RE: Frustrated with Covering
I totally agree with Bruce here. If the covering is completely shrunk before you start adhering it to the structure it will help keep the covering tight in hot weather. But there is another HUGE cause of loose covering that most people completely miss (including those factory workers assembling ARF's), and that is open bay structures. I'm talking about open bays in wings, open areas in stick built tail sections, or any other open area that will be covered up by covering. The problem here these bays are completely sealed and air trapped inside the structure has no where to go. So when you place the covering over the bay you completely seal that area in. As you heat the covering to shrink it the air inside structure expands which pushes out against the covering. The covering will shrink around the bubble of heated air. When the heat is removed the air inside contracts back down and now the covering has slack in it. This slack allows wrinkles to form later on. So how to you avoid this?? Simple, ensure that a structure has a path for air to escape from it. It's as simple as just sticking a pin through the side walls of that area. Keep doing this so until there is a route for air to pass from the outside of the structure to all internal areas. If you look at the attached pictures you will see how I prepared the wing on this LT-40 for covering. I used T-pins to create air vents in all of the internal areas of the wings. I made sure that there was a path for air to vent into all of the internal areas of the wing.
I use monokote on all of my planes and I have never had any problems with wrinkles forming in hot weather. My planes are stored in my garage and here in Southwest Oklahoma it regularly hits 120°-130° in my garage during the summer. I have also left planes in my truck during the day and have never had any problems with wrinkles. As I said above, the trick is to get the covering completely shrunk before pressing it down on the structure.
I hope this helps
Ken