Here is my new solar airplane (the previous version is here). 

As before, it uses the Parkzone Vapor's radio and motor, plus five Powerfilm solar cells.  In parallel with the solar cells, I include a tiny 20mAh lipo battery to keep the radio happy.  However before I hook up the solar cells, I make sure that there is not enough juice in the battery to run the motor (no cheating).

The wing is a vast improvement over the previous version.  It is stiffer torsionally, has more span, more area, and a better elliptical planform.  The wing and tail are covered with mylar from one of those emergency survival blankets.

Here are some specifications:

Wing span: 35in (89cm)

Wing area: 165 sq in

Total Weight: 42g

Last Saturday was the first calm and sunny day all year (Seattle).  Although conditions were not perfect (low sun angle, a bit too windy), I still managed to sneak in a few flights (see the video below).  I think with the right conditions, this airplane could fly for hours.  Finding a day with the right conditions might be challenging, though.  It is often very calm early in the morning, but the sun is too low.  By mid-day, when the sun is high, thermal activity tends to kick up random gusts.  I'll keep waiting for that perfect day...