Help re how large a reinforcement thing needs to be too not pull through a membrane

[adouglas089]

Can anyone help me with this?

I need to build a wall which is two layers of polyethylene separated by 200 mm, about ten feet high and filled with water. To prevent the sheets of polyethylene from coming apart, that is to constrain them to approximately 200 mm apart, basically two big buttons- like the buttons on clothing - will be attatched top each sheet, and fishing line used to attach the buttons, piercing the membrane. The size and number of the buttons that I need is the question.

I mean, suppose I have a button every 25 centimeters. At the bottom of the wall the water pressure due to weight of the water is about 10 kPa. So there would be 630 or something newtons exerted per button, and 16 buttons per square meter per side (32 buttons both sides). Ok. The plastic is 150 microns thick. The strength of the plastic is 8 MPa (ldpe vapor barrier from home depot).

What would the diameter of the button need to be too not let the button be pulled through the plastic? (or, the plastic being pushed over it, I guess).

I cannot quite figure this out, my knowledge of the geometry and calculus is too weak.

I suppose that the degree to which the plastic stretched and Bulges forward may have some impact?

It is going to be a soundproof room, building upon the document here:

http://www.arnopronk.com/bestanden/...of water and membranes (sound insulation).pdf

They used a nicer method to keep the panels together, but I can't do that... I need this for medical reasons and cannot afford to build a room out of concrete or anything else.

 

[3DDave]

You can test this by making a small frame and stapling the plastic to it and then setting up a button and pulling on it to see what happens. To simulate the water you can have use a sand pile and some cardboard to get enough column height to match the pressure.

Then you can figure out how the water won't leak out of the holes.

 

[LittleInch]

This is pure nonsense. The pl asti is too thin. The pressure at the bottom is 30 kPa, not 10 and the water will simply leak out of the holes.

Use two sheets of plywood and made as a box lined with your plastic might work, but what aoun d's like big plastic bag won't. Sorry

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[GregLocock]

LittleInch is right about the pressure.

Cheers

Greg Locock


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[prex]

The tension on your 'fishing line' would be of the order of 200 kg: is it capable of taking it?
For the plastic film, let's assume it will bulge assuming a cylindrical shape with a diameter of 25 cm: this is a very optimistic assumption, it is just to see how far we are. With this assumption the tension in the sheet would be 25 MPa, hardly an acceptable value for PE.
And if someone happens to puncture the wall? I agree: pure nonsense.
I guess that a steel plate with the same weight as the water would achieve a better sound insulation, if properly sealed all around.

prex
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[LittleInch]

Or just buy this stuff

http://www.insulationgiant.co.uk/Ro...ib14mzG5wOg2xXfCo9AxWbKsB4UaLl0-gUaAkFD8P8HAQ

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[Ron]

adouglas089....maybe if you tell us the purpose of this wall, in other than cryptic terms, we can provide more insight as to how to help. You indicate that you want to use it for soundproofing....there are many ways of soundproofing that are tremendously more effective than what you are proposing and a lot easier to construct. Some are also less expensive, simpler and certainly less problematic than your application.

Fill us in. There are some smart people here who might be able to help....give them a chance!

 

[Tmoose]

A simple staggered stud wall with a small airspace and fluffy fill has pretty decent performance.

http://insulation.owenscorning.com/assets/0/428/429/431/ed7a1d1e-d652-48f8-8047-e482c207ab37.pdf

http://www.piumamusic.com/articles/_sources/owens-corning-noise-control.pdf

Are you treating the ceiling, floor, and all the walls, and installing special doors and window?
"Flanking" sound can sabotage well intended sound reduction efforts.

 

[BrianPetersen]

"I need this for medical reasons and cannot afford to build a room out of concrete or anything else. "

So a proven, sturdy construction that will work is more expensive than a labour-intensive, messy, time-consuming contraption that won't stand up on its own and is sure to leak?

