Well I tried my first load of 8/4's red oak and well lets just say it was less than impressive.
I've dried a lot of 4/4's in my little home made kiln without any problems so I thought I'd give the 8/4's a try.
I loaded it, calculated how much was in it. calculated the safe drying rate. turned it on and away we went.
I pulled my test blocks out yesterday to check things and boy what a mess. there are surface checks that are 1/2" deep on the flatsawn face. (This load is all Q'sawn. )
It looked like I just pulled to much out to fast with the dehumidifier. I went back over the math and it was right. Right up untill I forgot to divide by 2 for the 8/4's. :( :( :( :(
I'm going to finish the load and see if anything can be salvaged. It's 2x6's. maybe I can trim the sides down and still have some table legs out of the middle. ::) ::)
The moral fo the story is to let my teenager do my math from now on. He knows that new math stuff ;) :D :D :D :D
Tom
QS oak is very difficult to dry, but depending on how many boards you see this on, there is still an outside chance you saw an anomaly. If you didn't cut away the wood within two or three inches of the heart pith, the edges of QS lumber will crack with heart check on one edge (center most) only. Hopefully that is what you saw. If you saw a lot of checks on both edges, then yes, you may be in trouble.
As I recall you have to divide by about 2.5 for 8/4, not just 2. The thicker the board, the rate of drying slows down exponentially.
Never have been able to dry 8/4 oak in either my solar or Ebac DH kiln without a lot of degrade. I can dry 6/4 pretty easily with little degrade.
Now I'm new to all of this so take it easy on me, but what is degrade? Obviously it is not good, but does it structuraly weaken the lumber, is it cosmetic? Someone please explain so I'll know what to look for.
Paul
Paul, Degrade has many interpretations in the timber world, from cell collapse / case hardening / twist / warping / cupping. Tom reckons he has kindling wood, so the charge has turned to "custard", ask Den Socling how to dry Oak Tom, I have seen turning squares 50mm plus come out of his vac chamber in absolute perfect condition
Richard
Larry
I was thinking of trying some 8/4 red oak in a solar kiln (still have to build the kiln, but it is not that far in the future). Do you think that even the solar kiln dried the wood too quickly?
The difficulty with drying oak comes from the rays. Mother nature designed them to carry water and they do a good job. Unfortunately, they carry water from adjacent cells and that causes the adjacent cells to shrink on both sides of the ray and that leads to cracks. Oaks in a vacuum kiln are easy but I have never run a DH or solar kiln. But I would advise you to watch those rays - check them everyday. You have to keep water migrating to replace what is leaving the surface and around the rays. Control of EMC, when you can do it, can be used to slow evaporation from the surface. Raising the heat can help with the migration.
Did you put this in dead green? That is the only way you can dry 8/4 safely. If it was air dried, the problems you see were created during air drying. They just didn't show up yet. The old story that drying lumber is like jumping out a 10 story window. The mistakes are all at the beginning but the damage doesn't show up until the end.
brdmkr, I think most solar kiln designs are optimized to dry 4/4 with little or no degrade. With my solar kiln I kept the vents closed to keep the humidity up and slow the drying but it was still to fast. Dr Gene has advised to cover up part of the collector to reduce the heat and slow the drying. I'm sure he is right but at the same time with a solar kiln and little control I think it is a risky proposition.
Don_Lewis also makes a valid point...but dead green into either a solar or DH is going to take a long time. Not for sure if there is a payback or not.
8/4 oak is not much fun to off-bear, stack, or sticker so didn't take long to give up on the idea.
The problem with Don's response is that it is too expensive to dry from green in conventional steam or DH kilns. You have to air dry to keep cost down. The biggest companies moving the most oak air dry if they don't have vacuum kilns.
These guys, for example, use us for convetional kiln control. They paid for the inventory to air dry before we had the vac kilns available and, as you will see, they have a lot of oak air drying.
http://www.siriannihardwoods.com/index.html
I like that "jumping off of a 10 story building" analogy. Man, is that graphic. :D
Tom,
You're right. I'll have to remember that one. :D
Den
6 Million FBM in stock !! assuming it is stickered whewwwwww ! (Sirianni Hardwoods), Wonder what their monthly FBM sales are and what there annual stock turn is?, and, what it would be if they deployed Vac kilns?---just wondering!
