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Drying thin (<1") slabs

Started by JoshNZ, November 21, 2020, 04:31:07 PM

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JoshNZ

Is this something that can be done with any reasonable chance or are through sawn slabs under 1" likely to cup?

I've got a customer wanting a bunch cut for serving platters in a new restaurant built. Wants them for January which I told him is super risky but he seems to want to push ahead, full warning received. I may be able to get them into a kiln but even if I do, are 1" slabs both live edge going to stay flat?

Likely will be Tasmanian blackwood

firefighter ontheside

I know nothing of tasmanian blackwood.  I have cut thin slices of walnut to get down to a good starting point and thrown them aside.  Months later they have dried well in a pile by the mill.  I have also had thin slices dry in a crown.  I think if you stack and sticker it correctly, probably more stickers than you're used to, you stand a decent chance of success.
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Ianab

For the Nth American folks, Tasmanian Blackwood is an Acacia species closely related to Hawaiian Koa. It does seem fairly stable drying, but it's prone to heart checks around the pith. 

If you are going to try I'd say HEAPS of weight on the drying stack, stack them in the lower 1/2 of a bigger stack, or some heavy duty ratchet straps that you can crank down every few days to keep the pressure on. With thin boards it's more practical to try and force them flat as they dry, and they will probably mostly stay that way. The centre cut ones will tend to crack in 1/2 down the pith, but the 2 pieces will be quarter sawed, and probably the most stable. 
Weekend warrior, Peterson JP test pilot, Dolmar 7900 and Stihl MS310 saws and  the usual collection of power tools :)

doc henderson

i am not familiar with that wood, but sticker and stack with weight on top.  not sure if it can go that fast, if not in a professional kiln.  i have to dry 1/4 inch stuff for coaster stock for my engraver.  dry, then plane it flat.  may need to allow for some loss.  does he want solid wood.  if they cup, can be sawn into narrow stuff, jointed and glued up.  planed, and live edge glued on.  lot of work if that is the plan.



 

here is my latest attempt to mill thin and dry and then plane.  in the heater at 120, in a press with clamps i tension each day.  battery operated fan.  @GeneWengert-WoodDoc may be familiar with your species.
Timber king 2000, 277c track loader, PJ 32 foot gooseneck, 1976 F700 state dump truck, JD 850 tractor.  2007 Chevy 3500HD dually, home built log splitter 18 horse 28 gpm with 5 inch cylinder and 32 inch split range with conveyor powered by a 12 volt tarp motor

GeneWengert-WoodDoc

The closer that the wood is to the pith (log center), the more likely that the wood will cup.  Cupping is a natural tendency in wood, but is accentuated by drying slowly, by rewetting partly dried wood, and by over-drying.  If the slab does not have any rings with about 15 rings of the pith, it is likely to remain flat.
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Ianab

Quote from: GeneWengert-WoodDoc on November 21, 2020, 09:04:59 PMIf the slab does not have any rings with about 15 rings of the pith, it is likely to remain flat.


Probably tricky with local Blackwood. It's a fast growing tree. Couple of logs I've milled were about 30" dia and only 30 years old. But apart from issues with the heart checking it seems to behave pretty well. 
Weekend warrior, Peterson JP test pilot, Dolmar 7900 and Stihl MS310 saws and  the usual collection of power tools :)

DDW_OR

Quote from: JoshNZ on November 21, 2020, 04:31:07 PM
Is this something that can be done with any reasonable chance or are through sawn slabs under 1" likely to cup?

I've got a customer wanting a bunch cut for serving platters in a new restaurant built. Wants them for January which I told him is super risky but he seems to want to push ahead, full warning received. I may be able to get them into a kiln but even if I do, are 1" slabs both live edge going to stay flat?

Likely will be Tasmanian blackwood
serving platters, 12x18 inches? or 30x45 centimeters
Just flat live edge boards
without bark
recessed hand holds?
center part recessed for plates?
did a search for Tasmanian blackwood, very good. wish i had some here in Oregon
"let the machines do the work"

YellowHammer

On North American species yes for which I have experience, yes, certainly they will try to bow and cup.  

Bow won't be a problem because the boards will be cut short into platters after drying.    

Cup won't be a problem if you mill them over size, use lots of weight in the stack, and plane them flat.  

I sell lots of 1" thick live edge for chakutery boards.  
YellowHammerisms:

Take steps to save steps.

If it won't roll, its not a log; it's still a tree.  Sawmills cut logs, not trees.

Kiln drying wood: When the cookies are burned, they're burned, and you can't fix them.

Sawing is fun for the first couple million boards.

Be smarter than the sawdust

JoshNZ

All great responses thanks. I'm doing them tomorrow regardless - I told him to have a backup plan in case it goes pear shaped. A month air drying is crazy but it's his decision I guess. I'll keep them myself if he decides not to, I can rip and glue up.

It is quite pretty wood, certainly easier to saw than the walnut logs I have. I was relieved to see the first opening cut not moving on me



 

 

 

I've got about a dozen logs ~35" wide that came with the walnut lot, but they were on the first truck so have been buried until now.

