Bridle Construction Techniques
This page provides useful hints, tips and general information relevant to the construction of kite bridles.
The easiest way by far to make any bridle from a set of measurements, is to first construct a "Bridle Stick". By measuring and marking lengths on a piece of wood, one has a simple ruler against which to quickly measure, cut and mark bridles.
To make a bridle stick, take a solid length of wood, at least a few centimetres wide on each side, and about a metre long (a little more than a metre is recommended). Mark a line (the "0-Line") at right angles across the wood and a few centimetres down from one end. Bang a thin nail into the wood at a point on the 0-Line roughly half way across the stick. Leave part of the nail sticking out of the wood so that loops of bridle line can be held around it. Measure down a metre from the 0-Line and mark another line across the stick (the "100-Line"). Bang a nail in here in a similar way to before. If your stick is less than a metre long, you might want to choose another convenient distance (75cm, 85cm, etc.)
Or, get a bigger stick.
When we come to build our bridles, we will pre-mark the lengths directly onto the piece of wood by measuring down from the 0-Line with a ruler or tape measure. Lengths greater than a metre long (or however far down your second nail is) will be measured down from the 0-Line, around the nail and then back towards the 0-Line. Here lies the convenience of having a metre between the nails: a length of 1.45m, for example, can simply be calculated to be 45cm (1.45m - 1.00m) from the 100-Line back up towards the 0-Line.
A bridle stick can be marked with measurements for many different kites, but be warned how easy it is to get confused when you have 11 versions of 3 different bridles all on the same stick. You may find it useful to mark measurements for different kites in different colour pens or on different sides of the stick (if you don't mind banging in more nails and marking more lines). Mark all measurements with the name of the kite and the name of the section or mark that it indicates (e.g. "OSpace Upper Leg Activator Mark") and don't be afraid to scribble reminders or makes notes on the stick. You'll be glad of them when you come back to it a month later and can't remember what any of the markings mean.
Use a good quality bridle line that contains a Spectra (a.k.a. "Dyneema") core. This prevents the line from stretching in use. For ultralight and indoor kites, you may wish to use unsheathed "raw" Spectra to cut down on weight. Line rated at around 70kg/150lb breaking strain proves adequate for the job.
The only problem with using unsheathed line is that knots are more prone to slippage. You may wish to add small overhand stopper knots in the end of the lines to prevent this, although you should remember to tie the knot at the required distance and then cut the line, rather than cutting the line and then tying a knot. The latter will shorten the overall length of the line. Where continuous lengths of line are joined, mark the correct position on the line with a marker pen, holding the nib in place to allow the ink to sink into the fibres of the line. The ink from the pen should provide enough friction in the bridle line to hold position as well as serving as a clear visual marker when assembling the bridle.
When measuring a single piece of bride line, I find it convenient to prepare one end of the line (which usually includes creating a flange - see following section), hold it up against the 0-Line and then pull the line down taut along the bridle stick. I can then read off the exact length required from the markings I've made onto the stick itself. If the end requires a flange then I cut it a little long, or if it's a bridle marking required, I simply dab a marker pen or metallic pen on the bridle line above the underlying marking.
When measuring a loop section, take a length of line a little longer (15cm, for example) than twice the required length. Fold the line in half and tie an overhand knot using a suitable spar to gauge the correct diameter of the loop. Slip this loop over the nail at the 0-Line, pulls the ends of the line taut along the stick, around the 100-Line and back if necessary, and hold the line up against the required marking. When cutting lines, don't forget to add 5mm or so to add a flange, if required. When marking points on a line, simply dab a marker pen or a metallic pen across the line on the relevant mark.
One elegant alternative to tying stopper knots in bridle lines is to melt "flanges" onto the ends of the lines. This technique was brought to my attention by Tim Benson who has used it successfully on his range of kites for many years.
When measuring the line exactly (preparing the first end does not require any such precision), cut the line about 5mm longer than required. Take the line and gently tap the end with a finger to open out the braid. Next, take a cigarette lighter and quickly melt the end of the line. As the strands shrink back and melt, tap the end of the line against a hard, fireproof surface. The metal surround at the top of a cigarette lighter is ideal for this. Your finger is not.
This process should create a visible flange of hardened plastic which opens out at the end of the line. This is usually all that is required to stop the end of the line slipping through a knot. A little further melting and pushing can be used if required to shorten the line further to the exact length.
We have so far been unable to solve problem of what to do when the line has been melted too short. :-)=
The Active Bridle requires 2 separate "Tracer" sections, one for each side of the kite. These are simply small loops that connect to the bridle with a Prussik knot and form the sections onto which the flying lines are attached. The length of the tracer section is not particularly important, within reason, as long as both Tracers are of the same length. A length of 10cm is adequate and can be marked on the bridle stick along with the other bridle dimensions.
Take a section of bridle line a little more than double the required Tracer length (e.g. ~30cm for a 10cm Tracer) and fold it in half. Loosely tie an overhand knot around the loop, tightening it towards the free ends. Slip the loop over the nail at the 0-Line, and make the final adjustment to the position of the knot so that it lies directly over the specific mark (at 10cm, for example), and then pull tight. Cut the bridle line 5mm or so past the knot and flange the ends, in situ, with a cigarette lighter.
The loop end will be attached to the bridle with a Prussik knot (next section) and the knotted free ends will form the point to which the flying lines attach.
When creating an Active Bridle for a kite, you may wish the leave the existing bridle on the kite. Attach the new bridle to the kite, leaving the existing one in place and then simply switch the flying lines between the different bridles to compare the flight characteristics of one against the other.
This method is strongly recommened when designing an Active Bridle for a kite from scratch. By leaving the original bridle on the kite, you have something to gauge your new bridle measurements against. The bridles can be held taut alongside each other to give an approximation of where the required connecting points should be on the Active Bridle. See the section below on "Designing and Tuning an Active Bridle" for more information.
When the Active Bridle has been properly configured and gives satisfactory results, the original bridle can be untied and removed from the kite.