# An idea for drying slabs



## BobL (Aug 25, 2007)

How does this sound as an idea for a drying shed for slabs?

A used seatainer resting on a steel frame about a foot above the ground.
Cut a series of 4" diameter holes in the bottom/sides and fit a couple of whirly bird (rain proof wind driven) fans on the top? Seatainers get pretty hot just sitting in the sun and especially where I live where it gets into the 90's and 100's (F) during the day?

The reason we are looking at a seatainer instead of a fixed shed is that even though the site is classified as light industrial, a shed will require a planning permit and the full scrutiny of the (difficult) local city council whereas apparently a seatainer does not. 

Any feedback about this would be welcome.
Thanks


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## dustytools (Aug 25, 2007)

BobL said:


> How does this sound as an idea for a drying shed for slabs?
> 
> A used seatainer resting on a steel frame about a foot above the ground.
> Cut a series of 4" diameter holes in the bottom/sides and fit a couple of whirly bird (rain proof wind driven) fans on the top? Seatainers get pretty hot just sitting in the sun and especially where I live where it gets into the 90's and 100's (F) during the day?
> ...



Sounds like a pretty good idea. The ones that we use for construction storage get extremely hot in the summer months.


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## banannabiker (Aug 26, 2007)

*another posibility*

I have been looking at various ideas, and am leaning toward a slightly different type of container you may want to consider . I recently contacted a company that sells trucks like you see delivering fish, furniture, etc. The box on the back is normally about 20-28 feet long, and when some guys buy a truck, they want a different setup on the truck frame so the 'box' is removed and they sell them for $1000-$1500 last I checked. These boxes are aluminum instead of steel so they won't rust, they look better than the cargo containers, and often times they are insulated with a plywood interior. Just a thought.


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## BobL (Aug 26, 2007)

banannabiker said:


> I have been looking at various ideas, and am leaning toward a slightly different type of container you may want to consider . I recently contacted a company that sells trucks like you see delivering fish, furniture, etc. The box on the back is normally about 20-28 feet long, and when some guys buy a truck, they want a different setup on the truck frame so the 'box' is removed and they sell them for $1000-$1500 last I checked. These boxes are aluminum instead of steel so they won't rust, they look better than the cargo containers, and often times they are insulated with a plywood interior. Just a thought.



Thanks - I know exactly what you mean so I'll have to look into it. The key thing for us will be what the city council says about them.

Cheers


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## Matildasmate (Aug 26, 2007)

*Great idea*

Hi Bob sounds like a great idea , should get a realy great air flow through the stack and free solar heating what a marvelous idea Bob


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## oldsaw (Aug 26, 2007)

Listen to Henry Ford and the Rolling Stones....paint it black (Although I guess the Ford quote is bogus, I always liked it..."You can have it in any color you want, as long as it is black.") or some other dark color. If you really want to impress them, you could probably hook up some ABS pipe in a box under a sheet of plexiglass as a solar "pre-heater", and make them feel guilty that you are using renewable power and are environmentally concious. Although, your idea is cleaner looking.

Mark


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## IndyIan (Aug 27, 2007)

Hi BobL,
How thick are your slabs? I have a tarp garage(metal frame with tarp stretched over, top and sides) and I couldn't slow down the drying fast enough to keep my 2" stuff from cracking alot... Most of the 1" was Ok. This was White Oak, which I hear is very hard to dry but I was surprised at the difference.
You have the advantage of a sealed container so I would make sure you can slow the airflow enough that you don't cause alot of checking.


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## aggiewoodbutchr (Aug 27, 2007)

IndyIan brought up a good point. I have personally had better results with thick slabs when they were dried slowly. If you search around on Google you will find several sites that detail building kilns from con-ex boxes and reefer trucks. There a little more to it than tossing your lumber in them and letting it cook but it's not rocket science.


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## BobL (Aug 27, 2007)

Thanks for the feedback folks. 

