RE: Ducted fan airboat?
Yes, I've built one. Gws 55 ducted fan on eight 650nimh, blue foam boat, about 30" long, 6" wide, slight vee bottom. Was started for inboard nitro, but wanted something for my son to tool around with. Actually went pretty well, so I tried two ducted fans, my son then drove straight under a dock, lost one fan, back to one only. Blows over easy. Was considering rebuilding it smaller, but already have too many projects.