Kite Simulations

At work, use computational fluid dynamics (CFD) to simulate air flow over aircraft, ships, things carried by aircraft, etc. I also get the chance to do a little bit of development work. This past year, some people have been asking for the capability to simulate catenaries — in other words, cables and systems of cables used to connect objects together in dynamic systems. These are used for all sorts of purposes, including towing objects behind boats, connecting a parachute to a jumper, lifting objects with helicopters, and (the thing that gets me excited) flying kites!

I always jump at the chance to do anything related to my hobbies for work, so I jumped at the chance to work on this. Without getting too much into technical details, here is the basic approach used to simulate a catenary. Each cable is divided into an equal number of segments. The mass of each segment is assumed to be concentrated in discrete points at the endpoints of each. Tension, gravity, and air flow apply forces to each of these points. Applying Newton’s laws of motion to each point produces a large nonlinear system of equations, which, when solved, gives the shape, speed, and tension in the catenary. The tension at the end of the cables then produces an equal and opposite force to whatever they are attached to, like a kite. The overall fluid properties (a.k.a. flowfield) and the motion of bodies other than the catenaries in the simulation are handled by the computation fluid dynamics code.

To test it out, I modeled my Barn Door kite and set up two catenaries: one for the bridle + kite line, and the other to model a tail. For now, the kite is assumed to be rigid in the simulation, and the bowing of the horizontal spar is built into the shape. The line is 200 feet long, and I made the bridle as close to the real 5-point setup as possible, with the mass and properties of the bridle and line intended to be similar to 200-lb-rated dacron line. In the simulation, the kite is flown in a steady, uniform, 7 mph breeze. I had to estimate the center of mass of the kite. At first, my estimate was too far back, resulting in the kite spiraling out of control:

Attempt 1: aft CG makes the kite unstable

This was a little surprising to me, because I was under the impression that an aft CG is always good for a kite. I guess there is actually a limit to that. The next test moved the CG forward, closer to the horizontal spar. That fixed the stability problems, resulting in a nice smooth simulated flight:

Attempt 2: CG problems fixed, resulting in stable flight

Encouraged by that success, the next step was to simulate KAP. An additional point mass of 14 oz was added 50 feet down the line to model a KAP rig. The results are kind of interesting. The shape of the line with the point mass looks right based on my experience with real KAP. The kite is also a bit less stable with the extra weight on the line, which is also consistent with my experience. The high-frequency “wobbling” motion of the kite happens in real life too, at least with the Barn Door design. My other kite, the Mini Dopero, doesn’t do that, so it might be interesting to try that kite in the sim too.

Kite aerial photography simulation

So what’s the use of this simulation? I’m not totally sure. Qualitatively speaking, it seems to produce results that are consistent with real life. CFD is computationally expensive, though; each of these simulations took a dozen or two hours on a couple hundred cores of a supercomputer. For now, they are somewhat limited in that the kite is assumed to be rigid, but some flexibility could be included in the sim using this CFD code (maybe not full sail billowing, but at least spar bending). Turbulence and gusts could also be included. For someone with the resources available, this type of simulation could maybe be used to study how sail shapes and mass properties affect kite stability. For now though, it was mainly for fun. I hope you enjoyed these videos!

Smooth Winds at Point Lookout

It was late November, almost four months after my first KAP session. Nearly all of my outings to this point had been two different parks, and mostly just trying to get the kite really high to take a picture of the landscape. I decided it was time for some variety, so I headed down to Point Lookout, the very end of the western peninsula of Maryland. There is a lighthouse at the end of the peninsula, and I was excited to have an actual subject for my photos this time.

Unfortunately, when I got there, I soon realized that was not to be. The last couple hundred yards of the peninsula were blocked off, as renovations of the lighthouse and other buildings were in progress. The wind was blowing from the east (across the peninsula instead of along it), so there was no chance of flying the kite over the lighthouse to take pictures. I could have still aimed the camera that way, but then it would have been pointing into the sun, and the pictures probably wouldn’t have turned out that great.

