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.. This category is somewhat arbitrary, like many in our catalog. many of the inboard designs have outboard options and there are designs in the cruiser and work boat.