DIY Plastic Speedboat For One

Coroplast (short for corrugated plastic) is an interesting material. It has a structure similar to cardboard, but since it’s plastic it’s waterproof and can be used for a unique set of applications. It’s typically used for political yard signs, but there are more fun things to do with this lightweight material than advertise. [Paul Elkins], for example, uses it to make speedboats.

The boats that [Paul] builds make use of a piece of coroplast which he cuts and folds into a basic hull shape. From there he begins to assemble the other things needed to finalize the boat, including strengthening the shape with wood, adding a steering wheel, building a transom to mount the motor to, and placing controls in the cockpit such as throttle and steering. The entire build is enough to propel a single person on a body of water at about five knots, which is impressive.

To make one of these yourself you’ll need a small outboard motor, but all of the other details of the build are outlined clearly in his series of videos. If you want to build your own boat but don’t like the idea of a noisy two-stroke motor right behind you, you can also look into building a boat with a silent mode of propulsion.

And if you’ve got a good supply of Coro, definitely check out [Paul]’s other projects, including a tiny house.

31 thoughts on “DIY Plastic Speedboat For One

  1. So yeah… how does one get a “good supply of coro”? I wanted some for an art project a few months ago and had a lot of trouble finding any reasonably-priced supply of large-ish panels. (Though you can get little yard-sign-sized pieces from any art supply store.)

  2. Not sure of your definition of ‘reasonably priced’, but I picked up some 4’ x 8’ sheets from a local sign shop. A little over $50 per IIRC. Not cardboard cheap by any means.

    1. Gotta get ’em online I’m afraid. Or used on ebay. The “used and pre-owned” category is your friend. I usually try not to buy anything new before checking that. Especially with tools; new tools are often worse than the old ones.

    1. I have one about that same size which I bought at a hamfest a couple years ago for $35. I spend another $30 or so on a carburetor rebuild kit, new points and a spark plug.

      On my aluminum fishing boat (10ft I think) it tops out at only about 7MPH but that has to be much harder to push than this little chloroplast boat. I like my little motor because it is small enough to carry, has it’s own built in gas tank leaving me room in the boat for my legs and at such a small horsepower I can let my daughter run it legally.

      I think I need to adjust the timing and maybe if I do I’ll get some more speed in my fishing boat. But this is so much lighter. I’d love to see what speed it would get up to in a small, lightweight boat like this!

        1. Isn’t this a planing hull (hull speed wouldn’t apply) rather than a displacement hull(hull speed does apply)? I guess they are all displacement hulls when they are underpowered/under propped.

  3. Coroplast boats seem like a good idea on the surface but they age badly, particularly if left exposed to sunshine (one of the reasons you don’t see it used in buildings other than maybe hothouses for early planting – we’ve used it for boat storage and it goes to pieces in a season or two. There are companies that make folding kayaks of the stuff.

    On the other hand, if you love to build and tinker with boat design, you’re now motivated to make the next generation on the cheap.

    As far as the motor goes, I’d love to find if there are people tinkering with really workable electric outboards on the general idea of the commercial (and overly expensive)”Torqueedo” that’s popular for dinghies and the like.

    https://www.torqeedo.com/us/en-us

  4. If you’re looking for new and cheap ways to make an automatic drowning machine, look up expanded foam and “PMF” (Poor mans fiberglass) construction.

    If you wanna bang one together out of wood, loads of vintage free plans at svensons.com

    1. “automatic drowning machine” +1
      Built/used many in my mis-spent youth, from the first, a found, leaky galvanized washtub paddled with a rotten 1x board (tippy – even though I was much smaller then…), discarded tires mounted on their rims and lashed together (unsinkable, un-paddlable, and un-dry. Then there was the massive Raft race raft floating on 12 55 gal drums that was so slow the Police politely “offered” to tow us the last 1/4 mile or so several hours and after dark (may have been adult beverages involved in that one). Last one was an 2 person punt made out of one sheet of 1/4″ plywood except for Bow and transom and some 3/4″ pine squares. Had that one a few years until a passenger just had to see if he could stand up in it (- he couldn’t), moment of silence for the Knot-a-Yot (1) that now rests at the bottom of a local bay….
      Lessons Learned:
      1) Not everything that floats is suitable for transportation on water.
      2) Wear a damn life jacket!!!!!!

  5. I think this would make a great project to build with one of my nephews but using an electric trolling motor as a safer propulsion method. No need for speed, just a fun “I made it myself” kinda deal.

  6. I used to collect 4×8 sheets of coroplast after campaigns were over. They just got left up for at least a month after, so I’d get in my truck and go do my civic duty and remove them. We built a lot of things out of coroplast then, which made sense when it was free! You can also build RC planes with coroplast, recumbent bicycle fairings, tents, whatever you want. Too bad it degrades in a couple of years, though.

    I have had good luck getting small cutoffs from sign shops, too.

  7. Coroplast (fluted plastic board) can be purchased from Sign Supply Wholesale suppliers like Montroy supply for around $18 per sheet in 1/4 inch. They carry true cut 4×8 with square cut sides (for a few dollars more) and just down and dirty 4×8 sheets with aok cut edges for $18. No need to be robbed by Home Depot.

  8. There was a Make mag article last year about a similar boat made out of wood. Since boats depreciate, this is a great way to enjoy lakes and rivers without major cost.

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