Sunday, September 6, 2009

Wicked Hard

Having never scratch-built an rc plane with mixed-materials it is pretty tough to get it right. Yeah, I suck, but this is more than that. Over the last two years my co-conspirators and I have tried about every technique to repeatably build airframes. We have come full-circle now and say that a normal composite construction system is probably our best chance to make a good quality product with the least effort.

Try to epoxy carbon fiber and Aluminum together, you will get sticky fingers and big globs of epoxy everywhere. It will eventually fix the pieces, however we find that we cannot get a great bond this way. You can scuff and sand all you want. The epoxy does not do more than touch the surface of either part. Meh. It works and you can do it, do not get me wrong. The difficulty involved is a bit more than I think is necessary. We are running some experiments now with some almost ready to fly (ARF) models. Sacrificing a few models to the Gods seems a good start, and par for the course.

At least they already have all of the places for servos, spars and wire harnesses precut and in a reasonable place. Why reinvent the wheel, we have our own wheels but need to practice a construction technique. It is a well-documented idea in the composites industry. Essentially we make negative molds that allow us to control composite gauge in the best places and create bumpy sheets of composite. These sheets are bonded and reinforced as needed. Finally, they are covered with a material so that they may be painted or have decals applied.

I will include some pictures a bit later when we get closer to a final product. We noticed that alignments are still an issue. Aligning six pieces is really easy compared to aligning and balancing forty pieces. That is really silly in my opinion. We tried a bunch of techniques to make airframes consistently. Maybe next time I will talk about some of our creative failures. None were failures, but some took a lot more work than others or cost a small fortune.

We are trying to be Orville and Wilbur-like not like that other guy. The Wright brothers got off the ground for less than $2000 and their main competitor was funded by the Army and had something like 50x their budget. He even built a special barge to take off from and that never worked either. It is time to get a good rugged system in place so we can go into nearly serial production of the airframes.