Once upon the time I decided to make the bed for my newborn son. At first I bought the mattress in local baby store (the part I am unable to make myself). The mattress size is 40 x 90 cm. (All sizes will be given in centimeters, you can always divide them by 2.54 to convert them into inches).
Also I bought a sheet of birch plywood (10mm thick) and three round birch rods (3cm in diameter) in local hardware store. Pine rods are too soft for this construction, use hard kind of wood like oak or beech to replace birch if you unable to find it. I used three rake handles for this.
The construction is pretty straightforward. It consists of 2 flat panels and 3 horizontal wooden rods. This construction carries the cradle made from fabric with plywood bottom.
Step 1: Mockups and Prototyping
You can see my mockups in attached photo. I used the cardboard to do full-size prototype. You can see some amount of different shapes drawn on cardboard which I choosed from. Finally you will find the shape which you are fine with. Actually flat rectangular board will do the job well, but I wanted to have some pleasure seeing it. So it is "cloudy".
Step 2: Cutting the Plywood Headboards
Nothing special, just take an electric saw (or use hand tool if you decided to use simple shape) and saw the previously drawn shape. The width of your bed headboard should be around 4cm wider than your mattress is. In my case it is 44cm, the height is 73cm.
Mark centers for holes (upper: 2 items, 40 cm between them, 61cm from floor, 1 item : at center, 21cm from the floor). Drill the holes. 7mm bit is good for this.
Take the sandpaper and a lot of patience and sand both boards. It is good if you have an electric sanding machne, but if you don't -- I tested it on myself, sanding is definitely possible but takes about 3 hours of your time :)
I decided to paint boards with acrylic paint for both beauty and wooden splinters avoidance.
Step 3: Cut the Wooden Rods
Add 2cm to the length of your mattress and cut all three rods to this size. Use the sheet of paper to draw perpendicular line. Use hand saw with small teeth to do the rough cut. After this take the sandpaper, and, you know, your sweet patience and make the rods smooth.
Drill 6mm holes in the end of each rod like it is shown in attached picture.
We will use the furniture screws (with blunt end and hexagonal slot) to fasten the bed. Please refer the picture, not sure about the correct name of this thing.
UPD: The correct word seems to be "Confirmat"
Step 4: Fasten Screws
If all went good, you will be able to see something like this. Wooden part of work is almost done.
Step 5: Sewing.
You will need to get the strong fabric. Sizes are pictured at step 1. If the fabric you like is not strong enough you always can use two layers of it.
You need to sew the rectangular cradle. Get two zippers with length about the length of your mattress and sew it like you see in pictures. Use strong tether doing this.
Hope pictures gives enough to understand how it works. Next steps will provide some more clue on this.
Step 6: Zip the Zippers
You are almost done. The bed looks pretty well, but the bottom is not flat yet (but it should!)
Step 7: The Bottom
Cut the plywood board the same size as your mattress. Fold it with polyethylene film (or any other water-resistant envelope you like). I think you know the reason for this. Put the board down to the cradle.
Step 8: Finally
Put the mattress over the bottom board. And voila, you did it.
As the bed is soft you can swing your baby without the need to take him\her from the cradle.
Step 9: Future Improvements
You might want to sew the rubber band to omit wrinkles. But even without this the bed works pretty well.
Thanks for your attention,
Russian Desman :)