Root main spar: before wing root ribs- we have to construct the root main spar- it's lenght is a function of the cockpit width- I've constructed my cockpit to be 24" so my main root spar is 25.5". The main root spar -due to the cost of large width spruce (spar quality)- can be laminated from (2) 1" + (1) 3.25" + (1) 4" spruce. Those particular spruce width are well in stock and you dont have to wait 3 month for a fancy 7.25". Both spar sides are glued with 1/16" ply vertical web. Notice that I've marked the hollow areas in the spar-it might be usefull if the optional additional fuel tanks will be added in the root trailing edge area.