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.