So instead, I decided to take pictures back up the coastline to the north. There was a boat close to the shore that should look nice, if it would stay there anyway. Besides, then I could see what the beach area, which I know well from the ground, looks like from the air.

With the wind coming from the east, there was only a very small area to launch a kite. The edge of the beach is covered in rocks, but there was a space with some sand where I could set up. Some fishermen were in the area, casting their lines down into the water while I hoped to keep mine up and out of it! There is a picture of the area where I was flying below, taken by the KAP camera when it was only about 10 ft off the ground.

The wind was about 10 mph and pretty steady, so I selected the Mini Dopero for the flight. I prefer this kite when there is enough wind, since I can set it up and have it in the air in just a couple minutes. It turned out that having such a small launch area was no problem at all. With the smooth sea breeze, flying the kite was as easy as setting it up and letting it go! No long-line running launch was needed to contact stable air as is often the case inland. In fact, if there is one term to describe this session, it is easy! Flying over the water was a new experience for me, but the wind was so smooth that there was never a concern about losing the rig. I should fly here more often!

With such a smooth breeze, I was able to attach the KAP rig less than 50 feet below the kite. I knew from past experience not to put it much closer than that, since it can cause stability issues and make for “interesting” landings. I didn’t bring my good camera for taking pictures from the ground, but I was able to snap the one you see on the left with my phone while the kite was still pretty low. Everything was soon up and away with little effort.

Like I said, the flight was very smooth, but that doesn’t mean the camera didn’t swing around a bit. One thing I like about an AutoKAP rig (in my case, just a fixed rig with an intervalometer) is that the swinging can actually be a benefit; though most of the time it results in pictures that are blurry, poorly composed, or with a severely tilted horizon, every once in awhile it turns up some good ones. Take, for example, the pictures below. Luckily for me, the boat remained nearby the shore for almost the whole flight, which added a nice extra element to some of the pictures. In these ones, the camera was swinging downward just as the shutter went. As a result, the boat became the main subject, even though that wasn’t planned.

There were also a few times during the flight when the wind reduced by one a mile per hour or two, the kite stopped pulling, and the line became a somewhat slack. It wasn’t enough to be concerned, and I was ready to wind it in very quickly or even run the other direction if needed, but it never ended up being a problem. A slightly more forward tow point would have helped. Eventually I got all 700 feet of line out, let it take some pictures, and then started winding it in again. Here are a couple more of my favorites.

The boat did end up being a nice element in a lot of the photos, like the first one above. The second one shows the beach area, which is shielded by some man-made rows of rocks out in the water, presumably to reduce the impact of waves and currents on swimmers. The fishing pier, a Civil War-era fort, and several other buildings are also visible from this altitude. Point Lookout actually has a rather interesting — albeit somewhat morbid — history dating back to the Civil War and even before. You can read more about it here:

Point Lookout State Park History

I’m looking forward to flying here again. Hopefully next time the renovations will be done, and I can take some pictures of the lighthouse and the other buildings at the tip of the peninsula.

Back to Chancellors Run Park

A couple weeks since my last outing, the leaves on the trees were a bit more colorful, and Chancellors Run Park was calling me for another KAP session. My goals for this time out were:

  • Take some pictures towards the north, where there should be some interesting things to see.
  • Capture some Fall colors.
  • If there was time, also take some pictures towards the south / southeast, which I hadn’t done the first time.

The weather forecast indicated that the winds would be best in the morning, so that’s when I headed over. When I got there, I went to the same softball field as previous time and set up the Barn Door kite. The Mini Dopero probably would have worked too, but I wanted to use the new one. The wind was gentle-to-moderate, so in the upper part of the Barn Door’s range. In this wind, the big kite was easy to get in the air. After flying for several minutes to be sure that the kite was trimmed and flying steadily, I attached the KAP rig and started the CHDK script to take pictures.

