I decided to increase the storage space over the cab in my van by building a shelf that extends the existing area.
First I marked and cut-out a cardboard template that matched the required shape.
To create a shelf that is both light and strong, I used a torsion-box design with 5mm ply used as the upper and lower surfaces. I used the cardboard template to mark out the outline on the plywood and cut the ply to the required shape using a combination of table saw and bandsaw.
For the internal braces of the torsion box I ripped several 40mm-wide strips of 18mm plywood. I didn’t have any lengths of the 18mm that were long enough for the lengthwise braces so I glued together strips of 5mm ply to make long 10mm-thick strips.
I arranged the plywood strips loosely to see how I would layout the internal skeleton
Once I had decided on a layout, I numbered the strips and marked their position on the face panel
The matrix of internal braces were to be interlocked using crossed edge half lap joints. These were cut on the table saw by clamping several pieces together and cutting them all at the same time. This required the removal of the saw guard and riving knife, something I’m not that happy about doing but a necessity in this case. I used an unwanted plywood off-cut to ‘back-up’ the cut to prevent break-out as the blade exits the cut.
With the half-lap joints cut, I dry-assembled the framework to check for fit.
Once I was happy with the arrangement it was time to start gluing. The thought of gluing all the parts together in one session was daunting, so I did it in stages. I started gluing the outer strips on first.
Once the long front strip was attached I started gluing the short cross braces, making sure I cleared the glue squeeze-out away from the areas where the cross-pieces would later fit
Once all the cross braces were fixed it was time to fix the long pieces
My large clamps could reach the first strip
…but the clamps would not reach far enough to clamp the middle piece so I had to improvise
This part required clamping in three planes at once
Before fixing the edging on the curved part of the shelf I test-fitted it in the van
Once all the framework was glued I added some extra pieces where I knew I would be screwing into the shelf to fit it
Along the front of the shelf I fitted 6 T-nuts so that I could attach things (like a lip to stop things sliding off) to it. Using a G-clamp, these required considerable force to press in
I took this photo with the ruler so that I could remember the location of the internal framework once I had fitted the remaining face piece, in case I need to drill into it or whatever at some future date
Gluing the final top face onto the rest of the shelf was the biggest glue-up task of the whole project. I had to apply glue to the top surface of all of the internal cross-members. It took quite a bit of time (and glue!). I had marked the positions of all the internal members on the outside. I didn’t have enough clamps to clamp every single part of the shelf so I used screws to secure the pieces while the glue dried.
Once dried, it was time to see what it looked like in the van (I had already fine-tuned the shape at various stages of construction to ensure a good fit)
I now just need to secure it in place and cover it to match the existing fabric.