This post could easily be part of the Open Forum, the Finishing forum, or the Classic forum. I am sure that all will not agree and that is OK:
I want to thank everyone who has been following the construction and recent problems of my “Sea Vixen”.
I now know that the problems have not been caused by poor silk span, or the grain direction of the silk span. Last night I took another look and promptly put another hole in a wing tip. The covering practically shattered to the touch! It is incredibly brittle!
It seems that the last stages of the project have certainly been snake bit. From cracks in the fillets, to a crack in the spray gun cup lid causing drips, to the super brittle covering. It is time to strip the entire covering and finish, and fix it. Unfortunately, this means I will miss VSC 2009, but I will be well prepared for 2010 with both a Classic and a new OTS airplane.
My major disappointment is letting Jack Sheeks down for this year.
Now for a discussion on want went wrong and hopefully we can all learn from it.
I have followed many of the finishing procedures that I have used in the past, including the medium silk span on the I-beamer. Unfortunately some of the newer materials obviously are not compatible. I used nitrate dope to apply the carbon fiber on the wood areas because nitrate fills faster. I also used the Nitrate over the fillets. Then instead of using Butyrate over the Nitrate I went right to the auto primer. This is when the headaches started.
I had small cracks develop in numerous places on the airplane, and major cracks in the fillets. I then used thin CA in the cracks and after numerous tries, I got most of the cracks fixed, but not all. Then, I continued while trying to meet a deadline. Can you say “Haste makes waste”?
Then after applying base coat colors, I had 2 splits in the covering, in the leading edge area, develop while the airplane was sitting over night. I repaired these splits and continued to apply some of the graphics. Then when I removed some of the aluminum foil that I use to prevent over spray getting into places that I don’t want it, I discovered the very large split in the from leading to trailing edge in the lower wing covering.
After many discussions with several people, we now know that all the problems were caused by the Nitrate dope, with no Butyrate dope applied over it. The Nitrate is not compatible with the modern materials we use for fillets. In this case it was SuperFil. But the same result will probably happen with AeroPoxy. The Nitrate also is not compatible when using auto primer over it without Butyrate over the Nitrate. The solvents in primer and the base coat further exasperate the problem. Simply put, the brittleness was caused by having both no butyrate and not enough butyrate dope under the auto primer.
Synopsis: 1) Never use Nitrate over the modern fillet materials.
2) Auto primer and base coats cannot be used directly over Nitrate.
3) Butyrate Color dope can be used over Nitrate
4) Haste makes waste
Thankfully I had not applied clear coat, and the auto base coat will wipe off easily with denatured alcohol. I will be able to re-cover the airplane, probably using poly span, and then finish the project. The only thing lost is time, but big lessons have been learned.
I want to publicly thank Bill Byles, John Miller, and Ralph Wenzel for their concern and valuable inputs. Friends all! The Stunt community is full of wonderful people.