making weights for top of stacks

[ozarkgem]

I couldn't find any post on this. How much weight do you put on your stacks when you put them in the kiln?  I am pouring some concrete this week and will order a little extra. I am thinking of using 2x12 to make a form 4' long and put a lifting eye in it. This would be a little over 400 lbs. I was going to put 3 per 8' stack. I have some Sycamore I want to cut into 1x12's and keep if from cupping while it dries. Maybe if anyone has pics of what they use that would helpful also.

[GeneWengert-WoodDoc]

If weights were really effective, we would see flatter lumber in the lower layers of a stack of lumber even without weights.  However, this is not seen, although keeping rainfall and direct sunlight off the top layers does indeed help reduce warp on the top layers.  So, discounting the effect of a roof, weights do little to help keep flatter lumber.

Research into weights showed a benefit with hardwoods when 10" thick concrete slabs were used.   Further, the benefit was seen only if the weights were used from the beginning of drying and then kept on the lumber stack for three days after the kiln was unloaded...moisture movement was still occurring after drying, so the weights were needed.  I saw this "post drying" effect at an operation in Arkansas drying southern pine.  They tried weights that were tied to the kiln roof and they failed unless weights were also used for three days after drying.  As pine warps a lot, so some benefits were seen with weights, but if there was a moisture change after drying, movement and warp were more...in other words, the weights do not stop warp permanently.

Ok?

[WDH]

I just put the best grade boards on the bottom of the stack and top it off with the lowest grade.  The lower grade provides some stack weight for the better grade stuff on the bottom. 

[mikeb1079]

i have very little experience drying lumber, but the little i do have seems to confirm that weight doesn't matter nearly as much as proper sticking, lack of direct sunlight and re-wetting, and the way in which to lumber was sawn (q sawn vs flat)

i try to do what danny does, just put the good stuff on the bottom.

[WDH]

I went from 24" sticker spacing to 16" sticker spacing.  That helps a lot, too. 

[red oaks lumber]

the only thing the weights do on top of bundles is make it dangerous. ;) if you take all the precautions while  stickering and stacking and storing you have a better chance of sucess than adding weight.

[WDH]

Every time that I go to Jake's for a project, I add weight  . 

[logboy]

Not sure about lumber, but if I dont put weight on my slabs when they air dry they curl up like potato chips. I have some white oak rocking slabs as proof. Now everything gets cement blocks right after it is stickered. I'm not sure its possible to have too much weight on top to keep them flat.

[Seaman]

Logboy,
I just got a free bander yesterday, that uses poly banding. My idea is to band under the bearer on bottom of the stack, and put a matching bearer on top of the stack to band across. Three or four per stack. I plan to band as soon as I stack, and leave them banded all the way thru the drying process. If the bands loosen a little I can drive window wedges under the top bearer.
I am hoping this will reduce the movement.
Anyone ever tried this, think it will work ?

Frank

[red oaks lumber]

wood movement cant be stopped, you can put a mitlitarty tank on top if the wood wants to move it will. if a person feels better by adding weight go for it.not for me.

[scsmith42]

Logboy,
I just got a free bander yesterday, that uses poly banding. My idea is to band under the bearer on bottom of the stack, and put a matching bearer on top of the stack to band across. Three or four per stack. I plan to band as soon as I stack, and leave them banded all the way thru the drying process. If the bands loosen a little I can drive window wedges under the top bearer.
I am hoping this will reduce the movement.
Anyone ever tried this, think it will work ?

Frank

Frank, I know of folks that use ratchet straps between the bearers on each side of the stack instead of bands.  About once a week or so, they will give each ratchet strap a click to take up the slack and keep tension on the bearers.  Most of them just use inexpensive 1" wide straps. 

A band approach + shop made wedges is probably more cost effective if you have a lot of stacks to do though.

[Den Socling]

I have in my notes that Gene said you needed only 50 lbs/sq'. That was on March 1, 2008.  ;D I have seen claims up to 400 lbs/sq'.

