Why don't catamarans have boom vangs?

[aqfishing]

Originally Posted by markiobe

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?

I would think you would need a traveler or traveller irrespective? Unless you just go for the A-frame type system as used on Leopards and Balance cats(probably plenty more, but I only know of these 2 for sure) I have seen threads on the comparison of A frame vs traveller on this forum. Works fine for me.

Fyi:

https://youtu.be/m-hr2xjVqHs

[foufou]

I believe there is another reason for travelers that has not been mentioned. The sail, with main sheet attached to the traveler act as a back stay. While catamarans have swept back shrouds that take loads from astern the leech of the main and the main sheet also take those loads. It is all part of the mast support system.

[Happ]

Originally Posted by markiobe

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 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?



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...

They are not 49’ers! The mains on Cats and Tris are massive. They also are extremely heavy as they have to be due to the load. They don’t heel therefore the loads are massive. The masts are raked very far aft to help upwind performance. They are not sailed. Deep downwind so the need for a Vang is moot. Often what is done is preventers are attached and can be used as a Vang.

[CarlF]

Coming from monohull racing myself, I found many of the rigging decisions on a cat perplexing at first. Most so the swept back shrouds that keep you from letting the boom out. I also said "Where's the vang?"

But I've concluded that cats rigs are well thought out - most certainly not done this way because cat sailors don't know how to sail.

Performance cats spend a larger percentage of the time close hauled than monohulls. There just isn't a lot of time that you want the boom out beyond the traveler length. I strongly urge the OP to consider an Oxley parasailer with a furled mainsail for those relatively few times when a performance cat has the wind aft of the beam.

The swept spreaders and wide shroud base make the mast stronger than a narrow monohull. This allows designers to reduce the size/weight of the mast section and shrouds. Not having a backstays allows the large roach of cat mainsails which greatly improves mainsail power due to the longer cord in the upper half of the sail.

But all this power in the mainsail means that a boom end traveler is the best system for leach control. A boom vang would require a heavier boom section and either raising the gooseneck or lowering the cabin top to not have the vang at too shallow an angle.

The traveler also allows you to adjust the leach with a powerful mainsail sheet winch. Most cat sailors (and mono sailors) sail with the leach far too open. It takes a lot of winch power to tighten the leach enough to get the battens parallel to the boom on these huge sails. To create the same force with a boom vang would require hydraulics. Block and tackle would not suffice.

If the OP must have his boom vang, then he should go all the way and use a monohull rig on his cat - with unswept spreaders, a backstay, and larger fore triangle. Picking a few things from column A and a few things from column B is not good engineering.

[rslifkin]

Keep in mind, the swept spreaders, no backstay, fractional rig, end boom sheeting with wide traveler thing isn't cat-exclusive, nor does it automatically mean you can't have a vang if the loads are manageable and there's space to install one at a good angle. Hunter did it on monohulls for years with the B&R rig and a traveler on an arch over the cockpit (and they typically had vangs).

[TOM-ROLPH]

You don't say whether or not you actually own a catamaran (unless I missed it somewhere)
If you do own one what class?

I don't know of an ocean going cat which doesn't have a full width traveller. I don't know of an ocean going cat that has a kicking strap (vang to our US EU shipmates).

That kind of demonstrates the point.
I own a 46ft mono, I skipper a 45ft FP cat, I sail a Finn dinghy.
Leech tension is critical in all these but there are different ways in different boats in achieving it.

The vang system on the 49er is a dinghy solution on an ocean going vessel it's going to be huge, hugely expensive and place huge strains on the mast.

There are some great articles on Cat sail trim on the Internet that explain all of this.

Cheers

[markiobe]

Originally Posted by aqfishing

I would think you would need a traveler or traveller irrespective? Unless you just go for the A-frame type system as used on Leopards and Balance cats(probably plenty more, but I only know of these 2 for sure) I have seen threads on the comparison of A frame vs traveller on this forum. Works fine for me.

Fyi:

https://youtu.be/m-hr2xjVqHs

Thanks for this, I was also discussing this topic with a friend and the A-frame idea is pretty appealing as it allows both a built in preventer as well as allowing a vanging action on the sail at a wider sheeting angle than a typical coachroof mounted traveller. The idea of having 2 attachment points either side is a good one for that reason

[SUNCAT365]

Speaking to my cat specifically, the boom is inches over the bridgedeck cabin. There's no room there for a vang. Also the traveler/mainsheet on a cat does the job better, from a cruising perspective. Easy as pie. One control vs two. This wouldn't work on a mono as the traveler would have to go 8 ft off the beam and would be buried in the water. Lastly, many Cats have full battened mains with extra long booms. That's a lot of leverage to put on a vang that is better handled at the end of the boom where there is more control over all that power. Lastly lastly, once set on a tack, the preventer firsm things up that much more. This isn't racing. Set it and forget it.

