Originally Posted by LSB
What if you fill the inner cooler and froze the whole thing solid before you put it in. I'll definitely try this summer.
When I was a kid, I remember my mom freezing a half gallon carton of ice cream in a block of ice for my Dad to pack into the Bob for my great uncle's 80th birthday a week later. It did the trick. They had ice cream and german chocolate cake on his birthday.
I think it would work awesome---especially to have some frozen treats at the middle or end of a long trip.
Frozen in water would prevent freezer burn, and it would be small enough you could take that small inner cooler to your friendly local meat cutter and ask them to put it in their flash freezer overnight so it's REALLY cold.
Ice melts faster when the delta-T (difference between outside temp and inside temp) is higher. If your main cooler is 32-33ºF and your inside cooler is 20ºF, it's going to last a lot longer than a 20ºF cooler in 85ºF outside temps!