Chris,
The video is awesome! It totally supports what PJ has been saying for years, and what I found when I tested them in 2011. Watch the little piece of yarn that is about half way out on the trailing edge of the wing. During the inside square several times when the flap came back to neutral the little piece of string was facing forward showing us the direction the air was flowing at that moment. PJ has stated before that he found they were most effective when placed top and bottom of the wing something like 6-8" off the fuse. Well, this would just be just outside the prop wash. This is about the same spot this little piece of string is placed.
After the VGs were added that piece pretty much stayed in place.
Are your hinge lines taped? I would think they would need to be taped so we can properly see the airflow without any interruption from air popping through the hinge gap. But even if they aren't taped the VG stopped that air popping through from snapping off that piece of string.
Plus, for the sake of experimentation, the model will need to be flying slow for that model. These things are in place to keep air on the wing and flaps in a slow speed situation. In our case the second of any square maneuver will be slower than the first and we will see more issues there, especially in calm air. If the model is traveling with enough airspeed to get through everything with ease there may not be much to see. But, for testing purposes, if the model is slow and you slow it down in a maneuver you may see real separation without the VGs and less separation with them. Just some thoughts about the tests.
As Frank suggests you would want a row of pretty tightly spaced pieces along the TE. This is where the issue lies. If there is ay separation what so ever then the consistency can be lost flight to flight. Taped hinge lines produce a positive effect as there is no loss of air on the back of the flap due to air bleeding through. Oddly enough I have taped nearly every stunt plane I have built since 1999, except this last one, and only did I ever actually notice a difference on that one model in 1999. I have tried it on the others with no noticeable difference in feel or performance. I have always wondered why I am not noticing the sealed lines....
I did a test in 2011 on VGs and here is what I found.
http://stunthanger.com/smf/index.php/topic,23110.msg222103.html#msg222103The next thing to do is to get a smoke bomb, the little round one we used to get on the 4th of July, and somehow place it on a stick or something out in front of the wing and watch the smoke go over the VG and see if the flow....