Originally Posted by Andycap
It improves airflow over the rudder
I assume we are talking about the same aerodynamical device. It started as a small "T-Tail" behind the canopy of F3A models and it continued to grow - in size and at the bottom as well.
What CPLR told about the effects:
I had a long chat with CPLR about his Axiome design details. A few things I notice about this airplane beyond just the rear sweeping wing, and giant canalizer. Firstly the main wing appears much smaller, Christophe told me that yes this is true, and what he did was subtract the canalizer area from the main wing area. The canalizer is about 10 dm^2 (~155 in^2), so the main wing is that much smaller than what you would expect or consider normal. The rear sweeping wing also requires more dihedral than what is normal for a monoplane, so the dihedral was increased a little from the original point which was to set the top of the wing flat (fairly standard on monoplanes). Also the main wing is placed lower in the fuse than you would normally place a monoplane wing.
Secondly, the stab and fin are very large relative to the wing, and also to other F3A models. Christophe said he was not happy with the directional stability in the Osmose, so he made a similar change to the Osmose Evolution and it was improved. So this is a carry over of that, my next question was obviously does that not make it more difficult in the snap, to which he smiled and said there are always compromises Indeed.
The side area of the fuse is also much less than other monoplanes as well, this is a result of the 1/2 bipe wing on top increasing the efficiency of the fuse in knife edge, so there is less requirement for a lot of side area. This helps in the crosswind he said by presenting less airplane to get blown around. The model is still pretty big, so I am not sure how much it helps, but its an interesting direction to take and the Axiome doesn't seem to lack and knife edge performance.