Well, if anyone remembers this bridge contest, it was about a year ago and by coincidence I've got my MKIII tuned up finaly and decided to cut out that "Improved" bridge I did.
Here's some results.

By the way, I wieghed my bridge with the piece of plywood and hook in it beforehand and it came out to all of ~5oz/0.13Kg.

The final wieght it held was 27lbs 15oz. After I took the picture of it holding that I was putting the camera back on the shelf before adding more sand and I heard the bridge start creaking. So I watched it and listened for a minute or so before it snapped. If I'd had someone else taking pictures then I'm sure I could have broken 29lbs before it gave up, maybe even 30lbs. I guess that's the difference between maximum load and constant load. I'll go to work later today to wiegh everything on there calibrated scales to make it more official, I've never used that fish scale before.

Now, I think I could still make it stronger, but I have a different challenge in mind now. How big can I make an aeroplane using nothing but FFF and glue? Plywood could only be used for hardpoints, not any structural stuff, and no tape to reinforce things. What do you all think? I've already started designing a 10ft wingspan and then I'll see where it goes from there. Attached files

 

Looks like my fish scale is pretty accurate, I checked on the calibrated scales at work and it wieghed in at 27lbs 14.56oz.

 

After carfully examining that bridge I figure it was a glue joint that failed first. I think I have enough room on the sheet of foam to give a larger joint for the glue and I'm gonna build another one using CA instead of Hot glue. Then we'll see how strong it is.