[logboy]

Frank,

I imagine you can use straps but you need to stay on top of tightening and never forget. Thats why I use concrete blocks. 50 pounds apiece, and I throw them on and walk away. I forgot to put them on a few times over the years (or took them off and forgot to replace them) and ended up with potato chips for slabs. In my experience if a slab is going to warp drastically it will do so in the first few months, not a year or two later. Another option is to saw some thick slabs out of your crappy logs that are split or just plain junk. If you open up a log with your slabber and realize its garbage, just saw it really thick and you have a big weight.  Some of the boys down under drying slabs told me they use jugs or containers and fill them with water or sand.

[Seaman]

 Thanks all, I agree that it is the first few months that make all the difference. I guess all these methods wilkl work as long as you pay attention.
I am using straps now, but sometimes the buckles get in the way. I am going to ry the bander also. My slabber is cutting so smooth now, no planing will be needed as long as I can dry them flat.
Frank

[scsmith42]

Frank,

I imagine you can use straps but you need to stay on top of tightening and never forget. Thats why I use concrete blocks. 50 pounds apiece, and I throw them on and walk away.

That is a very good point.  How many blocks do you put on top of the slabs?  To you totally cover the top, or space them X distance apart?

[Seaman]

I LIKE the crappy log idea too !

[longtime lurker]

A far easier to live with option then concrete blocks is to use 4 gallon plastic drums - the kind with the molded in handle - full of water. They're designed to stack on top of each other, individually are manageable weights, can have the water tipped out to make storage easy, etc etc. Cumulatively the weight in them adds up.

The best weight for a stack of timber though is another stack of timber  ;D just keep rotating the freshest ones to the bottom.

[logboy]

I sticker every 2' and put two blocks, 50 pounds each, every 4' or so. I may put more if its a wide crotch or something I suspect might cup. The thing I like about blocks is that they still permit airflow unlike a five gallon bucket or something that could leave a big black mold circle. Blocks are also cheap and easy to find. I got a couple ton worth for only $50 on craigslist. I've unfortunately sold a lot of discount slabs because I thought simply stickering them was good enough. The top slabs in the stack turned into potato chips or firewood. Now everything gets weight on top. Its definitely not like drying lumber. Slabs are easy to ruin.

[tule peak timber]

An interesting thread....I rotate the drier lifts on top of the greener lifts as we mill . The drier lifts are probably 3-4 thousand pounds. I dry on an 80 foot log concrete slab , and after it fills up (about 20 25 kBF) I start rotating off on to less desirable ground storage on bunks . Round and round we go,,,,Yes there is still degrade ,,,but works pretty well for me.  Rob

[YellowHammer]

I'll add my 2 cents for what it's worth. In my experience, inherently bad acting boards are gonna warp as they dry, not a whole lot can be done about that.  They have internal stresses that can be overcome temporarily with weights and force, but not permanently. A bad board is a bad board.  However, the majority of the boards in a stickered lumber stack are mostly stress free and will dry flat if left in a situation where they have an opportunity to do so, but they can be forced to dry crooked or twisted if influenced by external forces, such as a bad board in the stack that is allowed to move and disturb the orderly spacing of the stack.  I have seen many times where a warped or cupped board in a stack will lift or twist off its sticker and apply pressure to its neighboring boards in the stack and cause them to all dry with some of the same issues, and take on the same warp or crook.  This is especially true near the top three layers of an unweighted or unbound stack and that's why it's a good idea to put good boards on the bottom layers of a stack, to protect them from warping, or more importantly, to protect them from being warped by other adjacent boards.  So a bad board that is warping when it's drying will move and ruin proper sticker spacing, will lift the boards above it, or it's adjacent boards, and warp them if there isn't enough weight or force to keep that particular board squashed flat so as not to disturb its neighbors. It's a domino effect. One bad board can ruin its neighbors.  However, if a stack as a whole unit has a lot of weight or force on it to remain flat, to keep the few bad acting board flat and straight, at least temporarily, then when the stack is later unbundled, the stressed board will still spring and twist and not be flat, but the adjacent boards next to it in the stack, or directly above, will have been protected and will have dried flat because the stack, as a whole, stayed dead flat. 



