Notes on Kite Aerial Photography: Others
Over the 4th of July I had a brief visit with Wolfgang Bieck. Wolfgang is a personable fellow and particularly engaging on topics related to kite aerial photography. He has developed an impressive grasp the topic and graciously shares this expertise. I greatly enjoyed the visit, feeling literally like a student taking an advanced seminar. Wolfgang is an educator in Germany and there was a distinctly Socratic dimension to our conversations. I quickly filled a small notebook with notes about Wolfgang's cameras, camera cradle, Picavet suspension, and kites. This page will summarize those notes.
Figure 1. Wolfgang's rig with camera body and motordrive mounted. The rig's tripod legs allow for a soft landing should the camera rig lower during near-ground handling. One tripod leg holds the radio's antenna..
Wolfgang is using an early 1970's vintage Minolta single lens reflex camera. This is a heavy camera from the pre-internal-motordrive era so Wolfgang adds an external motordrive to advance the film of his airborne camera. He uses lenses ranging from 50 mm to 20 mm in focal length. The result is a substantial mass to loft. The camera's motordrive is triggered by an electric relay which is in turn triggered by the rig's radio receiver. (ACE Electronics makes a switch - # 14G10 - that replaces a servo for releasing electronic shutters on cameras.)
Wolfgang is a strong advocate of Kodachrome film for kite aerial photography. This choice is a bit counter-intuitive as the film's low speed (ASA 25) results in relatively long exposure times and thus greater chance of motion-induced blur. However, the proof is in the pudding and Wolfgang's portfolio is filled with sharply exposed images featuring the fine grain and saturated colors that are characteristic of Kodachrome. Incidentally, he exposes his Kodachrome at ASA 30 to produce a slightly greater density in the slide.
I note also that Wolfgang routinely uses two accessories for his camera. The first is a small cover for the SLR's eyepiece. This prevents stray light from entering via the "back door" and causing a poor exposure. The second is a lens shade. Mating the proper shade to each lens reduces lens flare and helps particularly when the exposure is in the direction of the sun.
Wolfgang has recently developed an airborne video setup that is used as an electronic viewfinder for the still camera. The setup includes a bicycle helmet-mounted monitor that presents video to one eye while the other sees the kite.
Figure 2. Camera cradle without camera mounted. The yellow gear in the center can rotate the camera from horizontal to vertical format..
Wolfgang's camera cradle is substantial and carefully constructed. The frame is painted aluminum. Connections are generally drilled and tapped holes for machine screws. The servo that produces plan rotation has been modified to rotate 360 degrees and this eliminates the need for reduction gears. The modification involves removing a stop on an internal servo gear and adjusting a potentiometer.
As mentioned above, the cradle has tripod feet in order to stand upright when lowered to the ground. These attach to lugs on the frame and are held in place with cotter pins that in turn have keeper strings. Plastic caps give the feet ends some grab.
The camera is attached to the rig using using a tripod screw alone. The camera-holding L-bracket has a couple of slots, one for each of two different camera bodies. Wolfgang emphasizes the importance of balancing the mass of each nested bracket and the slots help in this task. The L-bracket, driven by one-to-one gears, can rotate the camera from horizontal to vertical format. The rig uses modular electrical connectors to break the electric wiring at all hinge points. This helps when the rig must be disassembled.
The bottom of the rig's inner and outer U-brackets are rounded. There is a slot in the inner U-bracket that provides positive stops when the bracket encounters the vertical and horizontal planes. The cradle has small strings as keeper for the tripod screw, eyepiece cover, tripod leg pins, etc.
Figure 3. Wolfgang holding the camera rig with its Picavet suspension. Note the small dimensions of the Picavet rig. .
Wolfgang has developed very small Picavet crosses out of sheet aluminum (~1/8" tk.). These are as small as 8 cm across and have small single blocks mounted at their ends using small eye bolts and nuts. The blocks appeared to be about 1/4" across their face. Wolfgang's small Picavets seem to work so nicely because of the small precision blocks originally developed for RC sailboats. He has tested the Picavets to 40 kilograms of load. Single blocks are used at the ends of the Picavet and double blocks are used at the kite line attachments (via Prussic knots.) The rig seemed to produce both level and steady results.
The two innermost crossing lines of the Picavet suspension are joined with a small ring. This apparently makes the rig more resistant to turning. Wolfgang used a chain braid to organize the Picavet rig lines (seems to work) and then stores his small Picavet assemblies in ziplock bags.
Figure 4. The rig suspended from the kiteline showing vibration-dampening o-rings.
Kitelines are prone to vibrate,
particularly in strong winds. When transferred to the camera rig
these vibrations can blur photographs and loosen mechanical
components. Wolfgang, like many other KAPers, uses large o-rings
(actually muffler hangers) above and below the camera rig to stop
the travel of line vibration. The sticks that pin the muffler
hangers to the line are attached with string keepers.
Figure 5. Wolfgang flying his large Multi-Flare kite. .
Wolfgang calls the Multi-Flare kite he constructed a "tractor". It seemed an apt characterization when Wolfgang flew it in a breeze of about 12-15 mph. The kite pulls like a horse. Wolfgang used a single dog stake to anchor this 2.65 meter x 1.8 meter Multi-Flare. He estimated it was pulling at 20 kilograms (on 140 kilogram, 2.5-mm line). It seemed a substantial pull on the line. He uses a clove hitch to secure line directly to the dog stake. This knot can be easily slipped off when its time to handle the kite again.
When flying, Wolfgang uses a wide leather belt with a carabiner clipped to it. The carabiner held a short strap connected to a second carabiner which in turn held a figure-eight line brake. The figure eight is left hanging from the line between uses. Kite line hardware included a nice brass (plated?) swivel, two fairly heavy miniature carabiners and a stainless thimble used with the lines looped around the thimble secured by sewing. Wolfgang has a traveling set of spars which broke down to a very small package. They included two-piece longerons and a three-piece spar made of 10-mm fiberglass tube. The joints were achieved with an 8-mm x 20-mm insert which in turn had a 6-mm x 20-mm insert. Plastic tape was used to temporarily secure the joint.
The kite's tail was made from a nine meter by 30 cm strip of ripstop. A seam is stitched down the center (three layers) and lateral strips are cut at 2 cm intervals. This seems to work well and Wolfgang highly recommends it.
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All rights reserved. Revised: Saturday, June 26, 2010