An idea for drying slabs

[aquan8tor]

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!!!

 

[BobL]

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.

 

[aquan8tor]

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!).

 

[BobL]

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.