Wing of Morane-Saulnier L / Thulin D

[Mangrove]

Posted this one to theaerodrome.net too.

Could someone clear this one for me? Looking photos I have from Finnish Thulin D (Swedish license build Morane-Saulnier L) it seems like the spar is fitted to the ribs with a slot. In other words they didn't drill holes into the ribs like in modern aeroplanes but made a slot into the spar or ribs. The other choice is the spar is glued above the ribs. I'm I right or not?

I have the Windsock's book about Morane-Saulnier L, but it didn't help me much. Photo by Pentti Hyvärinen.

 

[FLYBOYJ]

I believe you are correct - they might of also used small nails to initially hold the rib/ spar together but the primary strength of the assembly comes from the glue.

 

[Arsenal VG-33]

From the looks of it, it appears this is because the aircraft uses wing-warping controls and not ailerons.