Skiffs up to 16′ for outboard, oars propulsion, or sail. see the dinghies category too.. Osprey 18 flats skiff. the osprey 18 flats skiff was originally designed for a client (who stiffed me on half his bill!) in louisiana back in 2008.. Proven boat designs, and how-to information for boat building. boat plans are for beginners and have been built by thousands since 1953..