Aerial Imaging - The Sky Surfer

After discarding the sailplane and the helicopter, and deciding that the X-UFO was nice, but more suited for aerobatics than aerial imaging, I became aware of yet another type of aircraft: a paraplane.

the Sky Surfer approaching for touchdown

Platform considerations

To sum up my experiences with the other RC aircraft:

The sailplane was too bulky, had too little motor power and was difficult to control because of its high speed and my difficulty with the elevator axis.
The helicopter was too hard to control even when it was slow and relatively close, and its mechanics required too much effort to adjust properly.
The X-UFO is easier to control, but with the mechanical gyro tends to suddenly flip and crash for no apparent reason. Also, it could not lift any decent camera.
The X-3D equipped UFO can fly in stronger winds, but requires skill and good sight to keep stable. It can't be flown higher than maybe 30-40 meters above ground before it becomes too small to judge its orientation properly. Also, it still doesn't have enough payload capacity.
The brushless multicopters I watch being developed in the forums have impressive payload capacity (beyond 1 kg!) but even though a lot of effort and money is going into the sophisticated electronic stabilization, they are not really easy to fly (to high altitudes at least) and definitely not safe. I have seen (or read of) several hard crashes, damaged aircraft and broken cameras due to pilot errors, stabilization system malfunction, loss of radio contact, or random motor controller shutdowns. This isn't something I'd want to risk...

With all these problems in mind, and still determined that I want to do aerial imaging, I looked at the Sky Surfer. It flies very slow (around 15-20 kph) and is controlled only by motor power and one servo that pulls on either side of the canopy (airfoil) threads to steer left and right - trivial to control, no elevator stick, no stalling. Also, it was designed for the old NiCd battery packs - thanks to the latest LiPoly cells you can save 100 grams on that. Useful payload capacity is then around 150g, and flight times will still be around 14-18 minutes with 1500mAh cells. The canopy with its 1.2 meters wingspan can be collapsed and transported very easily. Due to its inherently stable aerodynamic construction and idiot-proof handling, it can be flown extremely high and without permanent concentration on steering. Also, even a worst-case electronics failure would most likely result in a relatively soft landing. Therefore, the payload is much safer than on any of the other aircraft I had considered.

original configuration

Aerial Imaging setup, Summer 2006

During the winter and spring of 2006, I ordered, assembled and test-flew my Sky Surfer - an original Graupner/G-Con model, not the "Paracopter" clone that can be found on ebay these days, now that the original model has been discontinued. I affixed the ZTV wireless video camera to the trike in several ways, making interesting (and for the time, exciting) but low-quality aerial videos. I even flew directly over my house once, even though it is about 250-300m away from my flying field.

At the same time I also acquired a small and light 2-megapixel CCD digital camera, a Minolta Dimage X20. I damaged it (probably due to an ESD event) while modifying it for electronic remote control and had to order another identical camera, which I then called X-202 (just because it sounds cool). Originally aiming at adding a row of connectors for DC power input, power on/off, focus, shutter-release and composite video output, I only got the essential shutter-release pin working and didn't dare to open the camera again.
Then I macguyvered payload booms onto the sides of the Sky Surfer's trike which would carry the battery on the right side and the camera on the left, looking out sideways so I could aim up and down by going into a slow turn. I then also found out that by replacing the original plastic protection ring around the propeller with a simple, thin brass tube, the thrust effected by the propeller could be increased by 1/3 without drawing any more current.

With minor modifications, I used this setup from June to August of 2006 and made several flights that returned dozens of aerial images each. The quality was often surprisingly good and I knew I was finally going in the right direction.

In August however, the camera stopped taking pictures during flight and I noticed RF interference at relatively low altitudes. Also, I had to direct my attention more to completing my diploma thesis, so the Sky Surfer remained on the ground until after the completion of that work. In December, I removed the payload booms from the trike and returned to having the wireless camera on board, this time with a pan & tilt mount using two tiny servos. Equipped with video goggles and everything I was back on the flying field, but encountered strong interference on the downlink video, probably because the camera was powered off the flight battery using a 5VDC regulator. The next flight will be with a separate battery again.

Plans for Project ParaDIY

Currently, the aerial imaging project is on hold again, waiting for the high-priority task of passing the last two exams of my study to complete.
I have realistic plans to build my own Sky Surfer from generic materials like aluminium profiles, kiting airfoil textiles, standard RC model components and a brushless motor and to publish the construction schematics for this aircraft so others can build their own - a Do-it-Yourself-Paraplane... ParaDIY.
This paraplane should then be able to carry any digital still or video camera up to 200 grams with ease.

Stay tuned :-)

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