See these
http://www.rcgroups.com/forums/showthread.php?t=1107267&highlight=cardboard
http://www.feltondesignanddata.com/

you guys might find more. Please post them here.

The secons link is virtually like Spadtothebone. It contains all thats needed to work with cardboard. All you need is to get your hands on some good quality cardboard. Only disadvantage is that they are not waterproof.

Not only planes, check out these ships. Mind boggling.

http://www.rcgroups.com/forums/showthread.php?t=531343&highlight=queen+mary+birth+cardboard+titan

http://www.rcgroups.com/forums/showthread.php?t=558375

Wow, They are awesome. Does fiberglass cloth /resin stick properly to cardboard ?