Talking to a guy at work today and he said he has built a number of humidity chambers whereby he can control the rate of change of humidity over time. Looks like I'll be having a longer chat to this guy real soon. He says it shouldn't be too hard to rig up a couple of humidity sensors to control a couple of relays to open/close vents when the humidity inside the seatainer gets above/below a specific level. That way I can slow down the humidity loss on really dry days. I can see this is going to be a fun project.

Cheers


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## BobL (Sep 13, 2007)

*Seatainer Kiln - Project update*

I asked around about seatainers and with very little effort I found myself with a choice of 3! After some "to-in and fro-in" am now in possession of a used 20' seatainer in a dull medium- blue/rust colour.

At the same time a mate has given me two ceiling fans for internal circulation and BIL says he will cut out the openings for the whirlybirds.

Will post pictures once all is set up.

Cheers


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## oldsaw (Sep 13, 2007)

Very cool, keep us updated.

You may want to bolt a piece of sheetmetal under the whirlybirds to allow you to shut them down to slow drying. Just something simple that can pivot over to cover the hole.

You will want to put some vents down on the bottom too. Some of the screen backed vents that are used for sheds and attics. Put them along one side, then attach a tarp along one long wall to direct the airflow. You will need air movement (dry air in, moist air out) or you will have problems.

Mark


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## BobL (Sep 13, 2007)

oldsaw said:


> You may want to bolt a piece of sheetmetal under the whirlybirds to allow you to shut them down to slow drying. Just something simple that can pivot over to cover the hole.



Thanks Mark, yeah I was planing to do something like that. When the easterlies blow off the desert here in summer and the max temps reach 110F, a soaking wet towel in the shade dries in a couple of hours. Combined with a high direct solar input and it's going to get very hot inside the container. I have access to some portable temp/humidity loggers so I can monitor what's going - I need to find some info on optimal temp/humidty differentials for drying Aussie timbers.



oldsaw said:


> You will want to put some vents down on the bottom too. Some of the screen backed vents that are used for sheds and attics. Put them along one side, then attach a tarp along one long wall to direct the airflow. You will need air movement (dry air in, moist air out) or you will have problems.



Good point. This container has a thick ply floor and I need to investigate the directions the floor joists run in. If I could cut some holes in the sides of the container below the internal ply floor level and then cut some holes in the ply floor that could distribute the input air more evenly amoungst the slabs. Then I was also thinking about installing the ceiling fans in the middle of the ceilings and setting then to pull rather than push the air to create a circulation inside the container.


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## TrailBuilder (Sep 13, 2007)

Humidity controller. 

http://www.bghydro.com/BGH/itemdesc.asp?ic=AACTHC1&eq=&Tp=

Most hydroponics stores have a big variety. This is one of the best hydro stores on the net.


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## stonykill (Sep 14, 2007)

one of my neighbors with a band mill uses discarded 6 foot culvert pipes. He builds a platform on the bottom to make it flat, and loads it with lumber. It gets warm in the summer, but with the 2 six foot openings things don't dry too fast


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## BobL (Oct 21, 2007)

*Seatainer has landed.*

No milling this weekend. Spent the time clearing a space for the seatainer in the yard and organizing its delivery. 

The door was almost rusted on and need some convincing to open fully. I cut the holes for and installed the whirlybird fans and bottom vents. Sorry no pics - forgot the camera again. I will have to throw some anti rust paint at it next weekend so hopefully I will have something to show you then.

As a fire preventative measure I was thinking of adding a couple of sprinklers that are activated by fire - anyone have any experience with these? Maybe smoke detection might be better than temp as it will get pretty hot inside the seatainer. It's not because I actually think it might catch fire but even though it's in a fenced yard, the local yobs have a nasty habit of piling up rubbish next to seatainers and starting fires :greenchainsaw:


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## Matildasmate (Oct 21, 2007)

*Sprinkler's*



BobL said:


