|My working prototype|
All sizes are suggested, though the top was based on my body size. You need room for your arms on either side of the front radius. Since I have a working wood shop, finding the materials for this was a matter of diverting a few scraps headed for the trash bin. Of course, you could buy all the materials from a home center and I'm sure it won't cost much, though I haven't priced it out. I used 1/2" plywood too keep it light, but use whatever you like.
Here's what you'll need:
1 - 18" X 24" X 1/2 plywood (Home Depot sells 24" X 24" pieces pre-cut.)
1 - 6" X 18" X 1/2" plywood for the tool ledge.
18 pcs - 3/4" PVC X 3 3/4"
1 - 1 1/8" X 1/8" strip for front radius lip
2" X 1/4" strips for side and back edges
foam padding - whatever you have lying around. I used old interlocking floor mat
any kind of protective finish
Start by cutting the deck to 18" X 24". Layout the back radius (about 17 3/4" radius). Do not cut this yet. Mark a point back from the front edge about 3". Mark either side about 5" in from the edge. At this mark, layout a 45 degree angle in toward the center. We are going to layout the actual curve according to our body size. We want this to fit right up against the belly. The picture to the right shows how this lip will look when we're done.
The next part can be done alone, but a helper would be very useful. We're relying on the wood to bend naturally to a smooth curve by putting tension on the ends. Don't make any sudden moves and the 1/8" thick strip should bend to this radius without cracking. Maple or poplar is a good choice.
With the deck on a bench in front of you, clamp two small blocks to the 45 degree lines. Hold the strip against your belly to form the radius. With an even tension, move the strip to the deck and mark the radius. Clamp the strip to one block (left one if you are a righty). Put enough tension to bend the strip to the center 3" marl and against the right hand block. With a pencil, mark both sides of the strip.
Remove the clamps and block and cut out the inside radius. This cut needs to be done very carefully and to both lines. This space will be equal to the thickness of the front strip. The cutoff piece will help put pressure on the strip when clamping. If you make a good cut, you might only need one clamp. Add more clamps if you need them. That's why we didn't cut the back radius yet, a mistake I made on the prototype.
I cut it this way to show the gap. In reality, you will cut all of one line, then the other. You can use a sanding drum or the front cylinder of a belt sander to smooth out the inside radius so the strip fits without big gaps.
This needs to cure over night so the edge is sure to stay in place when you take off the clamps.
Go carve something! We'll continue in Part 2.