One of the most common questions about power kiting is what is the difference between the different types of power kites. Snow and water kiting uses kites that are quite large in size while kite buggying will use a kite nearly half or even smaller in size. So I have put together a basic blog on the differences between the different types of power kites. This was an anser to a post on one of the online kite forums. Hopefully it will help clarify these differences and help educate anyone else who may have the same question.
What the heck is a fixed bridle and why would you depower a power kite?
For a little bit more clarification.....and because you are most likely a beginner (which is very welcome on here) and also because there are tons of lurkers on here who have not yet asked the excellent questions that you are asking, I will go into a bit more detail on this one.
First lets explain what a Bridle is. The "bridle" of a kite is the line or network of lines that run from the sail of the kite or skin to the point where you attach your flying lines to. This can be a very complex network of lines that "V" off into several other lines which eventually attach to the kite....OR, it can be a very simple one or two lines that runs from the edge of the kite to your flying lines. Basically any line or lines that are permanently attached to the kite that you hook up your flying lines (or control lines) to is considered a bridle. There are many different types of bridles on the planet, for this purpose we will only be discussing the two most common bridles used in power kites which generalizes the kites into two classifications. This would be the "Fixed Bridle" and the "Depowerable".
A "Fixed Bridle" is basically what it says. The bridle is "Fixed" or permanently attached to the kite and is set up in such a way that it should not ever be changed. In most cases it is not recommended to change or adjust a Fixed Bridle. A Fixed Bridle is usually set up from the factory to give the optimum performance of a sail shape. By altering the bridle you will alter the shape of the sail which will usually negatively affect the performance and/or stability of the kite. To put it in simple terms, a "Fixed Bridle" kite is one that the bridle of the kite is permanent and the physical length and settings of the bridle cannot be changed during flight. With multiple bridles (dual or quad), you have the ability to change the angle of attack of the overall kite wing, but the actual shape of the bridle and sail is in a fixed position.
The other type of bridle setup that is discussed is a "Depowerable" bridle (also referred to as a "Depowerable Kite"). The easiest way to classify this type of bridle is an "Active Bridle System" that can be changed on demand from the pilot during flight. This type of bridle starts out similar to the "Fixed Bridle" in that the majority of bridle lines are still attached directly to the sail, but this type of bridle will usually be quite a bit more complex and usually incorporates additional pieces such as guide lines and pulley's to make the bridle active and adjustable during flight. With this type of bridle, the pilot will have the ability to change the physical shape/curvature of the sail as well as change the overall angle of attack during flight and pretty much "on demand". The most common setup would be with using a free floating control bar that can be pushed/pulled to change the curvature of the kite (through the active bridle) while you fly. The basic operation is that when you pull the bar towards you, you don't change the angle of attack of the sail but instead pull in the trailing edge of the kite (bottom) as well as the middle of the kite while the leading edge stays constant - basic terms, your changing the actual curvature of the sail while the kite is flying in the air. This is done at a ratio that will allow the kite to increase or decrease power while still maintaining stability and control. Think of it as having a large bed sheet and holding it in the wind. If you hold onto the very top of the sheet and let the rest of it hang loose, the bottom of the sheet will be picked up by the wind and it will just flap away in the wind with very little power. Now have someone else grab onto the bottom of the sheet and start to walk back towards you, pulling the sheet so it catches the wind. The Sheet will billow up and start to produce power. This would be similar to what is being done on a depowerable kite while you pull the bar towards you. You are "cupping" the kite in the wind to create more power. When you let the bar out, you spill the wind off the sail and the kite becomes "Depowered". Because of the overall design of depowerable kites, they generally produce less power per size than a fixed bridled kite. Remember that the curvature of a fixed bridled kite is set at maximum power all the time. A Depowerable kite needs to be adjusted by the pilot to find the optimum power setting for the current winds. Also, because a depowerable kite needs to be able to stay flying and maintain stability when not set at the optimum setting, extra design and material must be used to keep the kite inflated and flying at settings that are far from optimum (when the kite is depowered). This comes at a cost of overall performance. Because of this factor, depowerable kites are usually quite a bit larger in size than fixed bridle kites to produce the same power, Depowerable kites are usually slower and not as agile as Fixed Bridle kites because of their larger sizes and increased mass in the air.
To put it in a nutshell and in simplest form. Fixed bridle kites have the bridles that are in one "Fixed" position and (in most cases) should not be changed. Depowerable kites have an active bridle that can be altered on demand from the pilot during flight.
Fixed bridle kites will produce a lot more power per size and be more efficient. Depowerable kites will produce less power per size but will have more wind range that they can be flown in because they can dump the wind and power as it increases.
Fixed bridle kites are set in the power they deliver in a given wind/speed. Depowerable kites can give bursts of power on demand by powering the kite up in excessive wind conditions. (Think getting big air on your board at any time!)
I hope this helps everyone understand the differences between fixed bridled kites and depowerable kites a little better.