Steaming wood questions!

[JW_Halverson]

Dry heat for dry wood, steam for wet wood.  Got it!

I may be getting a mess of pretty green hickory cut in October and November and need it for a bowmaking class soon.  For those that have had experience steaming green hickory, what do you think of stuffing these staves into a box, plumbing in a line to a big old kettle of water and pouring the steam to them? 

Next, we have a small sawmill up the road from town and they steam kiln dry these huge multiple railroad car sized bunks of 1" ponderosa pine boards in their steam kilns.  What might happen if I can throw these staves on a pile going through treatment?

The place where I am doing the classes is a "maker space" woodshop and we are doing this in 1 1/2 hour classes once a week for two months. Because this is stretching out the process, the wood will also have more time to cure even as it gets smaller and closer to final dimensions week by week. 

Checking/cracking seems to happen when rapid drying takes place in wood with higher moisture content, in other words when there is a lot of moisture movement happening rapidly. Also, the larger the piece of wood, the more shrinking builds up tensions causing the checking and cracking.  If the steam kiln can push the moisture content down to 15-18% before we start hogging off wood, I believe we could put the now much smaller sticks into a closet with a dehumidifier and push the process a bit faster. 

Weigh in, folks.....pros and cons, no wild hair ideas unwelcome!

[BowEd]

You bet JW.Many don't realize that steaming actually pushes the sap out replacing it with water and that water leaves quicker so the wood actually dries faster in the end.A safer way than dry heat kiln drying I'd say.Reducing the staves to 1.5" thick by 2" wide should be ok from checking through this process.Just cut the staves plenty long I'd say.The first few days of drying seems to be critical to bot rush it in too warm of an area.After that it can be put in dryer conditions.this all hinges on the degree of thickness they are too.
Also another way to speed up drying many don't realize too although I've never tried it is to immerse wood into deep water of over 10' feet deep for a period of time.The low oxygen and pressure help to push the sap moisture out sooner too.Along the prairie trail future homesteaders used this to hurry up usable replacement hub and wheel parts for their wagons when broke down.

[DC]

I've done this with the handle section on Ocean Spray. Normally the handle splits wide open on OS but the one I steamed green stayed in one piece. I'm sorta with Ed on this except for the "replaced with water" part. I think that the temperature expands the sap, pushing some out, but when you pull the stave out of the steam it would either suck air back in or possibly just shrink. The checking is caused by the outside shrinking faster than the inside and if you can drive the moisture out of the inside then you're golden. It also gives you an opportunity to take out some kinks. I've been meaning to make a full stave sized steam box to try this but haven't got to it yet.Unless there is some way that the steam can damage the wood I think it's a great idea.

[Bryce]

Steaming works for both dry and wet wood. For some species of bow wood I prefer to boil, and hickory and oak (diffuse porous woods) I boil and then set with dry heat. Just my preference.

[BowEd]

I'm of the opinion that the denser type wood runs the fear of checking more so than moderately dense type woods to be ready for bow making.Example.... red cedar a less risk than osage.

[Pat B]

IMO, wet heat is a better option for hickory. I think I'd take the staves down to floor tiller stage. They will dry quicker plus a lot less work for the students when they get started. That's how Pappy used to do it for the selfbow challenge at the Classic. Hickory doesn't normal check much but sealing the ends and back will insure that they don't check. I think shellac works well and it is easily removed if needed plus most finishes can go right over the shellac.

[Badger]

   I just cut up a log of pear wood, very hard wood and sopping wet, I know pear is prone to checking and cracking so I am cutting it into 1.5 X 1.5 for the wood I will be using in laminations and I expect about 6 staves I will be using as self bows. I plan to just rough those out sopping wet and then wrap in siran wrap with a few holes in it here and there.

[chamookman]

What Pat said  ! Bob

[JW_Halverson]

Did anyone know that when the massive plumes of steam coming out of a kiln does not necessarily mean they are using steam to kiln dry the wood?  I didn't.  Turns out all these little small operation sawmills around here use straight natural gas.  The steam is just whatever boils out of the wood. 

Several of them offered to run a stave through the kiln, but they all agreed I was likely to see drastic checking.

Looks like I am hemmed in. Either I gotta build a steam box or deal with natural rates of drying/curing.  So, the question is now modified....who has built a steam box for staves to cure them out and what are your recommendations for procedure?

[Pat B]

John, I use my hot box for drying wood sometimes. You can build a simple hot box with a sheet(4'x8') of 1" foil lined foam a 2x4 and a few ceramic light fixtures and 100w bulbs.  Put a 1" hole in the top of one end and one in the bottom of the other to let the moisture out. For other used you just put a cork in these holes.

[JW_Halverson]

I have a hotbox similar to that, I put the staves in a small closet with a dehumidifier running.  It will get up to 115 degrees and near zero relative humidity! 

[Pat B]

I don't imagine high humidity is a problem out there in the winter.

[JW_Halverson]

I don't imagine high humidity is a problem out there in the winter.

In a good hard summer rain our relative humidity will sometimes break the 50% mark.  Meteorologists indicate that during Noah's flood we had two and a half inches of precipitation over a long three day weekend. 

[Pat B]

 

[Hawkdancer]

Wooden canoe makers bend hardwoods such as mahogany up to 20 ft or more with steam.  I think Rollin Thurlow has a video available, although it applies mainly to canoe making, it should have a lot of good information.
Hawkdancer