It's Friday morning - our last full day of Tinkering School. The end is in sight - we can all sort of see what we need to get our respective projects finished. With that comes the realization of just how much work it's going to take to pull it off.

Right now, anything is possible - we have an exceptional group this week, and each tinkerer is invested in the problem, and wants to pull it off. And one full work day is still a lot of time. The predominant attitude this morning is determination.

We start the day with another of Gever's Structural Engineering 101 talks - today's topic is tension. Zach helps him demonstrate how strong triangles and tension in the right directions can translate into a stable structure.

Caroline lights a votive to the secular patron saint of tinkerers, Nikola Tesla - with some of our trickiest tinkering ahead of us, we're hoping he'll watch over us.

And then it's back to work - the cart team works on mounting the rear guide wheels.

The Launch team has decided that a "bungee-slingshot" is the way to go for launching the cart, based on their extensive prototyping yesterday. Bungee cord should never be tied - instead, we make a loop and whip the ends with baling wire. Gever talks them through the whys, then walks them through the how.

The track team is running quite the operation. Track is raised, leveled, and a crew follows close behind, adding supports and braces. They're just chuggin' along out there - they have their routine down, but they've still got almost 80 feet of track to raise.

Meanwhile, Elijah and Noa discover they can power the cart with a drill - they've attached a skateboard wheel to the end, and are using the friction between the wheels to drive the cart forward.

Zeke and Alex tackle some serious math, trying to work out the angles for the body of the cart they're planning to build.

Jane's visiting from Beijing, where she's working to start a school.

Elijah and Kieran test the mounting system for the bungee slingshot. We just love getting to say "bungee slingshot" out loud.

And then they attach it to the base of the shop to test the stretch. Alex discovers that it's fun to test your strength against some bungee cords.

The goal of this game is for David (or whoever holds their hands palms up) to get the tops of Lil J.'s (or the other player's) hands before she can pull away. It spontaneously develops and then catches on.

Also, "Mercy" catches on. Zeke and Lily play. Lily's determined. [editor's note: This game falls into a grey-area because Rule #1 is "Don't hurt yourself or anyone else" and the challenge here is to make the opponent call "mercy". It's clearly about pain tolerance, but both players are fully cognizant participants. We are hoping that it doesn't catch on.]

Clapping games have some amusing failure modes.

Kieran and Elijah have become fast friends.

Portrait of a Thinker: Gever, captured.

Zack and Rodrigo have been a driving force behind raising the track - both have displayed an impressive doggedness to completing the task. They're also both from Mexico. Rodrigo labeled each piece of track he and his brother helped put up.

Noa borrows Caroline's kite. When it's not flying, it makes a pretty good hat.

It's beautiful in the sky, as well.

Sasha shows off the cart design.

The kids discover relics of Tinkering School past - some plywood from a project from Session A.

Jack works on smoothing out the track.

Down at the City, the team high-fives after completing another wall.

The track's been growing steadily all morning.

Claire lounges in the classic Greek style as she and Anna discuss their project.

Track team has it down. Here's a glimpse at an in-progress segment - clamped, leveled, ready to for legs to be added.

Track is slowly converging with the city.

Anna works on mounting the wall to the braces which keep it on the platform.

Claire has to leave us tonight, but before she goes, she wants one ride on the train car. It's perfect timing, because the launch team is ready to test there slingshot system. Elijah pulls her back, and Claire hangs on...

Most of the group heads in for dinner - the launch system is working, and the track now stretches all the way to the city, but the city team is running behind, so they elect to stay and work late.

Daniel brings out fuel for the away crew, to help them make it through their big push.

Which is much appreciated. Bananas are devoured...

Juice is guzzled...

And the work continues.

By 8:30, it's clear that a redesign is in order. Despite the valiant attempts of the tinkerers, we won't quite have enough time to put the parts together in the order they initially planned. We put a piece of luan on the roof as a visual aid, and discuss the possibilities.

The rest of the group sets off in search of the perfect s'more sticks. Alex and Zeke both know they've got it.

The City crew returns, and we gather all together to light the campfire.

We take a moment together to just enjoy watching the fire, then we open circle - at Tinkering School, we believe in taking moments to talk about the good things, and say aloud things we notice and appreciate in others. Fire night provides an opportunity to reflect on how others have shaped our experiences for the better this week.

Gever and Serena share a moment of mutual appreciation.

After circle, it's time for another Tinkering School tradition - playing with fire. We start with a bag of sawdust we've collected throughout the week. Thrown in just the right way, it makes the fire jump and sparkle.

Just like this:

For Seniors week, it's tradition to break out the cans of cooking spray to make fireballs. The first batch of cooking spray turned out to be non-flammable, to Gever's suprise. A resupply mission is sent to Safeway, while the group makes and enjoys s'mores.

So when he gets back, we're all pumped and ready to try.

Hayden takes a go, and creates his own (very fleeting) torchlight.

Lily bends fire.

It's fun to make fire fly.

Zack goes for low and slow.

Lily and Gever work in tandem to carry the fire farther.

Two cans are better than one. Gigi creates an epic ball of fire, and with cheers and applause, our group splits, and the first set of tired tinkerers head back for bed.

A beautiful close to an impressive day. We put up yards of track, put the walls for the second story up on the platform of the skyscraper, finished a launch ramp. We also enjoyed each others company, took a moment to reflect, and played with fire.

Session C: Day 6- Possibuildities