Materials Needed:
3/8" X 4' X 8' sheets of plywood
Bmx Bikes
8' 2x4's
electric, handheld or bench saws
handsaw
hammer & nails
electric sander/sandpaper
drafting compass
string & chalk
garden hose
sawhorses
nail punch
ink pen
wood screws
3/8" Pvc pipe
pushpin
1) decide on the type of ramp(s) you want to build, sketch out the invent and dimensions on paper.
2) derive the materials required, and as much wood as you can get your hands on
3) Find a work space to use (garage, backyard, etc.) and lay out your supplies. If you're planning to build a fairly large structure (permanent) try to build it on site.
4) For ramps with curved transitions, you will need to use the string-and-compass method*.
5) Once you've drawn and cut your templates, next comes the bracing.
6) Once you've done the framework, you'll most likely need to prep the top piece(s) of the plywood (which must bend to fit the transition without breaking). Do this by propping up the sheet(s)--already cut to size--at a sloping angle and soak with a hose at low pressure for an hour or so.
As the wood becomes soaked, apply an addition number of weight to the town of the board(s)--using bricks or something similar--until the wood attains the desired curve.
Now nail the wood onto the framework's 2x4's If your ramp is to have coping, make sure to leave adequate space for it to fit snugly. All the time go With the grain of the wood while bending and apply the ply!
For a smoother transition, sand the bottom edge of the top sheet at an angle flush with the ground. Check for jagged splinters. Sand or paint if desired. Paint will make your ramp faster! Duct tape, airplane or electrical tape or aluminum strips may be added to plane the transition's bottom edge.
* String and Compass Method
Figure how much transition curve you want (in feet & inches) and how much 'vert, if any. Tie one end of the string around the pushpin and stick it in the sheet as shown. Holding the string taught, part out exactly the number of transition and mark this on the string with an ink pen. Tie the drafting compass to the other end of the string and tighten it so the slipknot is right on top of the mark you made. Holding the string taut, swing the compass from the sheet's edge in a quarter-circle, marking the template with the chalk. You may need to move the contraption around to get the desired curve and best use of space! Place sheet on sawhorses and cut out templates carefully.
New addition On Decreasing Transitions:
If you want to make a ramp with a decreasing transition, you need to modify the above steps and instead of using a pushpin, use a round object that is 6 inches to 3 feet in diameter, such as a paint can or a round garbage can. Attach the string to the round object and somehow derive it to the wood in place of the pushpin.
As the string winds around the round object, it will get shorter and your transition will become tighter. This is called a decreasing radius transition and it is very cool when development get underway ramps and quarter pipes.
How to Build a Ramp Using Bmx Ramp Plans