Australians and New Zealanders your help is needed

[black]

I have tried over the last couple of years to dry Eucalyptus but can't come up with a win formula every time. The timber dries straight but still shrinks after 12-24 months drying. It is such a beautiful timber and there is a fair amount by me that I would love to master it. Some of u guys use Red River Gum (Camaldulensis) for flooring and that's one of the hardest to dry. I would never even attempt to use that inside a house as flooring.
I do roofing with big exposed beams and t&g boards/planks on top. I also use t&g boards/planks for flooring. That is what most of my wood gets used for.
My beams always go in "wet" and there is never a problem with them. My boards/planks get cut 140mm-150mm wide and 28mm thick. We sticker them and air dried for 12-24months. We start moulding them at 15% moister content to 130mmx22mm for roofs and floors. I do this work in Poplar and Pine wood which I don't have to wait so long for the timber because it could be kiln dried.
Is there any advise to get pass the shrinking of the boards?
On a outdoor wood deck the joint were the 2 heads of the walking surface meet will shrink in length with 5mm on each board making it look horrible.
I use a open groove with a 7mm tung and the some time move so far apart that there is a 3mm space.
Any advice please.

[black]

Here you can see the boards starting to move on the t&g.

  

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[JustinW_NZ]

Are you quater sawing it?
All our flooring and decking we quater saw it all - no exceptions..

Drying time seems high but i dont know what your climate is?

Camaldulensis is lovely stuff and not one of the biggest movers out there.
Also if you have material with big limb/knots/defects in the boards expect them to do weird things.

We also dry to 15% or under and profile it then, i see the odd bit still shrink however and we are moving to a kiln as we speak to drop it lower / more consistant.

Cheers
Justin

[Ianab]

Think you will need to get that Eucalyptus drier before you machine and install it. It's moving in place because it's still drying and shrinking.

You get away with partly dry wood with pine and other more stable species, but most Euc species are pretty unruly, with large amounts of shrinkage, and it's uneven which makes things worse. Not sure what your climate is exactly like, but I suspect that up there at the ceiling things are getting pretty dry? It would be worth going up there with a meter and and seeing what the MC of the wood is now?

We can usually get away with ~15% wood here because of our humid climate, wood averages ~13% inside. But a drier climate it will go lower.

Maybe a solar kiln to finish off the drying process? It wont take long to get from the 15% down to under 10. Then most of the shrinking and movement will be out of the way.

Like Justin says, quarter-sawn should give you better results, and selecting clear pieces, as any knots are going to move like crazy.

[longtime lurker]

Saying Eucalypt is like saying pine... theres a whole lot of them out there and they vary considerably.

Camaldulensis isn't a particularly difficult species. Relatively speaking of course.

Radial Shrinkage about 4%, tangental shrinkage 8%. Shrinkage after reconditioning 2.5% radial, 4.5% tangental if you have access to a steam chamber

So heres the thing...  if you expect big in service moisture shifts you should quarter saw it, otherwise you can just allow for the extra shrinkage in backsawn material.By big I guess I mean a seasonal change of 5% EMC or more, anything under that is negligible.

I dont know why its taking so long for your timber to dry but in any case the best bet would be to kiln finish it. Most eucalypt processors will air dry down to 18% or less before kilning. Its euc... bugs and fungus dont worry it and it can sometimes take a while to get the free moisture out... SOP  is not to try and kiln out free water because it just wastes electricity. Below that 18-20% mark it can be kilned relatively easily - dont quote me but its probably British Schedule C (US T3-C2)  which is pretty much the standard baking directions for eucalypt and related species.

If you do get big in service moisture shifts it might be wise to investigate using a VJ profile rather then T&G. VJ handles moisture shifts better.

[GeneWengert-WoodDoc]

Wood does not change size or shape except when it's moisture changes.  So, Ianab has the correct info.  Note that the ceiling of a home or office is usually or often one or two percent EMC drier than the rest of the dwelling, as hit air rises and hot air will have a lower humidity than the cooler air below.  So, 11% may not be dry enough for a ceiling.

[black]

Our summer temperature is between 25-27 degrees Celsius and winter 17-19 degrees Celsius. The cold nights at its coldest about 7 degrees but never colder than 5 degrees.
Rains in the winter months and summer is dry.
Humidity in the winter average 95% or more and in the summer about 51% but can go as low as 44%.
I am at the coast and the timber don't dry under 12% moister content. You can put it in a kiln and go to 8% but it will raise again when its out.
Eucalyptus diversicolor is also plentiful here and nobody wants to use it, could it be used for flooring?
Could the shrinkage be that much from 15% to 12%? How long would you say it should air dry before it goes to a kiln and at what heat in the kiln?

[black]

How long would you say it should air dry before it goes to a kiln and at what heat in the kiln?
Longtime lurker thanks (British Schedule C (US T3-C2) ).

[JustinW_NZ]

Our summer temperature is between 25-27 degrees Celsius and winter 17-19 degrees Celsius. The cold nights at its coldest about 7 degrees but never colder than 5 degrees.
Rains in the winter months and summer is dry.
Humidity in the winter average 95% or more and in the summer about 51% but can go as low as 44%.
I am at the coast and the timber don't dry under 12% moister content. You can put it in a kiln and go to 8% but it will raise again when its out.
Eucalyptus diversicolor is also plentiful here and nobody wants to use it, could it be used for flooring?
Could the shrinkage be that much from 15% to 12%? How long would you say it should air dry before it goes to a kiln and at what heat in the kiln?

