Has anyone tried making a mash tun from one of those heated coolbox's? They say they can get to 65C so I was thinking this might be a great way of reducing heat loss during a mash?
It's a lot of money to lay out and something else to break down so "No!"
I pre-heat my Mash Tun (an ordinary Thermos Cool-box) with hot water before pouring in the Strike Water and it only loses +/-2*C over a 60 minute Mash at 70*C with an ambient temperature of 10*C.
Two things I would speculate on. Firstly, I don't know where the gubbins is that heats / cools the unit, but you'd want to make very sure that you didn't disturb it when fitting the drain tap. Secondly, it's thermostatically controlled, so wouldn't be of any use (over a normal cool box) for any mash temp over 65°, which for me is most of them these days.