Trike wing Billow what causes it

[MILO]

I am aware that banking the trike wing causes billow on one side.
One side of the wing fabric tightens and the other (upper?) loosens a bit. This changes the airofoil shape/camber generating more lift/drag on one side.
Or because of the anhedral the lower wing vertical component of lift is less (opposite of what happens on most fixed wings)

I am battling to see what moves in the trike structure to cause the billow.
The wing keel is securely bolted to the wing leading edge tubes so cannot turn relative to the wing.
The only free moving part is the hang block and spreader bar bolting flange inside the wing. This is padded on the aquilla and is free to move left and right over the wing keel. It gives that thunk noise when the wing is tilted left and right when you are on the ground.

Anybody have and ideas?

[CR Tech]

MILO

This is indeed very interesting and my feeling is that not enough trike pilots have an interest in understanding the POF with regards to their wings.

I don't fly trikes but am currently busy fitting new fabric covers to my fix wing aircraft and its similar to a trike wing system. I think the slacking and tightening of the fabric is due to the low pressure across the top surface and higher pressure across the bottom. Also something to consider is angular lift in the bank/roll axis you described.

With regards to the movement, wouldn't the battens offer a slight bit of movement each, resulting in a few inches overall ?

[Biggles]

The billowing of the wing is caused by the flying wires moving the spreaderbar from side to side. When you bank right, you push the bar left that pushes the spreaderbar left "tightning the right side decreasing the mean camber (and amount of lift on the right) and increasing the mean camber on the left (increasing lift). As you turn the airspeed on the inside wing will also drop decreasing lift as well. So strictly speaking it is not purely a weight shift as meany people image. Trikes should really be called flexiwings not weightshift.

So the leading edge tubes are continuously hinging on the front where they attach to the keel tube. And the spreader bar is also hinging where it attaches to the leading edge bar.