weighing down a pile

[Dan_Shade]

is there a standard for how much to weigh a pile down?  I've seen 100lb per square foot, and even up to 500 lbs per square foot.

for a stack 4' wide, and 8' long, here's a small chart I figured up:

Code: [Select]

Width      length area load               total weight on pile
feet feet sq. ft        lbs/sq foot   lbs
4 8 32 100 3200
4 8 32 200 6400
4 8 32 300 9600
4 8 32 400 12800
4 8 32 500 16000

that's a lot of weight, am I missing something?

[Paschale]

I've not used nearly that kind of weight to hold the lumber I've air dried down.  I mean...as I'm thinking about it, for the upper middle to bottom layers, you've got the weight of all that wood above holding things down, so all you really have to worry about is the top layers.  From the books that I've read, there isn't a specific weight per square foot, but rather "just enough weight to keep it from warping."  I guess that's open to interpretation.  But quoting here from THE CONVERSION AND SEASONING OF WOOD, by William H. Brown, he says this in a section regarding air-drying, "The simplest form of cover to use is a sheet of heavy duty polythene placed under the top layer of boards or, if the latter are also to be protected, on top of the pile with something like old timber to weight it down." 

In the the Fine Woodworking book WOOD AND HOW TO DRY IT, they just suggest putting cinder blocks on a top layer of plywood, scattered across the top.  I can't imagine you'd need 16,000 lbs to have sufficient weight...it just seems a little overkill.  Just so long as those top layers aren't warping...that's enough weight, whatever that may be.

Makes you wonder though...   

[Dan_Shade]

I typically put about 400lbs on top of a 4x8 pile, but digging around, and seeing the 100lb/sq ft, I was like wow, i'm not even close to that...

the other side, is I sure don't want to lug 3200lbs ontop of the pile after a long day of sawing!

[scottr]

Dan , you want the boards to be able to shrink in width as they dry . Try six cement blocks on top of your 4' by 8' pile .

[Dan_Shade]

I can't see how only 6 blocks on the top of the pile can be enough to keep the wood from cupping...

[scottr]

Dan , on page 82 & 83 in your Wood and How to Dry it book the illustration shows a 4' by 8' stack with a sheet of plywood and two cement blocks on top .

[DanG]

Just because it's in the book don't mean it'll work.  Two cinder blocks would barely keep the plywood from blowing away.

[Brad_S.]

I use a few railroad rails placed on stickers on the top of the stack in my kiln. Was a cheap and easy way to add weight but since scrap steel prices spiked, it may not be cheap, but it's still easy.

[Tom]

Doesn't this stretched out page make it fun to post?

I still favor an Abrahms Tank parked on top for weight.

I've seen an oak board that wanted to move, raise the whole stack.

There is a lot of strength in a board that wants to warp.

[Part_Timer]

I use about 20 blocks with the holes filled with concrete. 

I also have a bunch of 1 gallon paint cans with lead in them.  When I need to melt more bullets I loose a can or 2.  fill a couple more blocks. 

If I have a stack with a bunch of tension I ratchet strap it first then weight it.  No way I'm keeping 3200 lbs of weights around.  My back is not that strong

[Dan_Shade]

page stretched?

sorry about that, i was trying to make a nice neat table   it works fine on my monitor.  I"ll edit out the metric stuff

Hope it works a bit better for you guys now...

for my weight, I typically use those green plastic planters, the 24" ones, I can get half a bag of 80lb concrete mix in one, which leads me to 80 lbs on top of each sticker, I guess i'm going to have to get a bunch more of the planters, I don't see me getting 3200 lbs, but I may double the weight on it, I'm afraid of crushing the wood fibers if I put too much weight on it.  is this possible?

[Rockn H]

  No way I'm keeping 3200 lbs of weights around.  My back is not that strong

Sure you've got that much weight and you don't have to lift it.  The first time I read 3200lbs of weight I pictured just driving a medium sized car , say a 4 door Chevy Caprice, up on a stack of lumber.   Seriously though, I've always just put enough weight on top to hold the tin down.  If I think a stack may move I'll put a few 2" ratchet straps on it.

[Don_Lewis]

I know one guy that uses water bed mattresses.

[Tom]

That actually sounds like it could be a pretty good idea, Don.

[Larry]

Excellent idea Don.  I used to use big patio blocks but it is just plain hard labor getting em up there and you need couple of tons to do any good.

Electric Al posted a picture long time ago where they were using about a 4" thick concrete slab on top of the lumber.  Betcha he was using a machine to put the slab on top or made Linda lift it up there.

[OneWithWood]

Does weight actually prevent wood from moving?  It seems to me that all that weight simply delays the movement.  Once the weight is removed won't the forces involved cause movement shortly thereafter?

[Tom]

I've not found the stuff to move much once dry.  If it gets wet again, then all bets are off.

Not knowing a better word, wet wood develops a "set" as it dries.   If you bend a piece of wood and hold it bent until it dries, it will retain a lot of the bend.  I think the same is true for holding it straight.

[OneWithWood]

OK.  Do you have a spare Abrams I could have?  Mmmm, I think I had better make my kiln chamber bigger to accomodate my top weight 

[Tom]

That's what makes Don's suggestion so viable.  You could put a flat surface on the stack and then put an empty water-bed mattress up there and fill it when it's up there.  Pretty ingenious, eh?

I still like the idea of the Abrahms too.  It would be dual purpose in that I could use it to move idiots, like double parkers, out of the way when go to town.