I'm thinking about milling it into outdoor decking for my place haha what do you think @Ianab I've never seen it done, I always wonder if it's too nice for that or unsuitable

YellowHammer

Bow and cup are reasonably predictable, no reason not to do it. 

What is the maximum allowable moisture removal rate for this species? That will tell you how much you can push it.  For example with poplar with better than 10% allowable per day, I can put fans on it and easily pull it down in a month.  You may be able to do the same.  
YellowHammerisms:

Take steps to save steps.

If it won't roll, its not a log; it's still a tree.  Sawmills cut logs, not trees.

Kiln drying wood: When the cookies are burned, they're burned, and you can't fix them.

Sawing is fun for the first couple million boards.

Be smarter than the sawdust

doc henderson

how many platters and what size for sure?  can you make a small heated chamber to speed and control the process.  Outside air dry will be slow, and they may not self destruct until months after in service.  sounds like he wants it done no matter what, so you can add on for expenses maybe.  make sure the he is aware (as it sounds like you have) so it does not come back on you if they curl or split down the road.  please cont. to send pictures so we can see how it turns out.  good luck.
Timber king 2000, 277c track loader, PJ 32 foot gooseneck, 1976 F700 state dump truck, JD 850 tractor.  2007 Chevy 3500HD dually, home built log splitter 18 horse 28 gpm with 5 inch cylinder and 32 inch split range with conveyor powered by a 12 volt tarp motor

JoshNZ

I don't know the max removal rate, I've only ever air dried so it's not something I've looked into. I did read an article saying rapid drying in kilns had been done successfully so I guess I will hammer it and hope for the best.

I think the goal was 80x 250x450mm boards, 20mm thick, so I'm at multiples of that each way (1 live edge was fine). I've cut at 25mm, not sure if that's a mistake or not, gives a lot of room to play with but also wastes 20% of what I've cut.

I couldn't stop taking photos of the stuff while cleaning up, seriously pretty. Too pretty for decking I think



 

 

 

 


doc henderson

they are great looking.  not sure of the dimension but I would get stickers out on the ends to keep them from twisting, and maybe another one in the pile.  so at least 3 on the short pile and four on the longer one.  strap them down or get weight on them.  If the stickers align, you could put one in front stack of the other and blow both fans on them.  might alternate the side the fans are on daily, since there is not baffle to force it all the way through.  let them dry, and plane them to a good finish.  like they say in preschool, "you get what you get and you don't throw a fit"!  if they have to be a little thinner, then so be it.  looks like it will a strong wood when it is dry.
Timber king 2000, 277c track loader, PJ 32 foot gooseneck, 1976 F700 state dump truck, JD 850 tractor.  2007 Chevy 3500HD dually, home built log splitter 18 horse 28 gpm with 5 inch cylinder and 32 inch split range with conveyor powered by a 12 volt tarp motor

doc henderson

some will put two stickers out near each end, to slow the end drying and checking.  so 80 is the total number.  so 25.4 mm = 1 inch.  so your 20 mm thick is just over 3/4 inches thick.  3/4 is common for us here.  could be less if needed to get them planed.  and about 10 x 18 inches.  I assume you will leave the width whatever the board happens to be to keep the live edge?  nice .  just converting for us SAE folks.  each place you see a knot, it going to try and bend, so more stickers.   :)
Timber king 2000, 277c track loader, PJ 32 foot gooseneck, 1976 F700 state dump truck, JD 850 tractor.  2007 Chevy 3500HD dually, home built log splitter 18 horse 28 gpm with 5 inch cylinder and 32 inch split range with conveyor powered by a 12 volt tarp motor

PA_Walnut

Quote from: doc henderson on November 23, 2020, 05:06:35 AMsome will put two stickers out near each end, to slow the end drying and checking.  


Yes indeed! Get some stickers as close to the ends as possible. Seems like sawing them thin and hoping for the best is false economy. Wouldn't he be better off getting material that's already dry? (unless it's his own log, I suppose, but then it's a risk:reward ratio that he'll have to own, based on your cautions.) Collect your funds sooner, rather than later! :)

I regularly saw super-wide poplar 1/2" or so for drawer bottoms, but it behaves well with weight on it and I am aiming for 1/4-3/8" so it works fine.

Best of luck.
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From what I can find for kiln schedules it is similar to a soft maple for the North Americans here.

Josh, for hardwood drying that basically means that it will dry in the middle of the pack. You should be safe at 8-10%/day. That's a cautious number on my part.

