Air Brakes for Dual Line Sport Kites
By Steve Millner--Yardly, PA                                                     December, 1993

During the past year, air brakes (or air dams, wind tamers, tail draggers) have been increasingly present on the competition circuit.  I first saw them used at Old Dominion last April; I do not know when they were first used.

The purpose of the air brake is to slow the forward speed of the kite in high winds.  I have been told that attaching the air brake also changes the kite's angle of attack, reducing drag as well.  Thus, the air brake extends the upper end of a preferred kite beyond its  stated limits.

Air brakes can be purchased commercially in width of 3", 6", and 12".  The air brakes can be used individually or in combination with each other.  Prices vary from about $8 for a 3" air brake to $13 for a 12" air brake.  A set of three generally costs over $30.

MATERIALS
The air brake consists of a piece of screening with Dacron reinforcement and bridle loops and lines at each end.  The "top" of the air brake attaches to the bridle clips or knots of the kite, and the flying lines attach to the "bottom" of the air brake (see illustration A).

CONSTRUCTION
For anyone who has made a kite, construction of the air brake is a snap, and the material costs are probably under $2.00 for any size air brake.

You can customize your air brake for your particular kite by measuring the distance between your left and right bridle clips when they are extended away from
the kite (in flying position, adjusted for high wind).  Commercial air brakes are about 28" finished length.

DIAGRAM

Any screening material can be used.  Weight is not a factor, since they are only used in high winds. Ordinary window screening can be used.  I prefer to use vinyl coated polyester mesh.  This material is much stiffer than other materials and hence easier to sew.  It is also available in several colors, including black, white, hot orange, green, etc.

The ends of the air brake are reinforced with 2"
wide 3.9 oz. Dacron (the kind ordinarily used for kite leading edge).  Dacron is also available in several colors.

1. Cut the mesh 2" longer than the desired finished length (standard finished length is 28"), and 1" wider than the desired width (make several graduated sizes).  Cut 2 pieces of 3.9 oz. Dacron the same size as the fin-
ished width of the air brake.  Cut 2 pieces of bridle line (300#) about 10" longer that the finished width of the air brake.

2. Hem the top and bottom of the mesh (the long sides): Fold over 1/4" and roll over (using 1/2").  Sew with a triple zigzag.

3. Prepare the bridle lines by tying an overhand knot in one end making a 3-1/2" loop, and tying a knot in the other end (ends should be hot cut or hot sealed).  Make sure both bridle lines are exactly the same finished length (exact overall length is not critical).  The bridle lines should be long enough to leave the loop clear of the top of the air brake and the bottom knot at least 3-1/2" long below the air brake.

4. Place the bridle line 1" from the end, fold over the screen 1", and fold over the Dacron on the outside of the sandwich.  The bridle line should be straight and in the fold line.  Sew all the way around the Dacron (4 sides) with a triple zigzag stitch.
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