> No milling this weekend. Spent the time clearing a space for the seatainer in the yard and organizing its delivery.
> 
> The door was almost rusted on and need some convincing to open fully. I cut the holes for and installed the whirlybird fans and bottom vents. Sorry no pics - forgot the camera again. I will have to throw some anti rust paint at it next weekend so hopefully I will have something to show you then.
> 
> As a fire preventative measure I was thinking of adding a couple of sprinklers that are activated by fire - anyone have any experience with these? Maybe smoke detection might be better than temp as it will get pretty hot inside the seatainer. It's not because I actually think it might catch fire but even though it's in a fenced yard, the local yobs have a nasty habit of piling up rubbish next to seatainers and starting fires :greenchainsaw:



Hi Bob No real experience with sprinkler's , a part from bashing my head on one in the Eucy pulpmill and setting it off , they have a glass vial that breaks when temp get's extreme , no idea what they call extreme , obviously temp must be high enough to make glass vial expand and break to set it off . Done some milling over the last few day's , just a bit of pine , trying to get enough timber together to build a Henry house , that's one of our pet pig's , weigh's about 200kg's now , meet Henry everyone  . Cheer's MM


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## woodshop (Oct 21, 2007)

BobL said:


> It's not because I actually think it might catch fire but even though it's in a fenced yard, the local yobs have a nasty habit of piling up rubbish next to seatainers and starting fires :greenchainsaw:



...that's a pretty nasty habit there... they do this why? ...just for kicks?


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## Al Smith (Oct 21, 2007)

I'm far from an expert on the matter.Having said that though I've found that using a good end sealer such as anchor seal or that stuff sold by Baileys will tend to keep the end splits to a minimum.

I've known people to get fairly good results by just tarping a pile with plastic and using a common household dehumidifier although I've never tried so myself.


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## BobL (Oct 21, 2007)

woodshop said:


> ...that's a pretty nasty habit there... they do this why? ...just for kicks?



Yep - a trash dumpster, seatainer or anything locked seems like fair game to these mongrels. The problem is that anyone driving on a nearby major road will easily see the container and might want to come noseying around. Its not a big risk and if the contents of the container were easily replaceable I would be less concerned, but given the effort required to produce the contents I though adding a couple of sprinklers would be a simple precaution.


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## Matildasmate (Oct 22, 2007)

*Sea container's*



BobL said:


> Yep - a trash dumpster, seatainer or anything locked seems like fair game to these mongrels. The problem is that anyone driving on a nearby major road will easily see the container and might want to come noseying around. Its not a big risk and if the contents of the container were easily replaceable I would be less concerned, but given the effort required to produce the contents I though adding a couple of sprinklers would be a simple precaution.



Hi Bob What's the average price for a container and did you need a crane to unload it , just wondering what it cost's roughly , to buy one delivered and unloaded . Cheer's MM


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## aquan8tor (Oct 22, 2007)

They sell for between $2500-3000 here. I have a cabinetmaker friend that's buying a couple of them for just this; one for storage, the other for a kiln. I see them advertised on craigslist all the time; they must have a short life, or just have to be inspected/repaired to keep them roadworthy or something. I don't know the logistics of it. They apparently will deliver the containers on some sort of rollback, and don't need a crane to be unloaded. I think my friend was going to get a 30 footer, but I don't know for sure. Perhaps the 40 foot versions need a crane. I'm not sure. I'd love to put one up at the farm behind the barn, but getting it across the river(s) would be a little problematic. Don't think the driver would be too crazy about the idea.


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## BobL (Oct 22, 2007)

Matildasmate said:


> Hi Bob What's the average price for a container and did you need a crane to unload it , just wondering what it cost's roughly , to buy one delivered and unloaded . Cheer's MM



Costs vary between states in Australia for some reason depending on supply and demand. A 20 ft medium quality used container in Perth costs AUS$2400 plus delivery. 

Delivery costs/methods depends on the location. In my case the yard owner arranged that as his contribution to the deal. 20' containers weigh about a ton so if you use a crane it needs a long enough arm that can lift 1 ton up of the back of a truck - that's a bit bigger than your standard truck crane. 

I got my container from a mate where it was cluttering up his space for slightly less than 1/3rd of the going cost. Admittedly it will need some rust converter and paint thrown at it but $100 plus time should cover that.


