The Starduster has been in a climate controlled office the last four months, including covering with silkspan and Polycrylic.  Wife out of town, so I brought it home this evening to apply base coat white dope. In the kitchen with windows open and I walk by and notice this sagging.  Never had this happen before, but I’ve never applied silkspan with a water based product, either. I also notice the top wing with primer does not seem to have the same problem. Any ideas ??  Im going to close the windows before I go to bed. Thanks !!

Hit it with a heat gun ...

 

I think I would have waited longer.  It's pretty typical for doped finishes to sag with each new coat, until you have considerable build-up -- and re-tighten as each coat dries.

Oh, it was actually covered a couple of months ago.  I just bought it home and sat it down. Was going to take the top wing off and spray color today, but it’s about 110 percent humidity right now.

    Going by what I have ben reading, experiencing and hearing from some other areas, I have my doubts about any sort of water based finishing system. I don't think they seal wood or covering material like they should, moisture can penetrate and things happen. If you just set it down, humidity got to it almost right away. If you are spaying white dope on it, I would have sprayed on a coat or two  of clear dope to make sure it's sealed and shrunk. The heat may have done the trick for now, will be interesting to see how this progresses.
  Type at you later,
  Dan McEntee