Thanks BB !
To be clear, the Rand scheme with unbacked foam is not ideal (Rutan was not a fan of it) but it has worked over a number of years.
Given the rear spar is a single bolt ( as mentioned by BB), the skin (glass or Dynel) is infact carrying wing torsion loads unlike a classic fabric wing. Rand essentially replaced the plywood skin of a taylor monoplane with Dynel/Glass and foam leaving the underlying wood structure.Think of the KR's as a fabric covered wing, but with thick foam backing up the fabric. It does give us some hope that a reasonable amount of foam can be left on the ground without being glassed on the inside...
Billski
To be clear, the Rand scheme with unbacked foam is not ideal (Rutan was not a fan of it) but it has worked over a number of years.