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It is bushfire season again in Oz. Just last February a fire
which
destroyed 72 houses came within a few hundred metres of
my
home.
I own numerous watercarts with watercannons so was better
off
than
most people but didn't like putting my employees, myself or
my
equipment in the path
of the fire. This meant it was down to
just
me
and one truck on standby at the house but, as the fire
danger
lasted several
days, it was
pretty
draining. If you left the exclusion zone for a rest you weren't
allowed to return.
I have been approached several times over the years by
companies
spruiking superabsorbent gels designed to be sprayed over
buildings,
plants and so on which provide a considerable amount of fire
resistance and longevity - especially compared to just plain
water.
This would
be costly and messy but still could
be
a option for protecting your property while allowing you
to decamp to safety.
The problem is that I could never put together a good
business
case
for selling the stuff. You don't want to spray the gel over
everything hours or days ahead of time when the fire may or
may
not
even reach you - but neither do you want anyone
workIng 1/2 hour or so ahead of a raging firefront.
My idea is to create a range of metre-high decorative
mushroom
shapes which could be strategically placed around one's yard.
They
would hold a quantity of this gel surrounding either a volatile
compound or merely a compressed gas. When the ambient
temperature reaches a pre-set threshold of, say, 65C then
the
whole
lot is violently discharged up through an aperture or spinning
nozzle on the top of
the
mushroom covering everything in the vicinity with fire
protectant
gel.
They could be any shape you wanted if mushrooms aren't
your
thing.
Gnomes, unicorns, or abstract designs would all work equally
well.
I
would like long snake shapes on either side of my
roof crests.
Firefighting koalas or beehives could be suspended in trees.
I am aware that it is possible to plumb up sprinkler systems
and
all
that but it is an expensive option which requires pumps,
multiple
waterlines and an adequate supply of water and water
pressure.
Electricity is often cut in fire zones, water pressure drops
and
diesel pumps run out of
fuel
so the power source is problematic.
I'd be seriously interested in hearing any suggestions from
my
fellow
HBers on how to best flesh this idea out.
Wikipedia description of fire fighting gels
http://en.wikipedia.../Fire-retardant_gel
[AusCan531, Dec 30 2011]
Fighting fire with explosives
http://en.wikipedia.../wiki/Oil_well_fire
Do not try at home (unless you are a Hellfighter or a fully-qualified Halfbaker) [Alterother, Dec 30 2011]
Types of Fire Extinguishers
http://en.wikipedia...i/Fire_extinguisher
Includes Fire Extinguishing Ball which is a similar concept. [AusCan531, Dec 31 2011]
The California version
Borate_20Bouncing_20Bettys
[normzone, Jul 05 2021]
[link]
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Brushfire season is dry. During dry weather, a moat is just
ground that's a little lower than the ground to either side
of it. |
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The exploding bit is easy to accomplish. First, use very
highly compressed CO2, which will have a brief smothering
effect in its own right. The discharge is triggered by a
consumable seal on the pressure outlet that just melts at a
certain tempurature (this is already baked, used in Xmas
tree extinguishers and elsewhere). Channel the pressure
however you want, as stated--through a directional or
spinning nozzle, or simply blasting your gel all over the
place. If the discharge is powerful enough, it might even
extinguish the flames with concussion as well, such as the
dynamite method used by hellfighters. <link> |
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[+] for exploding lawn ornaments. |
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//water cannons// Is there such a thing as a fog cannon ? A couple of those upwind would cool the air before it reaches the building, coat the building in water droplets and quench any ember light enough to be wafted in. |
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//Is there such a thing as a fog cannon ?// Maybe a
snow-making machine? |
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I don't think I quite understood the meaning of dry. Here dry means the bit in between the rains, what you call rain, we call fog. |
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That's what it's like here in Maine, too. 'Dry' means 'the
sunny parts
between the rain / snow / sleet / rhinoceroses / hail / all
of the above at once'. But in Australia, amongst other parts
of the world, 'dry' means 'one careless smoker can burn
down half the continent'. |
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^^^//snow-making machine// that's what I was thinking of, using fogging devices instead of refrigeration apparati; outside of [AC]'s specs though. |
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Actually, in warm weather, snowmakers like the ones used
at the large ski resort not twelve miles from my house
produce extremely fine mist that hangs in the air
like fog. Not much good for firefighting, but maybe for
prevention. |
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(D'oh! I knew that.)
I;m not sure that using a snowmaker would be best though: the particle size (in my sub-idea) should be small enough to simply be a fog that is carried to the fire-facing side of the building mostly by the wind. |
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A snowmaker would be ideal in that application. The
modern ones produce a very fine mist, almost a vapor, that
freezes in the air. No artificial refridgeration is involved.
By my observational estimate, they
project a 60-degree fan or cone to a range of 20-30 yards,
or a stream up to 50. The 'snow' thus produced drifts nicely
on the wind (for hundreds of yards, sometimes), allowing
one unit or a chain of units to cover several trails
simultaneously if properly arranged. On bright, sunny days
when the conditions are just right for snowmaking, the
mountain looks like it's boiling with huge plumes of steam,
like a frozen volcano. |
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Only
drawbacks: extremely high pressure requirements, cannot
be used in high winds, and they must have a
continuous high-volume
water source. If there are any interruptions or even drastic
fluctuations in the flow,
the entire
system must be bled of air (I overhear
the snowmaking crews bitching about it all the time). |
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I think the problem with snow would be the lack of volume of water...which wouldn't be much of a heat-sink. |
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Some snow machines spray both ice particles and water, others just water. |
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There are such things as fog cannons (my company makes fogging systems) but would be inappropriate because of the wild, swirling super-heated winds usually associated with fire fronts. The problem with fine droplets (or snowflakes) or foams is that within 15 seconds they'd be either totally evaporated or blown to the next state.