I use a pallet system to easily keep weight on my lumber stacks with little or minimal extra effort during each phase of the drying process,  Each pallet load of lumber weighs in at several thousand pounds and I typically stack my pallets in the air drying area for several weeks at 3 or 4 pallets high so there is a lot of weight on all but the top pallet of lumber.  With that much weight, a bad board in the middle of the pile may be trying to warp due to its internal stresses, but it doesn't have the force to lift the stack and mess up it's neighboring boards.  As the wood drys and it's time to cycle it in the kiln, I rotate the order of the stacks and put the top pallet of lumber on the bottom with the other pallets stacked on top of it.
In the picture, I put a couple pallets of already kiln dried, dead stacked wood on the right most pallet stack to protect the top stickered stack, and keep it flat.

YH

[ozarkgem]

Good ideas YH. I hadn't thought about a middle board putting stress on the other boards. I like your drying area.

[scsmith42]

I sticker every 2' and put two blocks, 50 pounds each, every 4' or so. I may put more if its a wide crotch or something I suspect might cup. The thing I like about blocks is that they still permit airflow unlike a five gallon bucket or something that could leave a big black mold circle. Blocks are also cheap and easy to find. I got a couple ton worth for only $50 on craigslist. I've unfortunately sold a lot of discount slabs because I thought simply stickering them was good enough. The top slabs in the stack turned into potato chips or firewood. Now everything gets weight on top. Its definitely not like drying lumber. Slabs are easy to ruin.

Good post and pix.  I like how you place some weight close to the ends of the slab too.  Also I noticed that your blocks totally span the width of the top slab - which makes sense as that way the weight is well distributed.

Thanks for sharing this.

Scott

[scsmith42]

YH, that looks like a good system for drying lumber.  Nice air drying shed too!  I've noticed the same thing about a bad board (or a thick sticker) in the middle of an unweighted stack causing the rest of the boards to have a bend in them.

Pretty clever to store your dried inventory on top of the stacks for extra weight too!

[red]

An old waterbed mattress can hold a lot of weight or 55 gal drums plus all you will need is a garden hose

[tule peak timber]

Where my wood goes for the first couple of weeks...

   The slab is flat and full of steel, while the rest of my storage is on dirt. Rob

[ozarkgem]

Where my wood goes for the first couple of weeks...

   The slab is flat and full of steel, while the rest of my storage is on dirt. Rob

are those all slabs?  what size stickers do you use? Do you rotate the top ones out after a few weeks?  Nice looking stack. I guess you don't worry about rain from what I read.

[tule peak timber]

Ozark, That pic is of a job we have ongoing with a college. Yes, all 2 1/2 inch thick slabs on 1/4 inch stickers. I do rotate drier lifts onto fresh cut lifts, then out to the storage yard on dirt ,bunked up. I try to handle the lifts as little as possible as it just eats up time/profits. This year - less than 1 inch of rain so far....

[YellowHammer]

Tule,
Very impressive, no crooked boards in the bottom of those stacks. 8)
What kind of forklift are you using to lift such heavy lumber packs so high?  Looks like the forklift can't get on the concrete pad, but must be sitting on the earth? Is it an all terrain or telehandler?
YH

[tule peak timber]

I call this my "truing slab ". The wood goes here after coming off the mill and doesn't stay here very long, only long enough to drop moisture significantly before going to other storage in pole barns or an open lot on bunks. Works pretty well for my style of work , but as someone pointed out earlier in the thread , errant boards still develop twist and crook - no matter what....I use a Champ all terrain forklift , and recently bought an additional Cat R-80. Both are high lift units . The reason I don't stack higher is because of the frequent earthquakes at my place and the seasonal high winds. I think I get better results with more weight...... Rob

[ozarkgem]

never thought about earthquakes knocking your stack over. That would suck.

