I have read the various topics pertaining to V tail design on your site, and I appreciate the reasoning behind sizing a v tail according to the total area of the conventional tail it is meant to replace.

My only concern lies with a situation where there is not any rudder function on the model ( ie. 2 channel slope soarer - aileron and elevator only). In this situation, would a simple projection method be sufficient?

From : Don Stackhouse

Lapo, that's an excellent question. No, in this case you should still use the same total area. Even though you aren't planning to make any rudder inputs, your tail still has to make the same stabilizing forces in both yaw and pitch. For this reason, you still need the same total area.

Don Stackhouse
DJ Aerotech