Position of boom vang cam

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Re: Position of boom vang cam

Postby DigitalMechanic » Mon Apr 29, 2019 1:47 pm

On the location of the cleat... (If racing) You would also want to avoid the boat responding to your motion negatively when using/reaching for the vang. It's location at the centerboard trunk allows you to keep the vang sheet with you (in lap). You should not have to move to adjust it (avoiding disrupting boat balance).
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Re: Position of boom vang cam

Postby GreenLake » Mon Apr 29, 2019 2:06 pm

Thanks for the explanation. Thistle must be a bit more responsive than a DS from your description and I certainly don't aspire to race at that level.

I've been doing a more modest job of using the vang to generally flatten the main in windier conditions, so easing the main becomes more effective in a gust. (Without the boom rising when the sheet is eased, you don't get the sail to power up when you ease the sheet, because it remains flat).

On a recent afternoon I was out by myself and had to go upwind across a windier section on our lake, where it was blowing a little harder than I normally like for cruising solo. As I was not racing, I just put on the vang, let the main out to where it just didn't flog, and sailed effectively with the jib (just enough contribution from the main to keep the helm neutral). Didn't even have to hike out. Before I had the vang, I might have put a reef in the sail, but that's not as quick to reverse when you sail into a wind shadow.

I'll have to make sure I'm not overusing the vang when not needed. Boat didn't come with one and it took me a while to get around installing one, so everything's far from second nature yet.
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Re: Position of boom vang cam

Postby DigitalMechanic » Mon Apr 29, 2019 5:10 pm

GreenLake wrote:Thanks for the explanation. Thistle must be a bit more responsive than a DS from your description and I certainly don't aspire to race at that level.


Yep, it is a pretty athletic boat, and mean too. I always get a bunch bites on my shins.

GreenLake wrote:On a recent afternoon I was out by myself and had to go upwind across a windier section on our lake, where it was blowing a little harder than I normally like for cruising solo. As I was not racing, I just put on the vang, let the main out to where it just didn't flog, and sailed effectively with the jib (just enough contribution from the main to keep the helm neutral). Didn't even have to hike out. Before I had the vang, I might have put a reef in the sail, but that's not as quick to reverse when you sail into a wind shadow.


That's probably the right attitude to have for cruise (which is what this boat was originally designed for). Granted the sails and rigging will support it, I definitely try and avoid pulling canvas. If you have the controls you will be surprised at how much wind you can actually deal with before pulling sail. The DS's controls are somewhat modest in this regard (No real adjustable cunningham, adjustable backstay, jib cars, etc), but is was not designed to be convoluted, it is "simple and fun". The racing guys have added some of these types of controls, more specifically the ones that attribute to upwind performance (races around the bouys only deal with 2 points of sail) and that comes at an expense, which some may or may not be interested in taking on (and may or may not really use). If your not racing windward/leeward, then why spend the money to sail so close to the wind, right?

What you did on the lake that day was make it where you could deal with a little more wind by (probably over) tightening the vang (made the sail flatter so it capture less of the overall wind). The more powerful it is, the more you will be able to flatten the sail shape, or reduce it's camber. You also are changing the twist in the sail (closing the leech), so it's kind of a double control (kinda of like an adjustable jib/genny car for the foresail). Then at the same time you essentially luffed the boat up by letting the main out (the tell tails surely would have been asking you to head down). That is essentially downshifting using the sail instead of the tiller :wink:

A neutral helm is good. A boat on her feet is always funner that one that is out of control. If it were just me on the boat in the same situation, I would have probably played the same cards :D My ambitions are ussually based on what crew I have (or don't have).

For upwind work on a boat without a traveler (such as the DS), a little vang can be used to keep the leech closed when easing the main in the puffs.
No vang = twist (slower, spilling wind, starting gear)
Closed leech (no twist) = power, as boat speed increases, bring mainsheet into full trim (closes leech because sail is being pulled directly down). Snug up vang. This will keep the leech closed when you ease the main in the puffs.
More vang = flatter sail, which I believe is a function of the change in shape to the luff (curve of mast from boom being pressed into it), will go into depower mode more and more as vang is continuously applied.

GreenLake wrote:I'll have to make sure I'm not overusing the vang when not needed. Boat didn't come with one and it took me a while to get around installing one, so everything's far from second nature yet.


