Diameters and dome strength
The hypothesis that increasing the diameter of a dome structure while maintaining its height will cause the vertical strength to be weakened has been proven to be true.
The use of domes in construction has been found in Roman, Christian and Muslim architecture. It has been used in constructing palaces, mosques, churches and tombs. The Taj Mahal in India, St. Paul’s Cathedral in England and Saint Basil’s Cathedral in Moscow all use onion-shaped domes.
The science fair project can be also be repeated by different types of wood like bamboo, oak or redwood.
The experiment can be modifed by increasing the width and thickness of the plywood.
Dome - http://en.wikipedia.org/wiki/Dome
Monolithic dome - http://en.wikipedia.org/wiki/Monolithic_dome