Contents

• Introduction
• The Static Bridle
• The Active Bridle
• Freestyle and Trick Flying
  • Stalls and Slides
  • Axels and Flat Spins
  • Fades, Flic-Flacs and Fountains
• Drawbacks
• Copyright, Usage and Distribution Policy

Introduction

In summary:

• wider wind range
• increased size of wind window
• better speed consistency across wind window
• sharper straight-line tracking
• smoother turning with more control over turn rate
• improved control in stalls, slides, tip stands
• smoother transitions into, and out of tricks
• positive Fades and Flic-Flacs
• kite remains controllable in almost any position

Static Bridle

Most dual line kites allow some degree of tuning in the bridle, by lengthening or shortening the relative lengths of these sections, to change the flight characteristics of the kite. In general, moving the tow point relative to the kite in the following directions has the corresponding effect:

Tow point moved up towards nose

kite becomes more responsive in light wind but may over-fly and become over-powered in higher wind. Precision is often improved but kite can become overly sensitive requiring more precise execution of tricks. Stalls are difficult to maintain due to the kite's increased forward drive.

Tow point moved down away from nose

kite has better high wind handling but may lack drive in lighter wind, refusing to move forwards. This characteristic can make stalls easier to hold, but the kite's tighter and faster turn rate can create a tendency to roll from side to side in stalls as well as a greater possibility of over-steer in turns. The "looser" feel contributes to a smoother and more forgiving responsiveness to tricks.

Tow point moved out towards leading edge

kite has faster, more responsive turning ability but may wobble when tracking or over-steer in turns.

Tow point moved in towards centre T-Piece

kite tracks better and performs crisper sharp corners, but lacks smoothness in turns.

The Active Bridle

As is typical of all dynamic bridle configurations, the Active Bridle allows movement of the tow point while keeping all sections of the bridle taut. This is necessary to maintain the best level of control of the kite and to optimise the responsiveness of the kite to user input. For the tow point to move in a static bridle, one or more lines of the bridle must go slack. The design goal for the Active Bridle is to allow as much movement as is necessary to improve the flying characteristics of the kite while maintaining the shape and tautness of the bridle as much as possible.

The first additional leg, known as the "Stabliser", shown in red on Diagram 2, makes a connection between the upper leg and the lower legs.

Diagram 2: Stabiliser Leg	Diagram 3: Activator Leg

The second additional leg, known as the "Activator", shown in red on Diagram 3, connects the inner and upper legs together, pulling them in slightly.

Diagram 4 shows the effect of the Stabiliser leg in allowing the tow point to move out towards the leading edge and in towards the spine. The effect of this is such:

• When the kite is being flown in a straight line, pressure is roughly equal on each flying line (i.e. the flyer's hands are at the same distance). In this state, the Active Bridle shifts to move the tow points further in towards the spine. This increases the precision in straight line tracking.

• When the flier pulls (or pushes) on one line to execute a turn, the tow point on the line being pulled moves out towards the leading edge. This improves the kite's turning ability.

• The turning rate of the kite can be more closely controlled. A slight difference of pressure on the lines will create a slow, arcing curve, while at the other extreme, a hard pull on one line will create a very fast and tight spin.

Diagram 5 shows the effect of the Activator in controlling the pitch of the kite, effectively moving the tow point relatively up or down.

• When the pressure on the sail is light, the tow point shifts up, effectively pulling the nose of the kite in towards the flier. This improves the kite's responsiveness in light wind and also at the outer and upper edges of the wind window.

• When the pressure on the sail increases, the tow point shifts down and the nose of the kite is pushed away from the flier slightly. This slows the kite down in high wind and helps to control speed in the centre of the wind window. It also serves to buffer gusts, making for a smoother flying kite.

• The effects of pitch control as described above give the kite a larger wind window and provide a more consistent speed across different parts of the window and in different wind conditions.

