[Ravensfort] showers / Re: [rfofficers] Gundy's Find
Catie Clark
cat at rocks4brains.com
Mon Oct 13 10:14:07 PDT 2008
SF Tester wrote:
> On Sun, Oct 12, 2008 at 10:44 PM, byzytym <byzytym at att.net
> <mailto:byzytym at att.net>> wrote:
> Good info.
> I think you are going too tick on the metal though. I'm talking
> about thin and light.
> The problem with thin metal is that it dents, fasteners rip through, and
> it rusts through way faster than you'd think. Think about how thick a 50
> gallon drum is and how quickly they rot at the site.
I agree strongly with the above. The drums I used to use
back in my superfund days were 10 guage or better. In
addition, you improve the yield strength by forming the
steel into the round and ribbed cylinder. The whole
cylinder can support a lot of stacking compression, both
normal and axial, which is one of the things it was designed
for. But it's still lousy on spot failures - for example,
the plastic deformation failure induced by a dropped hammer
(better known as a dent...).
Now consider the drunken kid in great kilt who takes his
great sword into the shower and falls, banging the big brass
pommel against the sheet steel... what, you don't believe
it's likely to get some clueless drunk showering in his
clothes and his sword??? It's the SCA, dude! I'm surprised
it doesn't happen more often!
okay, okay, maybe I exaggerate...but only a little...
> Ok, grab your latest Quoth. Open the cover, 1st, and 2nd pages. Those 3
> pages combined are about .010". 4x8 feet of that, in steel, would be
> somewhere around 13 pounds, but would last a few months. Wind would
> shred it pretty quick.
Okay, let's do some numbers. Pulling my copy of Abrose's
Building Structures (1993 edition), we find that the minimum
recommended guage steel for building applications is 22
guage. These applications include interior non-load bearing
walls and enclosure walls, regardless of suspension. This
is adequate to support maximum recommended lateral loads of
10 psf. So 22 guage (@1.6 #/ft^2) is good enough - but is
32 guage, which is close to the 10# weight limit requested?
Consider that the load bearing strength of a sheet should
drop by the square of the thickness. 22 guage is three
times as thick as 32 guage - so it has roughly one ninth the
strength. Seriously, I don't think we want to go there. It
might be light but it would be dead enclosure walling as
soon as the first severe thunderstorm blew though. I think
the assessment of 32 guage being shredded in the wind is
defensible. And I think Gundy et al. are dead on the money.
The new structural plastic and plastic composites are a
good way to go, and if you get the right stuff, it really
lasts and can withstand all sorts of weather too (excluding
tornadoes, of course...but nothing short of bank vaults or
nuclear hardening can stand up to an F4).
I crunched a couple of numbers [well, okay, the wind loading
equation to be exact, {(rho/2)(fps^2)Cd(area)] and the force
thus calculated on a 4 by 8 sheet in a 40 mph wind using a
drag coef of 1 is 132#. I can't begin to image an
unsupported 32 guage sheet surviving that kind of load.
Don't compare this to the 32 guage sheeting in those car
port things, since most of those use some kind of
corrigation AND none of the panels is ever bigger than 2x3
(and most are smaller); the reason those things work is the
design of the support frame, not the integrity of the sheet
steel. Nope, I really don't think unsupported 32 gauge is a
good idea.
Ahhhh...there's nothing like a little civil engineering at
lunch to make up for a lack of caffeine...
ttfn
Therasia's inner nerd
>
> Can you price the sheets of the stuff you are talking about and see
> if larger sheets are available ? I'm guessing that have the right
> UV inhibitor or gelcoat will cost more ??
>
>
> I'll see what I can dig up. I need to go find some stuff anyway. Don't
> really need the UV inhibitor if we paint it. House paint (at least the
> half decent stuff) has it.
>
>
> You will have to spell out the UHMW. Again, those of us that do not
> use the terms every day do not know what the hell you are talkin' 'bout.
>
>
> Didn't spell that one because it's long and multisyllable grunts aren't
> my bag ;)
>
> Ultra-high molecular weight. Same stuff pickle barrels are made of.
> Nothing short of a miracle will keep paint attached more than a
> nanosecond, but it's tough stuff.
>
> Another possibility is Tyvek. It's something like paper, but won't tear.
> If we came up with the right method to attach it, it may work out since
> it's cheap enough to replace it every couple of years.
>
> If I was making the decisions, I would weld a frame out of 2" square
> tubing, then mount FRP or ABS panels on floating studs so the framework
> can move some without stressing the walls. Throw in some cedar slats for
> a floor and it'll last longer than me (and I'm fairly well pickled after
> close to 2 decades in Swein camp :P)
> --
> Gundy
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