THe old way of finishing models, and it still works great, was to paint the wood with a product called dope. Dope is a thick, but very light weight , clear substance, that dries very quickly and allows the grain of the wood to be made perfectly smooth. Typically, two or three coats of dope are applied. Then Dacron, a man made cloth similar to silk is applied using another coat of dope, or other adhesive. Then the weave is filled in with another few coats of dope. And the whole thing is then sanded smooth with 400. Its fast, easy and allows a great paint job to go on top. Actually, they even sell colored dope, so this would complete the project.

It appears , that your man only applied dope before painting. He didn't apply silk or Dacron. So the plane has no "hide". A fingernail could easily be depressed into the finish and the vibration and stresses of flight often cause cracks to appear in the finish all along the structure. Many of the cracks in your pictures appear to be the result of the technique in which the modle was finished. And a few appear to be the result of a minor crash. He might have used a product called silkspan. Its very much like tissue paper. Its great for small models. But doesn't offer the strength needed for an aerobat of this size.