Our nephew wanted a TechDeck half-pipe for his birthday this year. We thought we'd kick it up and build him his very own real concrete fingerboard bowl park. The goal was to create a unique park from materials we had on hand. At 60 lbs., this park weighs a wee bit more than our nephew.
tub/form (we used scrap 3/4" plywood and spray glued some plastic film to it)
spray silicone or some type of mold release
and of course, duct tape
Step 1: 1. Create the Form
We built a tub from scrap 3/4 plywood and spray glued some plastic film to it. To create the bowl shapes, we used 1 larger wooden bowl and 2 smaller glass bowls. The transitions/gaps where shaped from a few chunks of styrofoam and duct tape.
Note: The mold needs to be smooth, so the concrete can release when cured.
We used caulking to make smooth transitions and rounded corners. Use your finger and a little water to smooth out generous beads/globs of caulking. Let the caulking dry overnight before pouring concrete.
Step 2: 2. Pour Concrete
We used a full 60lb. bag of basic post concrete mix since we had that on hand. It worked ok, but cracked because the form was too thin (specs state minimum of 2" thick). The trick to a smooth final finish to knock all of the air bubbles out. We tamped everything well with a small stick. Then we beat on the outside of the form with a hammer. You will see the bubbles rise to the surface. Let sit for at least 24 hours. (we rushed it and cracked the main bowl. as an easy fix, we glued the pieces to plywood with liquid nailsback in business)
Step 3: 3. Remove Form
Add the finishing details like: