As you can gather from the replies, there are many ways to build doors. I built my doors using the same section and materials as I used for my sidewalls.
There are two general ways to seal doors. The more traditional way is to use t-molding around the perimeter of the door with weatherseals around the edges of the t-molding. The other way is to make an interior door jamb and use weatherseals to seal the door to the jamb.
In building my teardrop, I was overly paranoid about its weathertight-ness. So, I constructed my doors using both methods. Following is a section of the door and sidewall.

I initially just placed seals around the t-molding. This has worked so well that I haven't found the need to appy the interior jamb weatherseals.
You may notice on the sketch that the door and the sidewalls are not on the same plane. I offset the door 1/8" further out from the sidewall to allow room for the weatherseal. You will need to do this if you are using t-molding. If you are using the interior jamb only, you can make the jamb depth 1/8" deeper than the thickness of your doors so your doors can be flush with the sidewalls.
Instead of an offset piano hinge, I used individual strap hinges. To offset the door, I made a spacer out of 1/8" thick aluminum.

You'll notice in the sketch that I used t-molding along the hinge side of the door. If you do this, you'll need to make sure that your hinge centerline is beyond the outer edge of the t-molding or your doors won't open.
Take care,
Tom