The answer is to have heavy, sticky droplets resistant to evaporation and somewhat resistant to blowing away. A moat just wouldn't suffice I'm afraid other than providing a place of refuge, if you have scuba gear, so you can watch your place burn. |
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It's hard to get across in words the nature of conditions but the video [link] I put up will help. Even my sticky gel would be windblown but if the house is surrounded by exploding mushrooms hopefully those upwind (which is where the fire and the heat would be coming from) would spatter their goo in the right direction onto the house. |
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Houses tend to go up either because of ember attack (where burning leaves etc get blown into crevices such as gutters or into evaporative airconditioners), burning trees falling onto the house or they simply burst into flames due to the intense radiant heat. I have cleared trees from near the house, built a screenmesh cover for my a/c and have everything I need to plug the gutters and fill with water. If I could cover the surfaces of the house and trees with enough gel to survive the most intense 1/2 hour when the firefront sweeps through I will have done all I could with this property. If I ever build a house in the bush I will design a fireproof one from the get-go. |
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But even if I eventually construct a totally fire-proof home/bunker for myself there will still be tens of thousands of houses needing a semi-automated gel spraying system. Awareness has never been higher after the last 2 years and any remedial solution for existing properties would be most welcomed. |
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The linked Wikipedia article on fire extinguishers does list "Fire Extinguishing Ball" which self-destructs when subject to heat but covers only about 5 sq.m. and is suitable for passive suppression but would be more suitable for indoor fire fighting. |
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Any ideas for really ramping up the spraying system other than just compressed CO2? I'm thinking solid propellant rocket motors to really give it some oomph as I want to move considerable mass quite a few metres into the air. |
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Well, solid propellants typically involve a certain amount
of, er, fire. Quite large amounts of it, actually. What you
want is an explosive, not a propellant. I don't
know how you'll deliver the gel without destroying it,
though; that's a question for [8th] or [MikeD]. |
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... asbestos house-cozy ? |
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You know, we're making this harder than it needs to be.
What if we just loaded up an 80mm mortar tube with this
firefighting goop? |
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If we'd all just build like hobbits... |
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Seriously though good idea. It should vent its gas/foam directly towards the strongest heat signature. |
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//other than just compressed CO2 ?// how about moving boilers into the woods ? when enough pressure has built up a pressure-valve breaks, steam rushes through the pipe and blows off the gel for that area. |
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//The answer is to have heavy, sticky droplets
resistant to evaporation and somewhat resistant to
blowing away.// |
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I recall having to eat it at boarding school and it
making you feel like you'd swallowed a few kilograms
of lead shot. |
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Everyone loves 80mm mortar tubes [Alterother]. That's a
given. But where's the whimsy I ask? Where is the whimsy? |
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99.999% of the time these devices are going to just be
sitting around the yard. Would your better half be
receptive to surrounding your abode with mortars clearly
aimed at the house? Mine's twitchy enough with my good
ideas now. |
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[FT]'s idea of boilers in the woods is good but rather than
water I'd prefer some other volatile that undergoes phase
change at less than 100C. |
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Ether, perhaps? Maybe not... |
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// Would your better half be receptive to surrounding
your abode with mortars clearly aimed at the house? // |
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Probably, but The Good Fairy Jenny is an exceptional
woman. I'm not saying she wouldn't go around and double-
check that I'd removed all the warheads, of course. |
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////The answer is to have heavy, sticky droplets resistant to evaporation and somewhat resistant to blowing away.// |
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break a gazillion eggs, spray them over the building, heat gets used up folding the proteins and making it cooked, and then everyone can have an omelette after the event... |
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Broken eggs and half bacon? |
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..and you could probably use potatoes in foil as a kind of protective wall...the heat gets used up cooking the potatoes...how much am I getting paid for these again? |
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Potatoes? They're pretty cheap. |
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Damn, there goes the patent |
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Sir Francis Drake got there first. They're about a 66c
a pound these days, for orders of a ton and up. |
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That's ok, my appearances here are strictly pro bono |
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I can't stand him, the sanctimonious Irish git. |
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//Everyone loves 80mm mortar tubes [Alterother]. That's a given. But where's the whimsy I ask? Where is the whimsy?// |
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Use gels in a variety of gay fluorescent colors: Green, pink, blue, orange, red... oh, wait... |
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//Use gels in a variety of gay fluorescent colors//
Now we are cooking... oh, wait... |
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I think [Alterother] is correct and what we need is a
verrry slow burn explosive. Something which could drive
a piston with enough power to forcefully eject 150
litres of gel through a nozzle in less than 2 minutes.
[8th]? |
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+ when I’m cruising * random*, I wonder how I
have missed so many great ideas! |
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Thanks [xandram]. I briefly did some research on this idea
with the half-assed notion of baking it in real life. For a
self-contained propellant I looked at buying airbag gas
inflators on Alibaba but couldn't calculate how many I'd need
to go off in succession to create the pressure I needed. The
whole idea is now relegated to the part of my mind labelled
'maybe someday projects'. (Think of a hoarder's garage). |
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//What if we just loaded up an 80mm mortar tube with this firefighting goop?// |
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...And then train everyone in their use! Not only will the nation be safe against fire, it will be resistant to fire bombing and to a lesser degree to actual invading armies. |
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//Houses tend to go up either because of ember attack (where burning leaves etc get blown into crevices such as gutters or into evaporative airconditioners), burning trees falling onto the house or they simply burst into flames due to the intense radiant heat.// |
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So the problem is clear: houses should not be built of material that easily catches fire. A reinforced concrete dome covered in a shell of copper should show some resistance, especially if the copper is continued into a large moat. |
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