Closed Cell Foil Bow Build

Prototype 1 – Foil Bow

The idea was to create a kite that follows the bow concept but replace the bladders with a foil kite design of cells and profiles.

Construction

The kite was constructed as a closed cell kite with one way inlet valves allowing the air to constantly flow into the canopy but trapping the air inside maintain internal air pressure and only allowing the air to escape through the seems. With limited bridles the kite needs to be as ridged as possible to hold it’s shape and maintain an aerodynmic profile.

The bridle needed to follow the bow style bridle allowing for minimun bridles to be used reducing drag. Two internal straps running the length of the kite spread the load across the canopy and help maintain the rigid profile shape in place of bridling.

Model showing canopy and bridle configuration with air inlet.
The finished kite hanging in the front room. How my partner puts up with me I don’t know!
First test flight. Head removed for comedic value!

Flight 1

Inland Park, Goldsythney

Lignt winds -10mph

10 meter lines and handles

Started with a simple back bridle connected to 3 of the D bridle points.  This was then dropped due to back stall and the tow points were connected straight onto wing tip D.  Kite didn’t seem to fly correctly.  Keep hanging in the window.  Shortened A’s by quite a considerable amount.  Fly’s better, but very slow turning.  Spanned a line across the D & C tip connectors.  Tow points connected in the middle of the lines.  Kite was much more controllable

Stalls on turns and can only be turned on brakes

Flight 2

Beach, Perranuthnoe

10 mph increasing to 12/13mph

Kite works well on a bar but has very limited depower range.  Front luff eliminated by shortening A’s resulted in good stability. 

Stalls on turns, limited depower range before it stalls and lands.

Have placed a number of knots on the tip span lines.  This allows for the back line pressure on the canopy to be changed in the field so pulling in the bar of the kite or turning the kite will apply the pressure to a different location on the tip.

Quick adjust knots for tail edge (TE) trimming.

Flight 3

Beach, Marizion

Medium winds, 15-18mph, Clean

Good stability, Almost arc like.  Produces a small amount of lift when flown from left to right through the zenith.

Limited depower throw, canopy deformation when the bar is pulled in (kite tips move towards each other when the bar is pulled in)

Added a pulley on the tip for a kind of VPS as per Peter lynn scorpion.  This should increase depower throw.

Flight 4

Gwithian, 30mph, Constant rain

Tested the safety features, but not on purpose.  Kite flags out on 1 back line perfectly with 0 pull.  Kite stalls onto the ground and stays there when both back lines are pulled in.  Kite needs a small bit of power to keep the back from flipping but not much. 0 pull.

Safety is perfect.

VPS has caused the back line to increase in length need to add leaders to fronts.

Flight 5

Gwithian, 20+ mph, Very Gusty

Wind tip pully on B.  Tip and shoulder instability but moving to C stability was better.  Still have canopy deformation.  Longer throw due to pullies.

Canopy deformation still exists, Front stalls in high wind if back line pressure is lost

Added span line to C bridle points to try to stop front stall and give more support in the canopy.  Removed pulleys and added a A tip ring.  Line from front bridle tow point runs through tip ring and connects to a back tip D line via a Tow point which is larks headed around both

Flight 6

Beach, Peranouthnoe

Less canopy deformation and stalling, flys nice

Seems to have lost steering on right hand side.  Need to check lengths

Bridle catches in ring. Rings need to be placed on lines to be lower than the bridles.  A bridle re-think is in order even incorporating 2 rings in a kind of UDS tip system achieving a smoother feel.

Flight 7

Beach, Gwithian

Gusty 25-30mph, Rain

Kite was virtually un-flyable due to the conditions and I believe many alterations made to the canopy that have slipped to different knots.  The kite became a complete tangle which wasn’t good for the bridle.  I know that I am on the right tracks with this kite and believe that it’s time to design a second proto-type.  This one is look a bit worn due to the tinkering and crash landings.  I will need to construct the tips batten pockets better next time as they are beginning to fall apart.

I believe the kite needs to be of a lower aspect ratio for more stability and have a back bridle to better the depower.  To increase the ridged ness of the kite I will need to increase the cell count.  In a LEI bow the bladders forces the kite to keep its shape.  With a foil kite there is no such structure so cell count, profile stiffness and quirks in construction need to be implemented to get the desired effect.

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