Overall, it was a pretty good flight. There were a couple times where thermals appeared, and the kite went to a very high line angle, but there were no loops or dives. The most nervous part of the flight was when the wind became stronger for several minutes, the kite flexed and billowed, and the drag pulled it down to a very low line angle (maybe 20 degrees). A few hundred feet of line were out at this point, and I had to keep walking around to keep the long outstretched line away from trees, stadium lights, and the back fence of the softball field. Thankfully, eventually the wind relented and the kite climbed high again. The people in the spin class in between the softball fields must have gotten a good look at it while it was low! I hope it wasn’t too distracting…

Eventually, I got all of the line out and got some very nice pictures to the north, one of which I currently have as the cover photo of this website! There were some Fall colors, but really they just don’t get as brilliant here as they do in other places, even a couple hours to the north. Oh well. With the year dragging on towards winter, the sun was fairly low in the sky and cast long shadows on the ground below. With the camera high in the air, Lexington Park, California, the Patuxent River, and the Gov. Thomas Johnson Bridge were all visible, making for a very nice representative view of Southern Maryland. You can see some of those pictures up near the top of the page.

After bringing the kite down, I had a little time for another flight to take pictures in the other direction. The sun was in that direction, so I wasn’t expecting great quality, but some of them did come out decently. Due to time, I didn’t fly as high. One of the better ones from that short flight is posted above. You can see all my aerial photos from this park in the Chancellors Run Park Aerial Photo gallery.

New Kite, Old Park

I had been thinking about making a new kite for a little while. The Mini Dopero has a nice wind range, but it struggles to stay in the air (much less lift a rig) in light winds, and of course it has an upper limit too, of about 20 mph. So the question was whether to make a new kite for light winds or for strong winds. Well, my frustrations over the last month of trying to KAP at St. Mary’s College convinced me that the light wind end of the spectrum would be more worthwhile to take care of first. Thus, the Barn Door kite was born!

This is a big kite, standing over seven feet tall and over eight feet wide, with a sail area of 41 square feet (almost 4 square meters), nearly twice that of the Mini Dopero. It is also light, weighing in at 18 ounces, only 5 more than the Mini Dopero. That combination of big and light should allow it to lift a rig in a very light breeze. If you want to read more about the kite itself, including tips and links to get you started on building one, see this page.

I surprised myself with how fast I built the kite. I guess having one under your belt helps, because this one only took a few weeks of my spare time at night before going to bed. After a couple successful short test flights around the open area in my neighborhood, it was time to try it out in a KAP session. I headed back to Lancaster Park again, which is a good place for test flights, being the biggest park around. Also, since my last KAP session at this park resulted in promising views to the north, I wanted to try again but hopefully with more altitude this time.

When I reached the park, the wind was blowing a little stronger than I had hoped for a first KAP session with this kite. Branches were swaying, and the wind seemed firmly into the Mini Dopero’s territory, so it definitely wouldn’t be a light wind test. At the same time, it’s not like it was at the top of the Mini Dopero’s wind range, so it might be a good opportunity to probe the upper range of this new one. Worst case scenario, if the kite seemed to be pulling dangerously hard, I would just bring it back down right away and switch to the other one.

Since the wind was on the stronger side, I attached a drogue to the kite before launching. I flew it for several minutes on 100 to 200 feet of line, just to get a feel for how it would handle the wind. It definitely had some pull, and the long carbon fiber spars flexed quite a bit, but it didn’t seem to be overpowered by the wind. The flexing of the spars and billowing of the sail seemed to allow it to “shed” some of the force of the wind, whereas a completely rigid kite would have pulled too hard. It’s good to know that this light wind kite can hold its own in somewhat stronger winds too! One thing I did notice about it was that if it faced a stronger wind over a sustained period, the increased drag from the flexing and billowing would cause it to fly at a low line angle. One could imagine that if the wind were strong enough, it would pull the kite right down to the ground (or worse, get it stuck in a tree or the line caught on something). That is probably the main factor that determines this kite’s maximum wind speed.

With the kite now flying steadily, I brought it down to about 100 feet, attached the rig, and started the intervalometer script. It was a fun flight, and I did end up with some nice views of Lexington Park and the Gov. Thomas Johnson Bridge to the north. That bridge really adds a unique element to aerial photos taken around this part of Southern Maryland. I will have to find a spot to fly closer to it one of these days for closer photos of the bridge and surrounding area.