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## Matildasmate (Oct 22, 2007)

*Cheap shed's*



aquan8tor said:


> They sell for between $2500-3000 here. I have a cabinetmaker friend that's buying a couple of them for just this; one for storage, the other for a kiln. I see them advertised on craigslist all the time; they must have a short life, or just have to be inspected/repaired to keep them roadworthy or something. I don't know the logistics of it. They apparently will deliver the containers on some sort of rollback, and don't need a crane to be unloaded. I think my friend was going to get a 30 footer, but I don't know for sure. Perhaps the 40 foot versions need a crane. I'm not sure. I'd love to put one up at the farm behind the barn, but getting it across the river(s) would be a little problematic. Don't think the driver would be too crazy about the idea.



They would make cheap shed's , no stuffing around with the clown's (town council) . thank's Aquan8tor , look's like there similar price to to container's over here too , going by BobL's post , roughly , I think I will get a couple of 10'l x 5'w x 7'h gable end to end garden shed's , $300-400au each , when I am ready . Cheer's MM


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## camojeep (Oct 22, 2007)

anybody ever tried to dry a slab in a vaccum venner bag read some place it would work seems vaccum kilns are very fast dryers


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## BobL (Oct 23, 2007)

Matildasmate said:


> They would make cheap shed's , no stuffing around with the clown's (town council) . thank's Aquan8tor , look's like there similar price to to container's over here too , going by BobL's post , roughly , I think I will get a couple of 10'l x 5'w x 7'h gable end to end garden shed's , $300-400au each , when I am ready . Cheer's MM



I would have gone with a shed if I did not need a bulding permit - especialy as I have the frame and the roofing materials for a 20' x 25' shed stacked up in my back yard.

What I like about containers is that they are self contained (I guess that's another reason why they call them a container ) with a built in ply and steel floor already about a foot off the ground. Because they seal reasonably well, controlling the air flow will also be easier.


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## Matildasmate (Oct 23, 2007)

*Container's*



BobL said:


> I would have gone with a shed if I did not need a bulding permit - especialy as I have the frame and the roofing materials for a 20' x 25' shed stacked up in my back yard.
> 
> What I like about containers is that they are self contained (I guess that's another reason why they call them a container ) with a built in ply and steel floor already about a foot off the ground. Because they seal reasonably well, controlling the air flow will also be easier.



A container is a great idea , very secure , especially where you have your's , by the sound's of it (apart from the vandal's with match's) , I reckon they would make cheap shed's also , no permit's required because it's not an erection , just a big box . One of the local blokes has recently had a shed erected for him , so far it has cost him over fifteen grand for a 40'L x 20'W x 10'H shed , concreted and wired . One thing , around here you don't need a permit to erect garden shed's . I got to thinking not long after my last post to this thread about garden shed's and thought hell why bother buying them either , just like you said in your last post about having the material's , I got enough second hand iron and it wont take me long to rip enough timber for a shed , I will line the inside with plastic , that way I can control the air flow and humidity , I can get cheap plastic also . Not sure where I am gunna get the time for all my project's though . Cheer's MM By the way good sense of humor Bob :hmm3grin2orange:


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## BobL (Nov 3, 2007)

Finally decide to stack some slabs into the seatainer today so I took some pics.







It's only been in the yard 2 weeks and the graffiti munchkins have had had a go at it already. Outside looks pretty scummy but inside it's OK.






Here's a shot showing the ventilator holes.





The roof was bowed slightly upwards which was good for rain runoff but as soon as I cut the front hole the bow sprang the other way. I'm gonna have to jack up the roof and then get BIL to weld a piece of angle either side of the hole across the roof to maintain the bow in the right direction


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## Matildasmate (Nov 3, 2007)

*When can you drop it off*

When can you drop it off Bob , nice setup mate , nice stack of wood . It didn't take you long to get it all setup . Thank's for the pic's . Cheer's MM


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## aggiewoodbutchr (Nov 8, 2007)

Nice work Bob!

