I really enjoy all things geometric in nature, but I also like things that are functional. So when I saw a number of these types of shelves appearing around the web, having a go at making one was a no-brainer. It turns out their construction is more more challenging than I first thought, but with a little prior planning and forethought, the challenge is easily overcome.
Before you start, there are a few things to consider. Firstly, the design, if you intend to replicate the design shown here then that part is already taken care of. However, if you intend to change the design to something of your own, then I recommend taking the time to draw it out, or even better, make a paper cut-out. The reason for this, is that it's not always obvious what lengths certain pieces need to be. For example, in my design I assumed that the three pieces that make the central triangle would be all the same length, only to find that one of them needed to be shorter. This wasn't a big problem to fix but it highlighted that it is not always so straight forward.
Secondly, how will you mitre? The design of this unit relies heavily on the use of 60° mitre cuts. There are a number of ways to achieve this including powered methods such as band saws, table saws, chop saws, sanding wheels, and probably more, but manual methods such as mitre blocks work just as well. Just make sure you select a method you're comfortable with and that you can make the 60° cut required.
(NB: Some equipment show the cut as 30° - this is because the default cut is already 90° so by adding 30° you get 120°, leaving 60° remaining from a 180° starting piece)
Step 1: The Outer Triangle
I started with two planks of pine measuring 2400 mm in length, 94 mm in width and 19 mm in thickness. Even though I bought them from the expensive DIY shop (If you're in the UK, you'll know the one I mean) they still came to less than £10.
I began by measuring and cutting three equal lengths to make the outer triangle. In my design this length was 600 mm but had I put some more thought into this and made it slightly smaller, I could have made the entire unit from only one plank and halved the cost!
I used a band saw set at 30° to make the required cuts. IMPORTANT: When making the cuts, make sure the work piece is the correct way around! The two mitres should mirror each other. A view from the edge of the plank should look like a trapezium, like in the example photo above (but much longer as this photo is just a short off-cut). If you see a parallelogram instead of a trapezium, you're going to have a bad time. This will be true for all the cuts in this design, so take a little time to make sure your work piece will be cut in the correct direction.
Step 2: Glue and Measure... Then Measure Again.
The next step was to glue the three lengths together to form the outer triangle. I used good quality wood glue and a ratchet style clamp to squeeze it together. You may wish to re-enforce the joins with screws or nails if you intend to keep heavy items on your shelf, but for me, just wood glue was enough. You'd be surprised at just how strong it is.
Once the glue was dry, I worked out what lengths were needed for the inner triangle. I did this by marking the half way point along each of sides of the outer triangle and then using a metal ruler to measure the distance across the triangle, from marker to marker.
It was at this point a mistake was made.
As each of the three measurement I had just taken were the same, and given that the outer triangle was constructed from three equal lengths, I assumed the same would be true for the inner triangle. This was wrong, as the inner triangle fits together in a slightly different manner to the outer triangle and actually requires one of the three pieces to be slightly shorter.
My recommendation to avoid making the same mistake is to only make two pieces using the measurements you just took and then, with those two pieces in place, re-measure for the third piece.
Step 3: Glue the Inner Triangle
Finding a clamp to glue the inner triangle proved difficult. In fact, I ended up improvising with a primitive device I made from two blocks of wood scrap, a pair of threaded inserts and some threaded rod. This worked well to hold each piece in place while the glue dried. After doing this I realised that there are a number of other solutions to the problem so you'll just have to get creative :)
After gluing all the sides of the inner triangle in place I then measured and cut two short lengths to add more shelf space and glued these in place. I didn't show this step as it is very similar to previous steps, just with shorter bits of wood.
By this point you should have something that looks like the photo above. You could finish here and have a naked pine look to your shelf unit, which is very nice, or you can do as I did and stain the pine.
Step 4: Finish!
I decided to stain my shelf with some generic "Walnut Wood Stain", walnut was the darkest colour I could get at the time, but you can use any colour you like. Simply follow the instructions on the tin and let it dry. I used a brush to get the stain on, but then wiped it with a rag to remove brush marks.
Let it dry and you're done!
The unit can be mounted on a wall using three wall screws (with wall plugs) that sit at the top of each of the smaller triangles. But if wall mounting is not your thing, the unit looks just as cool free standing on a side board or table.