A section cut from a conical solid along the vertical axis will give us a parabola. I don’t want to explain much on how it constructed however this parabola can be cut using straight line cuts. On sketch up, it looks like this -
From the looks on the drawing… a lot of planning came up with the following questions as my guide:
1. What wood should I use?
At first, I was about to use a plywood with flats be covered with veneer of two different wood color however, the veneer is not so strong to hold specially if cut into small pieces. The best solution is to laminate two kinds of woods. Here I decided 5 mm for the thickness. After lamination, a total of 10 mm brown and white wood. After thicknessing I have about 8 mm thick (3/8 inch). Probably will be thinner after final sanding and planing.
2. How do I cut the wood? ...
Before cutting, the pattern is directly penciled in the board… It will be possible to paste the pattern but I like to cut a wood with pencil line. I like to see and control the wood tearout during cutting.
The greatest challenge of them all is to cut the pieces… Using Circular saw will allow 2mm kerf and wider using others. Scroll and Band saw are not available. Finally, why not use a Japanese saw and my thinnest hacksaw available (Thanks LJ Philly Edwards had given me this hacksaw for free when I visited him in London.)
Okay, the challenge is on… My skill in freehand sawing is at stake… So I had to sharpen the hacksaw which is 17 tpi with a triangular file.. No kerf bending on the saw teeth… A combination style of rip and crosscut.. After testing the saw… I was satisfied… A little bit tight but I feel okay. It cuts also straight… TIP: IF YOU ARE NOT SATISFIED WITH YOUR SAW… DO NOT USE IN PRECISION CUTTING LIKE DOVETAIL.
CORNERS FIRST… Cut the 4 corners….. Actually 7 passes of cuts for every corner. Set them in groups.
ELLIPSE NEXT … started in the shortest cut using first the Japanese saw then backsaw. Set in groups. There are some errors during cutting but managable to be used. So far I was lucky only one breaks when I accidentally tap my Japanese saw sideways…. The wood glue manage to join them together. Another error is when I mistook the guide line which is the wrong as I have to flip it first before making the cut.
No pictures taken during the cut on the ellipse portion.
3. How do I glue it? ... using masking tape.. two pieces at one time. Waking up early, the pieces are glued together and taped. This is before I go to my office work. In the evening, I check the glue if dry and apply more glue. If it warrants, the adjoining pieces will be joined. Here is how it looks ….
notice the tape that holds the pieces together. The only challenge in gluing is to hold it firmly in place. My priority is to have lesser gaps than being offset from the design. The strength of the glue is found when the wood are close together. It is not wise to fill in the gap with a glue.
I hope you enjoy reading this…. I always welcome critics and suggestions.
TO BE CONTINUED