Richard
Hi Richard,
They may switch to vacuum drying someday but the problem in North America is this: companies have already invested in conventional drying. Few are willing to 'junk' what is working for them. And they know the limitations of what they have. A jump to vacuum drying is unchartered water, as far as they are concerned.
I could show you pictures of shocking amounts of surface and end checks that are closed and go through the system. They are trimmed off or surfaced off so what's the difference? The diference is the yield from a log. Look at Parker getting maybe three chairs instead of one from his $8000 burl. Or consider a recent, new customer here in PA cutting baseball bats. Yield is so good they are cutting billets smaller and getting more bats per log. It's coming. All major producers are going to see the error of cutting oversize to increase yield.
Den
Thanks for all the responce's
No it was not green it was air dried.
Yep your right 2.5 not 2
and yep the the damage at the end is a drag. :D
I'll finish this load and try another this summer
Tom
Hi Den and others, Well, I would just hate to be a stock holder of these companies who cannot see the wood from the trees, the basic principle in operating a sawmill is is ROI, meaning,
1. Log selection
2. Maximizing recovery of that log
3. Minimizing degrade by a grading regime (ie: selection of heartwood and sapwood etc)
4. Then the "BIGGY"----- drying the species as fast as possible and "SOLD"
You would think Den, that the number crunchers would at least do the sums of having these massive
stocks on stickers, then into conventional kilns, the time frame from buying feed stock (logs) to milling to air drying on stickers to any further processing is absolutely unacceptable, (well,-- here in New Zealand and other countries.
I would have thought "USE OF FUNDS" is #1 priority in any swithched on organisation
Surely, they MUST know there is USA technology at their doorstep in drying the Oak without degrade and much faster!!!
I shan't sleep tonight knowing knowing what you have just said :o :(
Richard
Richard,
SA is not the same story. it will be a giant market once we have the IP protection in place. NA will have to follow the lead.
Den
You are quite correct Den,--from my travels last week to Brazil the opportunities for your technology there would be awesome
Richard
When i spoke about the need to dry from green, I was talking about 8/4 Oak. 4/4 is often air dried or predried. The cost of kiln drying 8/4 Oak from green varies with the type of system and local fuels costs, but in most of the USA, it will take about 60-70 days and cost $300/MBF including energy, capital etc. How much does degrade cost?
You'll have better luck if you don't air dry 8/4 Oak in the summer. Do it in colder weather if you can
As for the time factor, certainly vacuum is faster, but the loads are smaller so the investment to dry a quantity is not a whole lot different than DH or conventional systems. For some, vacuum is the right choice because of the way the market or use their product. If you have a 60,000 BF kiln drying 8/4 and it takes two months plus, that means you then have a lump of 60,000 feet in stock. With a vacuum kiln, if you have a 6000 BF system, you can turn it over 10 times in two months and have the same stock, but spread out over time. One way might fit your needs better than the other and there is no "one size fits all" solution
Well I opened the kiln today and was plesently suprised.
While it is not completly dry the whole batch is not a loss. the boards on the outside have some checking but the ones in the middle are ok a bit of checking here and there but nothing major.
I'm going to pull the load out and put it in the loft to dry over the summer.
Thanks everyone for all the advise on this subject I'll give it another try this summer with something else.
Tom
glad to hear that all was not lost Tom !
I've learned a lesson also. Thanks for the tip !
I don't want to deflate your balloon, but, you may still have alot of checking. Checks can close up as drying progresses; they don't heal-up though. If they have closed up they may open when a liquid finish is applied or they may have turned into "honeycomb". In which, when you remove some of the surface you will see the checks or they will show up on the cross-grain surface when you open them up.
I hope I am wrong, but don't want you to have high expectations dashed later. My wife says I'm a pessimist(spelling), but I'm really a realist. :) ::)