I had a tail stand that I used when my plane was upside down for a while. I used the spray can type of urethane foam to make a cradle that exactly fit the tail section snugly.
After I was done with it I stuck it near the garage window and put some junk on it for a long time. I noticed that the part that had the sun shining on it turned to dust when you touched it from the UV and I wondered if the sheets of urethane did the same thing. Well, a few days ago while working on my garage I stacked some sheets outside and they were in the sun about ten hours. I was amazed that after that short time there was a very distinct color change in the foam. The parts in he shade were still pink and the parts in the sun were an orange brown. Scraping away with my finger nail showed the change to be over 1/8" thick. I couldn't tell any difference in the strength of the foam yet. This makes me wonder about problems with the glass pulling off of the foam being caused by UV degredation of the foam. I will always keep the plane covered with a tarp when I roll it out of the garage now until the smooth prime is on it. I have another piece of foam outside to experiment with. I will see if it turns to dust after a while. I have a piece of unpainted fiberglass sheet that I will put on a section also and see what happens. In the meantime, keep your unpainted plane out of the sun. Brian Kraut Engineering Alternatives, Inc. www.engalt.com
