It was 11m long and incredibly cheap. None of the mills wanted it, so I got it for about £30/ cubic meter.
The guy with the timber truck had to drag it along the road and through the gate to get it in the yard, as his crane couldn't lift it clearly off the ground. He must have had to slide it onto his wagon to get it here in the first place.
I might try and turn a couple of big bowls from it when I get a bit more practice with the lathe, and I suppose I'll have to get a bowl corer to stop the massive amount of waste.
After a 2:30am brainstorming session, I'm going to have to go back to the drawing board and adapt the tas de charge, as I won't be able to join it in the way I originally intended. I think the curve is about right, although it's a little long and a bit hefty.
So I'm going to have to treat it like a form of wheel hub and join into the top which solves the short grain problem (and gets rid of the nasty chunk I took out of it, Ooops!). It's supposed to take the load from the rib which is in compression and transfer it to the wall via a corbel.
“The timber vault is not “imitating” a masonry prototype. Rather it exposes with great clarity the way such a vault should be built – the function is expressed in the structure, whether the material be stone or wood. The structural forces resulting from the dead weight of the material are collected in the diagonal ribs, and passed through the springers to the buttressing system. “
From Heyman. 2006
The springer that Heyman refers to is the tas de charge. The ends of the ribs will have to be morticed into the top of it to transfer the load, but there's no room for pegs or fixings and I think gravity is our friend in this joint. Even though I'm making a suspended ceiling, I still have to consider the load path and treat it as a load bearing vault for it to be correct. So I'll have to add a few extra things to the fans to make that happen, as M&T joints don't do tension in real life.
Like so....
A bit of mocking up on the drawing and following the blue line, I reckon that's the answer.