The Forestry Forum is sponsored in part by:

iDRY Vacuum Kilns


Forestry Forum
Sponsored by:


TimberKing Sawmills



Toll Free 1-800-582-0470

LogRite Tools



Norwood Industries Inc.




Your source for Portable Sawmills, Edgers, Resaws, Sharpeners, Setters, Bandsaw Blades and Sawmill Parts

EZ Boardwalk Sawmills. More Saw For Less Money!

STIHLDealers.com sponsored by Northeast STIHL


Woodland Sawmills

Peterson Swingmills

 KASCO SharpTech WoodMaxx Blades

Turbosawmill

Sawmill Exchange

Michigan Firewood, your BRUTE FORCE Authorized Dealer

Baker Products

ECHO-Bearcat

iDRY Wood Lumber Vacuum Drying for everyon

Nyle Kiln Dry Systems

Chainsawr, The Worlds Largest Inventory of Chainsaw Parts

Smith Sawmill Service

Dynamic Green Products Inc.





Author Topic: Wood Science 101?  (Read 13627 times)

0 Members and 1 Guest are viewing this topic.

Offline L. Wakefield

  • Senior Member x2
  • *****
  • Posts: 1278
  • Age: 69
  • Location: Hollis Maine
  • Gender: Female
    • Share Post
Re: Wood Science 101?
« Reply #40 on: June 10, 2001, 06:51:44 PM »
   (Slightly off-topic)- one of the things you make me think about when you talk about old-rowth and rapid growth is the look of the new growth on the little pine and fir saplings. They are so prevalent in my cut-over areas- about 6 years old now- and it is INTENSE looking at the rapidly lengthening light green parts and wondering how much it will add up to at the end of the year. Thay aren't like adolescents yet (what would be adolescence for a tree?!)- but they sure are shooting up (vertically, not the bad way) like teenagers. Thank God I don't have to feed them- they'd be eating me out of house and home at this rate. Their real mother does that.
                  LW
L. Wakefield, owner and operator of the beastly truck Heretik, that refuses to stay between the lines when parking

Offline Ron Wenrich

  • Forester
  • Administrator
  • *****
  • Posts: 14159
  • Age: 72
  • Location: Jonestown, PA
  • Gender: Male
    • Share Post
Re: Wood Science 101?
« Reply #41 on: June 11, 2001, 03:45:06 PM »
I've been to a couple of antique lumber sites, and a few have stated the old growth as being more stable.  But, I haven't been able to nail down any why or why not.  I wish I could get ahold of Norm from the Yankee Workshop.  He's worked with antique lumber and seems to prefer it.

Stability is how much dimensional change can be expected from a piece of lumber.  Some species are more stable than others, and there is some variation within a species.  

I think that old growth would be the same as slow growth.  Those conditions can be replicated in the field.  Just start growing trees thicker.  You would get the same growth per acre, but it would be spread over more trees.  Economics wouldn't be as good, unless you can get more $/Mbf since rotation would be lengthened.

I remember seeing a post from a Finnish forester once where their stocking is much higher than ours.  Even their planting is much greater on a per acre basis.  Are they trying to get slow growth to overcome the problems with juvenille wood?

I don't know of any advantage to building a log cabin with old growth.  If the logs are dried, then they shouldn't move too much unless you get into crooked trees or where the logs would absorb a lot of moisture.

Moisture absorbstion comes mainly from the ends of a piece of lumber.  Water moves 12 to 15 times faster with the grain than across it.  

This thread has caused me to crack books I haven't looked at in years.  Mainly because I didn't crack them too much in school. :P :D

And when I get to tearing off more of my house, I will take pictures and post.
Never under estimate the power of stupid people in large groups.

