreman View Post
I have a vang that I hate and consider virtually worthless. I'm considering removing it and am looking for opinions. I get that on a smaller boat, the vang is very useful to shape the main as the wind increases. But on the configuration shown below with the mid-boom sheeting, I wonder if it is of any use...


In addition to what others have already offered, I can assure you that a vang is a necessary safety measure. In the mid 1970’s, while living in San Francisco, we were moored at Ayala Cove for a Thanksgiving Weekend raft up. Some friends with a Cal 25 rafted to us and at one point we all decided to take their boat for a round island cruise. Things went well but it occurred that we were hit by very heavy northeasterly winds as we rounded the southwest side of the island and turned into Raccoon Straight. Beating up-wind was exciting but not too problematic after we doused the jib and started the outboard to give us some extra oomph. Once we finally reached the Cove however, we had to turn down wind to get back to our own boat. Unfortunately the Cal was not equipped with reefing gear so we were dealing with a full main. With the turn we eased the sail out somewhat and with that, took off before the wind like a shot. In addition to heavy wind, there was a lot of wave action pounding into the cove and reflecting back off the cobble stone beach and at one point we were thrown over and the main gybed. With this, the boom lifted sharply and the little vang ripped off the mast. Unrestrained the boom slammed upward and into the back stay where it stuck! It did so because the owner had used a snap hook carabiner clip on his outhaul and that had pressed opened and snapped around the back-stay when the boom hit the stay. With this we were forced around, head to wind by the flogging sail and I had to climb up on the stern pulpit and hang off the back stay with one hand and try to release the outhaul carabiner clip with the other. Fortunately, we were able to finally free the sail (despite stained arms and shaking knees) and then make modest headway to windward, and stay off the beach, but in no small measure because the bluff’s overlooking the cove created something of a pressure bubble that mitigated the wind. Had we not been able to free that sail, we surely would have ended up in the surf at the foot of the bluff. The loss of the boat's vang could easily have been fatal for five...
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Last edited by svHyLyte; 01-30-2014 at 01:13 PM. Reason: correct typo
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Re: Is a Vang Really Useful on a mid to Large Boat?

Quote:
You'll have to help me understand what you describe.
I rig a preventer from the forward-most bail on the boom to a point on our inboard genoa track. The arrangement is similar to what is shown in the first photo in the following link. I don't like the angle in the photo because there isn't much down pull - I'd move the preventer aft to the first mainsheet block and attach the bottom to the outboard genoa track, further aft. That would make the angle more vertical with more down pull.
Avoid Boom Doom: Rigging a Preventer or Boom Brake | Cruising Compass ? The Free Weekly Newsletter for Sailors & Cruisers ? ©2013 Blue Water Sailing

Quote:
Can you get a better photo? Email it to me and I'll take a closer look.
I don't have a great picture, but this one shows the crummy vang angle.
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