20:1 vang

Moderator: GreenLake

Re: 20:1 vang

Postby TIM WEBB » Mon Oct 14, 2013 9:40 pm

Thanks for all the insight Mike!

1. What I did, after installing sail slugs on the main for ease of hoisting, was to lay the whole rig out on it's side on the lawn: mast, boom, sail and all, fully "rigged". "Hoisted" the main as far "up" as it would go, and cleated off the halyard. Used a block and tackle to pull the boom/tack "down" as far/tight as it would go, then set the gooseneck stop (tube/cleat thingy) a couple of inches below that. When I rig the boat, I cleat off the boom downhaul (gooseneck) to the cleat/tube, and when I raise the main, I know that I have it as far up as it will go, and as tight as I can make it, while having the boom as high (headroom) as possible. Results in the boom being a bit lower than I see in many of the pix in the galleries, and while I have no reason to believe that the luff is too long, I have a feeling my mast might be a bit short (OK, yes, I actually said that! :D )

So, I know that I always have as much tension on the luff as I can get, while having the whole thing as high as possible. When I want to reef the main, I leave the gooseneck where it is, and just bring the head of the sail down accordingly, thus also knowing that I have the reefed main "low" so to speak (minimum "lever arm").

Maybe that's why the use of the Cunningham has never occurred to me: I never have slack, or "speed wrinkles", in the luff to begin with?

Since my main is already on slugs, maybe I'll add another one at or just above the tack grommet, leave the tack pin out, and play around with the Cunningham some more!

2. I rarely mess with the outhaul - usually "set and forget", as tight as it will go. Only in very light air will I ease it, but it only goes 1-2" when I do that. I have no reason to believe that my boom is "short" or my main foot is "long", so is that pretty much the max travel you get?

3. Exactly how is the vang ratio calculated? I'm a dummy at math, and have seen all kinds of numbers thrown around re: this. I'll do my best to describe mine (adapted from a stock Precision 23 vang given to me by a friend): single line leads from the boom down through a block attached to base of mast. This line is attached to this 4:1 vang (as Ronstan calls it): http://www.ronstan.us/marine5/product.a ... RK10-430NC which is in turn attached to the boom right behind the single line. So, do I have an 8:1 vang? Assuming I do, then I am getting nowhere near the power of a 20:1. Can good results ensue anyway?

4. I have mid-boom sheeting, so N/A. Although, self admittedly, I have a tendancy to oversheet ... :oops:

5. I'm usually singlehanded, except when #1 and #2 are along (wife and very young daughter, or vice-versa, depending on the crisis at hand!), and in those conditions, we are just toodling around in very tame conditions, with no real concern for proper anything (yet)! :D

6. I hear ya there! Of late, in any kind of "dicey weather", when I have all other things pretty much set how they need to be for the conditions at hand, I find myself tuning the barbers more than anything else. Of all the improvements I've ever made to the boat, I can honestly say that they have been the cheapest/easiest/most useful ...

7. Oh yeah, we were discussing the Cunningham! At least now I know it's one of the "last ditch" (and I mean ditch!) solutions ... <grin>

Again, thanks Mike for imparting so much of your wisdom to us "peons" - it is greatly appreciated, even tho most of us here will probably never compete at a NACR. 'Course, you may never finish a FL120 or TX200 either! 8)
Tim Webb
1979 DS2 10099 The Red Witch
(I used to be Her "staff", in the way dogs have owners and cats have staff, but alas no longer ... <pout>)
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Re: 20:1 vang

Postby GreenLake » Mon Oct 14, 2013 11:17 pm

Usually, the number of parts immediately gives the ratio. In the picture there are 4 parts, plus the one you pull on. Because that pull is sideways, it's ignored, and you have 4:1. If you were using this block and tackle to lift something and the last part was pulling up (!), then you would have a 5:1, such a purchase would be termed "rove to advantage" but for that to happen the line you are pulling on must come out of a block that moves with the load (and you must be pulling in line).

