By putting as many double berths into the bridgedeck as possible, more "living space" is created in the boats, along with perhaps a bit more illusory privacy. In that a couple then gains a full ensuite
cabin along with their double, instead of the double berth being 90% of the cabin.
The design
concept is pulled straight from
charter boats, where they want to maximize the amount of berths & space in a
boat of a given length. Even if it means dialing back a boat's potential performance, or it's comfort due to bridgedeck slamming. But then given the
displacement of those boats, performance is far from their #1 priority.
For something with higher performance in mind, look towards something like this one by Kurt
Hughes Kurt Hughes Multihull Design - Catamarans and Trimarans for Cruising and Charter or some of the Schionning performance designs.
Here are a few links for kits in
Europe, & or designers with resources to steer you to builders who can provide kits. As can any reputable
designer. Though vet both them & such builders well first!
Dazcat Catamarans builders of complete boats, & kits in the UK
Erik Lerouge International
www.SailingCatamarans.com Richard Woods
Multihull Designs
www.Multihull-Maven.com a fairly comprehensive site, for; boats, designs, designers, etc.
Keep in mind too that with 90-some% of the custom
multihull designs out there, you can have major components of the boats, & or kits, built to any degree of finish that you like, by a yard. And then finish the build from there. Yourself, in conjunction with a yard, or via hiring a general
builder, or guys who specialize in certain types of boatbuilding
work. Like structural glassing, cabinetry,
electrical,
paint, etc.
Which, done right, actually gives you a much nicer
boat. Given that it's mostly custom. And since much of it was built by a "named" builder/builders, it's resale value will be higher.
For example, a good number of Kurt Hughes's & Chris White's boats are done this way. And even more so, some of Richard Woods's boats via
www.BoatSmithFL.com in Richard's Sagitta & Eclipse design. Where David & his crew put together whole package kits for those boats.
And several yards do similar things for Kurt Hughes's boats as well, for example @
www.multihulldesigns.com
I only name those designers as I'm fairly familiar with their
work, but there are without doubt, many, many more. As for example are done with numerous
monohull designs of Dudley Dix @
www.Dixdesign.com
Where kits for his boats are both done locally, & shipped globally, much like the Australian multihulls. Either as kits in CONEX boxes, or via computer files which then are put into
computers which are hooked up to NC cutters. And they create all of the full sized
parts needed to build whichever kit boat you ordered.
This technology is several decades old, & quite refined. With the pieces being cut coming in at tolerances of less than 1mm. And some cutters are actually lasers, so that they can work with any material. Even
sails, which have been being built in this exact way for 30+ years.
It's a construction method that's often far easier than having a kit weighing several tons shipped to you. Especially if you can source all of the materials locally, cheaper. Or buy them over time as your funds, & available building space allow.
And "boat kits" are often even done this way for many of the popular metal designs out there. Or done this way in conjunction with
shipping a
builder a "flat pack" of plates with which to build the boat's structure.
Look at some of the work done on Dudley Dix's designs by some of the yards which there are links to on his website, as well as some of the amateur builds being done this way thousands of kilometers from his office. The process WORKS!
The other thing is that
parts like
catamaran hulls can be assembled from raw materials to bare hulls, by a good yard, literally in a day or a weekend. As has been done with a lot of Kurt Hughes's boats. So the question then as an owner builder, is how much of a boat do you want the yard to do for you? As with some designs, if they've done them before, it's dirt simple for them to build her major structures.
Check out Kurt's boats
www.multihulldesigns.com