I just went out to fly my Avistar today (first time since last summer) , it was perfect outside (minnesota weather) 73 degrees out, and NO WIND!. I did my usual pre-flight checks, and everything seemed to be in order, except it seemed like it took an unusually long time to fill my tank, although at the time I thought nothing of it. But when I started up the engine, something was wrong. The engine bogged a lot even after needle tuning, and there was a little air bubble in the fuel like occasionally. Finally, after some more tweaking, and a new plug my engine was running well. I start down the runway noticing that it was handling oddly. I pull back on the stick after i had sufficient speed, and it climbed out... like a dog... For a second. It suddenly dove down, and i only had enough radio control to slightly pull up just before slamming into a curb. When i brought it back to my "pit" i took off the wing to see why my elevator was acting up. To my surprise, when i looked inside, the plane was full of fuel, and there was smoke coming from my elev. servo. I unplugged the battery as fast as i could, took out the radio tray, sucked the tank dry, and dumped it out. I had a towel and dried it as much as I could. Problem? The screw-type fuel tank seal had come out completely! It then dawned on me why it took so long to fill the tank... i was filling the whole plane! I am still drying and cleaning, and havent yet assessed the damage. Hopefully my radio gear will still work!

Total structural damage besides the fuel damage: a puncture in the wing coating, bent nose-gear, demolished prop, various scuffs and scraped to coating, and my vertical tail-fin snapped off. not too bad i suppose, considering...