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Welcome to the Frequently Asked Questions. Below, we have tried to answer the most common questions visitors to our Web site may have. If you find that your question is not answered on this page, please email us at bw.moore96@bigpond.com or Mike Richards at info@kitesite.com.au
Q - How big are the kites you use to attempt records?
A - Currently we use 11.5 sq meter DT Delta kites. These are 6 meters wide and 2.8 meters tall. They weigh approximately 3kg without instruments, lights and camera.
Q - What are the kites made from?
A - The frame is fibreglass tube and the fabric 1.5 wt ripstop nylon cloth. There are some other fittings such as solid tube joiners, end caps, webbing and 2mm Dyneema cord bridle. The cloth panels and spar sleeves are double sewn throughout and reinforced in key locations with nylon webbing.
Q - Do you fly the kite by hand?
A - No, except in very light winds the kite pulls too hard and the line so thin it may actually cut a hand off. In winds of 15 knots the line tension is 35 kg or 80 lbs.
Q - How do you fly the kite?
A - We fly from very thin and strong line which is controlled by an electric motor driven reel and winch system powered by a 5.5 Kw generator. The kite is always launched facing directly into the wind and our backs to the wind. The wind must be above 5 knots (10 kph) before our big DT Deltas will rise into the sky. The wind must increase in strength as the kite rises to compensate for thinner air and less lift and also more line weight and wind drag on the line. Our big kites fly just like smaller kites flown from the hand except we use a winch and need a little more wind.
Q - How do you launch the kite?
A - The line is always secured to an electric winch. We attach the other end of the line to the kite bridle which is simply a fixed length group of lines that distribute the load evenly on the front kite spar and also sets the angle of the kite’s attack to the wind. In strong winds we unwind 100 meters of line from the reel by reversing the winch then 2 assistants carry the kite until the line slack is taken up, hold the kite into the wind with the line tense and then release the kite, thrusting it upwards. The wind accelerates it upward, slowly at first, until it reaches it’s maximum angle of about 65 degrees, that is the angle of the flying line is 65 degrees to the ground. In light ground winds, we release a lot more line, up to 500 meters, then we wait for a gust of wind, release the kite at the same time winching line into the wind. Hopefully it will climb rapidly to over 1,000 ft and there is stronger wind higher up to sustain flight.
Q - How strong does the wind need to be?
A - For the kites used for record attempts, 5 knots or 9 kph is the minimum for sustained flight at ground level. Ideally 15 knots or 28 kph will enable high flight angles and release of line at a steady rate without loss of kite angle or line tension. For every 1,000 ft of height, the wind needs to be 1 knot or 2 kph faster. This is to compensate for lower air density and the weight of and resistance of kite line. By 18,000 ft the wind should be a minimum of 23 knots and ideally 28 knots. The maximum wind tolerated at ground level is 25 knots but the DT Delta kites have tolerated 55 knots at 6,500 ft but this is extreme and would unlikely result in high altitude flight due to kite and line drag.
Q - How much and what type of line do you use?
A- We have several reels of high strength synthetic line. The latest has two 6,000+ meter lengths of Dyneema joined end to end to make a continuous line of over 12,000 meters. Two other reels have 11,000 meters of 300 lb line made from Amika UHMWPE and 200 lb Spectra (Honeywell UHMWPE). These are backup line in case a kite breaks away, taking a large portion of the line with it. Dyneema is made from the strongest fibre in the world, HMWPE and the line made from this fibre is very light and thin. To break the record at least 7,000 meters needs to be used under ideal conditions. With marginal winds, 10,000 meters may be used to reach record height of 15,000 ft and an 18,000 ft flight as much as 12,000 meters.
Q - How do you measure the kites altitude?
A - We use GPS radio telemetry coupled with a base reciever, a laptop and software. We also place a small Garmin GPS unit on the kite as a backup recording device. Where feasible, two theodolites are used to read kite angles and position in conjunction a triangulation formula. The altitude and position is displayed in real time on screen using GPSflight software. The GPS unit is connected to laptop once the kite has returned and flight data downloaded to Garmin GPS software for display as a flight graph and tables of flight data.
Q - How cold is it at record altitude?
A - The temperature varies depending on the time of year but a 20 degree C ground temp will drop to about -8 deg C at 15,000 ft and -12 deg C at 18,000 ft. This could be a problem as the fibreglass tube spars may become brittle. Carbon batteries cannot be used so we use alkaline, NiCad or NiMh batteries. The electronics is in a high density styrofoam box and the heat generated by the radio telemetry should keep the temp inside the box a few degrees higher than the outside temp.
Q - Can you see the kite with the naked eye.
A - Yes, below 8,000 ft in clear skies. It’s a large kite designed to be clearly visible in a blue sky. Up to 5,000 ft it is easy to see but after 8,000 ft it becomes increasingly difficult to locate with the naked eye. We have theodolites, telescopes and binoculars to view the kite but the viewer needs to know approximately where to look to locate with binoculars. In hazy conditions it cannot be seen above about 5,000 ft even with the most acute vision.
Q - How long does it take for the kite to reach high altitude and return to ground?
A - It took 7 hours to reach 10,681 ft then return to the launch point but the winds were light and variable requiring lots of counter-winching. The flight time depends on the wind. Under ideal conditions a record altitude to 15,000 ft should be reached in 4 hours and a return achieved in 3 hours.
Q - How is the winch powered?
A - It is powered by 240 volt, 5.5 Kw generator driving a 1 hp 240 V AC motor through an inverter/controller. The motor drives through a system of belts, pulleys and a slipper clutch. The motor is capable of hauling up to 140 kg line tension at 10 kph line speed.
Q - Do you fly kites at night?
A - No, the conditions of flying stipulate that high altitude kite flying can only be attempted in daylight hours which is usually half an hour before sunrise and after sunset. We do have high intensity flashing lights onboard in case the kite is delayed being recovered until after last light.
Q - You are attempting the record in a remote area near Cobar in Western NSW, Australia. Why is that?
A - The Civil Aviation Safety Authority has located our record attempt in a zone with little air traffic below 20,000 ft. We chose Cobar because it has a weather station that releases radio Sonde balloons daily. We can access wind data to high altitude every morning which helps us decide on a launch and flight strategy. The weather forecast is also important to avoid any dangerous wind or storms.
Q - What are the biggest barriers to breaking the record?
A - Finding adequate wind throughout the height profile on most days. Line drag is the main physical factor. But not enough time to wait for good wind conditions has become the major barrier.
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