Now if you had a 5:1 block and tackle you can use it to pull on the line for a 2:1 purchase. That's a "cascade" and gets you 2:1 times 5:1 or 10:1 mechanical advantage. Repeating that trick gets you to 20:1 or (2 * 2 * 5) : 1. If you can't visualize a cascade, google it quickly.

The big advantage of using cascades is that each just adds a single block. The 5:1 is about the max you can do with multiple blocks, triple in that case, so you take advantage of that. Why doesn't one use 16:1 or 32:1 cascades instead? Well, the downside of a cascade is that the travel (from slack to tight) also goes by the same ratio. Giving up 3/4 of the travel is fine for a vang, but 15/16 or 31/32 - there things begin to look a little different.
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Re: 20:1 vang

Postby Mike Gillum » Tue Oct 15, 2013 12:11 am

We all started somewhere?
Racing is where I get my kicks and my wife Mardi will vouch I'm usually racing from the moment I leave the dock heading to the race course and then back to the hoist with actual races in between as icing on the cake as sailboats in my book are only meant to race!
As GreenLake posted a cascading 20:1 Boomvang is achieved using a 5:1 Block & Tackle that's doubled with a 2:1 Purchase and then doubled again with another 2:1 Purchase. Want 16:1 then start with a 4:1 Block & Tackle and cascade with a pair of 2:1 Purchases!
Mechanical advantage can be achieved with rope only but the blocks reduce the friction in the system allowing for quick and efficient adjustment which is critical.
Most all of my rigging ideas are copies of other systems from people like Dave Keran or walking the boatyard with a camera looking at other boats or other classes for ideas.
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Re: 20:1 vang

Postby K.C. Walker » Tue Oct 15, 2013 8:43 am

Tim,

Setting the stop for the sliding gooseneck at the proper length for the luff of the sail and not allowing the boom to get too low makes the boomvang work MUCH better. It really needs a solid pivot point at the gooseneck. I don't usually need cunningham tension until it's time to start depowering.
KC Walker, DS 1 #7002
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Re: 20:1 vang

Postby Mike Gillum » Tue Oct 15, 2013 11:58 am

Tim,
Remove the sliding gooseneck altogether and go to a fixed gooseneck as well as a fixed boomvang bale on the boom.
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Re: 20:1 vang

Postby TIM WEBB » Tue Oct 15, 2013 9:30 pm

Thanks guys! I think I'm safe in assuming that I have an 8:1 vang then (one cascade on a 4:1 vang?). And Mike, sorry, didn't mean to confuse, but the vang attachments on the boom are fixed.

I may as well go to a fixed gooseneck (gooseneck - where the hell did *that* term come from? Hmmm ... don't think I wanna know!), since I never move it up or down anyway. Just not sure how to implement that on the "stock" mast/boom setup I have ... ?

One thing I *did* do after installing the vang was to change the "U-joint" on the gooseneck. The stock U-joint is "open", meaning it's made of some metal formed into a box sort of thing that tends to compress and collapse under the tension of the vang. I had the guys in our machine shop at work fashion a simple block of solid stainless steel with the two opposing holes needed for the joint. This has cut down considerably on the annoying "CLUNK" I used to hear from the gooseneck every time I tacked or gybed with the vang on...
Tim Webb
1979 DS2 10099 The Red Witch
(I used to be Her "staff", in the way dogs have owners and cats have staff, but alas no longer ... <pout>)
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Re: 20:1 vang

Postby GreenLake » Tue Oct 15, 2013 9:49 pm

Gooseneck seems to be chosen based on the flexibility of the natural model...

How do you rig a fixed gooseneck?
~ green ~ lake ~ ~
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Re: 20:1 vang

Postby TIM WEBB » Tue Oct 15, 2013 10:31 pm

GL, there have been pix posted here, but I don't recall if they were pre- or post- "new forum"?

