Make test panels 12 inches by whatever. Square if you wish.

Cut them into strips that are 1 or 2 inches wide. Pick a size and stay consistent.

mount the strips so that 1 inch is held in the mount. Put your weight so that it applies pressure 1 inch from the other end. YOu are now working with a 10 inch long lever. Hopefully this will be a simple length to use for any calculations In fact, should the strips be 13' or even 15 '' long it would not matter. the force could still be ecerted over 10 inches of those strips., as long at the weight is applied 10 '' from the mount.

I'd get a big bucket, and mount a piece of angle iron under it to apply the weight to the test panel in a narrow area. I'd put a ruler next to the panel, set the bucke on top, and start filling the bucket with sand. when enough got into the bucket to cause some cracking you can write down the amount of deflection by reading the ruler. when more sand eventualy makes that bucke so heavy that it breaks your panel, you just lug the bucket to a scale and weighit. You can use a bathroom scale, and if that doesnt read high enough, measure the sand used in small loads and add them up. for a rough job, use bags of sand that are premeasured to 40, 60, or 80 pounds. ( you should be able to buy them off hte shelf like this. This is going to be a rough test anyhow, so precision to more than 2 decimal places is irrelevant. Not much difference between aosmethng that breaks at 500 pound and something that breaks at 550 pounds.

If you have made a wider panel and cut it into thinner strips, you can test multiple strips and average the results.

Good luck with this.

If people did not reinvent the wheel practically every day we would have no such things as bearings, hubcaps, tires, bicycles and cars, etc.

Paul G. Jacobson