• Post Reply
  • Bookmark Topic Watch Topic
  • New Topic

drying sawn timber

 
Antonio Scotti
Posts: 9
Location: Spain
forest garden fungi urban
  • Mark post as helpful
  • send pies
  • Quote
  • Report post to moderator
Hi,
what kind of infrastructure is needed to dry sawn timber at small scale to use it on site?
I've seen pictures of people using second hand containers (like those used for sea transport) for either storing the cut wood, not sure if those could also used/adapted for drying.
I also wonder if it is possible to build rocket stove powered/driven drying kilns/chambers
Cheers

 
Bryant RedHawk
gardener
Pie
Posts: 1819
Location: Vilonia, Arkansas - Zone 7B/8A stoney, sandy loam soil pH 6.5
121
chicken dog forest garden hugelkultur hunting toxin-ectomy
  • Likes 1
  • Mark post as helpful
  • send pies
  • Quote
  • Report post to moderator
There are two methods for drying lumber (sawn logs)
1. Air drying, you put stickers between each layer of boards so air can circulate well and the drying process will take at least 6 months but most likely a year or two.
2. Kiln drying requires a sealable box, most commercial units are 20 feet long, insulated and heated with natural gas.
You can make one from a shipping container that is solar powered by aiming mirrors (or mirrored plastic) so the sun light strikes the sides and heats the box up, you need an air intake low to the ground on one end and a vent placed high up on the other end.

Yes you can build one with a rocket stove to provide the heat. It is even possible to build one of this type out of cob with ends that open made from wood.
Again air flow needs to be from low entrance to high exhaust point.

Redhawk
 
Antonio Scotti
Posts: 9
Location: Spain
forest garden fungi urban
  • Mark post as helpful
  • send pies
  • Quote
  • Report post to moderator
Thanks for you reply.
I guess there should be some way to control humidity rate/% of dried timber, right? Does anyone know if there is any relatively cheap way to do this?

As for air drying is this the only measure to take to ensure the sawn tables do not become twisted etc?
Cheers
Sinergy
 
Bryant RedHawk
gardener
Pie
Posts: 1819
Location: Vilonia, Arkansas - Zone 7B/8A stoney, sandy loam soil pH 6.5
121
chicken dog forest garden hugelkultur hunting toxin-ectomy
  • Mark post as helpful
  • send pies
  • Quote
  • Report post to moderator
There are moisture meters just for measuring the moisture in lumber, it would be a wise investment if you plan to dry a lot of wood.

I air dry some woods the way I do it is to set up my stack on a tarp, once all the wood is stacked with stickers I wrap the tarp around it leaving the ends open.
Next step is the fan, I set up a fan at one of the open ends and turn it on, this gives me air flow even with no wind available, the moving air will remove moisture from the air surrounding the stack thus allowing the stack to give off more moisture.
After a week I spot check with a moisture meter. lumber stack probe
is a good unit, as is this one data collection meter

Air dried lumber can still twist, the best way to avoid twist or cupping is to dry the whole log then cut the boards.
 
Antonio Scotti
Posts: 9
Location: Spain
forest garden fungi urban
  • Mark post as helpful
  • send pies
  • Quote
  • Report post to moderator
Hi
it looks as if you build a sort of an open greenhouse for your lumber.

I guess leaving the whole trunk to dry out depends on the wood type, right? Some wood become very hard for them to be sawn afterward
is this correct?
Cheers
 
Bryant RedHawk
gardener
Pie
Posts: 1819
Location: Vilonia, Arkansas - Zone 7B/8A stoney, sandy loam soil pH 6.5
121
chicken dog forest garden hugelkultur hunting toxin-ectomy
  • Mark post as helpful
  • send pies
  • Quote
  • Report post to moderator
Yes my drying set up does look like a square-ish low tunnel green house when it is put together.

If I'm doing whole log drying it is usually for timber framing.
I do partially dry Hickory and White oak prior to sawing, it makes it easier to handle these since they are heavy when fresh cut.
The Rose Woods I work with come to me fully air dried.

If you cut your boards first, then dry them you will get checking. The way you prevent this is to coat the end grain with hot wax (use a paint brush to apply the hot wax).
The trick to waxing end grain is to have the wax very hot, that way it will seep into the end grain cells. You also want a fairly thick (1-3 mm) on the end grain to keep moisture from escaping to quickly.

Redhawk
 
duane hennon
gardener
Pie
Posts: 660
Location: western pennsylvania zone 5/a
32
  • Mark post as helpful
  • send pies
  • Quote
  • Report post to moderator


hi Bryant,

on this video about a wind powered sawmill
http://www.permies.com/t/56210/wind/Wind-Powered-Sawmill-Works-AMAZING
a little nugget right at the end

the operators say they soak their logs in water for a year before sawing them
the water removes the sugars (sap) and this prevents warping of sawed boards
 
Tam Deal
Posts: 61
3
  • Mark post as helpful
  • send pies
  • Quote
  • Report post to moderator
Generally people overthink wood production. Cut it, sticker it, coat ends, leave it in a sheltered & shaded place walk away for a year or so. It will be done with normally minimal loss. Anything you do to accelerate the drying is a lot more time and effort to do, and the possibility of loosing whole loads exists. The downside to the cautious approach is mainly that you are limited as to the time when you can use the first of the material, but once the process is set in motion and you have waited out the wood for the first year or whatever, you never have to wait again. If you need a lot of wood fast then you need another solution, but for careful work like furniture and boats, it is rare to move that fast through a stack of lumber. But with something the size of a house, where in addition the building techniques are normally fast, you could feel the hold up acutely.

One option is to investigate methods of building that take wood shrinkage into account. Few of the settlers had years to wait for wood to dry, or the infrastructure to build kilns, they just used methods where dry wood was not necessary. Even for fairly sophisticated furniture.

Warping is not normally a problem, sawing and drying wood do not cause it. Normally easy to avoid on small operations if one is carefully picking trees, and carefully cutting them (these would normally be the same techniques used to get good trees and reasonable yield). I never think about it other that at the level of the basics.
 
I agree. Here's the link: https://richsoil.com/wood-heat.jsp
  • Post Reply
  • Bookmark Topic Watch Topic
  • New Topic