[Green Jeanne]

I've been lurking for sometime soaking up as much knowledge as possiable to bring my project to life. Being well on the way at the drawing board, there are a few things, I've not found an answer for. OK, it will be chain driven, two seater side by side pedals, like on a paddle boat. It will be pretty heavy duty. I want the pedals to coast or engage depending on the need, by clutch or ? Not clear on centripetal clutch, or would it need a derailer? Any suggestion?