I also noticed it is a tone wood for the luthiers out there. Josh just became a source for you.
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doc henderson

you can add end coating to reduce end splits as well like ancorseal.  in a dark wood, the stickers being dry is not quite as critical as in light wood.  did these logs start green?  could cut up some of the same log scraps for stickers, but looks like you have a lighter wood already for stickers.
Timber king 2000, 277c track loader, PJ 32 foot gooseneck, 1976 F700 state dump truck, JD 850 tractor.  2007 Chevy 3500HD dually, home built log splitter 18 horse 28 gpm with 5 inch cylinder and 32 inch split range with conveyor powered by a 12 volt tarp motor

doc henderson

Timber king 2000, 277c track loader, PJ 32 foot gooseneck, 1976 F700 state dump truck, JD 850 tractor.  2007 Chevy 3500HD dually, home built log splitter 18 horse 28 gpm with 5 inch cylinder and 32 inch split range with conveyor powered by a 12 volt tarp motor

kantuckid

Maybe build a box with a regular home dehumidifier inside? The man I spent much time with learning more about chairmaking used basement humidifiers to dry his own wood. He'd done it for years when I saw his crude drying "box". The downside of his was that the acid woods ate the alu coils on his backwoods drier boxes. He used thin alu sheets over a scrap wood, crate style, break down frame.
Man made a living doing chairs and tables his entire lifetime. He used rocks and concrete blocks for top weights. 
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JoshNZ

Reading your suggestions I'm awfully dubious of whether or not you guys aren't just trying to trick me into building a kiln  headscratch lol

Which I would love to do... I've got my eye on a 20ft insulated container. I figure that is the easiest short term answer as you can always sell a container second hand. Dont know how many guys there are out there in the market for a second hand kiln.

It's a waste of time running these fans overnight when the temp drops right? I was looking at their nameplates yesterday, theyre not small fans. And they're sucking on all three phases, I don't know if their amp rating means per phase or combined. The shed space they're in must be over 300m2 and the whole place is drafty with them on. I crouched down behind the stack and it's still windy enough behind them to blow hair around etc. I guess I should find a cheap single phase fan to keep 24/7.

I'm getting around to restacking with stickers on end as suggested. I'll strap them up then I'm going to make a tin roof for them and leave them outside for the hotter days. We have a massive asphalt that gets really hot but I don't imagine direct sunlight will do them any good.

JoshNZ

I don't want to build anything because if I do it will be a proper kiln and I don't want to halfarse it to rush a single order of timber. Thanks for suggestions though!

doc henderson

not trying to push in the kiln direction for any reason other than help you get this done fast.  :) at least it will be a rustic product.  look at the temporary plastic wrap that mimics a solar kiln.  I have used it a few time and got down to 7% moisture.  timbergreen simple cycle solar kiln.

Timber king 2000, 277c track loader, PJ 32 foot gooseneck, 1976 F700 state dump truck, JD 850 tractor.  2007 Chevy 3500HD dually, home built log splitter 18 horse 28 gpm with 5 inch cylinder and 32 inch split range with conveyor powered by a 12 volt tarp motor

YellowHammer

You only need to run the fans when the air coming out is colder than the air going in.  Basically, the wind is evaporating the moisture off the wood and cooling the air going through the pack.  The hotter, faster and dryer the air goes in the front, the more wet cool wet air comes out the back.  The wetter the wood and the hotter the air, the better it works.  You should be able to feel the noticeaby cool wetter air coming out the back.  Most times at night when things cool down and the humidity of the night air comes up, the effect is reduced, you could turn them off.

The chart below shows how fast green wood can be dried with fans, assuming the outside conditions are right.  The drying rate on the left is % drying rate per hour, which can be real fast.  As the wood dries, the effect of the fans will decrease so they are great for getting the wet wood down fast.

I use two barrels fans blowing on the stacks to get the moisture down fast.  A stack in front of the fans, two fans side by side taking up 8 feet, then a pack of lumber on the back side of the fans.  Basically a fan sandwich.

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YellowHammerisms:

Take steps to save steps.

If it won't roll, its not a log; it's still a tree.  Sawmills cut logs, not trees.

Kiln drying wood: When the cookies are burned, they're burned, and you can't fix them.

Sawing is fun for the first couple million boards.

Be smarter than the sawdust

JoshNZ

Quote from: YellowHammer on November 26, 2020, 07:56:00 AM
The wetter the wood and the hotter the air, the better it works.  You should be able to feel the noticeaby cool wetter air coming out the back....
1.4C cooler, even! I thought it did feel cool and I knew I had a probe somewhere in the drawer there. ~2.5 degrees Fahrenheit across 500mm of board.
Days 2 and 3 were so wet here all my machining equipment had water dribbling off it. Shed doors closed, and so foggy the concrete floor on the back wall was damp. I really hate that kind of weather, have to spend a bit of time drying off and oiling all the machinery.
So I guess we are really drying as if it were day 2 now.
I had a look at your log processing thread there doc. Perfection haha xD.

JoshNZ

I had another idea today as we are getting sick of listening to those two fans running all day...

If I restacked those slabs into four even length/height stacks and put them on the floor in a square, could I put a piece of plywood overtop of them and have a fan pulling on a hole in the plywood? I've got a few more evaporator fans up in that coolstore that look a bit more tame, big broad blades that don't spin at mach1 I think they'd be more tolerable.

Right now I'm blowing about a horsepower of air at it and while plenty is going through I'm sure about 90% isn't. I worked out the pair of them cost about 22c an hour to run, not too bad but not so great after a month

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