Paul Symansky's Flybox.
Here are some pics, and diagrams, of a three piece modular flybox I recently built. It was designed for BMX, but could be used for anything. It consists of a launch ramp, landing ramp, and table top, is very sturdy, quick and fun to build, and the best part... it all cost around just $50! Here are the construction details for each part.
The launch ramp was made using 3/4" plywood for the sides, and 3/8" plywood for the surface, along with 2x4s for the supports. The plywood to be used for the sides was bought in a 2'x4' sheet. The string and compass method was used to trace out a 6' transition. After it was cut out using a jigsaw, the same piece was used as a template for the other side (please see the diagram). 5 2'x2"x4" supports were used to support the surface, and one 2'x2"x4" was placed at the base. The surface plywood was cut out of an 8'x4' sheet, and was placed so the grain was horizontal, thus the maximum length was 4'. The final length needed was about 4'6", so another piece had to be cut; creating a seem, which due to its short length doesn't always line up perfectly with the main piece. This, I would think, makes it slightly more difficult for boarders, although I really wouldn't know, not being one myself. Everything was secured using 2 1/2" ringed galvanized wood nails, including the surface (another possible downside for boarders.
The landing ramp was constructed in pretty much the same way. The only real difference was that the sides weren't transitioned; instead one 2'x4' sheet of plywood was cut diagonally. Other than that, the same supports were used, the same nails, and the same surface.
The table was incredibly simple, yet very sturdy. Two squares made of 2x4's were made, that measured exactly 2' by 2' (meaning two of the pieces in the squares had to be 1'9", not 1'8"!), one with a cross brace of 2x6 (2x4s could be used, I just ran out of them here). Then, the one with the cross brace was simply supported above the other with four more 2' 2x4s, and two layers of plywood (one 1/4" and one 3/8") were nailed on top. Again, everything was secured with 2 1/2" ringed galvanized nails.
This was a very easy project, which took me approximately only 2-3 hours. It doesn't follow some other traditional methods of ramp construction, such as only using one layer of surface plywood, and nails on the surface, but it works just fine for my purposes (BMX) and is quite sturdy. Feel free to make any modifications for your own needs, and have fun building it! Sincerely,