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How to make a coroplast boat

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What did you make?

I made a coroplast boat.  What is coroplast?  Coroplast is a plastic material that you can fold just like cardboard, but it is waterproof.  The hull is made from a folded piece of coroplast with a piece of plywood for the transom (the flat part on the back of the boat).  I used PVC to act as the gunwhales (pieces on the outside that hold the boat together) and thwart (the middle cross-piece) to keep the boat sides together.  I also made a steering wheel out of PVC that I attached to the motor with string and pulleys.  I bought the motor for $30 on craigslist.  It is an electric trolling motor, which goes on the back of a boat that allows a boat to move through the water quietly.   It is a working boat that anyone that is under or around 200lbs could ride around in.

How did you make it?

I really wanted to make a boat, but I wanted to make it myself, so my dad and I looked for a simple boat project that I could do all by myself.  We found a video of a plywood boat with an electric motor that a guy named Paul Elkins made that looked simple enough to make and it was also small.  When we went to Paul Elkins' website (http://www.elkinsdiy.com) we saw an even less complicated coroplast boat that he had made.  We knew that the coroplast boat would be easier and cool to build, so I decided to build that one instead.  

First, we watched the video many times to figure out what the folds would be.  I even made a model boat out of a sheet of strong paper to see what it would be like.  Then we got a sheet of 4'x8' coroplast and marked where we would fold and cut it.  We cut a slanted edge on both sides of the long edges so the stern would be lower than the bow.  Next, my brother and I used a hairdryer to heat the coroplast so we could fold the creases with a creasing tool.  We folded the boat like you fold origami and my dad helped me attach the plywood to the back.

Our carpenter friend Mark used a table saw to cut long slits all the way down each piece of PVC.  I put the PVC pieces on the outside edges of the boat to make the gunwales.  I used PVC "T" connectors to make the thwarts that hold the boat together.  Then, I drilled holes in the end pieces of the bow and used a piece of copper wire to keep the bow together.  

Before we put the motor on, I tested it with a paddle to make sure it didn't leak, then I made a steering wheel out of PVC and attached it to the front thwart T connector.  We put the trolling motor on the back and attached it to the front steering wheel with rope and pulleys.  Finally, we attached the motor to the battery and I went for a test run in our pool.  We even took it to Lady Bird Lake and tried it out there. 

My dad helped me with some of the cutting to keep me safe and helped with the gluing because he didn't want it to hurt my nose.  My brother helped with the creasing and folding and some of the cutting of the PVC.  Our friend Mark helped us with cutting some of the PVC because I couldn't make the cuts with the table saw.

Where did you make it?

I made the boat at home in my free time after school because I really like fishing and I wanted to make a boat that I could go fishing in.  I also really like instructables and am always building things.

What did you learn?

I learned that building a boat this way is very unstable when you're in the water.  I got really frustrated and wanted to quit the whole idea when I tipped over when I was testing whether or not the boat would leak.  The biggest challenge was working with the hairdryer and creasing tool.  The dryer made the creasing tool really hot and I burned my hand a couple of times.  I am most proud of the fact that I was able to drive it around Lady Bird Lake because it made me feel like I really accomplished something and made a real boat.  If I made another boat, I would make it out of plywood with a flat bottom so it wouldn't be so tipsy.

*UPDATE:  Some of you are trying to build the boat I made, so I posted some more pictures of the boat unfolded.  The red lines are where you make the folds.  The best way to make the folds is with a creasing tool and a hair dryer.  We did cut a small strip off of each of the long sides to make the bow not so high.  It is probably about 3 inches off the front and tapers down to the back. 




I'm Paul Elkins. Well done Bodhi. For people interested in how to get more detail on this boat, go to the link in Bodhi's article. The first revolving window gives you my Email address. Drop me a line.
Unlike Bodhi's recommended weight limit of 300 pounds, the safe limit is actually no more than 200 pounds. Again Bohdi, good job for not having a plan to go by!
The pictures are some other boats I'veI designed and built.
IMG_2780.JPGboat+2.jpglibertyside2 copy.JPG
BATbuilder (author)  paulwelkins1 year ago
Thank you and by the way your website is very fun to go on and what is the boat on the bottom?
Great work, Bodhi. I was just checking out Paul's boat on youtube today, and then I found yours. Nice to see kids working on boats with their dads. My son just helped me this past weekend build a flat-bottom plywood boat--and we completely fiberglassed the bottom and sides. Our maiden voyage is tomorrow--once the paint dries.

Keep up the good work and keep trying other boat designs!
What was the thickness of the coroplast
hi Bodhi, you didn't mention what folds you did or the dimensions of your boat and folds. do you mind telling me, or at least how you folded the back of the boat and or if you cut it?
swinkler11 year ago
excellent steering design we put a similar one on my jon boat, but we had the same issue of having to turn the wheel so much we're trying to fix that and when we do I'll shoot I'm not sure how good you are with wiring or electricity, but you could wire the toggle switch up front so you don't have to lean back to turn it off. All in all an excellent job good sir!
BATbuilder (author)  swinkler11 year ago
try a bigger wheel i tried that because it was to hard to turn
shoot you a link sorry bout that.
Thanks for posting this. And thank you Paul for doing the original one. Have been looking at kayaks quite a bit lately for fishing the local lakes, but my wallet disagrees with me on that :/

I am definitely going to give this a shot. I'm thinking a fusion of the 2 designs would be awesome. Plus with the PVC gunwales, I might be able to add outriggers to give it a little more stability if that winds up being an issue. You may have just inspired my first 'Ible :D
BATbuilder (author)  MidnighToker1 year ago
I am glad I inspired you.
BATbuilder (author)  MidnighToker1 year ago
I thought about doing outriggers because this boat is the most unstable
backflip111 year ago
Cool
milkdud551 year ago
Very nice
McClay141 year ago
cool! nice job
taic4541 year ago
Nice job
Kiteman1 year ago
It wobbles? Try a keel.
BATbuilder (author)  Kiteman1 year ago
How do you think I can do that?
Stick a fin under the bottom of the boat, maybe with a wright at the bottom.
rimar20001 year ago
Very good design, very well made!
BATbuilder (author)  rimar20001 year ago
Thank you
l8nite1 year ago
What a great little craft ! I think that it could use a deck just for looks. For a slightly more difficult but still doable small craft check out mouseboats@yahoogroups.com. Fair winds and following seas Captain