[fxykty]

Originally Posted by markiobe

…

- don't accomplish the goal as effectively as a vang/kicker especially at wider angles. This is an efficiency and also potentially a safety issue.

…

You are getting a performance cruising cat. The amount of time you will sail angles >130* other than near dead downwind will be minuscule - the whole point of a performance cruising cat is to sail the angles. Your aft beam or coach roof will be plenty wide to have a traveller long enough to handle gybing angles.

As others have pointed out, if you really want to mooch dead downwind use a spinnaker, parasail, or really big top-down asymmetric, with no main at all. In heavy air just use the jib on its own - if you keep your boat light you won’t need much sail area.

Regarding the A-frame, that is not a performance main handling solution. In particular, when hard on the wind with boom near centreline each leg will be at 45* and will need huge tension to provide enough leach tension. The A-frame is generally a solution for charter cats and inexperienced crew - it works well for reaching, is less expensive (but not necessarily lighter than a traveller - think about the reinforcement required at each base to support 5-8 ton of load), and more tolerant of mistakes.

Look at any performance cat or tri - you will see a long, possibly curved, traveller. It’s not because multihull sailors don’t know how to trim their sails.

[Shaneesprit]

I think the boom Vang is absolutely essential
Yes I have a CAT and Yes the traveller is quite long, I often don’t both to use it. but the main reason I see for the Vang is to ensure if the boom hits you in the head, at least it’s not come from a vertical position so lessening the impact. Not that I have been hit in the head in the last few years.
When the boom is fully out I have taken to adding a line from the boom to the Stern Port/Starboard cleat so it can’t come back.

[Icarus]

Originally Posted by markiobe

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 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?







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...

On most cats the main can't be squared of because the way the mast is rigged therefore sailing dead down wind is not quite successful with the main squared.
Tacking down wind is reducing the need for a boomvang.

[CaptainRivet]

For downwind sailing on a cat majority simply not using the main. Most use parasailor or code 0, i prefer the parachute round sail which can be used from 8 to 40kn from 150 to 210 degrees and is much simpler to rigg. Or during day Parasailor and nighg6
If the wind is stronger then 40kn I put the 100% genua with a block on the middle cleat and reff it accordingly. So a vang is obsolete.

[tamicatana]

I learned from years of sailing dinghy catamarans and my F-27GS that I would not sail without the main up when I have a big headsail flying.

The main will do two things:
-when you douse the chute, steer such that the main blocks the chute and thus facilitating the takedown
-acts as a backstay, supporting the mast.

Also, if the SHTF, the ability to stall the big scary sail (screacher or chute) is a safety feature. IMO it is absolutely dangerous to fly a big headsail by itself.

[aqfishing]

Originally Posted by markiobe

Thanks for this, I was also discussing this topic with a friend and the A-frame idea is pretty appealing as it allows both a built in preventer as well as allowing a vanging action on the sail at a wider sheeting angle than a typical coachroof mounted traveller. The idea of having 2 attachment points either side is a good one for that reason

[aqfishing]

Originally Posted by fxykty

You are getting a performance cruising cat. The amount of time you will sail angles >130* other than near dead downwind will be minuscule - the whole point of a performance cruising cat is to sail the angles. Your aft beam or coach roof will be plenty wide to have a traveller long enough to handle gybing angles.

As others have pointed out, if you really want to mooch dead downwind use a spinnaker, parasail, or really big top-down asymmetric, with no main at all. In heavy air just use the jib on its own - if you keep your boat light you won’t need much sail area.

Regarding the A-frame, that is not a performance main handling solution. In particular, when hard on the wind with boom near centreline each leg will be at 45* and will need huge tension to provide enough leach tension. The A-frame is generally a solution for charter cats and inexperienced crew - it works well for reaching, is less expensive (but not necessarily lighter than a traveller - think about the reinforcement required at each base to support 5-8 ton of load), and more tolerant of mistakes.

Look at any performance cat or tri - you will see a long, possibly curved, traveller. It’s not because multihull sailors don’t know how to trim their sails.

Last time I looked Balance Catamarans were most certainly high performance cats.
See the video in my post #61