Hi Mark I have had a question for some time, but was never sure who would know the correct answer.
I was browsing the Airventure Museum site and noted that you had contributed to establishing the history / evolution of the KR's it figured that you would be the best person to ask. The original (early) KR editorial always refers to polystyrene foam - never mentions polyurethane. Is this correct and, if so, do you know when plans changed to poly-U? Were some KR\s built with polystyrene 9styro foam)? Take care Steve J