[tule peak timber]

Not to discount the wind either...A year or two ago wind tumbled some oak boards across the yard and took out the running board and door panel on a blazer parked 50 feet away from the stack. If I run rain covers I use 1/2 inch rope to double tie the cover to the stack. We learn the hard-way around here  ;D

[jimF]

While some weight may be helpful, and non straight grain attributes to the problem, the biggest factor in lumber distortion is non uniform air flow.  More air flow on one side of the board is the cause of most lumber distortion, in or outside the kiln.  It does not matter whether the lumber is thick or thin it can either be kept flat with uniform airflow or made into a pretzel with nonuniform airflow.

[Den Socling]

I don't know about that. Thick pieces can have more grain variation and can be more difficult. I've seen them lift plates in my vac kilns. With no air flow.

[jimF]

there's your problem - no air flow 

[Den Socling]

 :D

[Kingcha]

I made a weight this summer and have only just used it.    I basically built a 4x4 pallet with built in stickers on the bottom to give plenty of air flow.   The top I just poured a 3" layer of concrete in a box.   I am able to lift it with my bucket forks and place it on top of the pile.   It seemed faster then hand piling blocks.

Matt

[ozarkgem]

I poured a floor the other day and I made a form out of some 2x12's 4' long and used the left over concrete to make some weights. I put a rebar lifting eye in them also

[Glenn1]

I was looking at Yellowhammer's post and the picture of kiln dried lumber sitting on top of pallets of green lumber.  From reading his web page, I understand that he will be out of commission for awhile recovering from a hip transplant.

I was wondering how long you could leave the kiln dried lumber  "out in the open" before the moisture content would considerably increase. Would it still be considered "kiln dried lumber"?

Yellowhammer, hope you are feeling better  and that you will be running marathons in no time.   ;D

[WDH]

If the kiln dried lumber is dead stacked, it will take a good long while for it to gain a lot of moisture except for the top boards that are exposed to the air.  I suspect that it would take months, but the kiln dried will eventually resort back to air dried. 

[Glenn1]

If the kiln dried lumber is dead stacked, it will take a good long while for it to gain a lot of moisture except for the top boards that are exposed to the air.  I suspect that it would take months, but the kiln dried will eventually resort back to air dried.

Does the term "dead stacked" refer to lumber where the stickers have been removed?

[WDH]

Yes, also referred to as "flat stacked".  This would keep the air from circulating between the boards and significantly slow down the process of the wood re-absorbing water from the environment.  Covering the flat stacked, kiln dried wood with plastic will also significantly slow down the process.

[YellowHammer]

 

Covering the flat stacked, kiln dried wood with plastic will also significantly slow down the process

Normally, our kiln dried lumber sells as fast as I can process it, so it doesn't get much of a chance to regain moisture before it's sold and gone.  However, whenever we have inventory that will not sell quickly, such as now due to our temporary shutdown, we wrap it in plastic to provide protection from insects and environmental moisture.  Below is a picture of some of our air dried and kiln dried lumber ready to go into a holding pattern.  We purchase bulk plastic wrap from either Lowes and Home Depot.

The unweighted and under length pallet of high grade cherry in the foreground is going to be a problem as it dries. 
Yh

[Brad_S.]

  I am going to try the bander also.

Since the lumber shrinks when it dries, the bands will loosen in short order and become useless. Just wastes banding. I know this from experience.  :

I have 13' pieces of railroad track that I put on my Koetter kiln loads. I feel it helps the top layers hold flatter and with each charge being only 500 bdft or so, every little bit helps.

[beenthere]

YH
Am aware that you are healing up from the new hip, but why would lumber sales need to go into the holding pattern? Just curious..

Hope the hip heals for a speedy recovery.

[WDH]

The lumber does not get sawn, stickered, put into the kiln, planed, then put into racks unless someone with with two hips does it  . 

[Den Socling]

And I can't imagine climbing on and off a fork lift with bad hips.

[beenthere]

I realize that, but was thinking sales could be just monitoring the buyer while they load the sellers lumber.
Was only thinking of the dry lumber stash here... not sawing, drying, stickering, stacking...etc.  ;)

But if not possible, then I understand sales can't take place. Closed sign up.

And I do realize one doesn't want just anybody running your equipment... or tearing into your lumber piles.
But is not like you are not there to give directions and monitoring your stash.

