FoilNose 3

Left Rear View This is the third L/D improvement investigation using chambers to stiffen a kite's leading edge. The idea comes from the Everett Parawing modification to NASA Parawings.

24 ram air inflated chambers run the entire length of the leading edge. Chambers are longer in the middle of the wing and shorter toward the tips. Each chamber has the same width.

This kite uses the same bottom skin, so it has the specifications as Foil Nose 2:

A view from the left rear of the kite is on the right side of this page. There are no bridles. Flying lines are run directly to the front and rear pigtails. There are no spars in this design, only shaped fabric and simple (no ribs) ram air inflated chambers.

From the rear view below, we see a nice progressive curve of both the leading and trailing edge, indicating that all sections of the canopy are providing lift. This is in nice contrast to Foil Nose 2 where the tips were just for show.

Rear View

The right rear view of the kite shows the outside of the right tip. Here we see that the chambers are evenly inflated up the side of the kite.

Right Rear View

The first flight was on a bar. The test flying lines are about 4 meters long. Front lines end in the middle of the bar; rear lines end at the tips of the bar. Wind speed is a consistent 4.5 meters/second. The L/D is about 3.5 by line angle measure.

Lift Drag Ratio: 3.5

Points of interest:

Below we see a front view of the kite. Each cell is well inflated. We also see that some of the cells not only open "upwards" but also open slightly "downwards". This should come as a surprise as the force of the flying lines is normally transferred through the skin of the kite, keeping it quite taut. There is a secret here, I have saved the best part of the description for last.

Front View

This kite has an additional line in between the fabric layers, running the entire length of the leading edge. This line is "floating" inside the chambers, taking the load from the leading edge of the kite.

Floating Tension Line

The "secret sauce" for this kite is the floating tension line in the leading edge of the airfoil section.

The leading edge tension line exits the kite at the leading edge tip of the kite. Both the pigtail connected to the canopy and the free floating tension line ends with a knot (which is not shown in the picture). The forward flying lines lark head to both these knots when attaching to the kite. The leading edge tension line is made shorter by untying the knot and moving it to a position closer to the kite. A shorter line will allow the tube openings on the wing sides to be larger and shorten the length of the leading edge in this section.

Pigtail Construction

The picture below shows how the floating tension line travels between the canopy and the airfoil section. Line is threaded through the layers of fabric just behind the binding. I use a small knitting needle to open the stitching up a little so the line can be pushed through. Sewing machines and knitting needles: this is not sounding very macho, but these are the right tools for the job. If you use a 6mm stitch length, there should be plenty of room here.

Floating Tensioning Line

Each wingtip has 6 tube sections. The center has 12 tube sections. The center and tip sections are made independently adjustable by fixing the line between the center and tip section. This is done with a small section of fabric sewn to the tensioning line as shown in the below picture. The small section of fabric is sewn down on each wing side 6 tubes from the tip.

Go back through the flying pictures and notice the slightly darker dots on the leading edge of the kite one quarter the way up from each tip. These are the the small fabric squares shown here which fix the line to the canopy at that point.

Fixed Tensioning Line

There is one tensioning line for the right side and one for the left side of the kite. Lines are threaded between the layers of fabric along the leading edge. The amount the lines are tied together where they meet in the middle controls the contraction of the middle part of the leading edge and how much the tubes open in that section. Moving the tension line wingtip knot controls the same for the outer sections. The amount of wingtip knot movement should be uniform on each side.

This floating tension line has several benefits:

This magic line is responsible for most of the performance in this kite.

For This Model

More testing and tweaking can be done without further touching the sewing machine:

For a New Model

Some things will require sewing: Since this model is actually flyable, I will keep it for comparison when developing new models. I have the bad habit of tweaking multiple parameters when creating new kite prototypes. Let's see if I can practice self-control by making a canopy with the same parameters, and only adjustng the items above.

Good news: I am out of orange fabric! Better color schemes are on the way. Stay tuned.

Learned So Far

Looking back on the foilnose series, I find:

Related pages:
Foil Nose 2
Everett Parawing
NPWC Foil Nose
Kite Design Parameters

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©2008 Bill Ola Rasmussen