The Spar

Finished spar before sheathing
The spar caps have been glued into a completed spar. You can now clearly see the taper from root to wing tip, and the 'V' shape for the wing. Curved blocks have been inserted into the spar about 3 feet out from the root. These will be the main landing gear blocks. When floating in over the runway at 70mph, and dropping the full weight of the plane on the ground, these blocks absorb the shock and transmit it to the spar. The spar carries that load to cockpit area, where the 'load' (pilot, passenger, and baggage) is. The curve in the block spread the sharp edge out over a larger area so the spar cap doesn't get cut by the concentrated stress.