[red]

you just dont want to make that pile to high 


i would hate to have to jump/climb onto that bed for a quick snooze

maybe a few waterbeds at different heights around the yard might work

one for the dog ...customer waiting area

[Furby]

How would the temp of the water in the bed affect the operation of the kiln?

[Tom]

Kiln??     

[Furby]

[SwampDonkey]

I find yellow birch is bad for twisting as it dries. My piles are relatively small (depth-wise) and I don't weight it down. Them warped peices just get used to make small items. Once in awhile I'll get a butternut warp like a bow, well that is either a tree that leaned hard or most likely someone thought they could make use of a limb. 

[OneWithWood]

How would the temp of the water in the bed affect the operation of the kiln?

Well, if the temp is just right I might not wake up in a timely fashion to start up the kiln.  So I would have to say the temp is critical to timely drying.

[Furby]

 
Good answer!

[DanG]

The waterbed ain't a bad idea, but it takes up a lot of space that could be used for drying/storing firewood.

[Randy]

Ok Guys all this weight is hurting my back. Why not do this--------say you have stacks that are 4ft wide by 8ft long---------Why not get 6-5ft wide brick lintel's------they are strong and not real heavy---Or you could probably use some 4x6 or bigger dried oak-----make a clamp by adding chain to each outer end of the bottom piece's and a large turn-buckle with a hook on the bottom to the top pieces or you could use chain binders. Slide the piece under the pile----lay the other piece on top--------take the chain and hook in onto the hook end of the turn buckle---tighten. Check them every few days-----re-tighten when needed. Would cost a little to get set-up, but would save your back and last for years. Adapt to fit your situation. Randy

[Part_Timer]

Randy we been thinking along those lines.  We were going to use painted unistrut and all thread in the kiln.  Just run the all thread through the slots in the strut.  Tighten down and check every few days. Should alow me to stack another 4 rows in it..  We'll see on the next load 

[Tom]

Checking every few days isn't going to do you much good.  That's why straps are so difficult to manage.  If a board is going to move, it will move when your back is turned. 

There is another disadvantage to too much weight on top.  you can actually crush the fibers in the boards on the bottom.  Take into consideration the amount of weight that is on a sticker on the bottom of the pile.  Then think of what you do to it by parking that Abrahms on the stack.

You will seldom see large weights on the top of stacks on commercial drying yards.  The stacks are covered and enough weight to keep the cover from flying off in the wind.   A lot of board movement can be curtailed by air drying in drying sheds rather than in the open.   If the stacks are narrow and tall, the number of boards that move because of no weight is minimal.

[ellmoe]

We use nylon straps and weights on top. The weights are peices of scrap metal, old pillow block bearings, big gears , etc.. We cross the bundle with 1x4's over each stick and stack one layer of weights on each 1x4. The nylon straps are pulled as tight as possible as they will loosen as the wood shrinks. I imagine each 8' bundle has 300-500 lbs on it. You are really trying to contol the top layers as the weight of the wood contols the lower. The straps help control during the initial drying and help control side-bending in the boards. If we can get in the kiln to tighten the straps during drying I will do so. Usually, the kiln is loaded such that I can't fit between the wood and the door.
Mark

[Ironwood]

I have 10" I beams under the floor of my moveable kiln. I welded 1" nuts to those and then threaded LARGE eye bolts in to those, I beleive there are four in the front and four to the rear. I sealed around the threads to prevent water seepage. I do trip on them occasionally when it's empty. Should I ever need to strap a load in to prevent warping, there you go to heck with all that tonnage talk. My back hurts just loading the wood! Also the eyebolts enable me to chain the main frame of the kiln to my 8000lb forklift mast to move it as no forks are long enough to fit to the back of the kiln.

                                             REID

[t_andersen]

That's what makes Don's suggestion so viable.  You could put a flat surface on the stack and then put an empty water-bed mattress up there and fill it when it's up there.  Pretty ingenious, eh?

that is.... unless it leaks!

[Riles]

I think you have to look at the math again. 100 lbs/sq ft across an entire 4 X 8 sheet is alot of weight. But if there's a row of stickers between the top pieces of lumber and the covering sheet of plywood, you need only center the weight on the stickers. 100 lbs/sq ft is 0.694 lbs/sq inch and on a sticker 4 feet long and 1.5 inches wide, you only need 50 pounds of weight along each sticker. Five rows of stickers is 250 pounds of weight and that sounds a lot closer to what people actually do.

Since you're keeping the lower layers of lumber straight with stickers, it makes sense that it would work for the top layer as well. The lower layers are certainly getting more weight (as well as being better distributed along the sticker).

Now if you could just find 4 foot long, 1.5 inch square stickers that weighed 50 pounds, you could leave the water bed back with the orange shag carpet and the lava lights.

[jimF]

I think you are looking at the problem from the wrong direction.  You could put enough weight on top to keep it from warping, but it would crush the wood under the stickers.
The problem of warping is either some abnormal grain in some cases but most of the time it is caused by too slow of drying.  The three positions that warp is observed most is: 1) in a very slow drying kiln setting (too high of RH), 2) where the air flow is blocked (like where some plywood is nailed in place to direct the air flow away from a spce between two piles or two stacks where the spacing does not line up vertically) and 3) at the top of the stack.  Because of most airflow arrangments ( baffles and decking separating the heating area from the stack) the airflow can be almost zero on top of the stack.  All these cause too slow of drying.
Even with abnormal grain, speeding up the drying will reduce warp.