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Author Topic: Jim Fuller's ideas  (Read 7747 times)

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Offline Den Socling

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Jim Fuller's ideas
« on: March 25, 2004, 04:50:36 PM »
I'm trying to start a new thread from what was posted in the thread about banding.

Den

Hey Jim,

You have an audience. And at this forum, no know-it-all is going to shoot you down. I may play the devil's advocate at times but there is no guru here.

Den

Unless you are using vacume drying you can not avoid casehardening.  It occurs whether you dry slow or fast - air-drying, dh, solar or conventional.  Wood only dries from the outside-in..  When you dry slowly,air-drying, solar-drying and poorly controlled kiln drying, you risk more damage and warpage than if you  dry fast with good control.  Naturally, drying fast with poor control you are demanding a disaster

Interesting JimF. What you are saying seems to go against conventional wisdom but makes sense.

Welcome to the forum and please continue to give us your insight!

Actually it is not against conventional wisdom.  With the advent of the energy crisis the solar kiln came into fashion.  And to sell that idea the conventional wisdom was pushed out the door.  Now we hear the altered wisdom.
To support the idea of drying fast, I have a patent for monitoring/control of wood drying that reduces the drying time by more than 35%.  While do so the drying stresses are actually reduced in the end. And you end up with brighter and more defect free lumber.

JimF
Do you have a resource (publication of results) that supports the "altered wisdom" ?
 

You are presenting some interesting (teasing?) ideas, that could use some additional support. Is the patent idea available on the market? Did you do vacuum drying testing?

Thanks for filling out the bio.  

Maybe too many questions!
 

Offline Den Socling

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Re: Jim Fuller's ideas
« Reply #1 on: March 25, 2004, 04:53:22 PM »
JimF.
Please tell us more.
Can your patented idea be used in vacuum drying?

Hey Jim,

You have an audience. And at this forum, no know-it-all is going to shoot you down. I may play the devil's advocate at times but there is no guru here.

Den

Thanks for the interests in my ideas.
Beenthere,
no it is not on the market yet.  It is easy to have a great idea.  It is another thing to get financial backing.  Venture capitlaists only come on the scene when the inventor is filing for bankrupcy, after all the hard work of development is done.  And regional economic development committees are only interested in flashy high tech stuff like biotechs because it looks good on their records, not improvement of  communities .
I'm told to find a doctor or airline pilot.  They have lots of money and will go for anything a good salesman puts in front of them.  Anyone know of any doctors or airline pilots looking to invest?
Den,
I like devil's advocates.  They help bring out the fine details of a discussion

you are controlling properly and are drying fast you can not over dry the shell.  That is controled by the EMC in the kiln and is what equalization is partially for.
The "altered wisdom" is air-drying is gentle to the wood - Myth 1.  Solar-drying is different from conventional drying - Myth 2. To name some.
 If you air dry white pine or maple, for example, the center of the stack is likely to get blue stain or sticker stain.  If you air-dry oak, you are sure to get large surface checks because of the up and down trends of the EMC.  The up and down trends of the EMC only makes the surface checks worse, that have developed from the lumber being exposed to the sun or breeze on the green chain.
Solar drying is claimed to be diferent than conventional and is gentle because of the EMC rises at night.  However, in conventional kilns the airflow is switched about avery 6 hours; causing the entering air side to become the exiting air side.  The causes the EMC to go up and down at the sides of the stacks.  The cyclic gain and loss of moisture in the wood at these points can be measured and the shrinkage and swelling can be measure as a result.  Because in a conventional kiln this can be controlled to some extent but is not in a solar kiln, the wood is exposed to more sever conditions in the solar kiln.  The surface checks will be extended further into the board than in a conventional kiln.  The some of the same people that promote solar-drying say never to start the kiln drying by adding steam to bring the EMC to set point because of the surface check problem.  


have never had the oportunity to try the new method out on vacuum drying.  As has been mentioned here there are numerous methods to vacuum dry.  They all produce important differences in terms of control and stress development.  In a past post I generalized vacuum drying as not producing casehardening.  It depends on the method.  If you use conductive heat source, like heat blankets or hot water pipes,  you still produce cashardening.  After the initial pull of a vacuum, the water still only evaporates from a liquid boundary line.  The heat can only travel through the surface of the wood to the water; heating up the water nearest to the surface first.
 Radio frequency while enters the dry portion of the wood and heats up the water inside it mostly only heats up the water nearest the surafce of the wood.  Therefore it produces casehardening.  However, there is one company that claims the frequency that there equipment uses penetrates the wet wood more evenly and heats up the water more evenly. I have not seen the data for that to know enough about it to comment on it.
The intermitantly heated method that has been mention here alot is another species all together and is much more complitcated.  I have not sat down to study how things occur within it yet.
Speaking on vacuum drying.  There is one method that intrigues me for very small operators.  It encloses the wood in a plastic bag, in essences and immerses it in hot water.  Then a vacuum is pull on the bag.  This is a inexpensive way to provide continuous heating.  Admittedly in practice it is for small chunks or a small number of boards, but it is a method most people can fabricate and operate.  It is patented and a company is working on getting it on the market.