It's essentially a fixed pin with a U-joint, attached to the mast with a plate/rivets/screws, that goes into a hole in the forward end of the boom. Don't know if the hole left over in the stock boom, after removing all the "silly roller reefing bits", would work ... ?
Tim Webb
1979 DS2 10099 The Red Witch
(I used to be Her "staff", in the way dogs have owners and cats have staff, but alas no longer ... <pout>)
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Re: 20:1 vang

Postby GreenLake » Wed Oct 16, 2013 10:30 am

If pix are linked in the old format in a thread, I can fix that, just point me to it.
~ green ~ lake ~ ~
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Re: 20:1 vang

Postby TIM WEBB » Wed Oct 16, 2013 9:39 pm

I think I found it here:

viewtopic.php?f=1&t=3670&p=16036&hilit=fixed+gooseneck#p16036

Is this what we were looking for? Doesn't show the "bidness end" on the front of the boom tho ... ?
Tim Webb
1979 DS2 10099 The Red Witch
(I used to be Her "staff", in the way dogs have owners and cats have staff, but alas no longer ... <pout>)
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Re: 20:1 vang

Postby Mike Gillum » Wed Oct 16, 2013 10:32 pm

Tim,
Photographs from the link would be the gooseneck on DS #2772!
Standard issue Thistle gooseneck from Great Midwest Yacht Company in Sunbury, Ohio and if it can handle the load vang sheeting a Thistle Main then it can easily handle the load vang sheeting a DS Main!
The butt/forward end of the Ballenger Boom on #2772 has an aluminum casting that accepts a 1/2" diameter SS Pin.
The stock Ballenger Gooseneck that came with the tapered Ballenger Mast has the same universal and SS PIn as the GMW Gooseneck but has a 1/2 x 3" Aluminum Bracket that is adequate but I perfer the pair of SS Small Boat Gudgeons.
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Re: 20:1 vang

Postby TIM WEBB » Thu Oct 17, 2013 8:40 pm

Thanks Mike - yeah, I remember now that those were pix of your setup. Very elegant!

I'd be REALLY tempted to go with a fixed gooseneck if it wasn't for the fact that, when at anchor, I like the ability to be able to raise the boom way up high in order to deploy my tent/cot and/or boom tent, or to just allow a bunch more headroom. I leave the main lashed to the boom, shorten the topping lift, slide the gooseneck up, then hold it in place with the jib halyard connected to the tack pin ... 8)
Tim Webb
1979 DS2 10099 The Red Witch
(I used to be Her "staff", in the way dogs have owners and cats have staff, but alas no longer ... <pout>)
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Re: 20:1 vang

Postby Shagbark » Wed May 18, 2016 8:40 pm

I'm wondering how this harken vang would work on the ds? It appears it's only rated for a sa of 125 sq ft. Another concern is that it looks like the lower end it fixed to the mast, not very practical for a boat that is trailered. Anyone have any experience with this vang, or recommend another that provides a greater force than the typical 4:1 that's commonly sold?

http://www.mauriprosailing.com/us/produ ... aQodXWMLsQ
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Re: 20:1 vang

Postby DigitalMechanic » Wed May 18, 2016 11:30 pm

That looks pricey. I used a triple and a double block (5:1) cascaded to a single block (10:1), using some dynema rope, and it bends my mast like a bow and arrow.

http://www.harken.com/productdetail.aspx?id=5332&taxid=411
http://www.harken.com/productdetail.aspx?id=5336&taxid=411
http://www.harken.com/productdetail.aspx?id=5629&taxid=411

If that is not enough, add another http://www.harken.com/productdetail.aspx?id=5629&taxid=411 and make it 20:1.

I added a mini cam cleat on a riser and fairlead to cleat the vang off on the top of the cuddy as well (for connivence).

That dingy vang from harken you posted seems like it is going to ride a bit high as well. Not sure what the reduced angle may mean.

There are other issues (annoyances really) that I ran into once changing my vang. Mainly the vang trying to cross up the halyards when tied off to the cuddy roof. I changed my boat so that they terminate on the mast now. These are the parts that fixed that problem http://www.harken.com/productdetail.aspx?id=39802&taxid=416
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Re: 20:1 vang

Postby Shagbark » Wed May 25, 2016 9:39 pm

Digitalmechanic,

How did you attach the triple block to the mast?
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