Next, draw a point along the 2x6 that is " off the ground (marked incorrectly as 6" in picture above). You will start the transition " off the ground because for this halfpipe there will be a flatbottom that is " high.
Now measure 6' 10" along the 2x6 from the point you just drew and put a screw into the side of the 2x6 there, attach a string to the screw. Here I use fishing wire (2 lb test line), Any string with minimal give/stretch will work.
At the other end of the string connect a pencil (I use a marker for video purposes only). Take your time doing this so that the pencil is lined up with the point you made " off the ground.
Step 3: Draw the Transition Now the String and Pencil does the work for you. VERY SLOWLY draw the transition, trying your best to keep a constant amount of tension on the string and keeping the pencil at a 90 degree angle with the plywood.
You are just about done, if you haven't already, draw a line from your point " off the ground to the ground, Then use a jig saw to cut the transition you have drawn. Use the piece you cut out to trace the second rather than drawing both using this method.