Now, lets see some pics of that container full!


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## BobL (Dec 9, 2007)

*Temperature data for the seatainer*

Here is some interesting data about my seatainer. I bought some USB portable temperature/humidity sensors and put one inside the container on top of a pile of slabs (blue line), one in a metal box on the side of the container (yellow line) and one I left outside the container. The last one failed to trigger (still getting the hang of the software) but managed to get local daily min (red rectangles) and max (Black rectangles) temps for the last week from the weather bureau.






It looks like the temperature in the container is consistently about 5 - 10 oC above the outside temp. I was hoping for a bit more but maybe that a good thing. The weather here is quite cool at this time of the year and this weather pattern is more like what we see in spring and autumn. It will be interesting to see what happens when we hit 40oC

BTW those temp sensors are interesting little gizmos, 32000 data points of temperature and relative humidity, from one reading every second to one every 12 hours.


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## woodshop (Dec 9, 2007)

BobL said:


> ...BTW those temp sensors are interesting little gizmos, 32000 data points of temperature and relative humidity, from one reading every second to one every 12 hours.



Now THAT is seriously interesting Bob. I agree, I would have thought the temps inside that container would be higher than that. Heck my upper (kindof an attic) portion of my shed is often 20 or more degrees hotter than outside on some days. Did you get those USB sensors locally or from a website I could also order from? I'd be interested in setting a couple RH meters into my piles of drying lumber if it wouldn't break the bank. You've got my curiosity, give us more details please!!!


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## BobL (Dec 9, 2007)

woodshop said:


> Now THAT is seriously interesting Bob. I agree, I would have thought the temps inside that container would be higher than that. Heck my upper (kindof an attic) portion of my shed is often 20 or more degrees hotter than outside on some days. Did you get those USB sensors locally or from a website I could also order from? I'd be interested in setting a couple RH meters into my piles of drying lumber if it wouldn't break the bank. You've got my curiosity, give us more details please!!!



WS don't forget, 20F = 11oC, so it is about 20F hotter inside the container. Also, don't forget the container is ventilated with those wind driven whirlybird fans on the roof and vents on the sides.

The sensors I have are these http://www.electusdistribution.com....D=12&keywords=&SPECIAL=&form=CAT&SUBCATID=112
The $99 is an AUS retail price, I paid about US$55 for mine by buying through work.

There are heaps of these types of sensors on the net. Use "USB Temperatire/Humidity Datalogger" as a search term.

eg http://www.dataloggerstore.com/p4459/microlog_lite_16.php.

We use these sensors all the time at work when we transport polar ice and snow samples around. We throw one of these in the "eskies" (Oz term for ice cooler) and if the sensor come out wet we know the ice has melted! (just kidding). The transport companies guarantee the ice won't be taken above a certain temp and the sensor is our way of checking this.

Cheers


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## woodshop (Dec 9, 2007)

Thanks, going to check that out. We use temp sensors attached to the water depth dataloggers we drop down our observation wells, but the only humidity sensors are on our full blown weather stations and REAL pricey, I guess because they have to be so accurate. So, a small stand alone USB humidity sensor is what peaked my interest. Doesn't really have to be that accurate, as long as it senses changes in humidity from day to day. Would be interesting putting one or two in my piles of stickered lumber as it dries. I'm going to pursue that.

Yeah after I posted that I actually remembered you are part of the real world and you did say degrees C, and that changes the number spread significantly. We of course only use degrees C scale in all our equipment at the USGS, but as soon as I leave work I'm back in the Fahrenheit world. 

thanks again


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## Matildasmate (Dec 10, 2007)

Good work Bob , I will have to look into some myself mate . Thank's for sharing mate . Cheer's MM


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## BobL (Dec 10, 2007)

Here's the Relative Humidity (RH) data for inside and out alongside the inside Temp (T). Haven't got all the outside T unfortunately.







It's interesting to see the RH outside varies by around 50% during the day/night cycle but inside it varies by only 30%and doesn't go less than about 40% . I have read on the web that this rise in RH during the night helps the wood recover from the stress of drying out in the day.


