I don't know why I've never seen another prepper with

>>32173190
I've got a couple. On a good day in the summertime I can almost ignite asphalt. I posted a few pics in a shtf thread about 3 years ago.

So a window used like a giant magnifier?

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>>32173190
>die of starvation on a cloudy day

NICE TRY BANDITO

>>32173190
A friend's dad had a huge one of these that got hot enough to turn steel red hot in no time when it wasn't even that sunny out.

Definitely pretty cool and even useful to boot, but not really something practical to carry with you unless you have a big ass bug-out RV or truck you plan to drive innawoods.

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>>32174293

Not a window. A mostly flat magnifying lens.

Fresnel v Nornal


I have a few from old overhead projectors we threw away.

You need a BIG one to get significant solar energy. You can melt a tiny spot on rock or light things on fire but their usually tiny areas. When you direct that energy toward a large mass like a pot of water it'll take quite a while to heat up.

Fortunately you can get big ones. Look for projection TVs on the curb - they're humped in the back but not as much as CRTs. They have huge fresnel lenses in them, large enough to collect enough light to heat a significant mass

>>32175960
Hmmm at work on mobile so can't work equations. Would an array of smaller ones or one larger one be more useful?

>>32176101
You'll have an easier time with 1 big one. Small lenses that add up to the same size would have the same amount of total energy but each small lens has its own focal point. You can't just turn the lenses to point them so you'd need reflectors. Much easier to deal with 1 lens and 1 focal point.

>>32173190
you're retarded. a bic lighter is under $2, and i can fit 100+ of them in the space of your sun dial bullshit wish-i-had-some-fire

fun fact - its pronounced freh-nell not frez nell. the guy was french.

>>32174299
https://www.youtube.com/watch?v=zsWJI3lKOlU
First thing google spits out.

>>32176177
All my lenses were free and don't require any kindling/firewood to sterilize water and cook all the food I want