Who'd have thought that I'd wake up this morning to a nice flame war on the piclist which apparently I started by simply referring to thrust in units of kg. Now I know why I love this place. Incidentally the manufacturer of the ducted fan I'm using themselves quote the thrust in grams: http://oos.modelengines.com.au/command/servlet/Command?command=display_item_pub&pkey=meng&itemid=HIM-DF96 Sloppy use of units is pretty common in the R/C world. I'm not going to try to justify it. In the end it's all about the most effective form of communication for the medium. Let's face it - even Olin knew what I meant and he's the one who made the fuss in the first place. If I'd given the thrust in Newtons how many people would have taken the time to think it through? Of course if I'd been writing a formal spec rather than a casual email I'd probably have expressed it differently. Cheers, Zik PS. I bet James is glad he un-moderated Olin -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist