I recently bought a tandem bicycle and didn't want to put it inside my
van, so I built a roof rack that I thought people might be interested in
seeing.  Tandem racks built by yakima or thule cost around $300-$400 and I
didn't want to spend that kind of money.  I think my rack cost me around
$50 or so to build and it should be fairly sturdy.

Here's a link for photos:

http://www.bothparentscount.org/blake/vanagon/rack/