Offline Den Socling

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Re: Jim Fuller's ideas
« Reply #2 on: March 25, 2004, 04:57:08 PM »
jimF.
What if one was to pre-heat in a vac kiln before he pulls a vacuume?Would this not bring the whole piece of wood up to the same temp?

yes, and the whole piece should loss water some what evenly.  But not all the water.  So the concern is after the initial vacuum pull, how is it heated?  With intermittant heating system mentioned here, it seems like this would happen each time, but with repeated occurances things can become complicated quickly.  Which is why I hold back my opinion in this ins

To stir the pot some, what are the concerns during drying - in all systems of drying?

jimF.
With square drying in a vac kiln the concern was honey comb and surface cracks.In flooring blanks and lumber the concern is with stress and un even moisture content.
Also in vac drying some people complain about the sap wood being to bright and the MC being to low.
There was a problem with bow in vac dried squares but that is an easy problem to fix.

I may also add that in the last 2 weeks I found that stress is not that big of a deal in vac dried lumber.

A lot of copy and paste. hope it works and please continue questions to jim from here.
Den

Offline DanG

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Re: Jim Fuller's ideas
« Reply #3 on: March 25, 2004, 07:31:30 PM »
JimF, I just want to welcome you to the ForestryForum, and encourage you to continue sharing your ideas and expertise with us. Maybe, someday, I will learn enough to ask an intelligent question. :D   Seriously, though, there are a lot of us who handle lumber on a regular basis, guided only by what we read here, and what we learn through our own experimentation. I just want you to know that the input from folks like you, Den, Don Lewis, and all the others that are operating kilns, is appreciated. Sometimes these posts don't get much response, but they are read by many who just don't have anything to add to the discourse.

Thanks for being here.
"I don't feel like an old man.  I feel like a young man who has something wrong with him."  Dick Cavett
"Beat not thy sword into a plowshare, rather beat the sword of thine enemy into a plowshare."

Offline old3dogg

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Re: Jim Fuller's ideas
« Reply #4 on: March 26, 2004, 02:05:02 AM »
DanG.
I have been reading a lot of post on all of the forums here and have not run across a question yet that was not intelligent.
I have been over in the sawmilling forum getting a ton of info.
Im thinking of setting up my own little mill and a kiln or two.
Who knows?Maybe even my very own vacuum kiln ;)
The really cool thing about this forum is no matter what the question everyone offers their insite,gives good information and doesnt treat anyone like they are dumb.

Offline Ga_Boy

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Re: Jim Fuller's ideas
« Reply #5 on: March 26, 2004, 05:03:48 AM »
Good move Den.
 
By the way, did thar feller with the questions about the WM vac 1K ever give you a call?

Jim,

I am starting up a Kiln operation and agree with the other postes here that your insights and ideas are valued.  Thank you for putting your thoughts to the banding stirng which created this one.  I'm looking forward to reading and contrubuting where/when I can.
10 Acers in the Blue Ridge Mountains

Offline jimF

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Re: Jim Fuller's ideas
« Reply #6 on: March 26, 2004, 05:21:19 AM »
Old3dogg,
As I have said I have not used a vacuum kiln, how do you avoid bow?  What do you do to avoid honeycomb?
The stanardl test for stress is the prong test.  It is a critical how you cut the test.  The KOM by USFS gives no details on how to do it.  It shows but does not say to cut a 1/3 out in the center and it does not specify what the result should be.  Just the difference of cutting the prongs 1/3 or 1/4 of the board thickness will given completely different results.  The KOM also does not mention the length of the prongs.  This is also important.  It takes very accurate methods to compare two different boards.Usually stressed boards can be used in most cases and not show any problems.  It is when the boards are used in critical situations that problems show up.

Offline jimF

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references
« Reply #7 on: March 26, 2004, 05:34:41 AM »
The three papers that directly support the patent are in Drying Technology: 18(4&5):1023-1031, 18(6):1349-1359, and and and (don't have the numbers for the third now, I think 18(10)).  The work started from three other papers in the same journal in some of the same issues.  These were on drying stresses and the test.  The first patent was 5,873,182 which can be down loaded from the patent office at www.uspto.gov.

Offline jimF

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« Reply #8 on: March 26, 2004, 05:40:03 AM »
If you follow the IMPRESSIONS given in books and conversation and seminars your answer will be off.  The key to the question is "during drying".  The answer: honeycomb, surface checks, stain, mold,etc, but not moisture content.  I'll let this boil some and I'll get to work here at the office.

Offline jimF

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Re: Jim Fuller's ideas
« Reply #9 on: March 26, 2004, 07:37:20 AM »
When MC is not a concern during drying and is not directly related to the other concerns why do we monitor it during drying?

