Since I live near a trout and catfish stocked lake, fishing is an activity I often do on weekends when there isn’t much else going on. Unfortunately, I don’t have a boat and fishing from shore seems to yield much worse results than if you’re out on the water. When talking to my housemate one day about buying a boat the problem of how to store and transport it arised as the biggest issue. He suggested to me a folding kayak which he has seen but those seem expensive for what you actually get. After doing some research I stumbled upon https://www.portableboatplans.com, a website hosting the design plans for various portable DIY boats designed by a retired NASA Mechanical Engineer. Most of these boats are made out of a single 8’x4' sheet of Coroplast - a corrogated plastic used for large signs.
I looked through his designs but nothing caught my eye as the immediate boat I wanted to build. I like standing up when I fish and the only design he had for a boat you can stand up in is designed to be made out of wood (which would be much heavier than I would like. Eventually I decided to just email him and ask if he could suggest a design for a plastic boat that I could stand up in and have maximal room to move around.
To my surprise he emailed me back saying he would draw up new plans for a design that met me needs, I was a little dumb-founded by his willingness to design a plan to my specifications but I suppose that is his hobby and he was looking for a new challenging design.
Building the design
After a couple weeks of back and forth I had in my hands a pdf for the design of The Coropunt, a boat design based off a punt boat and made primarily from a single sheet of Coroplast.
The frame and cross-bars would be made from wood for structural stability but the bulk of the body was simply folded and taped coroplast similar to his other plastic boat designs. The boat was designed to be folded in half to fit in the back of my 2010 Honda Accord and have enough structural load capacity to hold up to 250 pounds (enough for me, my fishing gear, a trolling motor, and any fish I could catch).
The design was relatively simple and just required a lot of folding and taping. The cross-bars were designed to have bolts screw in on the outside of the frame which my housemate desiged a handle for.
Folding and taping the boat, although simple, was not a short process. It took my housemate and I the better half of a day to get it assembled and I still had to cut all the wooden frame pieces which took another good part of a sunday.
Floating the boat
I took the boat down to the lake with life jacket in hand and nervously set it on the water. My housemate followed and brought he boat design he had built (the CPB-2016 - free planes available from https://www.portableboatplans.com) which I had helped him build while my coropunt was still in the design phase. We set out on the water and the boat didn’t immediately sink! The boat was so light that any wind made me rotate and drift but the water line was only a couple inches from the bottom of the boat (which only had 8 inch side walls). I tried to stand up but it was hard to keep my balance, the highest I got was a tall crouch. There are designs for sponsoons (also made from coroplast) that attach to the side of the boat which help stabilize it which I have yet to make.