Peter actcom.co.il> writes: > 2-blade top efficiency is given as >75%. Even two 2-bladed props one after the > other (tandem) are less efficient than one 2-bladed one. It is something to do Correction: 2-blade has >85% efficiency and I have seen 89% quoted Peter -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist