Basics / Kites /

The Kite Pull Cooperative Experiment

A Call For Help

If you are interested in contributing to KAPER but don't like writing, you could help by performing measurements of kite pull in various wind conditions. The results of these tests will be included on the page for that particular kite found on the Basics/Kites page.

The Guidelines
The Procedure
The Results

The Guidelines

Materials Needed

Wind Meter, (anemometer)
Accurate Scales (at least 50lb/25kg.)
Protractor - to measure the kite's average flight angle above the horizon.
Kite & Line
Paper
Pen
Anchor - A means of tying off the kite or an assistant

Results are only valid if the proper instruments are used!
Be sure to read the following information about anemometers and scales!!!

Anemometer

The anemometer in the picture to the right is of sufficient accuracy for these tests. These are relatively cheap (less than $20US) and surprisingly accurate. It is requested that you have an instrument at least as accurate as the one pictured. Estimates of the wind speed from your "experience", not using an anemometer, are unacceptable. I was surprised when I first used an anemometer how far off my previous estimates of wind speed were.

Scales

Make sure that you use an accurate set of scales. I originally bought a cheap set of spring scales sold in fishing stores. These were so inaccurate that I could not use them. I reluctantly spent close to $30US for the digital fish scales pictured, and they proved to be very accurate.

You will probably find most spring scales to be inaccurate. One could possibly make a new, more accurate dial or a conversion table by measuring known weights. Make sure that you use enough weights to cover the whole range of your scale, because many spring scales respond in a non-linear fashion. For example if the dial moves 1 inch from 1 pound to 2 pounds, it may only move .75 inches from 10 pounds to 11 pounds.

The Final Word: make sure your scales are accurate!!!

The Procedure

Find a flying field that has as little wind obstruction as possible so the wind will be as turbulence free as possible.
Launch and fly kite with 200 feet of line plus or minus 50 feet (60 meters +/- 15 meters)
Anchor kite.
Measure the wind speed for 30 seconds
Record the average low and high values observed during this period
Record the gust speed if it repeats more than once during the 30 second measuring interval.
- Average low and high means the range that the wind speed was in most of the time NOT the absolute lowest value when the wind died for a second or two and NOT the highest value when the wind gusted up for a second.
Tie a loop in the line at chest level between the anchor and the kite to attach the scales.
Measure kite pull for 30 seconds.
Record the average high and low and any peak spikes related to gusts that you may have recorded.
- It’s good to get a feel for what the wind feels like in its average range so you can tell if the wind speed has stayed in that range during the pull measurements. If you feel the average wind pick up or die down while measuring pull then start over at STEP 4.
Measure average angle of flight
Remeasure wind speed for 30 seconds. If the average wind speed is in the same range as in STEP 4 and 5 then keep the results
- If the average wind speed is significantly different start over at STEP 4.
Repeat the experiment on different days and in different wind conditions.
- The upper limit will arbitrarily be 25 mph

NOTE: If you have assistance then you can measure the average wind speed at the same time that you measure kite pull and then you will not have to remeasure in STEP 11

The Results

Send your results to:

If you send your results by e-mail remember that most e-mail programs do not handle formatting well. Send a copy of the e-mail to yourself first to see if it will arrive in a readable form. Below is an example of what you should send.

EXAMPLE

Date of Test	Type Kite (Size, Manufacturer, etc.)	Avg. angle of flight	Avg. Wind Range	Peak Wind	Avg. Kite Pull	Peak Kite Pull
?	?	?	?	?	?	?
?	?	?	?	?	?	?