Sounds similar too where I am in NZ.

I have some Euc stacks (e.regnans) at 12.5% out back right now and thats as good as i ever see them air dried. (10 months to get to that point)

For kilning them we have gone down the path of a dehumidification kiln as we can pop the wood in a little sooner and not have issues with it.
Simple recondition cycle at the end as well. (evens out the moisture in the wood so any movement is predictable.)

Otherwise good info from the others as always!

Cheers
Justin

[GeneWengert-WoodDoc]

A little help about vocabulary for some readers...in most of North America, getting the final moisture content uniform is called equalizing.  The kiln settings are usually 2% EMC lower than the final MC target.  Then to relieve the stress (drying stress is also called casehardening), we steam the lumber at the end using an EMC about 4% above the final target.  This process of stress relief is called conditioning.

  However, the drying stress when air drying is very close to zero, as the humid conditions in the early morning relieve a little of the stress every day.

As you know, the eucalypts species have a large amount of growth stress which is not affected by final steaming or even much by presteaming.

[longtime lurker]

A little help about vocabulary for some readers...in most of North America, getting the final moisture content uniform is called equalizing.  The kiln settings are usually 2% EMC lower than the final MC target.  Then to relieve the stress (drying stress is also called casehardening), we steam the lumber at the end using an EMC about 4% above the final target.  This process of stress relief is called conditioning.

  However, the drying stress when air drying is very close to zero, as the humid conditions in the early morning relieve a little of the stress every day.

As you know, the eucalypts species have a large amount of growth stress which is not affected by final steaming or even much by presteaming.

Presteaming? Not a term I'm familiar with, so would appreciate a translation.

Here, in mills that work with the high shrinkage rate species, a high degree of collapse is expected. it's common to have a dedicated steam reconditioning chamber. Timber is air dried to 20%, then the stacks go into the steam reconditioner and wet steam is applied. The application of wet steam allows the timber to rehydrate in such a fashion that most of the collapse disappears and it "bounces back" to pretty close to nominal dimensions. The timber then proceeds to the kilns for drying (and a reconditioning cycle at the end subject to kiln type.) we'd call the in kiln equalization process " final reconditioning".
When I quote numbers for shrinkage after reconditioning it refers to the application of a pre kiln steam reconditioning process, not a post kiln equalization process.

Are we talking about the same thing?

[longtime lurker]

How long would you say it should air dry before it goes to a kiln and at what heat in the kiln?
Longtime lurker thanks (British Schedule C (US T3-C2) ).

My understanding is that above 20% MC we're dealing with free water ( water between the cells of the wood) and below it we are removing "bound water" which is water inside the wood cells themselves.

Free water runs out pretty quickly, sometimes too quickly. For me here it might take anywhere from three weeks to three months depending on seasonal conditions to drop from "still got leaves on it" MC to 20%. Go west of me 100km and it might do that same moisture loss in 48 hrs and you run into issues with severe checking.

Bound waster is what takes time, or kiln time. It might take us another three months to 12 months to get to EMC which here is 14.5%. The rest of Australia requires lower MCs then us so no matter what we'd have to kiln to sell outside the local area. Regardless of my situation though the " year per inch of thickness" rule of thumb is pretty right for eucalypts if you've got decent airflow through your stacks.

Or bang it in a kiln and turn the timber into $ in a fraction of that time.  once you get the moisture level below 20% you can run the kiln hard without risk of too much degrade.

[GeneWengert-WoodDoc]

Note to L Lurker...it is indeed true that wood cells do not shrink until the free water is gone, at about 28% MC (sometimes rounded to 30% MC, and some tropical species are 22% MC).  However, for a piece of lumber, the cells on the surface reach under 30% MC very early in drying and begin to shrink or try to shrink.  The average MC of the lumber at this point can be over 75% MC.  Drying continues and more of the shell cells are under 30% and shrinking.  If they were fee to shrink, we would have no drying stress, but because they are restrained by the wet core, they dry in a stretched out condition, which is called drying stress or casehardening.  When the lumber is at an average of 25% MC, it is likely that some of the core cells are over 30% MC and have not begun to shrink...they still have free water.  Even though the AVERAGE MC is over 30% MC, you will see the lumber is actually shrinking.  So, we do need to consider the individual cells and then the total effect of all the cells combined.

Your description of collapse and recovery is exactly how we dry cottonwood and redwood...the two main species prone to collapse.  We do try to dry these species quite slowly, as collapse is much worse when we go fast.

In North American, we never (99.99%) use a separate conditioning chamber, but do the final steaming inside the kiln.

Pre-steaming is the process of steaming never dried lumber, usually on stickers, usually at atmospheric pressure and at 100% RH, in order to "soften" the wood and decrease the risk of collapse, wet pockets, and growth stresses, and perhaps to darken the sapwood and heartwood color.  It would be done at 95 C or a bit hotter, 100% RH, for 24 hours or maybe up to 76 hours.  Growth stress decrease seems to be slight.

[black]

Would air drying for 2 months be to short before kiln drying and how long would it be in a dehumidifying kiln? What would you estimate the moister content after 2 months air drying?

[longtime lurker]

E. diversicolour grows about as far away from me as its possible to get in Australia. Never seen it, much less milled it. But I have  a coppy of Bootle, which is one of the standard reference works for the Australian Timber Industry.

Attached scanned copy of page from Wood in Australia, Types Properties and Uses by Keith R Bootle.