Tuning Parafoils and Flowforms

Parafoils are powerful kites that will fly in a wide wind range. While they are easy to fly, their designs are complex and may require a modest amount of tuning to achieve optimum performance.

If the kite works, don't fix it! But if you have symptoms such as excessive movement, low flight angle, or lopsided flight attitude, these tuning 'tweaks' should improve performance.

Remember that wind conditions may be affecting performance. A properly tuned kite may still not appear to fly properly in swirling, unsteady and gusty winds. Smooth winds can be found in more open spaces and at higher altitudes.

Each style of flowform or parafoil is different and each presents unique tuning challenges. Experiment! The following suggestion are general and may not apply to each kite design. We've started with the easiest 'fixes' and worked our way up to the more difficult ones.

The Easiest Fix: If your kite isn't flying straight, before you start adding tail or fussing with bridle lines, check to see if one of the cells doesn't have a handful of sand stuck at the bottom...

Increasing Drag at the Base of the Kite: Suttons, Shannons, and SkyFoils all need some drag in order to maintain stable position. This can be accomplished with drogues, tubes, tails, or spinners. The purpose of these attachments is to steer the kite's nose into the wind.

Larger kites or stronger winds require more drag. It is particularly important that the drag be centered behind the kite. This can most effectively be done using a "yoke" line connected to tabs provided at the base of the kite.

Check to be sure that all lines are symmetrical from side to side. In other words, the left line and right line should be the same length. Longer yoke lines are more efficient and the drogue should never be attached directly to the kite since it will be caught in turbulence created as the wind moves over the sail.

Pilot Parafoils generally do not need tails or drogues.

Yoke Line for Drogue

Bridle Balance: Bridles are the lines that attach to keels on the kite and gather together at a "Tow Point". Your flying line is then connected to the Tow Point. In kites with multiple keels, lines from each row of keels will be gathered together and tied to a thicker "Main Bridle Line".

Balance Bridle Lines

It is important that pairs of lines from similar positions on the kite be equal in length. For example the upper right and upper left, or center left and center right should be equal. This maintains balance in the bridle.

Lines are supposed to be measured and set at the factory, but no system is perfect. If the kite is not stable, check the length of bridles.

Remember that bridle lines can stretch over time. If a kite flies well when new but later becomes less stable, check to see if any lines have stretched disproportionately.

The Pilot 75 is particularly susceptible to bridle stretch on the top four lines after exposure to strong winds. If the kite becomes sluggish and begins to fly at a lower angle, shorten these four lines by an inch at a time until performance improves.

Tuning: Tuning is a slow process involving small adjustments to the bridles and a lot of launches and recoveries. Pick a day when the wind is on the light side, 7-10 mph or so. You'll really beat yourself up trying to tune the kite in a howling gale. It also helps if you can tune at the beach or somewhere with smooth surface winds so you don't have to get it up very high.

By adjusting your Tow Point along the Main Bridle Line, you change the angle at which the kite leans into the wind. This is called the "angle of attack". The easiest way to check your tuning is to hold the kite near the Tow Point and see how different angles affect stability. But remember that the kite will perform differently once it is up and out of the more turbulent ground winds.

If the kite climbs sluggishly, sweeps slowly from side to side at low altitudes, or flies at a low angle, performance may be improved by decreasing the angle of attack. This will allow the kite to fly more parallel to the ground.

Move your Tow Point up along the thicker main bridle so that the bridles attached to the top of the kite are shorter, and those at the bottom of the kite are longer.

To increase pull or slow down erratic side-to-side movements, move the Tow Point down. This will increasing the angle of attack, pull the base of the kite more toward the ground and present more of the sail directly to the wind.

Angle of Attack

SkyFoils will fly best when most of the tension is on the top lines and the other bridles are nearly slack, serving only to maintain balance in gusts.

Tuning Range Each foil design handles differently. Generally, you can adjust "forward" until the kite stops flying. Then adjust back until the kite won't lift. The space between these two marks shows you the tuning range available.

Adjustments within the tuning range can affect performance for high or lighter winds, or flight angle versus lift/pull. Experimenting is half the fun!

Launching in Light Winds: For launching in general, there are three basic situations --- (1) line anchored, (2) launching with assistance, and (3) launching alone. In all cases, the trick in light wind is to get the cells inflated and then gain altitude.

In moderate winds, you can anchor the kite on a short amount of line, inflate the kite by holding cells open, and then let it go. You then just walk back to the anchor point and let out more line.

With assistance, you hold the line and have your friend(s) hold the cells open. Well intentioned volunteers tend to want to hold the keels rather than the cells and the trick is getting two people to let go at the same time. But once the kite is inflated, you can give the line gentle tugs to fill it and gain altitude. In lighter winds, you simply start with a longer line and pull it in to generate more altitude.

When you are alone and breezes are light, your challenge is to be close enough to the kite to inflate it and far enough down the line to give it a helpful tug. There are lots of different techniques. Mine is to hold the kite by the outside corners, arms outstretched, and 'shake' some wind into the cells. As they begin to inflate, I slide my hands down the keel to the outside bridle lines, and then slide down the top outside bridles to the tow point. In particularly light winds, I also walk backwards to generate a bit more wind. Once you get to the main flying line, you can continue moving back and letting out line until you gain enough altitude that the kite will hold and begin to lift on its own.

Bridle Alterations: If bridle lines are all balanced and neither tails or angle adjustments provide stable flight, it is possible that a sail stretch or small construction error has resulted in an unbalanced kite. As a last resort, fine adjustments can be made to individual bridle lines.

Line Adjustments

It is important not to make permanent changes to bridles until other alternatives have been explored. Temporary adjustments can be made by shortening lines where they connect to the main bridle, tying knots, or larksheading a small stick into the line. Test everything before finalizing the changes.

When the kite is flying, look for kinks in the bottom sail. These kinks will indicate where a row of keels is pulled in too tight or too loose. You want the bottom of the kite to look smooth front to back, and if you can see the top of the kite, the same applies. Adjustments are very small, 1/4 inch at a time. Adjusting one row will affect the other rows, so expect to do a lot of tweaking.

A Few Words of Caution: Large Parafoils are powerful kites, and can hurt you if you are not careful. Long-line launches are not recommended in anything but the lightest wind as the kite generates too much pull climbing through the power zone. Walk the kite into the air. Similarly, never try to fly from a free line. Always have the kite tied off to a good, solid anchor. Always bring the kite down by walking the line with the help of an assistant. And get a pair of good gloves!

Conclusions: If you fly larger foils, you need to learn how to tune. It isn't as hard as it looks. However, it will help to make your adjustments in smooth steady winds so that you don't have to tune again when the winds change.

Remember to make alterations incremental -- small bits each time, and not to finalize the changes until you are sure they work. Experiment and become familiar with your kites. Soon you'll be helping others and impressing them with terms like Tow Point and angle of attack...


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