Deep Ocean to Deep Space

I watched a Nova last night on the Filippo Brunelleschi who built the dome on the Cathedral of Florence. He was a most impressive guy. Not even trained as an architect or a builder but did not let that keep him from competing against those who were and then built the largest masonry dome ever built to this day, and he did it 600 years ago. But unlike Leonardo, he made no notes. The program was focused on modern architects and builders who are uncovering how he did it. The cathedral had been under construction for 80 years when the competition was opened for the dome.

Brunelleschi claimed he know how, but would not tell the committee what he proposed to do. He said he would show them when they gave him the job. They did a prelimary contract with them and he showed them how to get tons of materials 17 stories up, and back down using a lift that had never been used before. So they let him go for the dome. His trick was very clever, to use a herringbone brick pattern that helped lock the bricks together and transfer the load laterally so that the dome would not fail along the circumferential mortar lines.

I liked the idea that flying buttresses were forbidden by the committee. Yeah, to an engineer they are cool, but do you really want to look out through them? So much stuff in the view. And the dome was way to high to use centering, temporary supports that are removed after the mortar sets. And my thought is that centering allows you some imperfection. Once you get the last brick in place and the mortar sets, then some misalignment will be compensated for. For a  while anyway. I heard that in about 50% of the cases it didn’t. Many cathedrals were built more than once.

We know that masons use rope lines to check their progress but exactly how he did this would not be known if one of his very vocal detractors made drawings of the construction to prove that it would fail. Those drawings survive and know we know that the rope lines came off not a circle in the center but an eight sided flower like design, that gave each side and inverted arch to transfer weight diagonally down, not just straight down. So its good to have people who think you are full of crap checking your work.

He managed to get this done in 16 years!

But I wonder about something they did not mention. What kept the base together? were the crossings acting a buttresses. Most of the weight is transferred down, but some weight is transferred out, right?

I don’t see how the curve was maintained. Is the curve a section of a circle? So not only the rope lines provided angle, but distance from the pattern line in the floor? No, I think not. They were very long and there is a lot of stretch.