What is the easiest to build form of human powered propulsion for a cardboard boat(must be made of cardboard)?

Me and a group of people are working on a cardboard boat and the propulsion has to be made mostly of cardboard.  We want to use something better than paddles.  I have been looking around to try and find something that can be adapted out of cardboard and have only found a couple of methods of propulsion.

1. paddle wheel
2. normal propeller
3. impeller
4. hydrofoil wing

Anything else that might work that is not in this list would be awesome.  Remember, this is human powered so the RPMs will be low.

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jeff-o6 years ago
You could make a pair of cardboard flippers and hang one of your group members off the end...
BobS6 years ago
cardboard soaked in paint is waterproof. Cardboard tubes are sturdy and quite accurate (round).
seandogue6 years ago
A push stick!
Vyger6 years ago
You didn't mention a sail. Ever try to hold a piece of cardboard in the wind?
zack247 Vyger6 years ago
i think they might be doing something my class had done a couple years ago, "cardboard boat races", we had ours indoors, but there have been some outside, but inside a sail wouldnt be very effective..
lemonie6 years ago

Out of cardboard = paddle-wheel.
Not out of cardboard = the best motor you can get.