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Old 09-06-2022, 02:36   #1
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Why don't catamarans have boom vangs?

Does any know why cruising catamarans don't have boom vangs? Coming from a dinghy racing background I can't imagine trying to sail without one, it's a vital part of sail control, particularly for safety downwind. You can approximate its actions using a traveler, but that seems a big, heavy, complicated and unwieldy method of ultimately getting less sail control...

In order to keep the boom low over the coach roof you would need to use an above boom method like the 49er. The other advantage to this is that almost all of the leverage is in the swing arm and so you don't even need many blocks. Light, simple, really easy to fix if something breaks, what's not to like?

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Old 09-06-2022, 02:52   #2
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Re: Why don't catamarans have boom vangs?

Perhaps it is that the extra beam of the cat means that the traveler can be long enough that a vang is not needed. I only see the need when the boom gets beyond the length of my traveler and I can no longer use the mainsheet to control twist.
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Old 09-06-2022, 02:55   #3
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Re: Why don't catamarans have boom vangs?

Yeah I get that the extra beam allows a traveler to kind of work, but it's just a whole heap of extra, heavy kit to accomplish something that is far more simply done by a clever vang system... unless I'm missing something bleeding' obvious...

BTW is it traveller or traveler?
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Old 09-06-2022, 03:11   #4
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Re: Why don't catamarans have boom vangs?

Mainly due to the beam, length of traveller and the shrouds which are usually the limiting factor on how far the boom can be let out anyway. Also because there is no give, healing motion on a cat, that would relieve the force of a crash gybe a fixing closer to the goose-neck is inviting a broken boom. Few it any cats have the mainsheet anywhere other the end of the boom.
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Old 09-06-2022, 03:41   #5
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Re: Why don't catamarans have boom vangs?

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Originally Posted by Tupaia View Post
Mainly due to the beam, length of traveller and the shrouds which are usually the limiting factor on how far the boom can be let out anyway.
That is exactly that same as on a dinghy such as a 49er. Also the 49er is an apparent wind boat so you never let the boom out very far anyway.

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Also because there is no give, healing motion on a cat, that would relieve the force of a crash gybe a fixing closer to the goose-neck is inviting a broken boom.
I don't understand what you mean here... obviously we don't want to crash gybe but why does a traveler prevent this or a vang make it more likely...? And why would the fixing closer to the gooseneck be a problem as long as the boom/mast are built properly?

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Few it any cats have the mainsheet anywhere other the end of the boom.
True but I'm not sure how this is relevant. A vang is totally independent of the mainsheet system.


My question is not to explain how/why a traveler can work, I understand that. It's why nobody seems to use a vang when, as far as I can see, it's a much simpler, lighter way of achieving the same goal.

I'm wondering whether it's simply a hang-over from before anybody had thought of above-boom vangs and you needed a way to control mainsheet twist when the boom is very close to the trampolines/coachroof and there wasn't room for a below-boom vang. The traveler was the way that caught on and nobody has ever thought to challenge the status quo since?

The reason I ask is not theoretical, we are having a performance live-aboard built and I'm questioning lots of things, this simply being one of them. If there is a good reason NOT to use a boom vang then fine, I'm just trying to understand what it is/if there is one.

Without a good reason then I'm going to go with an above-boom vang and save money, weight and sailing hassle...
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Old 09-06-2022, 04:13   #6
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Re: Why don't catamarans have boom vangs?

Actually Voyage and others have always been equipped with fixed boom vangs. The main reason is because they have a boom gantry or "stinger' inside the boom for hoisting the dinghy. They do not come with davits. The stinger pulls out of the boom and you lift or lower the dinghy. I'm not sure if you also need to use a topping lift for this operation.
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Old 09-06-2022, 04:28   #7
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Re: Why don't catamarans have boom vangs?

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Originally Posted by markiobe View Post
Does any know why cruising catamarans don't have boom vangs?
Because most rarely put their mainsail up
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Old 09-06-2022, 04:56   #8
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Re: Why don't catamarans have boom vangs?

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Originally Posted by markiobe View Post
My question is not to explain how/why a traveler can work, I understand that. It's why nobody seems to use a vang when, as far as I can see, it's a much simpler, lighter way of achieving the same goal.

