This balsa tower was 12 inches tall, 8 inches wide at the base, and tapered to a 2 inch square at the top. I only have about forty pounds of sand, so I ended up adding any heavy object in sight to the bucket. After putting in the ceramic mug used to pour the sand, a chain, paper weights, the total weight supported was 50 pounds. The tower did not actually break, but one of the legs was bending almost to the point of breaking. The efficiency score was just over 2000.
As you can see, instead of using X’s, I only have a zig-zag pattern. That was because I wanted to see if I could “trick” the system. In a tower like the one above, the four legs are in compression. When the load is applied perfectly vertically, the rest of the members have no load until the legs begin to twist or bend.
Because the legs are square pieces, they have equal resistant to bending in all directions. The X’s only serve to break the main legs into smaller sections, which increase the strength.