This is no wimpy school backpack. This pack can hold everything you need for a week-long backpacking trip for about $25. Made mainly of duct tape and some PVC pipe it is light weight yet durable. Making the backpack does take some time, but it's not too difficult.

Materials Needed:
1 - 10ft length of 3/4'' PVC Pipe   ($1.60)
4 - 3/4'' Elbow Connections   ($1.30)
4 - 3/4'' Tee Connections    ($1.30)
3 - 45 Yard Rolls of Industrial Grade Duct Tape   ($18.00)
1 - Can of PVC Pipe Cement    ($2.00)
1 - 2" Buckle   ($2.50)

Optional:
Spray-paint for the frame
Buckles for bag openings
Foam padding for the waist and shoulder straps (The stuff I used was not high-grade, it still works great)

Skills Required:
Very basic PVC bending skills.

Step 1: Cutting and Bending the Pipe

Cut your 10ft length of pipe into sections.

Dimensions
2 x 19cm - lower sides of frame
2 x 24cm - upper sides of frame
6 x 36cm - middle sides of frame and cross pieces of frame

It's not as important to use these exact lengths as it is to make sure the pairs are exactly the same. Otherwise the frame will be lopsided, and feel funny on your back.

Now take four of the six 36cm lengths, and bend them to your desired angle. I bent mine with a 5 gallon bucket, but you can use whatever round object you may have.

eHow had a great explanation of how to bend PVC, so I'll include the link to their instructions. http://www.ehow.com/how_4796089_bend-pvc-pipe.html

My bent lengths are now about 33cm on a straight line from end to end.

Step 2: Fitting and Assembly

Assemble frame, gluing the pieces together with your PVC cement. Push the frame and connections down tight to make sure the fittings are secure.

If you want to spray paint the frame, do it now.

Step 3: Cutting Out the Bag

Now we're going to start making the bag of the backpack. I prefer to use a rotary cutting board like the one in the picture below. With these you can lay all the duct tape out face down on the board, and get your dimensions correct very easily.

Make the sides of the bag separately, and then match up the sides to ensure they are the same size.

Here are my dimensions if you would like to use them:
(Notice that there are only four pieces, I have two sides, the bottom, and the front. The back is going to be against the backpack frame, and the top we will do later)

Dimensions:
Sides - 52cm Tall x 28cm Deep
Bottom - 37cm Wide x 28cm Deep
Front - 52cm Tall x 37cm Wide

Step 4: Assembling the Bag

Tape the front and sides together securely. Next, tape the bottom to the front. Finally, tape the bottom to the sides.

Here's what the bag will look like. (The frame is just in the picture to hold up the bag for the picture. This is not what the bag will look like sitting on the frame).

Step 5: Attaching the Bag to the Frame

The bottom of the bag should rest on the lower cross piece, not the bottom of the frame. This will leave room for a sleeping bag to be tied on the frame. The top of the bag will be between the upper cross piece and the top of the frame.

Now start taping the top section of the bag onto the frame down to the upper cross piece. I took strips across the width of the frame because I want support bands across the top section. If you don't want these, feel free to just tape down the bag on each side.

Make sure to cover the sticky backside of these strips of tape.

Step 6: Trimming

There will be some excess at the bottom of the bag, cut it off in the shape of the cross bar. Tape that cut section down to the crossbar it rests on.

Step 7: Closing Up the Back of the Bag

Now run strips of tape between the two cross bars (should be covering the opening of the bag). Cover the sticky backside with tape.

Don't tape over the side bars until after step 8.

Step 8: Back Support

This step is quite important, but very easy. Simply run some strips across the area your back will be against. This keeps the back from hugging your back, which adds a lot of comfort.

Step 9: Shoulder Pads and Straps

Pads Shoulder Straps
Cut out two strips(42cm x 8cm) of foam. Make 4 strips of duct tape the same size. Layer each piece of foam between two strips of duct tape. Duct tape around the edges.

**You can also taper the ends of the foam to make it fit your body better. This is an improvement I wish I had done...but it is not necessary**

The rest of the shoulder strap (the skinny part) can be made next. I folded a strip of duct tape in half, and taped on two more layers to make it thicker.

Adjustable Straps

**There are a couple ways to attach the shoulder straps. I chose to use plastic sliders so that the straps would be easily adjustable. You could also probably make some sort of duct tape slider, or simply tie the straps down. **

Attach a buckle like the one pictured to each of the padded should straps by running a narrow strip of duct tape through the top loop. Then tape that strip to the bottom of the should strap.

Make 2 duct tape pieces 35cm x 2.5cm. Run these skinny straps through the bottom of the buckle.

Finishing
Attach the shoulders straps to the upper cross bar. You can put them as close or far from the sides as you want, whatever is comfortable.

Attach the skinny straps to the sides of the frame or the lower cross bar, whichever is more comfortable.

Step 10: Waist Strap

Now it's time to make and attach the waist strap. It is very important that this strap be functional and strong, because most of the weight of the pack will be held by this strap.

Begin by cutting out some padding(If you want it) and taping over it the same way you did with the shoulder straps. Here are my measurements:

Dimensions
84cm Long
12cm Wide

You may have to make this waist strap shorter or longer depending on your waist size. Strap should be snug enough that it sits on top of your hips, so they can bear the weight of the backpack.

Before you attach and tape down the waist strap, add some kind of connective device to the ends of the strap. This is where I used the 2 inch buckle, but there are many different options.

If not the buckle, I would recommend a two ring setup, where there are two rings attached to one end of the strap, and a length of tape on the other that can be wound through these two rings. This setup is easily adjustable, which is important for the waist strap.

No matter what setup you use for the waist strap connector, make sure it is adjustable.

Now simply tape down the waist strap to the frame (at the bottom two crossbars) so it is well-secured.

Step 11: Bag Flap

Make a duct tape rectangle 35cm x 39cm.

This is going to be the flap over the top of the bag. Cut out two corners (about 1 inch square) so the flap will fit between the sides of the frame. Tape this down to the top of the bag.

You can use buckles to secure the flap down, but I'm content with a strip of duct tape. Both will work just fine.

Step 12: Bag Support (Optional)

After completing the backpack, I realized that the bag was a little too flimsy, so I added a support in the bottom.

A wire hanger does the trick quite well, just bend it into the shape of the bottom of the bag. Place it in the bottom of the bag and tape it down.

Step 13: Accessories

An important feature of this backpack is the ability to customize it. Add pockets of any shape and size, and remove them if you need to.

Remember to throw in a roll of duct tape when you go hiking for any repairs or additions you need to make.