Drying a load of QS Red Oak

steveST · June 22, 2003, 05:55:15 AM

I put a BIG load of SQ Red Oak (very nice, very wide), white oak, poplar, and walnut in a friend's solar kiln over the weekend.

I have a few questions/concerns about it:

1. What is the MAX temp it should see? It rained every day since it went it 3 days ago, but it's supposed to get REAL sunny, and REAL hot in the next several days. I think he believes more is better, but I know that to NOT be true.

2. I brought my own stickers(all kiln dried), but had to use some of his (poplar). His were outside and were VERY wet from continuous rain. His stance is that it will not matter since they will dry real quick once we get some heat in there. Is this so? My QS is VERY nice and I do not want it stained or worse yet, rotted.

Thanks for any info.

solidwoods · June 22, 2003, 06:20:14 AM

Put a wet bulb and a dry bulb in the kiln. You can track the evaporation rate of the wood. Is this the first load in the kiln? I would hope not since you put in Oak (one of the harder woods to dry ). The wet stickers can go either way.
If the wood was green, the cycle starts a week or so slow, or the stickers were put on the poplar,, :omaybe stain.

Enjoy wood
JIM

DanG · June 22, 2003, 06:21:15 AM

I don't have any first-hand experience, but I understand that solar won't dry it fast enough to cause any degrade.

sawwood · June 22, 2003, 06:58:33 AM

Steve Larry Coppas has a solar kin and i have had him dry
wood for me. He only filles it with one type of wood at a
time. Most solar kiln will git up to 120 degs and larry has
a pin in some of the wood with wire hooked to them so he
can take readings and see how they are drying. May be he
will see this and give you more info.

Sawwood

Brian_Bailey · June 22, 2003, 07:11:44 AM

I find it's not a good idea to mix oak with faster drying species.

Using wet stickers is inviting stain.

Green oak @ high temp. in first stages of drying not good either. You'll get surface checking which will later develop into bottleneck checks as the oak approaches it fiber saturation point.

The max. m/c loss/day on R Oak is 1.5%, W oak is 1%. Drying at this rate is too slow for poplar & walnut. You'll experience a high degree of cupping and stain esp. with the poplar at this drying rate. Sap wood on the walnut will be blotchy.

Make sure your friend is able to precisely moniter the m/c loss on the oak, not just a quesstimate ( oh i had the vents opened just a couple of hours today ).

Don't want to be pessimistic about your situation, I don't think you have to worry about your QS rotting. I would be very concerned about honeycomb due to the high temps. I have seen a fair share of good oak ruined in solar kilns when not dried properly. Good luck

.

steveST · June 22, 2003, 08:01:50 AM

While the oak is "green" it has been air-dried for about 2 weeks.
I have not measured the moisture content, but I can tell you it was a LOT lighter than it was when I stacked it green.

I would prefer to favor the oak with the drying requirements...there's MUCH more of it, and it's nicer than the poplar and walnut.

Larry · June 22, 2003, 09:24:04 AM

Steve,
Way to many unknowns's to predict how your wood will dry. No two solar kilns have ever been constructed exactly the same so there will be differences in insulation, venting, fan speed, and glazing. Don't know the starting MC of any of your wood or even how thick it is. If the guy running the kiln has any experience he may be able to do a good job. After running a solar kiln for 9 years with very good results I thought I was an expert until I managed to stain some ash earlier this year.

The only way I know to protect your red oak for sure is to precisely monitor it as Brian suggested. To monitor it accurately you will need to cut a sample board, oven dry a section, and weigh a moisture section every day the sun shines to insure the oak is not drying to fast. Meters are not accurate enough until the MC drops below 30% and by the time your there most of the danger of checking is past.

Good luck.

Brian_Bailey · June 22, 2003, 07:00:37 PM

QS oak takes about a third longer to dry than plain sawn.

Most folks don't realize that most of the drying defects are created in the first couple of weeks after the lumber is sawn.

Like Larry stated once the wood reaches its fiber saturation point, approx. 28 % mc, the free water has been removed. Below that point, your removing bound water and you'd have to do something very drastic to damage the wood.

If you find that the chamber is getting too hot, you might want to consider partially covering the collector to reduce the heat buildup.

Don't open the vents to accomplish this as the hotter the air gets the more moisture the air can hold. By expelling the air, you're reducing the relative humidity in the chamber which results in faster moisture removal from the lumber. Something at this stage you don't want.

Fla._Deadheader · June 22, 2003, 07:58:11 PM

This has become a very interesting thread.
With the lumber I get, which is completely saturated, and with the high heat-humidity factor in Fl., how long or at what moisture content can I put this stuff into a solar kiln? Right now, I sell it right off the mill, but, will have to start drying to keep my buyer happy, by being able to turn the lumber. They don't have any drying capabilities either. :

Brian_Bailey · June 22, 2003, 09:44:15 PM

F_D -

I wish I could help you. You have a unique product that I would be afraid to offer any advice on.

Fla._Deadheader · June 23, 2003, 05:33:14 AM

Brian, anything you could offer would be appreciated. I HAVE to do something, and have NO idea where to start??
I thought about a quonset type structure, built with PVC pipe and covered with visquene. Put a large fan in the OUTFLOW side to draw the excess moisture off. Don Lewis, from Nyle, said that would be a good way to invite molds and all sorts of things. Why??? It would be a cover, of sorts, and have air being constantly drawn through?????? I even thought of a solar collector "breadbox" type device, that would pre-heat some of the air, before entering the dryer.
This stuff DRIPS water when we stack it ??????

Larry · June 23, 2003, 08:12:48 AM

Harold,
I checked my reference material and the only thing I could find was that sinker stock "tends to dry slowly and is prone to develop checks and honeycomb". That came from the Dry Kiln Operator's Manual.

There is probably some information at the Forest Products Laboratory but the only problem is finding it. I tried a search this morning and came up with zilch. :-[

http://www.fpl.fs.fed.us/pubs.htm

Brian_Bailey · June 23, 2003, 11:01:00 AM

F_D - Your product is unique and will require special handling to avoid ruining the lumber. I have no experience with this type of lumber, that's why I'm hesitant in offering any advice.

I would do like Larry has suggested. Also, read the sections on the "Stages of Drying" in Drying Hardwood Lumber. This publication can be viewed at

http://www.fpl.fs.fed.us/documnts/FPLGTR/fplgtr118.pdf

Once you understand the basic mechanics of how lumber dries, you should be able to customize a system that should work for you.

solidwoods · June 23, 2003, 11:46:04 AM

Another good pub is:
USDA Forest Svc Forest Products lab.
KILN PUBLICATIONS ON CD
I got one through an odd way so I don't know where to get it though.
JIM

Ron Wenrich · June 23, 2003, 03:37:48 PM

I got 6 sawmill publications on CD over at Ebay. Included is the Dry Kiln Operator's Manual, Drying Hardwood Lumber and Air Drying of Lumber.

Price is about $10. They seem to be always available.

One of these days, I'll have to read it.

Fla._Deadheader · June 23, 2003, 04:08:27 PM

Ron, that sounded familiar!!! I went searching around the old desk, and, VOILA' I got one of them CD's. 8) 8) All I gotta do is figger how to read it :

;D Thanks for all the ideas, guys. really appreciate it. ;) ;)