Here is a severe example of cracks probably starting around the landing gear and progressing into the main structure. Perhaps too some existing small cracks progressed rapidly to nearly contribute to a catastrophic failure. (contributed by Phil Sisson)

This link will show you some factory service bulletin information

WING BLOCK FIX

Compression ribs collapse or the blocks break loose because the rib is hollow between these small drag wire blocks.   You can see the block on the right has moved, and several others on this aircraft were broken or loose.  We typically find this during recover, and frequently becomes the cause or reason for recovering the wings.  The front blocks are solid and do not present this problem.  If an Eagle has loose drag wires, here is the cause of your problem !!  Many other biplane designs contain this weakness also.   The block should be solid, not two pieces.  Another solution would be to insert hardwood into the ribs at this location.  Its easy to see too if you drag wires keep coming loose and you keep tightening the wires, your smashing the rib and breaking the blocks somewhere.

The Start of a Repair. 

We use "West Epoxy" mixed with cotton fiber ( FLOX ).   About 1/2 onz. fills the gap between the blocks very solid.   You can let a fabric covered airplane stand on its nose to accomplish the same 
trick.   Loosen the drag wires first though, repair any block or rib damage, and sand off later to smooth out the surfaces.  When hardened, torque the drag wires for a permanent secure fix. 

Access holes.  

We like predrilling access holes prior to covering, so that a simple grommet may be used at a later date if entry is ever required.   Once the aircraft is covered, these cannot be seen but are easy to locate with your fingers. 
 

Hardware Access Holes

Inspection Access Holes 

Ventilation here is critical as well as the ability to inspect the wing attach fittings.  You can also run wires for navigation lights strobes or flare wing tips, that hide neatly under the cabane faring cover.  We leave these wide open.