While searching for whether anybody had created a boat purely from duct tape, I was surprised to discover a host of cardboard/cardboard and duct tape regattas (regattae?).
A number of official local events can be found through a simple Google search or two, and there’s a ton of hilarious videos on YouTube as well.
I sense a new challenge. Me being kayaker boy, I’d love to challenge a group of folks here in Richmond to do this. The main change being the boat would have to be able to make it through the pony pasture rapids. That would be a fun challenge.
If you could keep adding additional weight to the raft as it went through a set corse you could find the breaking point.