Offline old3dogg

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Re: Jim Fuller's ideas
« Reply #10 on: March 26, 2004, 10:46:39 AM »
JimF.
I control both bow and honey comb with schedules.
DB,WB,and chamber pressure.
Not all bow is avoidable.We still get some but I havent seen a piece of honycombed wood in over 12 years.
I dont watch MC's while Im drying.I stick meter 10 samples from 10 different areas of the load when it "looks" dry.
All of my schedules are based on time.
Now Im talking about drying squares here not lumber.
Thanks for the info on the stress test.I have never had to worry about it before with squares but I will have to learn with vac drying lumber.

Offline jimF

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Re: Jim Fuller's ideas
« Reply #11 on: March 30, 2004, 05:20:56 AM »
The strategies for monitor and control of processes is to look at the limiting concern.  Since, moisture content is not a concern which of the following concerns are the limiting ones? honeycomb,  surface checks,  stain, progress, mold

Offline Den Socling

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Re: Jim Fuller's ideas
« Reply #12 on: March 30, 2004, 06:08:54 AM »
Mike,

I do believe that it has been less than 12 years since I've seen honeycomb in BWP's squares. There used to be a lot, at times. It was caused by stress in your squares.

Jim,

The limiting concern is moisture gradient. You can have too little or too much. One or the other causes all drying defects.

Den

Offline old3dogg

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Re: Jim Fuller's ideas
« Reply #13 on: March 30, 2004, 06:13:26 AM »
You are right Den.I guess its only been 8 years.

Offline jimF

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Re: Jim Fuller's ideas
« Reply #14 on: March 30, 2004, 07:36:49 AM »
no, moisture gradient is in the equation but is not directly related to the limiting factor.

Offline Den Socling

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Re: Jim Fuller's ideas
« Reply #15 on: March 30, 2004, 07:55:34 AM »
I'll have to disagree  ;) and I'd like to know what you are leading to but I have to make a service call DanG it. Be back tomorrow.  8)

Offline jimF

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Re: Jim Fuller's ideas
« Reply #16 on: March 30, 2004, 10:01:33 AM »
Sure, as wood looses water it tries to shrink and produces stresses.  But wood reacts with visco, visco-elastic and mechano-sorptive strains.  Some research has been preformed in this country and alot in Europe on predicting stresses as it relates to water loss.  No one has achieved significant results.  You can not predict drying stresses by moisture content, moiisture loss nor moisture gradient.  But I do agree with your line of logic that drying stresses is the limiting factor (which I asume is why you pick moisture gradient as the limiting factor). and many people think that moisture gradient is directly related to it.  John Hill tried to come up with a control system of measuring the moisture gradient and did not get very far.

Offline old3dogg

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Re: Jim Fuller's ideas
« Reply #17 on: March 30, 2004, 10:22:49 AM »
jimF.
I feel that in vac drying wood,most stress is caused by heat and how fast you evaporate water from the surface of the wood.
Drying at a lower temp and keeping the temp around the load close to the temp of the wood helps in keeping stress and other defects to a minuim.
I also feel that no matter how you dry wood you are going to see some stress and some defects.
Den.
Im not leading to nothing.When you left us I just found a different way of drying in our vac kilns.Gee man!Are you thinking Im trying to pick a fight here?
I dont beat up old guys! :D
Again im just kidding.Age is a state of mind not a state of being.
Jeff B.
PLEASE PUT A SPELL CHECKER ON THIS FORUM FOR US FOLKS THAT CANT TYPE.
Mike.



Offline jimF

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Re: Jim Fuller's ideas
« Reply #18 on: March 30, 2004, 11:11:28 AM »
"how fast you evaporate water from the surface of the wood".  Now is not the theory of vacuum drying that all the wood through out is under vacuum at the same time and that the water evaporates all at once?  If it is evaporated in the center how can it evaporate again on the surface?
"keeping the temp around the load close to the temp of the wood "The wood surfaceis at or above the WB.  For heat to be transfered the DB has to be greater than the WB.  The greater the difference the more heat transfered.  (This assumes no true vacuum. Otherwise no heat is tranfered by conduction from air.)
"in vac drying wood,most stress is caused by heat "  Heat softens the wood if the EMC is kept constant otherwise when it does reduces the EMC too much you increase the MC loss rate and/or too low of MC on the surface..
I've only seen a vacuum kiln once and never used one, but wood does not change behavior just because the energy source is different. :
By the way I like your quote Old3dogg

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Re: Jim Fuller's ideas
« Reply #19 on: March 30, 2004, 11:27:53 AM »
Mike,
Most of us use iespell for a spell checker.  It's better'n we ever had on the forum and it's free.  When you can get something this good for free why bother shopping for some more software.  :D

Go to www.iespell.com and install the checker.  

It works in any update window on IE (maybe more?)  and is actuated by putting your cursor in the window and right clicking.

......and it's free......it's free!...it's free! :D


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