|Drawings from Aprovecho|
Cheap energy ain't so cheap, anymore.
A friend, who suffered from arthritis and heated with wood, once told me, "I want the best return in BTUs on calories invested." Mmm. There's a deep thought!
It's become much more common, recently, to consider efficiency in terms of insulation. But our crafty forebears applied it to cooking, upping that return on investment of which my friend spoke.
The general concept of a haybox is an insulated container, closely fit to a lidded pot. Anything with lots of air spaces trapped within it (hay, newspaper, foam, wool, etc.) may be used... 4 inches all round the pot being a good working minimum.
Historically, hay was a choice insulator. It would be chopped coursely and, while damp, packed firmly around a dedicated pot. Once dry, it would retain the pot's shape in a tight fit. Hence the name haybox. They were common by land and sea. Soldiers used them to cook rations in the field.
Bring the contents of the pot to a solid boil, put it in the container and close the lid. No more fuel necessary! Cooking continues at a simmer for hours. Recipes are similar to those for crock pots.
Piping hot soup on deck in the wee hours! WOO-HOO!! Don't even have to wake the cook (and a cook awoken is a grumpy cook).
Additionally, a thermal mass (brick, stone, shaped concrete plug) may be heated on the side, and inserted with the pot for dry baking. A metal liner is a safety feature for this method, as the thermal mass can reach scorching hot temps if not watched carefully.
A notable refinement is to line the container (outboard of the insulation) with a reflective layer of foil or equivalent. Tristan Jones (I seem to remember from One Hand for Yourself, One for the Ship) spoke of layering foamboard cut to fit a pot. Nomex cloth?
Here are some pics of various DIY solutions, and commercial thermal cookers (vacuum insulated). Search for any of the title terms under images for a quick overview, or go straight to any of the many excellent articles posted online.
|Looks like a Sailor's work!|
|How easy can it get?|
|Lanny Henson Green Pail Cooker|
|Here's a row from Africa.|
Here are a couple just to get the flavor... can be very spendy. Many claim advantage over a straight, retained heat cooker by enabling convection cooking vs. straight simmering. Anyone out there got one and care to comment?
Watch out for thin bottomed inner pots, which don't heat well. Some complain of warm spots and heat loss around the lids, especially but not always in cheaper models.
|Thermos Shuttle Chef Thermal Cooker by Nissan|
|Thermos Thermal Cooker by Thermos|