This light-weight and easy to make kayak can be built in a few hours, weighs less than 20 pounds, and best of all, costs under $50. While I wouldn't recommend taking it out in any rapids, it works great for calm water, so get out there and explore!

Materials:

Five 10' long, 3/4" Outer Diameter PVC pipes
Hacksaw
Scissors
Tape measure
Two or three large trash bags
2x4 wood plank between 3' and 4' in length (or similar) for the seat
3 rolls of Scotch Brand Tough Duct Tape (make sure it says waterproof on the label!)
Lighter (optional: used for easier PVC bending)
3 square feet cardboard (optional : used to make paddle)

Step 1: The First Cut

Cut two of the PVC pipes down to 8' with the hack saw, making sure to save the 2' lengths.

Cut two 4" lengths of PVC from the same 2' pipe. Make a cut 2" deep into each of these pipes lengthwise, and bend the wings back until they create an angle approximately 60º with each other. These braces are essential to give the kayak its tapered shape. Note : hold lighter under the area of the pipe you wish to bend in order to soften the PVC first.

Step 2: Shape the Kayak

Place one brace between the ends of the 8' long PVC pipes and secure by taping each wing of the brace to the PVC pipe with Scotch Brand Duct Tape. Repeat at other end of kayak, ensuring the pipes have an even bend across their length and give you the shape you desire.

Take the whole 2' PVC pipe and the PVC pipe you cut the braces from and make similar cuts in both end of each pipe, approximately 2" deep. Bend the wings back perpendicular to the pipe so each end is "T" shaped. Press pipe against a flat surface to ensure all four wings are planar to each other.

Tape the longer cross-brace to the frame approximately 3' from one end (this will be the front), and tape the smaller cross-brace 2' from the opposite end (back). Note: because the kayak is curved, the angle of the wings will have to be adjusted slightly in order to align properly with the frame. You have just completed the top of your kayak!

Step 3: Finish the Frame

Cut two more 8' lengths of PVC pipe from the remaining pipes, again saving the 2' lengths for later. At the end of each pipe, cut out 3" wedges of PVC by sawing from the end of the pipe at an angle. Tape these pipes firmly to the braces at both ends of the kayak using Scotch Brand Duct Tape.

Cut two 10" segments of pipe from one of the 2' lengths. Create cross-braces similar to the ones created in the previous step. Tape these pieces between the top and the bottom of the kayak where the longer of the cross-braces is joined to the frame. Repeat this process at the other cross-brace using 8" lengths of PVC pipe cut from the remaning 2' PVC piece.

Add cross-braces to the bottom of the kayak by measuring the distance between the two cross-braces you just added. Cut these pieces from the remaining 10' length of PVC. Don't forget to add 4" to each length to account for the wings that you will be folding back!

Congrats, you have now completed the frame!

Step 4: Trash It

Now that your frame is complete, cover the kayak in trash bags using Scotch Brand Duct Tape to secure the bags to the pipes. Make sure to leave the top of the kayak between the cross-braces open, but seal the space between the top cross-braces and the bottom cross-braces. To accomplish this, cut the bags open, and tape one edge to a piece of the frame. Wrap the bags around the frame, taping and trimming where necessary. The tighter you make it, the easier it will be to wrap the kayak in the next step. The plastic layer not only provides your kayak with an additional layer of waterproofing, but prevents things from sticking to the inside of the kayak once you add the duct tape skin.

Step 5: Tape It

Carefully add overlapping strips of Scotch Brand Tough Duct Tape to the outside of the kayak until the trash bags are fully covered (you don't need to tape the well where you will sit). I found it easiest to first add strips lengthwise on the bottom of the kayak and then vertical strips on the sides (from back to front) in order to minimize creasing of the tape . I then added an extra strip of duct tab on the bottom where the side panels ended for reinforcement and to ensure the side panels did not peel off. Lastly, I added Duct Tape to the top of the kayak.

Note: Carefully check your work here before advancing. Make sure there are no holes or gaps in your tape, and that the layers of Duct Tape overlap fully. This is very important if you want to stay afloat!

Step 6: Accessorize

To add a seat, place 2x4 (or something softer if you desire) in bottom of kayak, making sure it is supported by both cross-braces. This step will involve cutting a slit in the trash bags. Tape firmly into place and apply Duct Tape around the opening in the trash bags to ensure a proper seal.

To create a paddle, take the remaining length of PVC pipe and cut it down to between 210 and 240 cm. Cut out the shape of your paddles from the cardboard and cover in Duct Tape. Tape paddles to PVC shaft. I made my paddles rectangles, but you can find other ideas and templates for paddle shape online.

That's it! Now don your life vest and get out there on the water!