Here you go, posted by Don Stegall, another RCU member...

http://www.rcpro.org/rccalc/GForce.aspx

Sample: 100 mph, and a 100 foot radius turn is 6.72 G's. Interesting, because when you distribute even these "high" loads over the surface of a reasonably-sized wing, they're not that terrifying. I always build with the idea of at least 10 G's, on most planes, and that's not really too extreme.

The recent Dynamic Soaring record of around 262 mph shows that if the circle's radius was about 200 feet, (my guess) then the plane was pulling 23.07 G's. And that's sustained, too, not just momentary. I've heard that severe winch launches can put 30 or 40 G's on these things.