After being asked many times about the clamp storage I finally decided to give a little more details on the two racks. I made them at different times so the construction differs slightly.
I First made the rack for the pipe clamps. In my "newbieness" I thought the top board would need support between each set of clamps. This is by far overkill. The overall construction is of 3/4" plywood cut into 5 1/5" widths. Then I cut 1 1/4" holes with a forstner bit, holes were placed 4 1/2" apart to allow for clamp head space. Then using my jigsaw I cut from the side of the board into the hole so there would be a smooth transition. I made the slots deep enough to support two clamps. If I had to do it over again I would have made the board wide enough to hold four clamps, this would really save some wall space. The horizontal board on this rack was glued and screwed to the side of the vertical board, a basic construction misdesign. The supports were just 3" wide pieces cut at 45deg on each end, these were just glued to the inside of the vertical and horizontal boards. Finally the rack was screwed to the wall making sure the screws went into studs, remember, these things get pretty heavy when loaded.
This second rack was built much later, as a result the construction techniques were far superior. The horizontal board was glued and screwed onto the top of the vertical board. The slots were cut deep enough so that when the clamp is in place the beam would rest against the vertical board to keep the clamp from rocking. The spacing of the slots is 1 3/4" apart. Since the Besseys have a narrow beam I was able to cut the slots on the table saw with a dado blade. The horizontal board is 3 1/4" wide and the vertical board is 5 1/2" wide.
Here you can see I was able to put some of the smaller bar clamps on the rack. In between I snugged some of the tiny Quick Grip clamps.
No matter how big you make your rack it will overflow.