What did you install? Play around with tension on it next time your out. Look at the sail and see if you can notice a change in shape as you pull it on. The twist part should be noticeable (Watch the top of the sail/roach close up, batten come in), but if its not reducing camber, then your vang may not be powerful enough, or your sails may not be in good enough condition anymore to take advantage of the the vangs full adjustment (blown out sail).
Last edited by DigitalMechanic on Mon Apr 29, 2019 10:45 pm, edited 6 times in total.
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Re: Position of boom vang cam

Postby DigitalMechanic » Mon Apr 29, 2019 9:10 pm

Just thinking out loud here as well, not necessarily related to the DS... but on a racing rig, you will tend to see laminate sails used. This is because they do not loose their shape like dacron does over time (and they deal with radial patterns well due to the warp direction of the cloths, but that is another subject). Point is that there is a lot of tension that is put on the sails and the rig by the various "racing like" controls. I have ripped an older dacron sail before trying to shape it beyond what it could handle. Frank the tank... :oops:

Just relating back to what you were saying earlier, I wanted to get the boat flat and in control but could not shape the sail to do so, and was too stubborn to shorten the canvas. The end result of that stubbornness was the immediate need for a new sail... $$$

It is probably not a problem on the DS though, as the sails are pretty small (Dacron is probably more than adequate even for racing), and knowing how the DS is generally rigged, you probably are not pulling the sail a bunch of other directions (Halyard, cunningham, outhaul) while underway.

On the mainsail...

Halyard - Draft position top of sail
Cunningham - Draft position bottom of sail
Outhaul - Draft depth foot of sail
Vang - Draft depth of sail (above foot) / twist (which is technically angle of attack)
Mainsheet - Angle of attack
Traveler - Angle of attack (no real tension here from adjustments)

The only controls I use underway on my DS from that list are the mainsheet and the vang. The rest are either non existent (Cunningham, traveler), or set and forget at beginning of sail (Halyard, Outhaul). Well, maybe adjust Outhaul as breeze builds, but it is one-off and difficult. I have to luff the boat up to adjust mine.
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Re: Position of boom vang cam

Postby DigitalMechanic » Tue Apr 30, 2019 7:57 am

So, a different way I was thinking of to explain the trim exercise I mentioned earlier (keeping leech of the main closed on a beat)...

On other boats you have a functional traveler, so the vang is less important (close the leech and be done). Think about what the traveler does (upwind).

It changes the angle of attack without changing the shape of the sail. Upwind and in a puff, you just drop the traveler and you are ussually good (boat will come back onto her feet).

The vang is the dingy sailor's traveller when going upwind. If you have it snugged up, when you let the main out, it will keep the boom flat (not let it rise), and leech closed. Essentially it will keep sail shape from changing as the boom goes out, just like dropping the traveler does.

If you do not have the vang snugged up, when you ease the main going upwind, the boom goes out and up, and when it goes up you introduce twist which will spill even more wind. Something to play around with. So you depower horizontally first (with mainsheet, spilling less power). Then you have 2 options... adjust vertically (by easing the vang if need be to add twist) or put more vang on (keeps leech closed but flattens sail).

On a separate note, too much vang in heavy wind can cause damage to the boom or mast. If you have it hammered on don't forget to ease it before you head back downwind :shock:
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Re: Position of boom vang cam

Postby tomodda » Tue Apr 30, 2019 3:31 pm

Digital Mechanic:

Thank you for the succinct explanations. I'm still new to the DS, I'm a keelboater (last boat was an old IOR quarter-tonner) and grew up on catamarans.. always had a traveller. so, still wrapping my head around using the vang/kicker for anything other than keeping the boom down at deep angles off the wind. My first sail of this season was a chance to try out your techniques - aggressively and smartly use the vang upwind. It was an eye-opener, thank you!

Just background (again) of where I'm coming from, my quarter-tonner was extremely foresail-driven.. the main was a blade, more of a "trim-tab" blade the 110% jib than the principal driver. So I'd use the traveller to balance out the rig and the helm (neutral helm or slight weather) then steer with the foresheet. Trying to bring that mindset to the DS, I used the vang to balance the helm (and make my mains'l twist look "right"). Then I steered with my butt :) ... sliding back and forth on the rail changed the CLR enough to steer me. Is that the right way to sail the vang on the DS or am I wasting pressure on the main? Was trying to keep as flat at possible too.. I'm 6'1" tall, 260lbs, so I'm not hiking out just leaning back a bit. Anyway, your thoughts, tips, tricks are much appreciated!

Tom
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Re: Position of boom vang cam

Postby GreenLake » Tue Apr 30, 2019 3:38 pm

Well, that's a lot to digest here.

I have a 12:1 vang and still-new sails.
The vang can be adjusted under way, but isn't set up to be "played".
I do adjust outhaul for major changes in wind conditions. (If I don't forget).
I have a Cunningham, which I tend to set once. (Take out wrinkles after I get out on the water).

While I "race" the boat, the course is a fixed triangle, so it's anything but windward/leeward. Combined with local conditions, you can get all points of sail, sometimes in interesting combinations (like the day all three legs were upwind). In principle, that means that I should work on getting the best boat speeds in all points of sail. For the vang, it means that I may need to understand if its use changes (and if so how) between close and broad reaches. . .

(If I haven't shared that in an earlier post, I have pictures of my setup in my personal album in the gallery).

Season is starting again, so I will have many chances to practice.
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Re: Position of boom vang cam

Postby DigitalMechanic » Tue Apr 30, 2019 5:21 pm

GreenLake wrote:Well, that's a lot to digest here.

