RobH,

If you really want to get involved into small ducted fans, check RCJI mag, I remember they published an article about this a few years ago... The guy also used RC .21 car engines.

Just bear in mind this is not exactly easy to yield good results from such a setup. Great model manufacturers have tried this (Kyosho with the F86 for example) but did not succeed in making great performing models.

Have u ever flown any aircraft ?

Keep us posted about your results.