[YellowHammer]

Beenthere, very good question, and I've started a new topic in the Full Membership Business Board where I will try to reconfigure our Mom and Pop business to prevent it from literally crippling me.

And I can't imagine climbing on and off a fork lift with bad hips.

It doesn't work well...7 weeks ago, I hung my left foot in the tractor steps because my right hip suddenly locked up, hit the ground with my foot trapped, and ended up tearing my meniscus in my left knee. Duh!  That surgery will be sometime in December.
YH

[5quarter]

I don't weight any of my stacks. After the stack is built, I lay one more course of stickers and lay down sheets of 3/4" OSB. On top I lay 2 good RR ties to keep it from blowing off. on top of that I screw down some corrugated tin to keep the rain off. if its Oak, I use a Shade dri type material under the OSB that curtains the front and back of the stack to restrict airflow. I'm with Jim F, uneven airfow is the primary cause for many drying defects.

[logboy]

I sticker every 2' and put two blocks, 50 pounds each, every 4' or so. I may put more if its a wide crotch or something I suspect might cup. The thing I like about blocks is that they still permit airflow unlike a five gallon bucket or something that could leave a big black mold circle. Blocks are also cheap and easy to find. I got a couple ton worth for only $50 on craigslist. I've unfortunately sold a lot of discount slabs because I thought simply stickering them was good enough. The top slabs in the stack turned into potato chips or firewood. Now everything gets weight on top. Its definitely not like drying lumber. Slabs are easy to ruin.

I came across this thread while looking for something else and figured I should add a couple points in regards to drying slabs. I have to say it again, slabs are not lumber. They have their own issues and challenges to overcome that are a lot different from lumber. What works for lumber usually doesn't work for slabs.

Adding weight to the top of my slabs keeps them flat during air drying, but there's a tradeoff. Remember, wood shrinks more around than it does across (tangential shrinkage is greater than radial shrinkage). Because of this, slabs always want to warp toward the outside of the log. So above the pith they cup up, and below the pith the cup down. The pith slab usually does a bit of both, but because it's trying to warp in both directions, cracks.  That right there should tell you something. Its essentially a battle between warping and cracking. If you don't want it to warp, then you have to overcome the structural integrity of the cells so that they crack, and the slab stays flat. Those are your two choices: a warped slab or a cracked slab. In a perfect world we could cut slabs that were cupped toward the pith and then let them dry without weight, and they would warp toward the outside, end up flat and without cracks. (Im good with a slabber, but not that good.)

Please note that this tactic I use to keep them flat doesnt really work in the kiln. In air drying the process is much slower and its easier to make them crack. In the kiln the drying, warping, and shrinking process happens a lot faster and its a lot more difficult to make them crack. Ive tried hundreds of pounds and they still warp. I will say this, the longer you can air dry them with weight on top, the flatter they usually stay in the kiln. I have planed massive slabs that I cut for other people that they kiln dried, and mine are always flatter. When a slab I cut at 3" thick still doesnt clean up at 2", you know its warped. And if the slab doesnt clean up at 2" and gets thinner, then its no longer a slab, its just a wide board. Most of the warping in slabs happens during air drying, not in the kiln. Keep them flat and weighted during air drying and you'll have better success in the kiln.

Just my two cents, take it for what its worth.

[Seaman]

Good addition to this thread, thanks. My banding idea never got off the ground good, I came across some blocks, so just do it your way. hanks.
Frank

[YellowHammer]

I've been sawing more slabs myself, lately, as I've always had drying issues with thick stuff.  I've been a lot more selective of where I take my slabs from the logs, and have been getting much more stable and flat results. 
Air drying boards, I still like to stack high and heavy. 

[logboy]

Good addition to this thread, thanks. My banding idea never got off the ground good, I came across some blocks, so just do it your way. hanks.
Frank

Don't band, it's a waste of time. Not only do they never stay tight, but remember, you are only trying to apply force in the downward direction to keep them flat. Banding squeezes them in all directions which is completely unnecessary. I've seen photos of other people's operations where they prided themselves on how careful they were about stacking and banding their walnut slabs to keep them flat. You could actually see the bands hanging loose on the stacks, not doing anything.

