Originally Posted by
PDR1
There is something very strange going on in that video - I'm struggling to see what force the forward rake of the thrust vector is opposing. I'd need to look at it in a lot of detail to understand what's going on.
I would hazard a guess at the lift from the 'wings' below the four props. The video states that 20% of hover lift is generated by these wings. If you look at them as a wing surface with the flow from the props providing the high speed flow over the top of the wing, you get a lift vector that's angled back and up a bit. The upwards bit is useful for hover lift, the rearwards bit needs to be offset by the canted thrust from the props.