Table Construction

This will be a multi part entry regarding the construction of the table. There are two main components to the table: the top and the legs. The top is similar to the bottom and basically the same for all practical purposes. I’ll begin with the leg construction.

As mentioned previously, the legs are very unique with their various curves. I had decided to use bendable plywood for their construction and build a form to hold them in the proper shape while pressing them. I picked up 2 sheets of 1/8″ bendable plywood that makes a 4′ column (versus an 8′ column). I also was able to score a deal on some 3/4 melamine coated particle board, basically a throwaway so that I could cut it to pieces and create the form. I toyed with various ideas that would save me material but finally decided to pursue a a laminated form consisting of stacked melamine. In designing the form I took a two step approach. The first step was defining the curves in the vertical plane. The second step was extending the curve in the horizontal plane. The transverse plane movement will be had by the wood as it is being pressed as this is literally a twist in the wood.

Back to the vertical curves… I created a template from cardboard cut to the desired constraints (18″ high and 12″ wide) and sketched out the curves with the help of a handy technique involving a string and a pencil. Tie the string around the pencil and then immobilize the string at your desired radius and voila, perfect circle! Making two circles, one at 6in radius and the other around 10in, I made a pleasing sinusoidal curve and then blended the two arcs freehand. After obtaining pleasing results, I cut out the cardboard template and obtained the necessary wife approval. I then transferred the template to a hardboard sheet and cut it out with a jigsaw. I cleaned up the rough edges by hand with sandpaper and a dremel with a sanding disk. In the future, I will have a spindle sander and use that.

Now that I had a solid and sturdy template, I first used it to test to see if the bendable plywood would follow the curve without snapping. Having accomplished this I then used the template to transfer lines to my 4’x8′ sheet of melamine particleboard. This helped to maximize the amount of copies I could get from the sheet. I rough cut 20 pieces from the sheet. with this giant stack of melamine pieces I then used my template to create the final perfect form. I screwed the template onto each one individually and then cleaned up large amounts of material with a bandsaw. The remaining trimming was done with the router table using a flush cut bit with bearing that tracked the template. When this was completed, I then used brads to fix together all the sheets and create the 3D form.

The layers of the laminated legs will be pressed onto the form while being held at the 30 degree form vertical angle. I had to do some trigonometry to figure out the form and it’s physical dimensions. Because I knew the height and the angle, figuring out the other parts of this triangle fell into the trigonometry arena. Outlining the process is simply H=18″, angle =30 degrees. Setting up the equation is tan 30=x/18 or restated, 18tan 30 = x. I added 4″ to this number to add to the thickness of the leg.

Now the form is built and I have to figure out how long to cut my pieces of bendable plywood. I took a new sheet of cardboard and oriented the corrugations along the direction of the bends of the mold. After trimming the edges to fit the surface of the mold, I removed the cardboard and created two parallel lines that were 4″ wide that extended from one corner to the opposite corner. I cut the piece out and came up with a perfect fit for each piece. It created a parallelogram versus a rectangle.  I am now ready to start cutting the pieces for the legs. I’m worried about the directionality of the bendable plywood. My measured angle of the piece of cardboard from the parallel ends is definatley not 90 degrees and the 1/8″ plywood is very fragile and snaps very easily especially if you bend it wrong or too much. My test was made with the flex parallel to the curves of the mold but hopefully it can take a little twisting that it would require to make it around the curves. I cut a piece of 4″ that was rectangular and the flexible direction was perpendicular to the long edge. I took this piece and applied it to the mold along the edge. It conformed to the mold perfectly in the vertical direction. I then began angling the piece so that it would stretch from corner to corner and create the angle I had in mind. I began bending it to fit the mold and SNAP! The piece was not flexible enough to accomodate any twisting at that severe of a curve. Time to brainstorm… I went back to my template from cardboard and recehecked the fit. It was perfect. I measured the angle I had. Surprisingly, it was 20 degrees from the long edge versus the 30 degrees I had designed. This is a result of the curve taking up material and decreasing the angle. I don’t know enough enginering but from the vertical it is 30 degrees but the piece is not… I thought about it and decided to try to orient the most flexible part of the plywood parallel to the curvature of the mold. This requires me to waste a good amount of material due to me having to cut 20 degrees off. I got this done and once again tried to fit it to the mold. The bottom, larger, curve was fine. Bringing the material up around the top curve, once again, SNAP! I recut another and ended up with the same result… Time to take a break and figure out how to make it work…