Shapeways 1/72 PowerPlane

I work at Ampyx Power where we are developing a new way of harvesting wind energy, called PowerPlane. The concept is novel: we use an unpowered, unmanned aircraft. The aircraft is connected to a winch on the ground by a long cable, and the winch drives a generator. The aircraft uses the wind to generate as much lift as possible, driving the winch and thus generating electric power. Once the cable length is exhausted, the plane glides back to the winch while the cable is reeled in, and the process starts over again. The main advantages compared to wind turbines are that this concept supplies electricity 65% of the time compared to 30% for wind turbines, and the concept uses just a fraction of the materials of an equivalent wind turbine. This should result in a kilowatt-hour price comparable to the cheapest kind of electricity, coal-generated. We are currently flying a relatively small aircraft with 5.5 meter span to demonstrate and develop the concept on a 10 kilowatt scale.

At one point we decided to produce a desk model. I built simple plastic card sample models in various scales, and the team selected the 1/72 scale version. I didn't mind since it fits nicely in my collection :-) Jesús Blasco made a simplified CAD-model so we could have it 3D printed. The model was printed by Shapeways using their most detailed method, called Frosted Ultra Detail. Compared to my first 3D printed model (the Eaglet from 2006) I was surprised by the lack of progress in five years. The printing steps were much more prominent on this model. Furthermore the model was deformed, one wing tip completely lacked dihedral. Lastly the parts were very greasy/waxy. To be honest: I did not contact Shapeways to discuss these problems, maybe they could have solved them.

Construction

I corrected the dihedral problem by cutting of the tip and reattaching it at an angle. Next step was repeated spray painting and sanding to eliminate the printing steps. But the Humbrol enamel paint refused to cure. This was caused by either the printing material or the wax, because the same paint sprayed on a regular model cured as normal. Out came the thinner to clean the parts. I then tried Mr Surfacer, and fortunately that worked fine. It finally allowed me to make the parts smooth.

The nose section looked slightly undersize to me, and indeed it was 0.2 mm too small in both height and width. I glued 0.1 mm plastic card to all four sides to solve that. The three main parts can be seen in the photo. The model was done in three parts to allow resin casting.

Fast forward to the finished model! I had to paint and decal it in a big hurry to have it finished in time for an IPMS meeting. First I added some details to the basic airframe: a 0.3 mm pitot tube on the nose, four antennas on the side of the nose, two GPS antennas on the tail boom (cut with a Waldron Punch & Die) and lastly a small video camera to the tip of the vertical tail. The tail boom is a piece of 1 mm carbon rod.

Time for paint. The 1:1 design had evolved into a full carbon fiber structure, so the exterior was black throughout. Because of the previous Humbrol problems, I used acrylic paints, Vallejo Model Air. The color is a attempt at simulating carbon fiber, mixed from 71.056 Black Grey and 71.073 Gun Metal Metalizer in a 5:1 ratio.

Last to add were the decals, that were done on an Alps. The whole set of 13 decals occupied a decal sheet of 15 by 20 millimeters! They were applied using a bit of Future floor polish. After a minimal drying time I applied a clear finish. I first attempted to use Vallejo Satin Varnish 70.552, but the completely fresh bottle contained a drabby substance that definitely could not be sprayed (later it turned out to be a faulty batch, and was replaced by the model shop). I then switched to Future, which gave a slightly rough surface. The model lacks conspicuity markings, we hadn't decided on them at the time.

You might wonder how big (small) this model is. Well, it's 76 mm span and 55 mm length including pitot tube. To my surprise a BD-5J is approximately the same size.

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