Says the guy who overestimated the weight of a mosquito by four hundred times. But hey, keep going with that “reasonable numbers” thing, it really seems to be working for you.

“It’s pretty straight forward to see that a screen designed to keep skeeters out is a non structural member ”

How do I know it was “designed to keep skeeters out”? What about the screen makes that clear? “oh well it’s obvious” Really? Obvious like the weight of a mosquito, maybe?

“Because it’s a window? Not load bearing wall.”

Ho, ho, ho. I look forward to you going to Japan and putting your arm through a door because, hey, how were you supposed to know it was actually made of paper?

Because it’s a window?? Not load bearing wall. Not a structural support beam. Not a…a…floor! Don’t lean against windows, bookshelfs, appliances, small children, etc.

What is it that they say about assumptions. The mother of all fu… err… lawsuits. And people wonder why common sense is dead.

That’s the point of these warnings. Somebody had a freak accident and attributed it to thinking this thing was not just a window for looking through and feeling the breeze. It’s so obviously designed to support the weight of a person-or should be. Let me sue! How long until all windows at any hieght above ground have to bear the weight of a full-grown adult…and then we all bear the costs of such nonsense? Oh, wait. We’re already paying the extra costs for these lawsuits.

Oh, its physics…you know, F=mA type stuff. F*t = m * V And yes, you really only need to pluck reasonable numbers out of the air to scope a problem.

You see, here’s how it works in engineering when approaching a new problem: Make all conservative assumptions / ball park estimates and run the rough calculation, you know using PHYSICS from that old fuddy duddy Newton. Then make all sporty / favorable assumptions and run the rough calculations again. You’ve just bounded the problem. If neither answer gives you a workable solution, seek a different approach as you’ve just quickly (and inexpensively) eliminated a possible solution.

If either or both calculations indicate that a solution to the problem is possible, then refine the calculations with more more detailed starting conditions (say by using 0.0025 grams instead of 1 gram as the mosquito weight) and a more refined analysis. In this case, the 1 gram initial estimate for the skeeter was conservative.

Using this process, many potential solutions to engineering problems can be investigated and the possible solution space narrowed quickly to only those that are workable.

It’s pretty straight forward to see that a screen designed to keep skeeters out is a non structural member – you know, to not keep a child IN. A few plastic clips (typically what holds a screen in place – they’re what hold in the screens on my home) aren’t, on inspection (you know, that experience thing), robust enough to withstand the impact of a child running /jumping at the screen, or even leaning against it with any force. But hey, you just go on and quibble about stuff you clearly don’t comprehend, and ignore the magnitudes of difference in forces that holding in a child relative to keeping out bugs.

Why should I assume that it isn’t?

Is the purpose of a wall to hold me up if I lean on it? Maybe we’ve all been idiots all along, going around just assuming that the walls of the room are capable of bearing our weight.

I thought it was for allowing light (and air if opened) into the room. Pretty sure that I could break through a window if I leaned on it, or ran into it, or any other number of obvious things. Don’t need a sticker to “inform” me. After all, the header over the window is what gives it support. The window and composite framing is just filler. No real “structural” support at all. Now, that’s not to say that it isn’t strong enoough to do the job for which it was purposed, but that’s only going to add a little support in the space it’s using.

I have a floor to ceiling sliding glass door that is stronger (maybe tempered?)…still tell my kids not to bang on it, lean on it etc.

How did people get to thinking that glass is designed to hold up to your weight?

About that flimsy plastic/metal screen…

Gimme a brak….

How am I supposed to know that? I didn’t buy the screen or install it.

“Note: weights and speeds plucked out of the air”

Give me a damn break.

Okay, so, setting aside the dubious notion of someone who claims to be an engineer doing a safety analysis on numbers that he “plucked out of the air”, let’s assume that you actually went and got the actual numbers first. Then you did the math–based on a further assumption, that the impact of an individual mosquito was the design load case–and found the expected bearing allowable for out-of-plane tension membrane loading, determined the load for someone leaning on the window (unless you wanted to pull that out of the air, too), and compared the two.

Or you could have just looked at the sticker. But hey, only silly people would look at a sticker, right? I mean, it’s obvious that someone would have known that the screens were exempt from the local building codes about load-bearing capacity of window coverings, and been able to perform the structural engineering calculations necessary to determine that they’d fall out if they leaned on it.

Heck, I just Googled “weight of mosquito” – the wiki article was the first thing up. It claims a “skeeter” is on the order of 0.0025 grams (~25 milligrams). Although “grams” is a unit of mass, not weight (the engineer in me quibbles about such things).

You are very generous with your weight for a mosquito. A raisin weighs about 1 gram so I think we’re on the order of 1 gram ≈ 35(?) mosquitos…

When the covering was designed to keep OUT insects having a mass of far less than a gram that have a maximum speed of on the order of a couple KM / hour, one could conclude that they’re not designed to keep in a 30kg child running at 10 KM/hour.

Lets see, doing the math, momentum is mass x velocity, so that mosquito is 0.001 KG x 2 KM/ H x 1000 meters / km divided by 3600 seconds per hour = 0.000556 N-M while the child is at 83.33 N-M, only a factor of 150,000 higher. If it’s kinetic energy (KE = 1/2 * mass * velocity squared) and not momentum that is more important, the child only carries 750,000 times as much kinetic energy as the mosquito.

Note: weights and speeds plucked out of the air, but in the ballpark, for illustrative purposes, but do manage to show the order of magnitude scales between keeping mosquito’s out and children in. I think I’m being extremely generous on assigning one gram as the mass of a mosquito, so the magnitude is certainly higher. Also note, this illustrates how engineers think – doing rough order of magnitude calculations to see the scope of a problem. To a lawyer, it’s “well, its OBVIOUS that a screen to keep bugs out is designed to keep people in”. How foolish are lawyers, anyways? Are they so divorced from physical reality? Yes….yes they are. See Density’s comment for proof. QED.