Why do you "... need this for medical reasons"?

Why does it have to be built from polyethylene? There are countless better, proven sound-insulating materials.

If the "... need this for medical reasons" has to do with constructing a "clean room" to exclude biological or chemical contaminants, why does it need to be sound-proof?

If you need a soundproof clean room, build a normal sound-proof room then put your polyethylene inside it.

Costs much less to do a job right once than it does to construct a failure, clean up the mess, and then still have to re-do it right. 'Course, some people insist on finding this out the hard way.

Just because a research paper did something with some sort of prototype, in NO WAY means that it is practical in the real world.

 

[rb1957]

I suspect that the panels your paper talks about are maybe 1m square and installed inside a rigid frame.

It looks like the plastic membrane they used is a bit more substantial than "vapour barrier film".

another day in paradise, or is paradise one day closer ?

 

[LittleInch]

adouglas089

I realise we've kind of trashed your initial idea, but we do want to help so give us some feedback and lets see where we go or is it going to be "The sound of silence" ???

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[Nescius]

He can't hear the criticism. He actually built the room and is inside at this very moment.

However, try this cheap experiment to get a feel for what's going on: Buy a decent air mattress, stand it up in a frame, and fill it with water. Many air mattresses are constructed similarly to what you're describing...front and rear surfaces joined to keep the mattress from turning into a big, round balloon. Keep a mop handy...

 

[adouglas089]

I am so sorry I didn't come back sooner, I just have been scrambling from ine airbnb place to another... The engineering comunity is so awesome sometimes, I am glad I chose it for my life path. Sorry, Sorry....

Yeah, I messed up on the pressure, you are right indeed. The buttons will need to be sealed with bog standard silicone sealant, yes.

I was kicking myself for not tryi gto this years ago, when iI had indeed calculated that the pe was not strong enoigh to be practical.

Bit maybe silnylon fabric, then, I sill habe tp try my calculations again.

I think with enoigh buttons of siitable diameter even pe might work, though. I might be impractically many.

The water wall is to ise instead of a cpncrete wall, for aa soundproof room. I suffer severely from ptsd that is triggered by noise, and even highway noise in relatively rempte placea is impossible. Plus the accumulated barriers of escaping the city without freezing etc are too high. I need a soundproof room.

I think the water wall approach has a lot pf potential, though?

 

[LittleInch]

I would try something like tent material which is at least rated for xxmm of water. I just can't see any thin material withstanding multiple small holes without leaks and tears. Like the report says though sound often leaks around the sides. Maybe think about a smaller igloo shaped thing you can sleep inside??. Making a frame to take the weight is the only practical way to go.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[adouglas089]

Thank you all for the input.

 

[rb1957]

tent material ? most tents i've had wick water like nobody's business. I'd look for a heavy gauge plastic ... if you weren't on a budget I'd suggest sailcloth.

But I think you're stuck on the frame ... the water bags on their own will (in my expectation) collapse without a frame. Personally I'd start with a simple framed wall and add sound proofing (insulation batts, water bags, acoustic panels, ...).

Is the problem limited to noise, or vibration as well ?

another day in paradise, or is paradise one day closer ?

 

[ivymike]

From what I've read on the internet (in preparation to eliminate noise entering my master bedroom from noisy neighbors) one of the best things to do is add a second layer of drywall, especially the special noise attenuating drywall, over the top of your existing drywall.

 

[IRstuff]

Have you bothered to analyze your "fishing line?" I think it'll need to be made from Zylon or Dyneema, and still be quite thick.

TTFN (ta ta for now)
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[dgallup]

The paper linked by the OP does not find the water & membrane to be very effective. It's less effective than thinner brick or concrete panels and those are not especially good sound barriers. As Ron & Tmoose listed above, there are plenty of simple conventional ways to block sound.

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[SnTMan]

Isn't it true that water carries low frequencies especially well?

Regards,

Mike

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