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## roy clarke (Dec 10, 2007)

Bob, the important thing to measure is the moisture in the wood. I can't remember the figure, but I think it should be no more than 1% to 2% less at the surface than it is 1 inch in from the surface. You can use test blocks cut from the logs if you need to. 

The temperatures you have are a bit low, but not a problem (120 - 130 F is ok), and it may be because you have too much ventilation. The RH ought to be more than 90% so the wood doesn't have too large a gradient across it. When you get to those temps and RH, lots of things like to grow, so it's worth spraying the wood with a mixture of borax, boric acid and bleach. That stops fungus and beasties.

Drying wood in a kiln can take 3 months (or more) but the worst thing is to try and dry it fast.


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## BobL (Dec 10, 2007)

Thanks for the info Roy - very helpful indeed



roy clarke said:


> Bob, the important thing to measure is the moisture in the wood.


Yep, have my moisture meter waiting to do this measurement after I have been going for a few weeks, 



roy clarke said:


> The temperatures you have are a bit low, but not a problem (120 - 130 F is ok), and it may be because you have too much ventilation. The RH ought to be more than 90% so the wood doesn't have too large a gradient across it. When you get to those temps and RH, lots of things like to grow, so it's worth spraying the wood with a mixture of borax, boric acid and bleach. That stops fungus and beasties.


Yep I almost certainly have too much ventilation. Over the In the next few I will slow down the ventilation, and the outside temperature will also increase as summer kicks in. it will regularly get to 90-95F outside so I'm confident I can get them temp will get up around 130F without too much trouble. Do you have a specific recipe for the Borax/bleach mix?



roy clarke said:


> Drying wood in a kiln can take 3 months (or more) but the worst thing is to try and dry it fast.


That's why I thought I'd like to try and start slowly till I get the hang of it.

Thanks again.


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## roy clarke (Dec 10, 2007)

I'll hunt around for the recipe, though I haven't seen it for 15 years. 

The moisture gradient in the wood need to be measured every day to begin with, then less often as the moisture levels reduce and you are happy that things are progressing as planned.


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## BobL (Apr 30, 2008)

Here some temperature data for January of this year (that's mid summer for us) for my drying shed (a vented seatainer) which as about 2/3rd full of timber slabs when these readings were made

Firstly a couple of explanations.

The red line shows the air temperature in the middle of the inside of the shed.
The blue line shows the outside temperature of the shed in the sun - its effectively the skin temperature of the seatainer (I place a temp sensor inside a steel box attached to the outside of the shed).
the Orange line shows the daily max temp - you can see we had quite a few days above 90F, and 5 days above 100F
The Green line shows the daily min temp. It never went below 50F and was generally above 60F overnight.






Some observations:
The highest temperatures are the skin temp of the shed which reached 55ºC (131F) on a day when it was 41ºC (106F) outside air temp.
The maximum air temp inside the shed is always greater than the daily maximum by ~7ºC (13F) but never more than the skin temperature.
The shed air temp never gets outrageously hot - The hottest it got to was just 46ºC (115F) when it was 41ºC (106F) outside. I could probably boost that by reducing the air extraction (two full sized whirly birds or self powered roof mounted fans)
The lowest temperatures of the skin are equal to or slightly more than the overnight minima,
The minimum air temp inside the seatainer is ~5ºC (9F) greater than outside air temp.
This is an excellent demonstration of how a shed full of timber acts as a buffer against low and high container temperatures.

What I should be showing you is the RH data - it drops to less than 20 during the day but shoots up like a rocket during the night to over 90% when the air temp drops because the timber is still toasty warm and as I said in my first post, this rise in RH during the night helps the wood recover from the stress of drying out in the day and reduces splitting. This would be not good for thin boards but seems to be fine for 2"+ slabs for most wood because there does not appear to be much splitting.


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## aggiewoodbutchr (Apr 30, 2008)

Great info.


