note that a wing that has a single-surface profile needs to be mounted with a few degrees of positive angle of attack (aoa). it can be seen that the design of the clark-y Results in about three degrees of positive aoa; when the wing is mounted at zero-degrees aoa, relative to the lower surface of the profile. cheers googletranslate
at 4:10, it is not clear What is going on, with the elevator control.!!! is IS clear that the control horns are not correctly located. cheers googletranslate