A couple of the pictures I liked from the session are shown in the gallery above. In addition to being close to the upper end of this kite’s wind range, the wind direction was also changing periodically, and I found myself walking back and forth over the width of the soccer field to try to keep the kite away from the trees on one side and the parking lot on the other. In the second picture above, you can see me far below standing right at the edge of the field — the wind must have been coming more from the west at that point. The leaves on some of the trees were just starting to turn colors, too, adding some character. Maybe in another week or two they will be brighter.

While bringing the kite down, I took the opportunity to secure the winder to my big-ol’-bag-o’-rocks(TM) by wrapping it around the strap a few times and take some pictures of the kite from the ground. This was not an easy task, because the kite was directly in front of the sun most of the time! I managed to get a few decent ones, even one with the rig in view. As a bonus, the airborne camera took a picture of me at the same time, so I came away with the twin perspectives below!

St. Mary’s College

St. Mary’s College is a small school scenically situated on St. Mary’s River a few miles from where it empties into the Potomac. I had made a couple attempts to fly here in prior weeks without much success. The first time out, the wind seemed plenty strong all day but then died right when I went to fly. The second time was similar, although that time the wind was not quite as strong but steadier most of the day. During at least one of those attempts, the weather report still said there was a 9 mph wind while I was trying to fly, even though I could barely feel anything from the ground.

I think part of the problem with the wind here is the terrain, especially if the wind is primarily from the east. There is a hill at that end of the field where I was trying to fly, on top of which are tall trees, so if the wind is coming from that direction, it will be turbulent and weak near the ground. The other directions are also obstructed, but not quite as badly.

This time out, the wind started out fairly strong, with gusts definitely over 15 mph. I hadn’t flown the Mini Dopero in winds like that before, so it was a bit of a new experience. I came equipped with a drogue chute that I had recently made out of a plastic painter’s drop cloth, which would hopefully help stabilize the kite in these conditions. I got the kite flying without too much trouble, but it was definitely tough dealing with the gusts. The bridle wasn’t quite adjusted right, so it was pulling pretty hard and tending to head to the right. Nonetheless, the Mini Dopero can manage winds up to about 20 mph when properly adjusted and with a decent-sized drogue (mine is 2 feet long, with a front diameter of 9 inches and a back diameter of 3.5 inches).

I pointed the KAP rig towards the school and attached it to the line. Since I was uneasy with the wind, this would be a short flight, and I didn’t get too many good pictures due to the unsteadiness. Another factor might have been that I inadvertently set the camera to Auto mode instead of the usual Program mode, and that seems to give the KAP UAV CHDK script fits setting the proper exposure. I did manage to get one nice picture of the college with the lake as a backdrop, which you can see above. It’s certainly better than my previous attempts, which resulted in no pictures! Obviously, the closest part of the school is under construction, so this might make an interesting target to come back to again once it is finished.

The wind had been fairly strong and gusty all day, but then the wind suddenly dropped off, as it had in my previous outings here, and the kite and rig came down to earth again. The wind didn’t completely die, though, so it was worth trying to get the kite back into the air again. The drogue would no longer be necessary, so I took it off to reduce weight. I also reduced the bow in the spars a bit and made the bridle adjustments identified during the previous flight.

A few long-line launches ensued. I came close to getting the kite up and flying a couple times, but without fail it would start to descend about the time I tried to attach the rig to the line. I was about to call it a day but decided to give it one more try. This time, I decided to just try to fly the kite, not worrying too much about the rig. Finally, on close to 200 feet of line, the kite found enough breeze to remain aloft on its own, and I was able to attach the rig. Lesson learned: it’s better to attach the rig far below the kite than not at all, if the goal is to take aerial photos. Or, in other words, get the kite flying first, and worry about the camera second!

Another change for this flight was to angle the rig more to the west rather than northwest, in order to see more of St. Mary’s River as it opens up into the Potomac. A nice relaxing flight ensued, in which I was able to unwind all the line and capture several more good shots, a couple of which I’ve put in the gallery above. Some students walking by seemed confused about what I was doing at first until they noticed the kite far above in the sky! Overall, it was a good day, and I was glad to finally conquer this location.