[GeneWengert-WoodDoc]

Banding, especially if the bands are tightened every day, does indeed help in at least two ways.  It keeps the loose slabs on the top of the pile from falling off the pile, especially in high winds or in a kiln with monster fans.  Plus, I have never seen any elephants in a yard where the bands are used, so I think bands also repel elephants.

When I first started in this sawmill industry 50 plus years ago, a slab at the sawmill referred to the first piece cut from a log...flat on one side and rounded on the other.  It was never used to make lumber, but it was trash and usually burned.  It seems that only recently, with the high popularity of the small sawmill, that a thick piece of lumber and a thick piece of wood that has been not edged has been called a slab within the sawmill industry.  Years ago, a partially processed piece of wood at the mill was called a flitch or a cant...such pieces needed further processing to make lumber.

So, what does a person today mean when calling a piece of wood a "slab?"

[xlogger]

I've been in the forestry business for over 40 plus years now also, just 10 short of Gene (just a kid here Gene) and I know what he talking about with the slabs. When people call and want a slab I have to ask if they want a live edge for woodwork or a slab off the first cut of a log to burn.

[YellowHammer]

When I first started in this sawmill industry 50 plus years ago, a slab at the sawmill referred to the first piece cut from a log...flat on one side and rounded on the other.  It was never used to make lumber, but it was trash and usually burned.  It seems that only recently, with the high popularity of the small sawmill, that a thick piece of lumber and a thick piece of wood that has been not edged has been called a slab within the sawmill industry.  Years ago, a partially processed piece of wood at the mill was called a flitch or a cant...such pieces needed further processing to make lumber.

So, what does a person today mean when calling a piece of wood a "slab?"

The slabs off the logs that go into the burn pile are "slabs" spoken with a grunting caused by the exertion of taking them off the mill and throwing them away.  

The other slabs are pronounced with special cash money emphasis on the ends of the word, spoken as "slab$$" and some of the best examples I know are from FF members @POSTONLT40HD, and @WDH, et al) who have cracked the code on them.
New experiment for me. in General Woodworking

[PA_Walnut]

I would like to revive this old thread to get some ideas of how you all put weight...REAL weight on top of air drying stacks. I've noted a recurring them from Yellow about this and how to keep boards true and straight, so need to re-focus on this on my end.

Any tips of pics of what it looks like on top your piles, would be great! Thanks!

[WDH]

Mostly I use other stacks as weights.  I put the most recently sawn stacks on the bottom of the drying pads and stack other stacks, that have mostly air dried, on top for weight.  I also have one pallet with a single layer of cement blocks that I use to top the stacks that go into the kiln. 

[scsmith42]

Similar to Danny I'll use other stacks as weights, or concrete slabs.

Years ago I scored some 4" thick concrete slab sections from a sidewalks that was being removed.  They work great forked on top of the stacks.

[YellowHammer]

Weight on top of stacks help save money and wood.  Other stacks of wood, concrete, septic tank lids, marble, bricks, block whatever will make a significant improvement, especially in the top few layers of drying stacks.    

For thick slabs, it's a little more complicated.  The slabs should be stacked with their major predicted cup opposite the one below or above it on the stack, or they will all try to cup the same direction and if there is flexibility in the stickers they will all try to conform to the same cup.  So I stack the cup contrary to each other, so they fight each other, and will reach a neutral flat common plane.

The meaner and thicker the slabs, the stronger and less flexible the stickers I use, and the fewer layers of slabs on each pallet.  The runners on the pallets are very stiff and will provide some physical isolation between packs of slabs.

My weight stacks generally weigh from 3 to 5 thousand pound, and every load that goes into the kiln gets one.  These weights also significantly reduce "stack bow" in air dried wood.  I also like to keep some sort of weight on the stacks as they cool down.  Personally, my favorite weights are waste marble countertops loaded on full bodied pallets.  Marble is very dense and keeps the weight stacks shorter, so as not to lose much kiln capacity. 

[WDH]

Remember, wood cups toward the bark, not the pith.  This is counter-intuitive.