java.lang.ClassNotFoundException: org.apache.log4j.FileAppender

A fan with no blades?

Wow Dyson have done it again: http://www.dyson.co.uk/technology/airmultiplier.asp Interestingly they talk about the fact they had to do “Hundreds of iterative tests” to get the design right: http://www.dyson.co.uk/insidedyson/default.asp#Air_Mult_Tech_Dev