If you love to experiment in photographic techniques, or if you are a professional photographer, you probably need to travel with a very complete equipment. You can buy very good photographic bags of the type with interchangeable dividers, or you can build yourself a personalized backpack.
Step 1: The Bag
With that purpose I've bought a good quality rock-climbing backpack, which is used to keep all the equipment to reach the starting point of the ascension. This bag has many advantages, it's very capacious, it opens completely, it's light and it has the exact dimensions of the hand luggage on the planes. And, differently than professional photographic bags, it doesn't appear as a gravy train for thieves!
Step 2: The Materials
To build the partitions for your equipment you need to choose the most copious combination of gears you could probably use. Then arrange in the bag those camera bodies, lenses, flashes, and anything else, looking for the best marching.
When you're satisfied you can draw the layout on a big paper sheet, so you can follow it to cut, bend, glue the pieces of frame. This frame could be made of wooded boards, probably plywood, or made, as I did, from plastic baseboards. Indeed that material is often very malleable if heated up, and you can cut it with a pair of big scissors. Pay attention to find the right material, not all the baseboards are good.
I've glued each piece with hot-glue, then you probably want to paint everything black.
You also need some cushion material, as you see in the picture I've cut each shape to fit the right compartment.
Step 3: The Frame
At the bottom of the frame I decided to glue a thick sheet of foam underneath the lens of the big camera (like Canon 1D or a camera with battery grip) and a thinner sheet on the rest of the surface. I left an empty zone where I don't need a massive padding, and underneath the body of the big camera.
The two "arms" are intended to keep the frame steady in place pushing on the internal corners of the bag.
The compartments of the lenses have on the bottom edges some foam pieces with triangular section, so to obtain a rounded stand.
I've also cut apertures to avoid that the viewfinders interfere with the plastic frame.
Step 4: The Stuffing
It's time to glue every foam piece in place. I've used a neoprenic glue. Apply some glue to both sides, wait 10 minutes, then make the two surfaces stick and push strongly. Pay attention to the layout of each piece, some have to be glued before than others.
Step 5: Almost Finished
When every foam shape is in place you'll have a great specific rigid and padded frame which can be inserted in your backpack.
Yes, it' not very nice to see, but I'm sure you'll be able to make a better work. I should have painted black the frame before gluing the foam sheets...
Step 6: Close the Gaps
If you want to be more meticulous than me you can close the joints between the foam sheets. There are two different way to do that, I took a picture of both possibilities. In the first you can apply glue the external face of the foam pieces, wait some minutes, and close the gap pushing one face on the adjacent one.
The other method is simpler but not so effective, only add glue on faces between the two foam pieces and close them.
Both methods will be anyway better than leave everything open as I did. I'll soon close everything with the first way.
Step 7: Fitting
Push the frame into the bag and check that no sharp border of the frame could damage the bag material.
Step 8: Bon Voyage
Here you see the backpack with a 40D camera body, four Canon lenses, a lensbaby, two Canon flashes, a mini-tripod, my motorized gigapan gear, my battery PSU, an IR filter, a remote (in the net pocket) and there is plenty space for a second body and other tools.
I've inserted a big very soft foam in the big square pocket to have a comfortable pressure on the back, although the backpack already has a very good padding, so if you need more space you can avoid additional foam.
It's time to wish you bon voyage ;-)