I am laying out the wing upside down and using the center section as a mounting jig. This I hope will keep the wings not only square in itself but also square overall
I had some problems with the “D” section. I first made up the whole length of the wing section from scarfe jointed ply. I temporarily nailed the top of the leading edge and placed wet cloth along the leading edge ply. I held the underside in place with rubber bands and tried to glue the ply in place. I found I couldn’t bend the ply enough to form a good fit. I eventually ripped it all off and started again.
This time I used smaller sections of ply and bent each piece over a small diameter steel pipe. The ply was soaked in warm water and bent around the pipe. I held it all in place with clamps until it was dry
I made up some clamps with a cut out the same shape as the leading edge profile. These are held in place with large rubber bands (cut up inner tube). I masked off the area to be glued and varnished the inside of the wing section and ply. When dry I applied glue to the exposed ply and stapled in place on the wing. The clamps held the ply in place while I applied the staples. The blue tape is to make removal of the staples easier. A much better looking job altogether!
After a trip down to my local hardware store, I found these tie down ratchets going cheap. These made the job of holding the ply tightly in place much easier (the wing is upside down) and did not need anywhere near the same amount of staples as the picture above