Sandbags

[MarkXIX]

This kid is pretty damn smart. There's hope yet for the country...

http://www.nbcnews.com/science/11-y...r-sandbag-named-americas-top-young-8C11371015

Video of his work at this link:

http://www.youngscientistchallenge....ios.html#5a0a27d2-514f-4549-b954-bb7a68f5b77e

 

[Gooberlx2]

That....that's amazing. Seriously, I know a couple people who might have benefited from something like that to keep recent flood waters out, for exactly the reason that the sandbags were too heavy and performed poorly anyway.

 

[dougp]

Yeah, that's pretty cool - and surprising it was never thought of before. I hope that kid got a patent ...

 

[Anubis]

holy crap that kids voice is annoying as fuck

cool sandbags. and yea im shoocked this was not thought of before

 

[lxskllr]

Did they mention cost? Sand is cheap. Cool idea in any case

 

[Meghan54]

I've got just one question.....what happens to the salt once the bag's wet? In the article it states to use the bag, you wet it after placing it. But even rock salt will dissolve in water eventually. So, for a fairly long term solution to keeping flood waters out of a home, say a week, wouldn't the salt begin to dissolve and leave the bags less than full and potentially leak?

 

[Gooberlx2]

Did they mention cost? Sand is cheap. Cool idea in any case

Definitely would want to see the cost of a finished product.

However, while sand itself is cheap, transporting it isn't necessarily so, and neither is the limited human time and labor investment when you're trying to prioritize what to save before flood waters arrive. My understanding of the project is that bags would be reusable, and certainly the potential savings in reducing flood damage could far outweigh the cost savings of using sand.

 

[Brainonska511]

I've got just one question.....what happens to the salt once the bag's wet? In the article it states to use the bag, you wet it after placing it. But even rock salt will dissolve in water eventually. So, for a fairly long term solution to keeping flood waters out of a home, say a week, wouldn't the salt begin to dissolve and leave the bags less than full and potentially leak?

The whole point is the salt dissolves in water. The saltier water gets absorbed by the polymer, which is also in the bag, and expands. You need the salt, because fresh water-filled polymer bags might float off in an ocean flood.

 

[dougp]

The whole point is the salt dissolves in water. The saltier water gets absorbed by the polymer, which is also in the bag, and expands. You need the salt, because fresh water-filled polymer bags might float off in an ocean flood.

Yup, the increased salinity makes them weight heaver than the oncoming salt water, so in theory they won't move against rising water.

 

[Slew Foot]

Im impressed by his golf score. 70s?

 

[Mixolydian]

I hope that kid copyrighted what he did ...

:|D:

 

[RedRooster]

Im impressed by his golf score. 70s?

From the fronts, big whoop.
But that is still good, yes.

 

[Gooberlx2]

Yup, the increased salinity makes them weight heaver than the oncoming salt water, so in theory they won't move against rising water.

I guess the question is what stops the salt from dissolving and washing out of the bag entirely over time? Might have to stack the wall higher such that the weight of the bags above water is sufficient to continue securely weighing down any bags below the water line.

 

[dougp]

:|D:

Yeah, whoops. Patent!

 

[dougp]

I guess the question is what stops the salt from dissolving and washing out of the bag entirely over time? Might have to stack the wall higher such that the weight of the bags above water is sufficient to continue securely weighing down any bags below the water line.

The salt is supposed to absorb into the water, that's the point - that's what makes it salt water. Take a pot of water and pour in some salt - before you stir it or anything, take a small sip. Still tastes like water, right? Now stir the water until the salt is dissolved. Tastes like salt water, right? Now boil it - the salt remains at the bottom.

By making the salinity of the water higher than that of salt water, it means the bags will not absorb that water either - therefor, the only water to evaporate over time is the higher salinity water - and the salt remains after the water evaporates.

I think I have that down right - trying to remember 6th grade chemistry that was 20 years ago might be asking me too much.

 

[Brainonska511]

I guess the question is what stops the salt from dissolving and washing out of the bag entirely over time? Might have to stack the wall higher such that the weight of the bags above water is sufficient to continue securely weighing down any bags below the water line.

The salt is going to dissolve no matter what. What you need to be worried about is that the salted water is going to exchange with water outside of the bag. The swelled polymer probably has minimal exposure to the water outside the bag, so the loss of salt through dialysis or solvent exchange, should be minimal. Because the polymer-trapped water would be saltier than the sea water, water movement would actually be in towards the bag, in an attempt to equilibrate the osmotic pressure

 

[IEC]

"...who invented an indoor cookstove that reduces harmful carbon dioxide emissions."

I'm pretty sure the design is to reduce carbon monoxide emissions, but I'm also sure neither the writer or the editor would understand the difference...

 

[Gooberlx2]

The salt is supposed to absorb into the water, that's the point - that's what makes it salt water. Take a pot of water and pour in some salt - before you stir it or anything, take a small sip. Still tastes like water, right? Now stir the water until the salt is dissolved. Tastes like salt water, right? Now boil it - the salt remains at the bottom.

By making the salinity of the water higher than that of salt water, it means the bags will not absorb that water either - therefor, the only water to evaporate over time is the higher salinity water - and the salt remains after the water evaporates.

I think I have that down right - trying to remember 6th grade chemistry that was 20 years ago might be asking me too much.

I guess I was thinking of osmotic principles. Over time solutions try to find a balance, right? If a bag is submerged, the polymer is stopping the water from getting through, but the higher salinity inside the bag isn't repelling the seawater. The side of the bag exposed to the seawater should have salt leeching out and/or fresh water absorbing in over time to find equilibrium. I assume the sac isn't a semi-permeable membrane of some kind.

Or maybe I'm forgetting how it all works.

 

[Brainonska511]

I guess I was thinking of osmotic principles. Over time solutions try to find a balance, right? If a bag is submerged, the polymer is stopping the water from getting through, but the higher salinity inside the bag isn't repelling the seawater. The side of the bag exposed to the seawater should have salt leeching out and/or fresh water absorbing in over time to find equilibrium. I assume the sac isn't a semi-permeable membrane of some kind.

Or maybe I'm forgetting how it all works.

Water would also be trying to simultaneously enter the bag to balance the salt concentrations. But then you're relying on diffusion to equilibrate a very large system. Only the surface would be readily accessible, making the process very slow.

 

[Gooberlx2]

Only the surface would be readily accessible, making the process very slow.

Yeah, that's what I figure. Combine that with the weight and compression from bags above the water line, I expect diffusion would take a long time. I wonder actually, if water didn't recede for a long enough period, if you'd have to re-saturate the dry side of the bags to prevent uneven evaporation, which could make the wall unstable as the dry polymers deflate.

 

[techs]

As an 11 year old I built a bitchin' fort out of blankets and pillows.

 

[Red Squirrel]

That's pretty cool.

Though the best solution in places that get floods and other natural disasters all the time is to not live in those areas.

 

[Pray To Jesus]

$$$$$$$$$$$$$$$$$$

 

[lozina]

Did I hear that right, that the polymers expanded to 200% their volume? So the bags would still be 50% the size of a sandbag when dehydrated? Thats not saving too much space for storage if so....

 

[Jeff7]

That's pretty cool.

Though the best solution in places that get floods and other natural disasters all the time is to not live in those areas.

Or work on developing a more permanent and effective solution than "Lose several billion dollars in repairs and lost productivity every few years."


(I assume there'd eventually be a point where the ROI would make it worthwhile. Or, yes, live somewhere that doesn't flood constantly.)