Trimming a free flight model

This is not meant to be a definitive guide on how to trim a model but I filmed our attempts to get this model to fly and thought some comments on what we did may prove useful to others. The model is made from the polystyrene sheet sold on a roll for lining wallpaper and is stuck together with Copydex. The model is a Sport Biplane from Model Airplane News scaled down to 12" span. The tail size has been reduced slightly from the original plan too. The first and possibly the most important stage of trimming, to balance the model on the cg point and test glide is missing from the video but before trying any powered flights get the glide right first. As the side thrust was added to counter the torque from the rubber motor left rudder was used to turn the model also a small 1" length of 1/16" square was added to the lower left wing at the tailing edge. This is a Gurney flap and produces drag which helps turn the model but also increases lift helping keep the inner wing up in the turn