Brake Vang!

[William Hogan]

As promised:

https://picasaweb.google.com/wfhogan...eat=directlink

The vang-brake is simply a Black Diamond brand aluminum figure 8 that mountain climbers use for rappelling. It is similar to the Winchard "Gyb'easy", except its smaller, lighter, uses the same attachment point as your present vang, and costs oh, about 20 times less than the other product.

(of course you don't get that cute Winchard logo, or the cleverly named "Gyb'Flex" line to rig it with)

I integrated it with my boom vang with the brake as a result of a flash of insight while I was rigging it:

" Ooooo look how cool it.....DAMMIT!!! Now I have to buy and install another bail on the boom for the vang...No, WAIT! - if I simply clip the vang to the....."

(Being a cheap lazy bastard has its advantages)

Then I scrounged up a couple of 1/4" harken micro blocks I had lying around, and u-bolted them to the forward spreader stay chainplates.

I rigged 30 feet of 3/16" 3 strand nylon line through everything (next time, I'll use 40 feet). and back to a couple of Hershoff cleats I already have on the combings for preveters and such.

The nylon line is cheap, stretchy and abrasion resistant. 3 strand rope seems to have more friction for a given tension than braided, but I'm not positive about that.

Stretchiness is good because it acts as a shock absorber for the dynamic loads of the boom as it stops.

The key to its effectiveness is proper tension on the brake line. Too little, and it does nothing. Too much, and it locks the boom in place acting as a preventer.

Somewhere in the middle is a range of tension that will allow slow, graceful jibes.

The system has a huge safety advantage over a traditional preveter in that it prevents broaches to leeward (the most dangerous type) along with crash gybing. Once enough wind gets behind the main it will come about no matter how much tension you put into the device, but it will come about SLOWLY. This is not the case with a regular preventer. In a leeward broach you have to either cut the line, free it, or wait for it to part, or the boat will stay pinned down by the backwinded main.

This can quickly sink a boat via down flooding through the companionway.

You don't have to switch it in the middle of a gybe either - it is self tending.

I currently use my sheet winch to tension the line, but that's a hassle. I'm going to try rigging a tackle next. If that works, I will no longer need the cleat, and can use padeyes, and permanently rig it to them. Then I'll mark the tail of the tackle at the appropriate tensions I arrive at so its easy to repeat.

Having the vang attached to the underside of the figure 8 works great. They complement each other by pulling from different angles.

Rig one up and play with it. You will be amazed at the difference it makes for controlled downwind sailing.

=)

Belay Devices:
http://tinyurl.com/4nqdbat

Micro Blocks:
http://tinyurl.com/4vyjy9j

3 Strand Nylon Rope:
http://tinyurl.com/49z6uvz

Cheap, eh?

[Brion Toss]

Hello again,
If your are going to reinvent the wheel, you might at least make sure that it is round. Do you know what the max load might be on that preventer? Do you know how that compares with the load on those micro blocks, which approaches twice the load on that line? Did you know that nylon is much more chafe-vulnerable than Dacron, that there is now a significant torque load on your shroud chainplates, that this setup can still, in many circumstances, result in a locked-in-place boom, and that it might not be a good idea to hang two crucial components on the same fitting? And so on. I applaud your innovative spirit, but recommend more thorough field testing and analysis before making recommendations to others.
Fair leads,
Brion Toss

[William Hogan]

Hi Brion -

I must admit I'm a bit taken aback by the vehemence of your response - I was hoping for constructive input, not browbeating. I'm not making recommendations. I'm simply sharing ideas and rigging that works for me in the hopes we can collectively improve the enjoyment and safety of sailing.

That said, here is the engineering data on the hardware I used:

Belay Device:
http://www.amazon.com/Black-Diamond-...ef=pd_sbs_sg_5

Micro blocks:

http://www.harkenstore.com/uniface.u...?409Z56LC3VXJE

1/4" 3 strand nylon:

http://www.westmarine.com/webapp/wcs...4&ci_sku=25499

Belay device rated at 22kN -

I kN = 224 LB and 22x224=4928lbs

SWL of Harken 348 blocks: 330lbs, ultimate strength 1000lbs

Ultimate strength of 1/4 Nylon (3/16 was a misprint) 2000 lbs - SWL therefore equals 200lbs (10% rule)

The blocks and line are well matched, with the SWL of the line well under that of the blocks. I have empirically tested the setup and it needs only direct hand tensioning to function effectively - no purchase - maybe 70 or 80 lbs ...

As far as loading and vectors, I am a licensed Architect with an extensive engineering background, so yes I'm aware that load paths and angles effect actual loading in structures due to leverage and mechanical advantage.

I chose nylon for its elastic properties.

All lines should be regularly inspected for wear and chaffe, including dacron. 3 strand nylon is cheap, elastic, and its structure provides a lot of point loading friction against the aluminum.