Freestyle and Trick Flying

Dynamic bridles have previously had some considerable degree of success in improving the freestyle performance of kites, but usually at the cost of precision. Careful analysis of the dynamics of a kite during different kinds of flight (tracking straight, turning, stalls, Axels and Flat Spins, Flic-Flacs and Fade, etc) has identified the desired movement of the bridle in each of these conditions. The Active Bridle configuration is designed such that the bridle not only moves, but moves in the right direction, when required to do so. Whilst it is possible to break down the movement into horizontal and vertical components, as described in the previous section, it is important to realise that the combined effect is a synergy of movement in all 3 dimensions that, when carefully tuned to the size, shape, and aerodynamic qualities of a given kite, can afford a remarkable diversity of control and flexibility to the flier.

The specifics of the movement of the Active Bridle and the effects noted are discussed here in further details:

Stalls and Slides

The Active Bridle makes it easier to control the kite in a stalled position. Kites that are traditionally more precision-orientated are often solid and steady in a stall. Kites that are aimed more towards freestyle flying tend to have greater responsiveness to turning. This sensitivity makes stalls hard to perfect. The kite will typically roll one way or the other, rather than sitting steady with the nose pointing straight up.

A kite with a static bridle will normally stall best when adjusted with the tow point slightly low. This pushes the nose of the kite away from the flier and reduces its forward drive. The relative pressure is increased at the top of the kite as more air bleeds over the nose and leading edges. This force, being applied above the centre of gravity of the kite, further increases its tendency to roll sideways.

The stalled position with the Active Bridle has the nose of the kite being pulled in towards the flier. More air bleeds over the trailing edge and the relative pressure increase is concentrated below the centre of gravity of the kite. This creates a much more stable stall with significantly less rolling of the kite.

The nose is pulled in by the action of the Active Bridle responding to a drop in overall pressure on the kite. When the flier adds slack to the lines, as is typical when executing a stall, this sudden lack of pressure causes the tow point to shift far up, pulling the nose right in. The angle of the kite reaches a point where it will no longer fly forwards and it effectively remains "parked" it in mid-air. While the lines remain slack, the kite will remain stalled.

Taking up the slack on the lines increases the overall pressure on the kite and the Active Bridle shifts the tow point down to allow the nose to drop back again. This permits the kite to power up and fly off. The transition between stall and flight is fast, positive and crisp. There is no "nodding" of the nose of the kite as can be experienced with other dynamic bridle configurations.



The Active Bridle's pitch control not only allows the flier to adjust or correct the orientation of the kite in a stall, but also helps to keep the kite level when executing side slides. To correct an imperfect stall, or to introduce a side slide from a stall, slight pressure is applied to one or other line. In normal flight, pulling one wing towards the flier would cause the kite to rotate in that direction. In the stalled position, pulling gently on one line causes the tow point on that side of the kite to be pulled outwards towards the leading edge as the Stabiliser shifts. The tow point remains high due to the relatively light pressure on the lines and is now in a position above and outside the centre of gravity of the kite. This has the effect of keeping the wing lifted upwards to counteract the natural turning moment induced by pulling the it in towards the flier.

This is shown in Diagram 6.


When holding the kite in a Tip Stand, or when executing a Tip Drag or Leading Edge drag, the same action of the Active Bridle moves the upper tow point out towards the leading edge when pressure is applied to that line. This helps to keep the kite stable and lifts the nose up enough to counter the tendency for it to roll downwards and snag on the ground.

This is shown in Diagram 7.

Axels and Flat Spins

The range of tricks based around the Axel and Flat Spin share the common characteristic that the kite rotates in a flattened orientation with the face of the kite pointing towards the ground. The Active Bridle makes this kind of maneuver easier and cleaner by smoothing the transition into the trick. An Axel is executed by pushing on one line and then giving a sharp pop on with the same hand. The initial push is the setup required to cause the nose to dip, bringing the kite into the flattened position.

The action of the Active Bridle, when slack is applied to the lines, is to raise the position of the tow point, effectively pulling the nose in towards the flier. The push given as a pre-cursor to the Axel "pop" causes the Active Bridle to act in the same way, quickly lowering the nose ready for the transition into the trick.

