About a year ago I decided I'd lived too long without a cordless nailgun. You see, I'm a do-it-yourselfer. I like to build things. Most of that drive to build, (and now knowledge to do so) comes from all the ramps I've built over the years, starting when I was a kid. The ramps led to doing building stuff around my house and for friends, and well, ultimately to a cordless nailgun. I know, dreamy.
Decide what size transitions you want. Bigger transitions will be mellower, smaller will be steeper. We went with a 4' radius on a 2' ramp. Attach a measured string to the apex of a frame of two 2x4s (or you could stake it into the ground) and draw a perfect arc. Then cut along the lines. You can save time by cutting both transitions at once, or tracing the first transition onto the second to make sure you get accurate templates. Note: a wider ramp may require additional templates for stability. Don't span your 2x4's longer than eight feet.
Set up your transitions about where the ramp will sit. Figure out how wide you want to make your quarterpipe and subtract the width of your side pieces (templates) from this width. This is how long you will cut the studs.
Cut your ribs (2x4's). Lining them up and cutting more than one at a time makes quick and easy work, but make sure to double check they are all lined up perfectly and don't move, so they will all be the the same size.
Start nailing in studs. First do the back supports, top and bottom. Then put in the the top rib, placing it in with the skinny end flush with the top of the transition. This is where you will set your coping, and the way to place the rest of the studs. However, the stud closest to the ground goes in flat, so you can get it all close to the ground as possible. To make the ramp sturdy, put in a stud every six inches or so.
Frame out your deck. Make it wide enough that people can stand or do tricks on it. About a skateboard length is pretty safe. Now you will have the bones of your ramp. Because of the small nature of this quarter, we built our deck different than a larger quarter, as width-strength wasn't an issue. For a larger deck frame it just as you would a deck off your house, 16-inches off centered studs.
Ply it up. Using 1/4 inch plywood, screw it to the studs. Quarter-inch plywood will bend easier but you'll need two layers to make things extra sturdy. One layer would be too spongy, and would break through in no time.
Figure out how you want to set your coping. This is done by lining up the sheets for the top deck and the masonite. You may need to add more sheets to get it to set right. This should be accounted for when building your deck, and laying down your plywood.
Screw on masonite. Be sure to counter sink your screws so that they don't stick out. Draw lines along the studs or use a chalk line, and don't be shy with the screws. Every six inches is a good rule.
Cut your coping to size and screw it in. Do this by drilling holes, bigger on top and smaller on the bottom. The screw will actually sit inside the coping, and the larger holes you can angle back so you won't notice them when you are skating.