Chancellors Run Park

For my fourth KAP session, it was time to try a new location: Chancellors Run Park. This park is not quite as spacious as Lancaster Park, but it has four softball/baseball fields right in the middle that provide plenty of space to fly a kite.

Walking out to the field with my kite rolled up, my picavet rig dangling from my hand, some gardening gloves, the winder, and a gallon jug of water — which I intended to hold the winder down while I attached the rig but which ended up being totally inadequate for the purpose — resulted in a strange look from the groundskeeper. “What are you doing?” he said as I walked to the softball field. I’d been told before that flying model aircraft from this park is not allowed, so the question made me a little nervous. “I’m going to fly a kite,” I responded. “Oh, okay, have fun!” That’s a typical example of the difference in attitudes towards kites versus drones.

The wind was from the north but sometimes shifting 90 degrees to the west. I took the Mini Dopero kite to the far end of one of the southeast softball field, set it up, and propped it up against the home run fence. The usual struggles with intermittent inland winds near the ground ensued, but eventually the kite was up. As mentioned earlier, the jug of water didn’t work to hold the winder down. It was just not heavy enough and also too slippery. So I did a dancing act of standing on the line while attaching the rig. Eventually I got it attached, about 100 feet of line below the kite.

I pointed the rig so that it would be facing east towards the Patuxent River, the Chesapeake Bay, and Solomon’s Island. The picture above is the best one I got from that angle. The foreground contains Chancellors Run Rd. and a lot of trees. In the distance, the south end of Solomon’s Island is visible, along with the Patuxent River, the Chesapeake Bay, and even the control tower for the Patuxent River Naval Air Station. There’s also a big boat out there in the Bay.

Rather than flying higher, I decided to bring the rig down and rotate it 180 degrees. St. Mary’s Lake is a few miles west of Chancellors Run Park, and I wanted to see if it was visible from here. Having the camera pointed that direction meant that sometimes it was pointing towards me, resulting in my first KAP selfie!

I really like this image, because it gives a unique view of the park from the height of the stadium lights. Plus, with the kite line in view, there’s no mistaking it for a drone photo.

It turned out that the views to the west were not that exciting. The sun was in that direction, so the landscape was backlit, and it was hard to make out details in the distance. I think St. Mary’s Lake is visible in the first picture below, but there’s not much else interesting about it. Hence why I didn’t bother rotating it or uploading the high-resolution version. In the future, if I want to try again to capture the lake from this park, I’ll need to fly in the morning when the sun is in the east, get the camera as high as possible, and try to get most of the pictures more towards the southwest instead of the northwest.

My favorite picture from this session was the second one above, which shows the park from a few hundred feet in the air. There’s a baseball game going on in the adjacent field; I hope the kite didn’t distract them too much! Anyway, this was a fun and successful session, and I have some ideas for pictures I want to take when I come here park again.

One More Try at Lancaster Park

I decided to return to Lancaster Park again. If you read my last post, you’ll know that I had a lot of lessons learned. The purpose of this session was to try to incorporate some of those lessons. Plus, I knew from my first time out that looking north from this park had the potential to produce some nice views of the Patuxent River and Gov. Thomas Johnson Bridge crossing the river, so I’d use this session as an opportunity to take pictures in that direction.

The main thing that I wanted to try this time was attaching the camera after that kite was already flying steadily, rather than attaching it to the line on the ground. I had learned by now that having the camera hanging very close to the kite makes it less stable, and trying to launch and land the kite with the rig still attached is just asking for trouble. (Read my previous two posts for all the juicy details. 🙂 )

The wind was from the west this time, so I flew my Mini Dopero kite from a soccer field on the north side of the park, which runs east and west lengthwise. The wind strength was marginal for this kite, and it took me a couple attempts and bridle adjustments to get it in the air, and I was thankful that the camera rig wasn’t attached during the failed attempts. Finally, it was in the air flying pretty smoothly on about 100 feet of line. I didn’t have a way to secure the line while I attached the rig, so I resorted to putting the winder on the ground and standing on it. That was a little awkward, but eventually it worked. (For future sessions, I filled a duffel bag with rocks to take care of the line-holding duties.)

