Otto, thanks for your suggestions, rope was the easiest and quickest way to asses effectiveness, it will be replaced by something more permanent when I'm satisfied that I've optimised the size and shape of the 'stall strip'. In the meantime, the rope or something similar will stay, I wouldn't want to be without it now.
I have a copy of 'The worlds fastest Indian', one of my favourite movies.
After reading Tony Foal's article on aerodynamics (again), noting that a side wind combines with the head wind, to create an airflow at an angle to the machine. I set the fan at a 30 deg. angle from 'straight on', this seemed to have the most effect on the tufts.
I was careful to ensure that fan was not moved, so all the parameters apart from the stall strip were identical in both videos.
According to Tony Foal, an unstreamlind shape causes eddies and a low side force and is less affected by side winds. So I was looking for an early separation of the flow with the stall strip installed.
To be honest, I can't see any discernible difference, but then again I don't know what I'm looking for.
Here are the videos, I had to use my mobile phone to record so the quality is not special. Make of it what you will.
Click on the image to play.
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