First you have to ask yourself, "Have I ever seen a catamaran sailing with its boom extended outside the width of the boat?" ....I doubt it. On my Nacra the traveler track extends along the entire width of the aft crossbeam..... that's 8.5 feet on a 17 foot boat. I can't ever recall extending the boom out that far, because you never sail them directly downwind, they tack downwind instead(zig zag). When they sail on a broad reach, the boat's high speed moves the apparent wind way forward.. so the boom never extends out past the traveler car track... a vang is unnecessary... the powerful mainsheet handles it.
Besides a vang, another piece of common rigging you'll rarely see on a catamaran is a BACKSTAY. Why? The just don't fit... the mainsails have a huge roach so the battens would be constantly hanging up... and on beach cats the very long tiller extension that controls the twin rudders must be swung back around the mainsheet when changing tacks. A backstay would make that impossible. Plus all catamarans have swept back shrouds so the mast doesn't need it for support.
In catamaran sailing, bending the mast is a common depowering method ( Have you ever seen a mainsail reef on a beach cat?).. So how do you bend the mast without a backstay? Okay, I'll tell you..... they use a high powered CUNNINGHAM to tension the mainsail luff, putting curve in the mast the way a bowstring does to its bow. I rigged up an 8:1 on my Nacra... and 16:1 is common on racing.
What else, you say.... well, did you know that catamarans are commonly set up with devices that allow the crew to ROTATE the mast to improve the mainsail's aerodynamic properties? Yep, very common.
On most serious cats all these controls can be accessed from either side of the boat so you'll see mainsheet and traveler tied together end to end for one continuous control line, the jibsheets are rigged as one continous line also. The mast rotator, cunningham and barberhauler are often rigged as contious lines or two separate ends led to both rails.
Just a few of the things that make catamarans so intersting..