I have a 12:1 vang and still-new sails.
The vang can be adjusted under way, but isn't set up to be "played".
I do adjust outhaul for major changes in wind conditions. (If I don't forget).
I have a Cunningham, which I tend to set once. (Take out wrinkles after I get out on the water).

While I "race" the boat, the course is a fixed triangle, so it's anything but windward/leeward. Combined with local conditions, you can get all points of sail, sometimes in interesting combinations (like the day all three legs were upwind). In principle, that means that I should work on getting the best boat speeds in all points of sail. For the vang, it means that I may need to understand if its use changes (and if so how) between close and broad reaches. . .

(If I haven't shared that in an earlier post, I have pictures of my setup in my personal album in the gallery).

Season is starting again, so I will have many chances to practice.


12:1 is plenty, and if your sails still have good shape then you should be good to go. Off the wind or downwind, I really only ever use the vang for it's traditional purpose. Keep the boom down.

What I was mentioning earlier is really a close hauled technique where the boom is at centerline while sailing close to the wind. If you ease the sheet (close hauled) you are spilling wind on the angle of attack as the boom goes out (horizontally), and also spilling wind when the boom goes up (vertically) due to the twist you create. The idea of this is to keep the boom from going up, and only going out (like dropping the traveller would do). Reducing the spills to 1 instead of 2 (if that makes since). A more subtle sheet easing...

Once over powered (easing is not quite getting you there) if the boom is already snugged up (boom is already all the way down), you can quickly depower by over tightening the vang to flatten the sail. You can only pull the boom so far down, and after that point it becomes a "sail flattener".

Vang loose - open leech, twist is open, spilling wind, depowering (starting gear)
Vang snug - closed leach, twist is closed, capturing wind, power
Vang beyond that - Boom is already as far down as it can go, leech is still closed, but we are starting to depower by flattening the sail more and more as more vang is applied (the luff of the sail is getting more and more curved from the bend in the mast exaggerating as more vang is put on, which continues to flatten the sail as more is applied).

Note - If you had an adjustable backstay you would probably reach for that before "over-vanging". It is not exactly the same thing, but a mast bender (depowerer) as well. (We are trying to do things with less tools on a smaller boat, over-built vang as a substitute traveller and/or backstay).

You can probably play around with this idea without relocating anything. Go sail and tinker, just remember to loosen that vang back up a little before heading down wind.

I have mentioned triangle courses to the fellas in the past, but have little influence. These guys pretty much do windward/leeward. Reaching is the most relaxing point of sail, and the fastest... but apparently the least interesting.

We have pretty big shifts here at times (90s are not uncommon), but never remember a 360 shift. That had to be interesting. What is the lakes geography like?

The cunningham is to adjust the draft position. Pulling it on will allow you to bring the draft back towards the front of the sail. As power increases the draft can start to go to the aft end of the sail. I am not sure how much influence one would have on the DS (never pay attention to that because I do not have an adjustable one), but we use it on bigger boats. I just tie it down with some line (set and forget).
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Re: Position of boom vang cam

Postby GreenLake » Wed May 01, 2019 1:32 am

Will definitely bookmark this and go tinker, when I get a chance.

Will need to observe again to see how far beyond "snug" I've tended to tighten the vang.

Some part of the season I have expert crew, someone who can call puffs and help evaluate conditions, other times, I have novice crew and then I'm focused simply getting around the course. This particular event has boats of all sizes, and quite a few of them, so sometimes, all you can do is manage traffic.

The lake has three main "openings" for the wind to get in/out, so there is a certain amount of wind bending going on, with the overall wind direction determining which one of the the three dominates which part of the lake. So you get stationary wind shifts (persistent in space) and shifts that change over time. The triangle course we sail has a long and short direction, so a windshift S-E-N or similar, if timed right relative to the race will have you sail upwind. (While the course is fixed, the start line may be somewhat adjusted to conditions. While it may not be a 'fair' race it is more entertaining that way).
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Re: Position of boom vang cam

Postby DigitalMechanic » Wed May 01, 2019 8:22 am

GreenLake wrote:Some part of the season I have expert crew, someone who can call puffs and help evaluate conditions, other times, I have novice crew and then I'm focused simply getting around the course. This particular event has boats of all sizes, and quite a few of them, so sometimes, all you can do is manage traffic.


Having experienced crew is helpful when you are experimenting. I feel you one the traffic scenario. Our annual Mug Race is this weekend. They call it the longest river race in the world (though there are definitely longer races). It is roughly 40 miles. The attendance is ussually over 100 boats, of all sizes and shapes. The start can be pretty interesting. They try and break it up into 2 starts, one for multihulls and another 10 minutes later for monohulls. The idea is that if you start the catamarans first nobody should be able to catch them... but that theory has been proved wrong. We will be using my Catalina 22 for this one, she is my "Flying Piglet"! Will have a crew of 4, but really only need 2. So we will keep the galley and furniture aboard to keep her accommodating :wink: Hopefully we can still stay fast enough to be the first C22 in!
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