Some sail plans want the boom right on the boat's centerline when sailing close hauled. You can't reasonably achieve this with just sheet + vang; you need a traveler so that the mainsheet can exert pull to windward. And then I imagine the thinking goes, "as long as we have to have a traveler, may as well make it a big wide one the full width of the deck, and do away with the need for a vang."
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Old 09-06-2022, 05:04   #9
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Re: Why don't catamarans have boom vangs?

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Because most rarely put their mainsail up


That’s really funny, and so original….
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Old 09-06-2022, 05:16   #10
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Re: Why don't catamarans have boom vangs?

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Originally Posted by ChrisOwens View Post
Some sail plans want the boom right on the boat's centerline when sailing close hauled. You can't reasonably achieve this with just sheet + vang; you need a traveler so that the mainsheet can exert pull to windward. And then I imagine the thinking goes, "as long as we have to have a traveler, may as well make it a big wide one the full width of the deck, and do away with the need for a vang."

This!
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Old 09-06-2022, 05:51   #11
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Re: Why don't catamarans have boom vangs?

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Originally Posted by markiobe View Post
That is exactly that same as on a dinghy such as a 49er. Also the 49er is an apparent wind boat so you never let the boom out very far anyway.

[/I]Last time I checked, catamarans are apparent wind boats. Notable exceptions are the latest crop of condo-cats[I]


True but I'm not sure how this is relevant. A vang is totally independent of the mainsheet system.


My question is not to explain how/why a traveler can work, I understand that. It's why nobody seems to use a vang when, as far as I can see, it's a much simpler, lighter way of achieving the same goal.


I'm wondering whether it's simply a hang-over from before anybody had thought of above-boom vangs and you needed a way to control mainsheet twist when the boom is very close to the trampolines/coachroof and there wasn't room for a below-boom vang. The traveler was the way that caught on and nobody has ever thought to challenge the status quo since?
Actually, you have it backwards AFAIC. Vangs are heavy, especially for the loads the cats will deal out (will need hydraulic doodads).

Traveller is simple (a track and a car), weighs less, allows control of the leech, and in the higher performance boats, are curved to facilitate consistent leech tension. Go sail a beach cat and you'll see how it works.

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Old 09-06-2022, 06:07   #12
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Re: Why don't catamarans have boom vangs?

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That’s really funny, and so original….
Yeah I know, wasn't original as everyone knew that
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Old 09-06-2022, 06:36   #13
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Re: Why don't catamarans have boom vangs?

I think Sailorboy's signature line says it all: It is OK if others want to do it different on THEIR boat

Looking at cruising cats now for retirement boat, and I would guess that in addition to the comment Markiobe started with (no room for a triangular vang under the boom), there is also the desire for most cruising cat owners for simpler sail controls. The great majority of cats are built for 1-week charters for one or two sailors to take their wives and friends around the islands for a rum cruise of 25-mile passages in trade winds. Getting an additional quarter-knot out of the boat for off-wind is not worth the extra costs or maintenance.

If you want great sail trim, go ahead and add that fancy above-boom vang. I would guess that this mechanism would constantly touch sail cloth and lead to chafe. For a dinghy racer where you replace sails due to stretch every three years, not an issue. For economical cruising where that sail will cost you $20K, perhaps having holes at the clew may bother you.
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Old 09-06-2022, 08:04   #14
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Quote:
Originally Posted by John_Trusty View Post
I would guess that this mechanism would constantly touch sail cloth and lead to chafe. For a dinghy racer where you replace sails due to stretch every three years, not an issue. For economical cruising where that sail will cost you $20K, perhaps having holes at the clew may bother you.
This is certainly the most compelling reason quoted so far
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Old 09-06-2022, 08:12   #15
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Re: Why don't catamarans have boom vangs?

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Originally Posted by ChrisOwens View Post
Some sail plans want the boom right on the boat's centerline when sailing close hauled. You can't reasonably achieve this with just sheet + vang; you need a traveler so that the mainsheet can exert pull to windward. And then I imagine the thinking goes, "as long as we have to have a traveler, may as well make it a big wide one the full width of the deck, and do away with the need for a vang."
You can actually achieve centreline sheeting with a vang, it's also dependent on the height of the mainsheet blocks. However, regardless of what people might say, nobody actually wants the boom centrelined, that's just a means to an end. What you actually want is a well controlled leech which may start close to the centreline but then twists away from the centreline to match the wind direction change the higher up the mast you go. That is totally achievable with a vang!

Anyway, even if that was the goal, I can't believe that's the reason given that the number of times a cruising cat would actually need that is vanishingly small...
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