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How do people feel about sand loading? I think our technique might have cut us short over 1kg, or even a few kg, of sand last weekend at states...

Height: 70cm
Tower weight: 10.16g (went heavy for states, upping the density in mostly the legs of chimney and the base)
Mass held: 11.6kg
Score: 62.795

We let the sand trickle in at the beginning for the first few minutes, to ensure that the bucket "stabilizes" while holding the mass and does not have too much movement. Once we feel that the trickling is down, we slowly bring up the speed to a "slightly slower than reasonable" pace. When the tower shows signs of stress or lean, we max out the sand flow. At states, although we sanded the tower to be as perfectly level as we could (I live at school, therefore its harder to have a ton of resources. I don't have a garage where I can just grab what I need or go get it on my own), the chain made contact with the chimney/base connection in the longer horizontal direction (I guess at around 7 or 8kg). The tower appeared to be "settling well" and supporting the load, but we became very conscious (and maybe overly worried) with the chimney/chain lean. We maximized sand flow, and it appears that this rapidly increased flow caused a slight jerk to go through the tower right before it failed. The point of failure was in the upper diagonal bracings in the long horizontal direction on both sides of the tower, once these broke under compression (very obvious in the video we have), the tower tipped in the longer horizontal direction. Would a more greater, but still moderate, amount of sand flow be a more viable option once the tower is supporting enough mass to minimize bucket sway/jerk motions?

Any thoughts? If you want me to post the video, I can do that and put up a link.

Any last predictions or thoughts about this weekend?

My guess is that the winning C tower will be a bit under 6.5g holding full at 70cm. That said, it'll be interesting to see who can pull that off given that the two time defending champ builder is no longer competing this year.

I'm basing these results off of last year, when C division had better towers.

C div- 6.25-6.5 gram, full amount, 70 cm.
B div- 6.5-7 gram, full amount, 70 cm.

I think the following towers could medal:

C div- 6.25-7.75, full amount, 70 cm.
B div- 6.5-8, full amount, 70 cm.

Well, I'm placing the worst in tier one...

I still have yet to see a really light sub ten gram tower hold full or even come close. I should have a highlights video up in a few weeks though

Out of my own curiosity I've been building both div. c and div. b towers even though I'm not going to nats just to see how well I could do. Here are the best:

Div. B tower:
Mass: 6.13g
Height: 70 cm
Weight Held: 15 kg
Final Efficiency for nats. level: ~110

Div C tower:
Mass: 8.11g
Height: 70 cm
Weight Held: 15 kg
Final Efficiency for nats. level: ~83

So, it's obviously much easier to build a good Div. B tower for me...

Thsom, you would have been very competitive here at nats in division b or c. The day isn't over yet but your 8 gram holding fifteen would medal as of right now, mostly sure I have been here 4/5 time slots. And Troy hs had a 7 gram that didn't hold all, I don't think it was within a few kilos-not sure though.

I believe others and myself have brought up this point a few times. Really, some of the best devices never actually make it to nationals and in some cases state. I know of a kid in IL who had a 7ish gram tower at the time of regionals (70 cm full mass, and still improving) who didn't even make state let alone nationals. Similar things for other building events since only top 2 and in some cases top 1 team go to nationals many times the best devices are not represented in the tournament.
This applies to thsom and many others, so you couldn't really say you would have placed since if you had gone, others too would have and thus the actual curve for medalling would of been much higher where I'd bet most of the actual qualifying teams wouldn't have placed over the thsom, me and many others in the situation of not going but are considered much higher seed devices in their respective events.

For this reason I advocate for the national level being represented by top 2 in each EVENT not in top 2 teams. That way the best does actually go to nationals. I understand the logistical problems with that but merely the idealistic tournament

Totally agree there mrsteven. But of course I said 'would medal' assuming no curve due to every other builder being at nats (whose team did not make it). And btw my teammates chinook hit a respectable score of 2:38 we will see how it places. Back on towers I saw way too many rectangular based that did not implement t-sections, and near every time the rectangular base towers broke in the base because builders were trying to get away with 1/8^2 for the legs. Awards tonight

From what I just heard through the grapevine, Solon's C team got a score of around 97.

Nats top 6

Div b
1. Magsig ms
2. ExCEL Homeschool
3. Solon ms
4. Drake ms
5. Muscatel
6. Tie: grand haven and auburn

Div c

1. Solon
2. Centerville
3. Fayetteville manlius
4. Troy
5. Harriton
6. Adlai e stevenson