Tuesday, September 15, 2009

9-13-09 Building a Wood Crib

Now that I had all those lovely peeled poles, I had to try my hand at rustic construction. Considering the amount of firewood Gungnir was foraging in the nearby woods, I thought a wood crib or two for our back deck would be just the thing. What’s a wood crib and why do you need one? Basically, a wood crib is simple pole box that you can stack your firewood in so that it stays dry under cover, has plenty of ventilation from all (or most) sides (including the bottom), and allows you to build your wood stack up much higher because the walls keep your logs from rolling or the pile from swaying and falling over when it gets top-heavy. Those last two are very important if, like us, you’re living in a tent without a convenient sturdy wall on your porch! Another great advantage to crib is that it makes it much easier to determine how much wood you have and how fast you’re using it.

Before building my crib, it was handy to know a few things so that it would be most efficient. First, that a standard cord of wood is 4 feet by 4 feet by 8 feet… or 128 cubic feet (the linear dimensions aren’t as important as the cubic volume). A standard stove length of wood is 16 inches, so three runs equals 48 inches (or 4 feet)… one of these runs 8 feet long and 4 feet high is the true definition of a face cord. Now, the firebox in our stove is 26 inches, which means that our stove lengths (or bucks, or billets) are 20 inches (leaving 6 inches to rake the coals forward and add new logs to the back).

Our deck is 5 feet deep, so leaving 6 inches on the back for ventilation and 6 inches on the front to protect it from the weather meant that the maximum depth of the crib could be 4 feet. The eave of our rain fly stands at just over 5 feet high, so the maximum height of the crib at the eave could be 5 feet. Our deck is 17 feet wide, with the tent opening in the center, if I wanted to make two cribs and still have a usable entry, I couldn’t really make the crib wider than 7 feet… however, not al l the wood we use is stackable firewood, so we still need space for bundles of sticks and kindling, as well as our lumberjack tools and boot racks.

Three runs of 20 inch bucks equals 60 inches (or 5 feet), so, I decided to make the crib 4 feet deep by 5 feet wide by 5 feet high… for a total of 100 cubic feet (just shy of a cord – and a full cord if we stack a little over the top of the crib as we reach the peak of the fly). Putting on one either end of the deck, with kindling boxes in front of each, allows us to keep approximately 2 cords of dry wood right there outside the back door (and the stove!) at all times. I’ll also be building a small crib inside the back door that will hold a face cord handy for tending the stove (warm wood ignites faster than cold wood and doesn’t rob heat from the stove). 2+ cords should be enough wood to get us through the worst cold snaps and blizzards when trekking to the larger woodshed out back might be ill-advised or downright impossible.

So anyway, I now had my dimensions, I just had to figure out the best way to keep the whole thing stable and keep the wood neatly stacked and well ventilated. What I ended up doing was creating the front and back walls with four stout poles 3 inches in diameter as the four corner uprights, and running smaller poles (2 inches) horizontally. At this point, I cheated a bit and used screws to hold the poles together rather than conventional lashing… but, hey, I was working alone and it’s damn near impossible to hold something square while you’re lashing it if you only have two hands. After I made the “squares” for the walls, I lashed some ropes diagonally to provide cross tension so the whole wall assembly wouldn’t collapse like a scissor. Once I adjusted the ropes to maintain some assemblage of square-ness, I added two additional uprights to act as stops should the logs decide to roll (which every wood heat person knows WILL happen when it’s most inconvenient – like the middle of the night during a rainstorm). In hindsight, it would probably have been better to use three uprights, but I’ll fix that on the next one.

I then stood the two walls up facing each other and loosely tied them together so they wouldn’t fall over while I added the back wall. The outside wall consists of a top and bottom horizontal (4 feet long) connecting the two other walls, and one upright in the middle to keep the wall from bowing outward and add lateral stability to the stack. I then added 4 foot horizontals on the “floor” such that each 20-inch buck would be supported by 2 “joists”. This adds stability to the stack, but also allows for air flow under the wood so the bottom logs don’t rot out.

The inside wall posed a little bit of a challenge since we did need to be able to get in and out of the crib to load and unload it, so I couldn’t just build a wall like the outside one unless we wanted to be ducking and dodging poles every time we went in and out (no small feat with an armload of wood!). So, instead of placing a horizontal at the top, I took a length of rope, tied bowline knots on either end, and looped it over the opposing posts so that it keeps the walls from splaying out but can be easily unhooked for entry like a gate. For added support, I attached a diagonal from half-way up the back wall to halfway into the inside floor joist. The diagonal still forms enough of a side wall to keep the stack from swaying, but is safely out of arm and foot’s way when climbing in and out of the crib. I added plastic sheeting to the exposed outer walls to further protect the wood from rain and snow, but made sure there was still adequate ventilation.

A little safety note, I aligned the tapers in my poles, and the directions of my joins, such that if the crib should fail when it’s full of wood, the stack will fall safely off the deck not back into the tent and stove. Never assume that whatever you build, especially not using green wild timber, will never fail… always design and construct it so that when it does fail, it will fail safely!

1 comment:

Anonymous said...

cool. i need to build a crib down here in NJ. Good to know how to use wild lumber, pics helped a lot, too !!! Thankx !!!