Defend against Wind, Water, and Fire.
Three days and $3000 (or was it $4000, I forget).
I did not like this challenge. It did not play to my strengths (probably my weakest challenge). I don't think the team did well either. The challenge focused heavily on materials, an area where we had relatively little experience, especially soft materials as our team used (guess that part was our own fault). On the previous challenges, we failed, but I always felt like we did a good job and just got a detail or two wrong. This one just felt bad.
There were two major rules that we found out about after the blueprint challenge:
There was no specific weight limit besides movable by a single person. Other than that, weight would be taken into account during judging. Our device ended up 20 or so pounds lighter than the red team's, but both were quite heavy. I think we both ended up tearing the bag and either getting a new one or repairing it.
I was not too excited about being captain again, but I tried my best anyway. Without knowing about the two rules mentioned above, it seemed like an easy challenge. I therefore decided that the best solution would be the one that allowed the rescue worker to continue going about his/her business with as little obstruction as possible. I figured an off-the-shelf fire suit would be fine for the fire. The wind was kind of underwhelming, so I decided the only real danger was from airborn projectiles. To protect against this, I proposed a suit of roman-style armor extended to cover the arms and legs better. I had made a simplified version for a Halloween costume a few years previously and was impressed by how lightweight, non-restrictive, and protective the stuff could be. Also, as a result of this previous project, I had a pretty good handle on how to fabricate it already.
The water was the only element powerful enough that it would require stopping your work and hiding. For this, I designed a low, sloped single-piece shelter that was designed to be carried. I drew a few different shapes for it depending on how omnidirectional the protection needed to be. (I think I drew a unidrectional option, an omnidirectional option, and an intermediate shape for if you knew approximately, but not exactly, which way the water was coming from.) The judges didn't like that my solution had separate parts for each element.
We had a low metal frame assembled with tube-in-tube joints. Over it, we had a fabric covering with canvas for strength and a separate (actually 2) heat-resistant fabric sown to it. The person was suspended from the roof by straps both to hold the structure down and to isolate them from impacts by allowing some swaying. We also added an inflatible tube, which was to provide cushion around the occupant. Additionally, it would help to support (for strength) and bow outward the fabric walls. The hope was that bowing the walls outward would prevent the fabric from cupping around the water blast and allow it to deflect better.
We didn't really worry about the wind. We figured it didn't do anything the water didn't do worse. It did end up moving around the fringes of our fire-resistant skirt allowing the fire to get more easily underneath.
We (correctly, I believe) considered the fire to be a secondary danger compared to the water, which we focused our design on. Unfortunately, we neglected it a bit too much and it ended up getting us. During the demonstration on the shed, the fire never got near the ground, so we focused most of our fire protection (an extra layer of fabric) higher up. During the actual test, the fire focused right where our structure met the ground, which we hadn't sealed very well and the skirt had gotten blown up by the wind. If we'd had more time (another hour or two), tidying up those edges was the next thing on the to-do list. Also, it's possible that enough heat leaked through the fire-resistant fabric to scorch (or even burn) the canvas underneath. It certainly could take the temperatures, but I don't really trust the insulation test we did with the tiny torch in the shop.
Despite bits of fire getting in, the internal temperature actually did not get too high - certainly not hot enough to kill the occupant. Unfortunately, it did manage to burn/melt a hole in our inflatable, releasing CO2 into the interior, asphyxiating our dummy. I sort of want to argue that he could have held his breath long enough, but even I recognize that's a bit silly.
The short answer is it was the only thing available that we could get compressed enough to fit in the bag and inflate the entire tube.
For the long answer, ask Andrew or Joel.
We knew this was the hard one, but we didn't really understand how hard. We saw the demonstration of it destoying the shed, but before the demonstration, several people came out and removed all the screws holding the shed together, so it was unclear just how powerful it was. We did the calculations for force and impulse but weren't really sure how ideally their cannon behaved and sure didn't have a proper visceral understanding of what the numbers meant.
It punched right through our fabric and sent us skidding across the pavement to hit a wall. (Note that there was no wall behind the red team to bring them to an abrupt stop.) Neither team survived the water test, though we did experience less acceleration than them (25 g's to 40 g's if I remember correctly). If our inner tube had still been intact, it probably would have helped some, but I doubt enough to make it survivable.
I was assigned by Alison to work on self-aligning fasteners to make assembly of our frame faster. This was a non-essential reach goal. The ended up working, but we decided not to use them anyway because they only sped assembly slightly and we were being schedule due to some longer-than-expected lead time for the steel in our frame. I ended up grumpy about being asked to try something that we weren't going to use even if it worked, and some of my teammates ended up annoyed at me for being unproductive. In my opinion both of these reactions were understandable and nobody made any drama about it, but it was one more thing that made the build frustrating.
Assembling tube-in-tube joints for a triangle is quite difficult. If everything is rigid, you have to slide 3 joints together at the same time. So, I worked on designing alternative joints that assemble from the side rather than having to slide axially. It turned out that the system had just barely enough slop to be assemblable with the regular joints by the stronger members of our team. (I could do it, but had to brace it with my feet and really strain, taking way too long to assemble the whole thing in 5 minutes.) So this was yet another thing I worked on that didn't get used - more frustration for everybody.
After the last build day, we had a long late-night folding and practice assembly session. Tom was too big. Me and Alison were too weak. Joel was still a bit sick. Andrew was the only one left. He did a great job and actually finished in the required 5 minutes.
The worst part about losing a challenge is having to go up there and say bad things about people you like and respect. Any one of us could have been eliminated on that challenge. I wouldn't have felt cheated if it had been me, and I doubt anybody else on the team can genuinely say otherwise. Alison for being in charge of the failed fire protection (and because everybody likes to blame the leader for some reason). Tom, for costing us most of a day by ordering long-lead-time metal, resulting in too little time to get details right. Andrew, for asphyxiating the dummy. Myself, for spending so much time on stuff we didn't use and therefore contributing very little to what we did use.
I selected Alison because the flame was where we failed and flame protection was her job. I don't really get the fuss about her leadership style being too collaborative; I thought it was fine, good actually. My only qualm was getting blamed for working on useless stuff when she's the one who asked me to work on it.
This is the only challenge where it's not immediately obvious in retrospect how we could have succeeded. I think the key to surviving the water is to get low with very sloped sides to get the water to glance off. We put some effort (but not enough) into this. Our sides were sloped at about 35 degrees from horizontal, as opposed to the 50 degrees from horizontal for the red team. The downside of this is increased surface area. The red team was able to use rigid panels, but we were forced to use fabric because we had too many square meters to fit anything rigid in the bag. Our shelter was also overly large. It could easily fit Tom in it. Sizing it to barely fit an average person would have allowed us to make it much flatter for the same surface area.
One of the first decisions our team made was whether to put our occupant in a prone or a fetal position. We went with the fetal position (as did the red team) because it required less volume and a lot less surface area. Also, it lent itself more easily to providing 360 degree protection. I argued in favor of the prone position, but without any great conviction. In retrospect, I'm pretty sure the prone position would have been better, allowing us to get much lower and with shallower sides.
I'm still not sure what we could have made the panels out of. It would be difficult to fit the required surface area in the bag. I'm not sure if the shallower slope would be enough to make fabric walls work, and it would take considerable engineering to get that much area of hard panels into the bag. I have some ideas that might work, but nothing that I'm confident in, especially for a 3 day build, where there isn't time to source exotic materials.
Maybe Joel was right after all: just buy a raft, wrap it in a fire blanket, and call it a day. (Or 3 days.)
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