badform to flowform 2

The next action to stabilise the Didakites ff4 is to cut out the side keel panels ready for the mesh. It was a bit risky to fly it in this state but I wanted to check the effect of this so back to the common:

The effect of the hole in the side keels is dramatic: the concertina collapse of the cells as the kite moves sideways is stopped completely. Adding the mesh to fill the holes will add strength and sharpen the shape of the keel as opposed to the flapping edges seen here.

The hole is cut with 2cm edging all around to take the seam to the mesh.  The wind was freshening and the kite was being bashed around a fair bit, but although it tipped over it did not suffer from collapsed cells- it just powered into the ground Stuka stye. At least he could pull up!

Whuump!Progress? Yes. It crashed in shape!

I think the lateral stability required can be achieved in 3 ways,

  1. I can dull the AoA with further bridle adjustment, in fact the bridle is well designed for this and, with a bit of fiddling about, you can fly this kite and vary the AoA as you fly and see the effect.
  2. I can incrementally reduce the lift by increasing the airflow through the wing (and thus the speed and power with which the wing moves) with the uppper and lower cell vents 2 cells at a time.
  3. A bigger drogue will slow the yawing action.

A quick look at Steve Sutton’s 1975 patent drawing for the flowform ‘chute shows how much venting is used for the principle to work. The great benefit of the flowform is that it can adapt to a wide range of wind speeds by virtue of channelling excess airflow into a stable flow through the wing; un-vented or ‘ram air’ parafoils meet an upper wind speed limit and become very unstable. Flowforms give you plenty of warning (usually in the form of being gradually pushed to one side of the airflow- not inverting and power-diving into the ground parafoil style!) as they approach their upper wind speed limit and consequently they survive gusts well.

As the wind dropped to Bft2 in the evening I flew the Didakites FF4 again, it’s really hard to launch in a light wind but with much patience I’m able to wind it up over the tree tops and catch a ‘light air’. It flew smooth as silk.

Clearly light wind is what this kite is good at, the label on the bag says its good for Bft 1-5:  anyone flying it in Bft 5 is in for a big surprise!

I’d class it as Bft 3 maximum and even then it needs modifying to be stable at 7 or 8mph windspeed.

I’m off to the haberdasher for some Tutu net Tulle, thread and bias binding tape…

Christian Becot’s brilliant research on stabilsing the flowform is here. Follow the links to ‘Flowform’ and then ‘modifications’

More on Steve Sutton’s remarkable flowform design is here

About billboyheritagesurvey

Heritage worker
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