steam to quick-season cedar

[pchilders]

Looking for thoughts regarding steaming northern white cedar to season it rather than wait a year (I've also heard that if I stand it on end I get it dry enough in four months).
I've got 5/4 (building clinker and spile and cut once, then rip it into two planks and have a matched set),
1) Should I steam it twice: once in 5/4 to season it and then once again while fastening it (after ripping to 2/4)?
2)Or, should I just get out the plank, rip it and steam each one once while fastening (knowing I'll probably have to get creative with the garboard, etc.) making sure I steam each plank just to season it?

Or, ... ? What are your thoughts?

I am concerned that double steaming may need a lot of experience with broken planks before I figure out how much it will take.

I am leaning towards just doing a thorough job of steaming all planks while building and leaving it as is ...

Thanks,
Peter

[dmede]

Don't know anything about steaming to season (sounds fishy). I do know that WB has published an article or two on solor kilns you can make in your backyard. Might help you speed up the drying time without risk of over cooking your planks. Search the article index.

dave

[pchilders]

Dmede,
Steaming wood seasons it (drives out the sap among other things). Even for cabinet-work, you can steam green wood to season it and then let it air-dry for a few weeks to get rid of the water (depending on thickness) and you've got good stable wood. But where I'm gonna bend this wood, I don't want to ruin it by over steaming and making it brittle. I had not thought of a solar kiln ... I will give it some thought. My gut reaction is "scary," just because weather is one of the greastest variables and I feel like I'd be baby-sitting the kiln all day long, but maybe not, and for getting my wood good and dry sooner than a year it's probably worth it anyway! I'll be sure to check out that article!
Thanks,
Peter

[Bob Smalser]

Trade it for some seasoned cedar....there is surely someone like me in Maine who has several stacks he doesn't plan to use for a year or more.

Or send it to a local kiln, which will be kinder to the wood than double steaming. Woodweb, The Forestry Forum and other sites advertise kiln operators. If yours is the only wood that goes in the kiln and your boards have no major variance in moisture content, kilning to 10-12% for planking stock won't do much harm. Kiln damage happens when 30% boards are mixed with 60% boards. Cedar trees growing next to a stream have wetter logs than upland cedar, and trees fallen in summer droughts have dry lower logs and wet upper logs where the limbs are. Plus if there's a lot of sapwood, in summer-fallen logs the sapwood can be 100+% while the heartwood can be as low as 30%. Rip yours away before hand, as you won't use it anyway.

Racking the boards by standing them on end in the sun and wind is a common practice to rapidly take the surface moisture from wet hardwood boards before stacking and stickering, so mold doesn't form beneath the stickers. As cedar is very forgiving in drying, racking will speed things up without the same danger of warp as in hardwoods. But 4 months for 5/4? Maybe 6 months from April-late October, but that's a full drying season anyway.

[dmede]

Seasoning, as I understand it (in terms of boat wood) has always meant that the woods moisture content is down to equilibrium with the surrounding air. This usually means the water held within the cell walls as well as between cell walls has evaporated out to a level equal with the air around it. Takes about 1 year per inch of thickness when stickered and doesn't seem to have any effect on the sap. Steaming wood temporarily adds back water plus heat as far as I know, so I still don't get how that seasons the wood. Maybe it speeds up the loss of cell bound water? Breaking cell walls (which you don't want I think).

I think we may need to hear from Mr. Smalser on this one. <--- cross posted

Hey Bob can you eloborate on steaming for seasoning?

[Bob Smalser]

I'm not up on steaming, other than in bending wood. Various quickie methods have been tried by mills and manufacturers over the decades and have all failed. The "salt cure" being the most notable. The wood was fine but the hardware all rotted, and when the hardware was a 3000-dollar shotgun, the customers were a bit upset.

I do know that Mediterranean Briar for smoking pipes is steamed before air drying, but steaming is to remove the bitter-tasting sap, and afterwards the thick briar blocks are then airdried for several years before using.

A kiln operator will take a week or more to dry the cedar in question. Gentle heat for a week has to be kinder than 212 degrees for a couple hours.

[pchilders]

Thanks Bob.
Dmede,
As far as steaming for seasoning, it does just what it is used for in those briar pipes, it drives out the sap; it also does some other things (I can only guess that you're relieving any tension in the board that would otherwise want it to warp easily in a desired direction once it got the teasing-power to do so from some moisture; kind of like steaming it flat rather than steaming to a curve, it'll prefer to remain flat than to warp once those intercellular bonds firm up again after steaming. It works well in cabinetry.

[Ron Williamson]

If you have a warmish spot to sticker it,airflow will do wonders in a few weeks.
We dry ours in a shop-built dehumidification kiln,but you could tent your material along with an old furnace fan and a dehum. under some 6mil poly.
R

[emichaels]

Contrary to popular belief cedar does not take a year to season. If you stand the boards up, similar to the way the cedar is kept at WBS, you will see usable stock at equilibrium well within 4 months. The key is standing it up so the water from our monsoon rains (here in 'temperate' Maine) will run off of it. White pine will dry nearly as fast when properly stickered and covered. If you stack the wood the center of the stack may take another month or so depending on how windy the spring comes.

