Just brainstorming..
It might be good to keep the attachment system on the inside of the hull, so the exterior is smooth enough. Lets say for example that you just bolt together the two bulkheads of both halves. You could plan the storage part in the same area, so you have access to work on the inside. You could isolate that area of the rest of the hull with another bulkhead, so any possible leak is limited to that volume.
Now bolting the two bulkheads might not be the best idea, because bolts are doing a lot of work. What about creating a male/female piece on both bulkheads so you you can bolt on a surface perpendicular to the bulkheads, where the bolts would make a lateral force. It would also add strength to the structure.

Or maybe overlap both halves, like a telescopic device. Still bulkheads on both parts, but one of them shifted inside the hull. An exterior non ivasive (and non leaking) attachment system might be easy to implement

He is not the only one in light clothes anyway..


I think it´s part of the desing concept

Tow a second inflatable platform with your gear strapped to it.

There is one big limitation in car-topable design nobody mention yet. It is weight of the boat. I believe there is a limit of how much you can put on the roof of the car, something like 85 kg. You will be hard pressed to design folding cartopable catamaran that light, unless it's inflatable <img src="http://www.catsailor.com/forums/images/graemlins/laugh.gif" alt="" />, or some very expencive exotic materials.

Inflatable car-topable catamaran, made in UK
http://www.catapultcats.com/

From my point of view inflatable boat & a couple of drybags can solve your problem. 5 meter inflatable carry all nesessary stuff for monthly trip in cold White sea, for example.
But if you want sectionable boat, it is not a problem. 8 M8 bolts more than enough to connect bulkheads. But keep in mind, that divided Tornado will not be strong enough to carry full rig. IMHO, 10-15 m2 of sails will be better.
Some examples of sectionable boats from Russia.
"Yantar" (Amber) sectional aluminium tri. Central 6 meter hull cut in 4 sections. Weight 130-150 kg, sail area 7 m2.

Homebuilt 5 meter plywood tri. Central hull cut in 2 sections, weight 140 kg, sail area 10.5 m2. This boat is used for 2-3 weeks trips in coastal areas of seas and big lakes.

EVERYTHING depends on money, weight, time and performance, from building space shuttles to buying new socks. Save time and money: start with a model.