It's Thursday morning. After beach day yesterday, we're ready to get back to our train cars. The group gathers at the build site, to sunscreen up and prepare for the day.

Portrait of a Junior Collaborator: Zack, observant.

Ethan, Collaborator Caroline, and Robbie make a plan for the bike propulsion system. They're hoping to develop a bike-based cord collector which will reel in a line and pull the train along. They're encountering trickier problems than they anticipated.

Team Sqiki has decided to add a fold-up table to their train car, for all their dining needs on the journey from Terminus Station to the City.

Team Nooi is determined to get their propulsion system up and working. They're installing the infrastructure on the track that they need to make it happen. They check in and make a plan before getting to work.

Liv contemplates the future of her cart.

Portrait of a Tinkerer: Amelia

Potter and Axel take the old cart for a (very slow) joy ride.

Sadie and Sylvia take a break to beautify the track.

Through the Portal: Lauren and Serena work on building frame pieces for the train car wheels.

As the morning picks up, we settle into our groove. The atmosphere down here is playful. Nik photobombs.

The goofy faces are contagious - Potter catches the bug.

J-Wolf shows his style.

But it's no real contest - not with Fox here. She's got the goofy face honed.

Even Collaborator Caroline catches on.

The fun with photos continues - Wolf takes a high-res selfie.

Daniel shows the kids how to turn their handwriting into a computer font. It's fascinating to see your own handwriting appear on screen as you type.

After lunch, it's time for a Tinkering School tradition - knife training. Each tinkerer will receive their very own pocket knife, as long as they follow the rules and use it safely.

Collaborator Caroline goes over the knife safety rules, and then it's time for the campers to demonstrate their knowledge - who wants to go first?

Let the whittling begin! Juan proves his knife prowess.

Axel misses a step in the process for knife use. Caroline takes the knife back - he'll get to try again once everyone else gets a go. He does, eventually, earn his knife.

J-Wolf checks his blood bubble - the area surrounding him the size of his extended arm to the tip of his knife blade. This is the area whittlers are most likely to slip and cut someone else, so it must be treated with utmost respect.

Now that they have their knives, the tinkerers set off in search of sticks they can make pointy.

Benjamin enjoys a moment of relaxation in the Sky Bench.

Avigael tries out the new bench she's installed in the Piki cart. It's comfy!

What's up, J-Wolf? It's fun to interact with the photographer (in this case, photo cred to Wolf).

Junior Collaborator Lauren, after six summers of Tinkering School, know the tools of her trade - she carries a sharpie and knife in her back pocket. Here she cuts the slots we need to tighten the PVC-pipe and metal axle assemble into place. She's getting good at making these grooves.

Amelia learns to use the circular saw in order to cut a part for her team's cart.

"And though she be but little, she is fierce" reads Jaya's T-shirt. Throughout the week, Jaya has demonstrated ferocious commitment and shown us her fierce side. She's also shared her talent for and love of gymnastics with the group.

Sadie and Rob work on the Kablooi cart walls. Rob's trying to work out what size piece to cut.

Portrait of a Tinkerer: Rob gets in on the goofy.

A group heads up the hill for an afternoon adventure to the playground and to visit the animals. Everyone's excited.

Sylvia rides the pony.

Tire swinging: the intense version. Robbie and Reed are masters.

Compost pile, goat food edition. Code name: "goatpost".

The tire swings are a huge hit. Avigael takes flight.

Then Fox just has to go, too.

Then we visit with the animals - the goats, and then the bunnies. They're super soft and fuzzy.

We captured some of our funniest/most epic non-tinkering moments of today on videotape.

Sadie gives her interpretation of how cows make babies, with guest appearances from Fox, Avigael, and Gandalf.

And especially for Gever - from Nik and Wolf, our two dope MC's . Together, they're unstoppable. So, here and now, from our studio to your home, folks, what may be the greatest diss track of the year.

If there's one thing to be said about Tinkering School, it's that those of us who have been doing it the longest have developed a persistence in how we approach problems, and a steady obstinance to being told that what we're attempting is impossible. For context: Nik and Team Nooi have designed a cart propulsion system this week which Gever was seriously skeptical about.

Gever, you know we all love you anyway.

Zach, Serena, Elizabeth, and Lauren, with help from Nik, have been working to produce specialized train-base parts throughout the day. With another big push after dinner and into the night, we manage to trap one cart base together. To our massive frustration, the custom train wheels Gever spent hours on just aren't self-centering the cart base quickly enough. We'll have to think of another plan.

Elizabeth and Zack, testing by headlamp light.

The kids really hit their groove today - we're having fun while making progress. Most of the carts have gained benches, roofs, and/or doors, and the tinkerers have a knack for turning even tough work into play. We've received knives, petted goats, painted track, and enjoyed ourselves immensely. The evening ended with a showing of the movie The Sandlot. Tomorrow is Friday, our final full day together.

Tonight's blog written by Serena, with Lauren co-piloting.

Session D: Day 5 - Finding Funky Flow