Kite 101 : Flying Characteristics

Behaviors noticeable after attachment of cradle to kite line.

Frequently individuals who are interested in KAP (Kite Aerial Photography), but have never flown a rig, have false expectations about the stability of a flying KAP rig. A KAP rig is almost constantly in motion because of small changes in wind speed and wind direction. The periods where the KAP rig appears fixed to one point in the sky only last for a few seconds.

#1. Yo-Yo Effect

The wind constantly changes speed. The amount of pull on the kite line will also be constantly changing, producing the yo-yo effect. The KAP rig will gain and loose altitude with every small change in wind speed. The magnitude of this effect varies with different style kites, and some locations may have steadier winds than others.

#2. Lateral Swing

A picavet and a properly designed pendulum will keep the rig level as the angle of the line changes, however neither will prevent lateral swinging caused by the kite constantly changing horizontal direction.
(see l’arc stabilisateur below for a solution)
Most KAPers wait to trip the shutter when the swinging motion has subsided and the rig is level to prevent motion blur and to achieve a nice level composition. In high winds this problem is more persistent.

Read also : Measuring Wind Speed

#3. l’arc stabilisateur by Christian Becot

Christian Becot published this solution to lateral swing in the aerial eye (4:2). Two small sails are placed on a bowed horizontal spar. This creates a dihedral between the two sails which helps dampen the lateral swinging motions. Notice that the crosspiece is mounted high on the pendulum near the kite line, this keeps the stabilizer from pushing the pendulum back from vertical. Brooks Leffler used a variation on a picavet mounted stereo rig (the aerial eye 4:1)

#4. Camera Distance From The Anchor Point

This is an overhead view of a person flying a kite with two cameras attached at different locations on the line, the camera furthest from the person moves a much greater distance in the same amount of time than the camera closer to the person. The furthest camera is therefore moving faster than the closer camera.

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This faster speed will cause greater lateral swinging. The combination of increased swing and greater lateral speed could cause blurred photographs. In turbulent winds moving the camera closer would lessen the chance of blurred pictures.

I think that’s all. Any question? 🙂

 

Measuring Wind Speed

windmill pointing east

When measuring the wind speed with an anemometer you discover that the wind is constantly changing speed. It makes more sense to refer to the wind speed as a range of speeds. For example you would say that the wind speed was between 4 miles per hour and 8 miles per hour.

This is the beauty of the Beaufort scale it groups wind speeds into logical groups and assigns a single number to that group of wind speeds. This makes it easier to refer to the speed using a single number. This number can then be understood by anyone whether they are more familiar with mph or kph. I suggest that you become familiar with using the Beaufort scale.

The National Weather Service has an interesting article about the Beaufort scale. It includes a history and pictures that show what the sea looks like at each Beaufort number.

I would caution you not to make numerical estimates of wind speeds if you have not used an anemometer to verify your estimations. It is ok if the estimates are for your personal use, but be careful to qualify your observations when sharing them with someone else.

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Before I had a wind measuring device my estimates were as much as 6 mph too high. This would translate to a Beaufort number higher by 2. Learn to read the wind signs for Beaufort 1, 2, and 3. Kite selection in these three ranges is more critical. In Winds of 4 Bft. and above just about anything will fly.

0 Beaufort (Bft)– Too light for flying any type of KAP equipment unless you are using the “No-Wind” techniques.

1 Bft.– Still too light for most KAP applications. You might be able to use a Dopero to lift a rig that weighed 0.5# (227g). That would be a disposable camera with an ice trigger and a balsa cradle.

2 Bft.– The upper half of 2 Bft. is where serious KAP work can begin although you need the right kite and light cradles. My LASS rig with a Dopero works great in this range.

3 Bft.– You can lift most cradles with most kites.

4 Bft.– Winds generally dictate going to smaller kites to cut down on the amount of pull.

Bft. 5 and above– I don’t fly. That is my personal preference. At these wind speeds the experience ceases to be fun.

Bft. 6-7– I have lost a kite and cradle in winds that were between 6 and 7 Bft. when my 200# line broke.