So after many months of gnawing on how to reduce the construction time of uavs and model aircraft, we finally decided to watch a million youtube movies. Sating ourselves on anything that had anything to do with composite lay ups we set off onto our own project. The first version of this idea is a proof of concept experiment rather than a real product. Aircraft Spruce sent us some great almost silken 2.5oz/yd^2 fiberglass.
This is an experiment in how to create multi-cell,internal structure in composite structures. If an airframe just needs a few reinforcements, that would go a long way to reducing the production costs of a unit model. Having built several models now with varying levels of success. It is clear, the longer it takes to produce a model, the more likely it will have issues. It could be as simple as being heavy, due to liberal adhesive use. Or just general issues such as fiber breakage or delaminations due to mis drilling or toughness issues in large unsupported panels.
After watching many others' techniques and lots of research into how successful airframes are created. It is about reducing the handling of each piece. The best paint jobs are ruined by finger prints, finishes scratched, just because they had the most chances to get ruined before delivery. Our concept centered around simple low curvature lay ups, that could be lain individual. Then stiffeners installed before the final layers are put down. Each mold would then be set to cure. Final assembly, would be put in place in the planes perpendicular to the molds to join the sides together and to increase the technical stiffness of the airframe.
Our design required a center web and some easy radii transitioning each of the perpendicular webs. We sectioned our fuselage to have three dorsal access bays. The fuselage was then bisected so that we had two symmetric halves and three continuous doors. Empennages and noses are difficult to build and to shape. There is always an issue with the symmetry or the strain in the materials during the curing process. Careful attention was paid to each of these areas to reduce the known issues that had ruined some of our previous projects.
Our split molds were then mounted to three inch styrofoam wall insulation. Not the ball stuff, this is the small,closed-cell material with wood glue. Everything was painted several times with latex enamel. The enamel did not stick during the first few coats. It probably has to do with the static charge that built up during the work. There was an eventual critical coating area that finally whetted the surface. Once the surface finally whetted, the coats proceeded quickly.
We found several movies about hand-lain composites that kind of tipped us off on how not to complicate our chemistry. They all had a few things in common, latex paint and paste wax as the sealant and release agents. After fourth coat of latex paint, Johnson's paste wax was applied liberally and hand-buffed to a shine. Each mold and the foam several inches (3-4") from the model was covered and buffed.
Then it was all let rest for a day.
Buzz Labs' unmanned vehicle blog and cool DIY remote controlled stuff blog. For techies by techies, maybe also some interesting tidbits about small business and international business.
Follow us on :