With the rig now attached to the line and the KAP UAV intervalometer script running, I grabbed the winder again and began letting out line to lift the camera higher. It was slow going. Besides the wind being just barely strong enough, the bridle might have been adjusted with the tow point a little too far forward still, because the kite just wasn’t pulling very much. I eventually coaxed it to a few hundred feet in the air, but with the weight of the rig and the line already out, it wasn’t going to get any higher than that. This was one day that would have been perfect for a bigger kite like the Barn Door, except I hadn’t built it yet!

View looking north from Lancaster Park, with the Patuxent River and Gov. Thomas Johnson Bridge in the distance

This certainly wouldn’t be a day for high-altitude pictures, but I was still very pleased with the results. The new things I had tried worked. Attaching the camera well below the kite and using a faster shutter speed resulted in a high percentage of the photos being sharp and close to level. Angling the camera view down a little bit resulted in having more ground in the frame while still being able to see off to the horizon, and the exposure was correct in most of the shots. The picture above is probably the best one of the bunch. It’s not that high, but it’s level (I rotated it just 2.5 degrees in GIMP), sharp, and shows a little bit of the park and also the surrounding area, including the Patuxent River and Gov. Thomas Johnson Bridge. It’s the first of my kite aerial photos that I think is deserving of the watermark down in the corner. 🙂

Are you getting bored of this park yet? I am. Next time out, I’ll try somewhere else.

Lancaster Park – Take Two

One week after my first KAP attempt, I returned to the same park with 200 more feet of line (for 700 feet total) and a new camera — a Canon PowerShot Elph 160. It was equipped with a simple intervalometer script provided by CHDK. The goal this time was to get the camera as high as possible to see what the landscape looked like from hundreds of feet in the air.

Despite my stability struggles the last time out, I decided to still attach the rig to the line while the kite was on the ground and do a long-line running launch to get it in the air. I did attach the rig a little bit farther down from the kite this time to hopefully improve the stability a bit. Another change was to point the camera level with the horizon, since the goal was to see far off in the distance.

The launch went a lot like the first time. There was even less wind though, so I had to run the whole length of the soccer field while letting out line until the kite was away on its own. About halfway through the run it started to descend again, but it was saved at the last second by a gust of wind that lifted it into stronger air. The sequence of images at the right illustrates the harrowing experience!

The flight itself went pretty well. I managed to get all of the line out, which promised to return some very high-altitude shots! Being a warm summer day, thermals abounded, and several times the kite got lifted up in them. Bringing the kite down, I struggled with the line angle becoming very high. That’s not uncommon when winding in a kite, since the line tension increases as it is wound. But combined with the thermals and the fact that the kite was less stable with the rig so close to it, it became a bit stressful, since the kite seemed to want to be directly overhead. I started getting worried that it would dive into the trees on one side of the field or the parking lot on the other. I decided to put down the reel and try to just walk the line down by hand as quickly as I could to reduce the chances of the kite crashing somewhere other than the soccer field where I was flying.

This strategy was somewhat successful. While the kite didn’t crash into a tree or the parking lot, it did crash in the field. Once it was below treetop level, the wind became light and variable once again, and the kite started to dive when it was still 50 – 100 ft above my head. It ended up going in nose first, with the rig crashing into the grass in front of it. Thankfully, the ground was soft, and the camera and kite weren’t damaged at all. The rig did sustain some damage though, since it took the brunt of the impact when it came down. The bottom part of the frame came unglued along two edges; nothing that can’t be repaired!

View looking south towards St. Mary’s City

The pictures themselves turned out a little disappointing. They were definitely high, but the quality wasn’t as good as I had hoped for. I realized that this was due to a few problems. First, the shutter speed wasn’t fast enough. The maximum speed was less than 1/1000 sec, which resulted in a lot of the pictures having motion blur. Second, the camera being attached very close to the kite, which meant that any motion of the kite was transferred right to the rig. Having a relatively slow shutter speed only made that worse. Third, with the camera pointed level, the it had to keep adjusting the exposure as it swung towards the bright sky and then the darker ground below. As a result, lots of the photos were overexposed or underexposed. And finally, I was trying to take pictures towards the sun, which just made properly exposing the photos more difficult. A couple of the pictures did turn out okay though, as you can see above and below.

