Expanding a little on the method for boards in the 24x40 article I will be making higher end boards to backstop our goal. Will using single stakes, level with the top of the board, still be reliable here with a 4' board height but perhaps using 2x4 instead of 2x2? This as opposed to using angled braces.

I would say no. Water pressure and wind pressure would cause me great concern with only having it secured with some stakes. I don't know exactly because all my boards, especially the 4' sheets are framed with 2x4s, bolted to each other and then secured in place with 2x4 angled supports. My boards are not going anywhere!

Kevin

I agree - I think using vertical stakes (be they rebar or grade stakes) ceases to be adequate once your boards exceed about 18". I've built dozens of rinks in the last two years, some with 4' tall boards. The important thing to remember is that you need to take care to brace both at the TOP and BOTTOM of the boards. What I typically do for full sheets is, like Kevin, run at least one 2x3 or 2x4 across horizontally, about 2/3's of the way up the board, which both stiffens it and gives you a place to wedge diagonal supports. Sometimes I'll also put some vertical supports on either side to further stiffen it. I've attached one example, and can include more when I go back out to this year's rink's to fill them. In the example below, what is missing is a support at the bottom of the board. Shortly after I took this picture, we banged in a bunch of rebar to support the base.

Absolutely make sure that you brace the bottom, especially where the ground is low (=more water) as you don't want all your water sitting in your neighbour's yard after the bottom of your boards blows out from all the pressure of the water weight. (Been there done that)

Kevin