Check for the on line  calculators in the "<span class="oldpost"><font face="Verdana">Aerodynamic tools, calculators and test links </font></span>  " sticky thread.  There's a couple of calculators there for you.

These will provide the load on the servo.  But you need to figure on getting a servo that will provide 50 to 100% more torque than what the calculator says.   You do not want to be operating too close to the stall torque on any servo and the max torque given in the specs is always the stall torque.  Sizing the servo to keep the max surface load to 50 to 60% of the stall torque will ensure you keep the control surface response speeds up.  If you're using two servos per aileron to help avoid flutter issues then the total torque should add to the same spec.