Boom vangs are not critical components - I did without one for over a year. My brake sorta is, but the way it's set up, the boom will move slowly rather than overload the line the way a boom end preventer will if the boom and main trip in the water badly enough during a roll or broach.

At that point something is going to give, and I'd rather have micro block flying across deck than a stanchion carrying part of the deck with it.

If the block bail or pin fails, the cheeks and sheathes are still captured by the line. If the line fails....big deal - the boat performs a "normal" (-deadly-) jibe.

You have to duck when jibing no matter what, but I'd rather be hit by a boom moving 2 feet per second than one moving 10 feet per second if I'm distracted by a hot chick or something while jibing.

( You know: F=MA and all that...)

Everything on a boat is a trade off. I've found the additional cost, complexity, and small risk of injury from my setup is more than offset by the boat handling advantages and safety it provides by controlling the boom downwind in challenging conditions.

Here is a video that shows how it works:

http://www.youtube.com/watch?v=GWJRfLGwex8

Booms can and do kill and maim people all the time aboard sailing craft.

Micro blocks?

Not so much.

Rather than give the next guy who posts something you consider dangerous or not well thought out a hard time, why not try to help him? You never know - that guy might have a good idea, have actually thought it out very carefully, and be an expert in a field related to yours.

You might learn something from him, and he from you.

You say "Fair Winds"?

I say "Following Seas"

Bill Hogan

[Brion Toss]

Hi again,
I am sorry if I seemed vehement, but I have seen similar -- very similar -- setups, if on a larger scale, injure and kill people. One of those times was when a block similar to those micro blocks hit somebody in the head (vectors). You might not have thought you were recommending things, but you did urge us to "Rig one up and play with it. You will be amazed at the difference it makes for controlled downwind sailing." Also, it is precisely your credentials that might lead someone to apply your ideas badly. And unfortunately your credentials do not make the turnbuckle foul lead go away, nor the added load and lack of redundancy at the vang connection. And don't get me started on using the word "maybe" to describe a max load. And so on.
I was sincere in saying that I admire your innovative spirit. Perhaps a strong qualifier might precede contributions like this, including component loads and failure consequences.
Fair leads (fair winds are too much to hope for),
Brion Toss

[Brion Toss]

Hello again,
I've been thinking about my previous post for some days now, and wish to apologize for my harshness. It is one thing to try to head off potentially dangerous recommendations, quite another to be unkind while doing so. One of the reasons I keep working this board is the spirit of innovation, generosity, and kindness that pervades it; I do a disservice if I lower the volume on any of those factors.
Fair leads,
Brion Toss

[Ian McColgin]

It seems to me that the use of nylon rope and the claim of broach prevention are problematic at best, and that Brion’s critique was both gentler and more on target than the defensive response.

The choice of nylon line is not really helpful for the vang function. With all that stretch to take out, what you really have is a poor vang. Properly engineered, a vang-preventer will provide adequate braking as the boom transits the boat that it will not require further shock reduction in a stretchy line.

The claim that the vang prevents broaches to leeward is misleading at best. Perhaps the claim is based on misunderstanding the sequence of events.

To back up on this issue a bit, the vang-brake may reduce slightly the turning speed of a boat with the sail aback. The trade-off is that by letting the sail gybe, it completely eliminates the ability of an alert helmsman to get back on course before the sail is so fully aback that it forces the boat around.

Further, even with the sail shifted to the other side without hanging up on the backstay or damaging gear, the boat will often continue rounding up at least to wind abeam and none of this considers what’s happening to the spinnaker.

But all this is about accidental gybes. Language varies but many of us view an accidental gybe and any consequent misadventures as something different from a broach, which is induced by a following sea where the stern essentially falls past the bow. Power boats and human powered powered boats can broach, not just sailboats.

The gybe and broach may or may not be combined. Obviously if your stern is square to the seas, you can err in, and thus broach in, either direction. Only the broach to leeward results in an accidental gybe which, if you get the spinnaker aback into the bargain, may result in the “death roll” - a good time to reflect peacefully on the fact that you secured all hatches, clipped in all crew tethers, and have made your peace with whatever all-mighty you know.

Finally, I don’t think that Brion’s remarks were too tough. Rather, they contained the information about the risks of this vang-preventer that should have been made plain from the start had the developer gone far enough to fully trouble-shoot the rig. In development, a fully potential failure analysis is not always available but the developer should at least be conscious of risks and provide safety thoughts, especially in the case of gizmos that may work on a boat of a ton or so and sail under 100 feet versus a 6 ton boat with four or five hundred feet of main. This exact vang-preventer is considerably safer than things rather like it that one can easily make from these directions but the developer does not provide information showing these risks to the imitators he seeks.

There are some pretty over-engineered over-priced goofy bits of “innovative” hardware out there and the efforts of all who look at problems with not only fresh eyes but also with a zest for using ordinary, available and cost-effective materials in their novel solutions are to be encouraged, sometimes with a splash of cold water about safety but still encouraged.

G'luck