View looking southwest towards Great Mills

So, even though the pictures didn’t come out quite as nice as I hoped, I learned a lot of things from this session:

  1. Fly the kite first, then attach the rig at least 50 feet below, while the kite is already flying. This way, the rig doesn’t significantly affect the stability of the kite, the camera moves around less, and there’s not as much worry about it crashing into the ground while the kite is being let out or brought back down.
  2. If using a camera without built-in shutter speed control, use the KAP UAV Exposure Control script in CHDK to make sure the shutter speed is 1/1000 sec or faster.
  3. Even when taking landscapes off into the distance, it’s best to angle the camera down at least 10 degrees. That way, you get more ground than sky in the shot, and the camera will struggle less with constantly-changing light levels.
  4. Generally speaking, it’s better not to take pictures towards the sun. The subject will be shadowy and the sky overexposed. If you are using a good camera (particularly one that can save RAW images for editing later) and you know what you are doing, you can still get good results, though.

My First KAP Session

The day had finally arrived. I finished building my Mini Dopero kite a little over a month before, and now I’d finished building my first picavet rig to lift an old Android phone up into the air. I’d flown the kite several times by that time and was feeling pretty confident with it. The phone was all set up with the Open Camera app, which seemed to work fine on the ground. And today there was a nice south breeze of about 10 mph, which would lift the kite right above the baseball and soccer fields at Lancaster Park in Lexington Park, Maryland.

My first time out doing KAP, I was a little hesitant to try to attach the rig while the kite was already flying. For one thing, I didn’t have a good way to hold the line down while I worked on the rig. For another thing, it just seemed like too much to manage at once for a beginner like me. So instead, I set up the kite and laid out about 100 feet of line for a running, long-line launch. I attached the camera and rig while everything was still on the ground. In retrospect, it was kind of amazing that this worked. (It’s definitely better to get the kite flying up in smooth air first, then attach the rig. There’s less that can go wrong. To hold the line down, now I just use a backpack filled with a bunch of rocks. A primitive but effective solution!)

The Mini Dopero lifting a rig during my first-ever KAP session

Prior to attaching the rig, I had flown the Mini Dopero for a few minutes to make sure it was all trimmed out. Then, with it laying on the ground, I attached the picavet to the line only about 10-15 feet below the bridle. I put on my gardening gloves to protect my hands, walked back to the winder, and started simultaneously pulling, running into the wind, and letting out line. The kite took to the sky, smartphone in tow. The wind was a bit light and variable at ground level, so I wasn’t totally confident that this would continue to work once I stopped running. As luck would have it, right about the time I had run the whole length of the soccer field and was coming up to a row of trees, the kite contacted some stronger, steadier air above treetop level and was now rising by itself.

One thing I found out quickly doing this approach was that, with the camera attached so close to the kite, the kite’s trim was considerably different. The weight pulls down on the line above it, increasing the line angle that the kite experiences, which lowers the angle of attack. That in turn reduces the lifting force and makes it a bit less stable, especially near the ground where there may not be a sufficient steady breeze to keep it flying. That resulted in an “interesting” landing with a couple cartwheels involved! (No damage though, thankfully!) That’s yet another reason that the rig should be attached once the kite is already flying, on at least 50 feet of line.

All told, I ended up with at least a few nice pictures from the flight, some from a few hundred feet up in the air. I was quite pleased with the results for a first attempt. Here are the ones I liked the best. My next goals are to get better at attaching the rig and flying the kite, and also to get a better camera.

The dog park and fields adjacent to the flying site
A view of Lancaster Park and Great Mills, Maryland from a few hundred feet up
The kite swung east, giving a view of the softball field, Lexington Park, Maryland, and Gov. Thomas Johnson Bridge to the north