I covered my PT-40 about a week ago with ultracote now these wrinkles and bubbles are everywhere were the ultracote touches balsa. I tried to iron them down could not do it I realized they were air pockets so I went all over the plane with a #11 razor and poked holes in the ultracote then I was able to iron them down now every other day I find new ones. why did this happen?

When covering a fully sheeted surface, you have to be careful to shrink the covering such that there is a vent path for any trapped air to escape. I always use a heat gun over sheeted surfaces rather than an iron. This prevents the covering from being forced to adhere before the trapped air is out. I use the covering iron to seal the edges most of the way around, but leave openings. Using the heat gun allows you to heat the covering over a broader area, which pulls the covering tight over the entire surface. Once its shrunk tight, then i use a soft cloth to gently rub it down and adhere it to the balsa.

To get rid of the bubbles, you need to heat the covering to raise the bubble, then quickly poke a small hole with a pin in the center of the bubble. Again, a heat gun works better here than an iron. The air will escape allowing the covering to adhere properly.

Many people use a "wood peckering" tool on sheeted surfaces to allow the air to collect below the covering. It will then slowly diffuse out through the wood and will help prevent bubbles.

Brad