Eric

[JGPierce]

Is there a magic number the water content has to be near before using it for planking?

A bit of a divergent question: I just picked up three more flat sawn 12" AWC planks and planed the roughness off both faces this AM. As opposed to my older AWC the new stuff has areas of reddish mottling, mostly centrally. There is no sapwood. Is this a normal variation or could this be related to the wetness of the wood?

http://www.imagestation.com/picture/sraid225/p8a7725f769dae13f38c60b4bc5117007/ea7d463a.jpg

[Bob Smalser]

Is there a magic number the water content has to be near before using it for planking?



Scroll down to "Compression Set 101".

Any pigments in the heartwood generally come from the soil the tree grew in, and aren't an issue.

If you are drying wood fast, make sure your 5/4 stock isn't still wet in the center before resawing into planks. It's difficult to get cedar to warp, but not impossible.

We also may not be on the same sheet of music. When I talk of "5/4", I mean a full inch and a quarter thick, not a nominal dimension. If "5/4" to you means 7/8" or 1", there is a significant difference.

[bob goeckel]

for canoe building i've gone from the mill to the saw to the steambox without any long waiting. the stock is very thin though (5/16ths) for ribs. i wasn't aware of a need for drying it. i don't believe the steam adds any moisture to the wood, the exact opposite is true.

[Thad Van Gilder]

I figure on a couple of weeks to season 1/4 inch local cedar...

That's from plenty of experience with doing just that.

-Thad

[pchilders]

Thanks for the input!

I am still leaning towards thoroughly steaming all planks just once during fastening ... any good reasons why this is a no-no with green wood. As far as I can guess, the wood would be the same after steaming whether it went in green or two years old, as far as moisture content is concerned. And I know steaming drives out sap. So is there a reason that planks dried year+ before steaming will shrink/warp less while drying on the boat?

"We dry ours in a shop-built dehumidification kiln"
Hey Ron Williamson, do you mind sharing the general design of your kiln?

[Ron Williamson]

Picture an insulated box about 5' wide by 2' longer than your lumber and a couple of inches taller than you are,with a door that swings up vertically on the long side.
On a shelf mounted as high as possible that runs along the back wall(long side) install a furnace blower fan,with the outlet cut into the shelf so that the discharge blows downwards.Get a household dehumidifier and plant it on the shelf as well,with a hose in place of the drain bucket.
Load your lumber, close the door(s) and wait.
Drying time is highly variable,depending on temp.,lumber MC,airflow and dehum. capacity,but with two fans and two dehums. we get 2k Bd.Ft. of dead green 8/4 Arbor Vitae to 10% ish in about 14 days.
R

[pchilders]

"we get 2k Bd.Ft. of dead green 8/4 Arbor Vitae to 10% ish in about 14 days."

Wow! That's great. Two questions: why the insulation if your not heating your stock, and (because I know nothing about dehumidifiers) what kind/ how big did you get?
Thanks a ton!
Peter

[Ron Williamson]

Actually,we do heat it,but not like you think.
The fans and dehumidifiers run warm,but from the way I understand thermodynamics,when you condense water,you release it's latent heat of evaporation,with a value of 1000 Btu/lb..
We have two 44 pint(thats the model number on the front,IIRC) household dehumidifiers,that will condense 44 pints per 24 hours.
If you do the calculation using the weight of water at 1 lb./pint that's 44k Btu/day.
It gets damn hot in there(38C,wazzat,a hundred F?) in the winter,without the doors sealed)and the waste heat keeps the warm part of the shop(1800 sq.ft.) at about 10C(50F) all by itself.
The guys on the Woodweb claim that this set up won't work well, long term,but the only mechanical problems I've had so far are dehum fan motors that get crud in them and seize.A new one is $70 installed.
In seven years,I've needed one per machine.
R

[pchilders]

Thanks Ron, great info.
So I'm back to my final question for everyone :) :

Is there going to be any difference experienced (warping and shrinking) between planking that is dried for a year before it is steamed/fastened and planking stock that is green before it is steamed/fastened. Won't they both be at the same EMC when I pull them from the steam box?
Thanks,
Peter

[Bob Smalser]

Thanks Ron, great info.
So I'm back to my final question for everyone :) :

Is there going to be any difference experienced (warping and shrinking) between planking that is dried for a year before it is steamed/fastened and planking stock that is green before it is steamed/fastened. Won't they both be at the same EMC when I pull them from the steam box?
Thanks,
Peter

No. Steam only imparts tiny amounts of water into the spaces between the wood's cells, and that dries quickly. Green wood has cells, cell walls, and the spaces between the cells chock full of water.

I think Ron's dehumidification kiln is the cat's meow if you want to build a kiln. Solar kilns often get mixed results. Pete Wagner of Pacific Western Timbers near me installed a vacuum kiln a couple years back that is even kinder to sensitive wood, but it was expensive.

[pchilders]

Thanks Bob, of course! That makes a lot of sense now that you mention it!:)
Yeah, that dehumid. rig sounds great!
Thanks again,
Peter