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## aquan8tor (May 1, 2008)

*Excellent Post!!!!!!!!*

WOW!!! Bob, you're full of great information! I see where you're from has a massive temperature difference between night and day. I've read that a lot of people here have either a timer or photocell controlled flapper vent that closes or almost closes the air exchange at night, while an inside fan continues to circulate air to keep condensation from forming. I have a friend that is going to be doing the same thing with a seatainer, but is just using it for lumber storage right now. 


Are the walls of your seatainer insulated at all?? Do you think that would increase the temp during the day, or conversely decrease the temperature drop at night? I'm trying to follow what you mean about increasing the relative humidity at night; would the RH drop if the temp inside the container stayed higher? 

Thanks for posting this information! Nothing like getting your data straight from the source!!!


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## BobL (May 1, 2008)

aquan8tor said:


> WOW!!! Bob, you're full of great information!


I dunno, some of the guys at work say I'm really full of "it"! 



> I see where you're from has a massive temperature difference between night and day.


Humm . . . the daily max and min only vary by about 30F - I wouldn't call that massive. The skin temp of the seatainer varies about 40 - 45F but the inside also only varies by 30F



> I've read that a lot of people here have either a timer or photocell controlled flapper vent that closes or almost closes the air exchange at night, while an inside fan continues to circulate air to keep condensation from forming. I have a friend that is going to be doing the same thing with a seatainer, but is just using it for lumber storage right now.


 I'd like to do that but I don't have any elect power to the unit just yet.




> Are the walls of your seatainer insulated at all??


No , it never or rarely drops below freezing here and even in mid-winter we usually always reaches 50F during the daytime and at that temp it reaches 85F inside the seatainer so the wood is still drying - just a lot slower. 



> Do you think that would increase the temp during the day, or conversely decrease the temperature drop at night?


Yes it would but the current arrangement is easily drying the timber faster than we can use it, so I'm not worried about getting it drying any faster.



> I'm trying to follow what you mean about increasing the relative humidity at night; would the RH drop if the temp inside the container stayed higher?


At night the wood is warm and trying like crazy to dump water out of itself but the air is cool so the RH goes up and reduces the loss of moisture from the wood during the night time. What this means is the wood is undergoing pulsed drying. During the day the moisture in the wood gets a little (or big) shove - "gotta get outta here" - it says. Then that night the high RH says - "WHOA!!! slow down with dumping the water, you're going too fast". This gives the wood that has dried out a chance to relax and reduces checking. It's kind like drying wood in an oven for a few minutes and then putting it in a sauna for a few minutes. It sounds dumb but the Aussie wood boffins say this is OK and even good considering one is paying zero for the energy to dry out the wood. 



> Thanks for posting this information! Nothing like getting your data straight from the source!!!


No worries - happy to help.


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## aquan8tor (May 1, 2008)

Thanks for all your answers. The "massive" difference I meant was your outside air swing day/night. Here in VA, USA, we're in a bit of a muggy area during the summer; the temp may go to 100+ during the day, but it might only drop to the upper 80's at night, often nearly 100% during the day. Last night it was in the upper 40'sF, but it got to about 75F this afternoon. From what I understand, around here, most of the drying is between dec. and march. (our winter!).


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## BobL (May 2, 2008)

aquan8tor said:


> Thanks for all your answers. The "massive" difference I meant was your outside air swing day/night. Here in VA, USA, we're in a bit of a muggy area during the summer; the temp may go to 100+ during the day, but it might only drop to the upper 80's at night, often nearly 100% during the day. Last night it was in the upper 40'sF, but it got to about 75F this afternoon. From what I understand, around here, most of the drying is between dec. and march. (our winter!).



That's because you have low RH in winter and high RH in summer.

The high humidity, high 80's to high 90's temps are what we usually have in late Feb and March but that did not happen this year!

In Jan we had an average night-day swing of 26F, ie 70's to mid 90's and the air is dry. In winter we typically have mid 40's to 60's when its raining and mid 30's to 60's when its dry. So our day-night temperature swings averaged across the year are usually about 20F.


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