This week I started filling the scratches, using a totally different approach. Different for me, anyway.
I first started with the brake covers. (They are made of three layers of BID and no foam). First, I scuffed the surface to allow good adhesion, then applied a single thick layer of pre-mixed Super Fill. I allowed it to cure for a couple of days, then sanded it down with 36 grit, then some 80 grit paper.
Those of you who have finished their planes will be familiar with the look of the filler material, at this point. There were lots of holes in the filler, pinholes and much larger, and major sanding scratches. But, this is what I wanted, I wanted to test this new method.
In the article "Finishing Composite Aircraft" the author says he sanded with 36 grit then some 80, then stopped. Cory Bird, builder/designer of the Symmetry (the only perfect aircraft I have ever seen), did an interview where he says he sanded with 36 grit then stopped. If it worked for him there is a slim change it will work for me.
So anyway, my brake covers had the desired contour, but were full of scratches and holes. I mixed up some Gouegon Bros. Pro-Set epoxy, squeegeed it on, then squeegeed off as much as I could. I repeated this every day, for five applications. (Cory Bird made five applications). I didn't sand beetween applications since the expoxy was still tacky.
The result was that all of the holes and scratches are nicely filled! I remember all the trouble I had in the past, filling pinholes and this completely eliminated them. After the last application cures for a couple of days, I will sand it with 150 grit, then start with the primer.
Since the results with the brake covers looked so promising, I started the expoxy treatment on the wheelpants. As of last evening, I have three applications complete. There were MAJOR scratches in the wheelpant filler. In the past I would have spent lots and lots of time sanding, and probably re-filling. This epoxy method seems to work great and I will definitely use it when I finish my new wing.