The movement created by Active Bridle allows the flier to take up the slack and apply further controlled input during the execution of Axel-like tricks. Multiple Axels and Multiple Flat Spins become easier to achieve by the fact that the bridle compensates for incorrect or badly timed input. The required "point" at which a trick requires further input to continue, becomes a wider "zone", making such tricks easier to get right and smoother in execution.

Fades, Flic-Flacs and Fountains

The pitch control provided by the Active Bridle allows some movement of the nose, forward and backward, to regulate the kite's handling of different wind conditions. This movement also proves to be of some considerable benefit when executing tricks such as the Fade, Flic-Flac, etc., where the nose is deliberately pulled far forward or thrown right back.

The Active Bridle makes this transition between states smooth yet positive. It produces a cleaner, more controlled performance that looses little or no height. An Activated kite tends to lock into a Fade and hold it far better than normal. This behavior often implies a limited ability to Flic-Flac in a kite, but the Active Bridle does not appear to have any such limitation. It is possible to hold Rising Fades (Elevators) and also to execute Rising Flic-Flacs with the same kite without requiring any manual bridle adjustment.

The Active Bridle can also significantly improve the performance of Cascades and Fountains. The 3-step "Pop, Pause and Pull" approach to these maneuvers - "pop" the Axel, pause while the kite rotates half a turn or so, then pull the other line to lift the wing up - makes precise control of a Cascade much easier to achieve and also helps to reduce the amount of height lost in each iteration. This allows the flier to perform longer Cascades and eventually progress to the point where the kite gains height rather than loses it: The Fountain. This becomes significantly easier with an Active Bridle.

There are a number of clearly distinct benefits that the Active Bridle gives, such as those discussed already. Going beyond the specifics of certain tricks, the Active Bridle has a feeling and a forgiveness that seems to enhance the flying characteristics of a kite in almost any situation or position. This opens up new windows of possibility and allows the flier to discover so much more about what the kite can really do.

With an Active Bridle, the kite will accept input from almost any position in the sky (and in many cases, on the ground), and behave in a controlled and predictable fashion. This allows many existing tricks to be executed in new orientations and in different ways.

Drawbacks

There are drawbacks, however, but these manifest themselves in the design, construction and understanding of the bridle configuration.

The fact that the bridle is more complex than a static, or other dynamic, bridle makes it harder to design for a specific kite. There are more sections to adjust, more parameters to change and more for the designer to understand about the perceived effects of changing these elements.

To compound the problem, the Active Bridle is more sensitive to tuning than most other bridles. Whilst it is a fairly easy matter to simply get the kite flying, the hard part is the fine tuning required to balance all of the bridle's features against each other. Getting the kite to Fade and Flic-Flac, providing both precision and extreme trick-ability, and have the kite stall well without losing firm, positive drive, are all examples of the contrasting characteristics that can be achieved without compromise, with the sufficient amount of time, patience and understanding.

Copyright, Usage and Distribution Policy

Permission is hereby granted for any person to use or modify the Active Bridle for any purpose, under the following conditions:

1. The Active Bridle, and any technology or design based on the Active Bridle, must remain free for everyone to use, forever, under these same terms.

2. The Active Bridle must not be renamed. Significantly different derivates may be renamed, but should indicate that they are based on the original Active Bridle by Andy Wardley, where that is the case.

3. Original credit for the bridle should be given, where appropriate, to Andy Wardley. It is not necessary for this to be stated anywhere on the kite or accessories. Credit should be given if the Active Bridle is used or mentioned in accompanying documentation, sales or advertising literature.

4. No royalties or fees are due for using the bridle on commercial kites. Please feel free to donate money to a charity of your choice if you feel indebted in some way for the Active Bridle. The proceeds of sale from a single kite would probably be an appropriate amount, but it is entirely at your discretion.

This document is © Copyright 1998 Andy Wardley. All Rights Reserved.

You may freely copy, mirror, print or distribute unaltered copies of this document, provided that no charge is made for it. Please contact the author if you wish to reproduce the document in a commercial publication or in an altered format.