Ok, Im in science olympiad in my school, and one of my projects is boomilever, so far, I have tested the first one I made, and it held about 15 pounds of sand in a bucket before braking, but it did not shatter into peices when it broke unlike the other two people who made theirs, which means the problem with mine was a single point of failure, which I now know and will fix in my next one. Mine was also the lightest. Maybe there are some engineer people on here who can give advice, it has to be as light as possible and hold as much weight as possible.
This is a picture of what mine looked like, it broke into three main peices, the failure was the crack at the bottom peice which snapped the whole thing off the base, so the base is perfectly good. Some of the rules are the center of the hook to hold the bucket has to be 40cm away from the mounting wall, the boomilever cant go 20cm under the hook, it has to be made out of wood and glue ONLY, and only the base can be made of laminated wood like plywood. Pretty much the only wood thats good for the boomilever is balsa, which I used, and max size is 1/4" by 1/4"
After it holds 15kg, no more weight is counted, so if it holds 15kg, then the weight of the boomilever will be crucial to the score, as the score is a ratio of weight and weight held, which is up to 15kg