Elevated Bridge B/C

[croman74]

Wow, that's really interesting. I had always had the impression that drying would decrease strength. Thank you for posting that up here. That's definitely going to help. Now we know that drying not only decreases weight, but also increases strength.

[rino]

State of Indiana (B) 1st - 2nd above -2000, 4th place-980.

[Allirog24]

OMG! How did you get a 2000 efficiency? Our high is 440. Any advice? About how many grams lighter would balsa wood be if we dried it for 20 or 30 minutes in a 200 degree f. oven? also, what kind of glue is the best for everyone?

[croman74]

I think I'm going to try baking my next bridge. dholdgreve, thank you for that useful info. That definitely changed my views on baking. I was just wondering how many grams would baking knock off of my bridge?

[Valpo Towers and Trebs]

State of Indiana (B) 1st - 2nd above -2000, 4th place-980.

Yeah that was me, Valparaiso won with an efficiency of 2186. 6.86 g holding all 15 kg. Unfortunately we finished 3rd overall so we won't be at nationals.

Some advice, you won't get above 1500 without doing the math and figuring out the optimum shape and the exact force on each piece and then the exact necessary size/material of each piece. The forces involved for this event are much more complex than any other structural building event so this is critical to be the best.

Good luck to everyone at nationals

[rino]

The bridge we had was 4th, it was 12.1 g and held about just under 12 kilo. The bridge for regionals was 17.5g and held
15 kilo. We used all bass wood that seemed to be what was used by all the top bridges at state. We used a simi arch design and the base span was 36cm. There was alot of good designs.

[11madmic]

Who you think div. B or div. C will have the highest eff.? Div C---spans 45cm. Div B--- i think spans 35cm

[Allirog24]

How did anyone get an efficiency of 2000, what was their design like and what wood did they use? I think this bridge that we are working on will get a 500 efficiency, so how did you get it to hold 12.1 kg weighing 12 g?

[11madmic]

How did anyone get an efficiency of 2000, what was their design like and what wood did they use? I think this bridge that we are working on will get a 500 efficiency, so how did you get it to hold 12.1 kg weighing 12 g?

that would be 1000 eff. not 2000

[andrewwski]

State of Indiana (B) 1st - 2nd above -2000, 4th place-980.

Yeah that was me, Valparaiso won with an efficiency of 2186. 6.86 g holding all 15 kg. Unfortunately we finished 3rd overall so we won't be at nationals.

Some advice, you won't get above 1500 without doing the math and figuring out the optimum shape and the exact force on each piece and then the exact necessary size/material of each piece. The forces involved for this event are much more complex than any other structural building event so this is critical to be the best.

Good luck to everyone at nationals

Agree, and I'd be surprised if you even get to 1500.

2000 should be very possible under Division B specs. It'll take a good builder, yes, but I'm not surprised by it. 2000 in Division C may surprise me though, although I'm still expecting some at nationals probably will hit it.