Offline Don P

  • Senior Member x2
  • *****
  • Posts: 7243
  • Location: Southwestern VA
  • Gender: Male
    • Share Post
    • Calculator Index
Re: Wood Science 101?
« Reply #42 on: June 12, 2001, 07:30:27 PM »
I guess I used the term old growth interchangeably with slow growth and wouldn't know a difference to look at the wood. My point was that some Manufacturers are touting there high ring count as being superior and I'm wondering why.
I got more theories than the Bush girls have fake ID's :D
Ron, you stated maybe the higher stocking rates slow growth and make for less juvenile wood. Is there a basic cutoff point for juvenile wood...and now you see another place I want to go.
Does slow growth contain enough extractives to bulk the cell walls impeding shrinkage...or lessen response to a changing equilibrium.Kind of like a finish on the inside rather than out.(Ron, you are backpriming that siding aren't you?)
Is it like 13 ply vs. 7 ply where more alternation disperses stress.

Anyway I whipped out the crayola's to try to explkain what I think I know.


The blue represents the lumen or empty space within the cell. The left cell would be earlywood,the right late. The outermost layer S1 would be a very few microfibers of cellulose thick,fairly diagonal,a spiderweb to build upon. The layer between the outermost(s1) and the lumen,the S2 layer, is where the cells properties as far as stability occur. The lamellae turn more in line with the axis of the tree (although another of my theories is that in red and southern pine its still too diagonal) and put on the meat of the cell wall.
Shrinkage,and stability (which I guess to me is shrinkage and swelling in response to varying conditions after initial drying has happened) is a function of how freely these fibers can absorb (adsorb?) moisture into the individual fibers that make up the cell wall.

Another way is
Is juvenile wood seriously diagonal s2 cellulose?
Is slow growth more vertical?
Should I quit before you guys hire a hit man?
A laborer works with his hands
A craftsman uses his brain and his hands
An artist uses his brain, his hands, and his heart

Offline swampwhiteoak

  • Senior Member
  • ****
  • Posts: 385
  • Gender: Male
    • Share Post
Re: Wood Science 101?
« Reply #43 on: June 13, 2001, 07:50:30 AM »
I'm getting in here pretty late and I'm not sure I'm adding anything new.

My understanding is that juvenile wood has a very diagonal S2 fibril angle.  As a tree ages the S2 fibril angle gradually straightens.  In an old tree the angle is nearly straight (in the outer rings of course).  This makes for less defects during drying and more overall stability.

"Old growth" would still have juvenile wood with a diagonal S2 angle.  However since, we assume, the tree grew without management the rings will be tighter and therefore the volume of juvenile wood will be smaller.  Therefore in total volume the old growth will have less juvenile wood as a percentage of total wood.

IIRC juvenile wood is independent of management and basically dependent completely on tree age and genetics.  

For the best wood quality you would want to grow a tree as long as possible and as slow as possible.  But who has time for that?

At least that's what I remember in wood science class. :)

Offline Don P

  • Senior Member x2
  • *****
  • Posts: 7243
  • Location: Southwestern VA
  • Gender: Male
    • Share Post
    • Calculator Index
Re: Wood Science 101?
« Reply #44 on: June 13, 2001, 11:43:27 AM »
 8) 8)
Thanks Swamp! now its starting to jell for me (I was figuring my theories on this were as valid as those ID's)
I don't know the term IIRC, can you define it?
So is it fair to say that the wide growth ring wood I want to use has a diagonal angle and is just more prone to twisting?
Is there a table that lists species and fibril angle?
A laborer works with his hands
A craftsman uses his brain and his hands
An artist uses his brain, his hands, and his heart

Offline Ron Wenrich

  • Forester
  • Administrator
  • *****
  • Posts: 14159
  • Age: 72
  • Location: Jonestown, PA
  • Gender: Male
    • Share Post
Re: Wood Science 101?
« Reply #45 on: June 13, 2001, 03:50:41 PM »
Fibril angle may be an answer.  However, my 1964 textbook says fibrils are an "obsolete term".  Maybe the term has been revived.

Juvenille wood is the wood closest to the pith.  It has distinctly different cell structure than the outer part of the trunk.  For example, fiber length in hardwoods is much shorter.  Juvenille wood has excessive longitudinal shrikange, causing unusual warping.

Formation of juvenille wood is associated with the prolonged influence of the apical meristems in the regions of active crown.  As the tree crown moves up, the cambium at a given height becomes less influenced by the elongating crown and adult wood is formed.

Often juvenille wood has similar properties to limb wood.  Ring size has little to do with whether juvenille or adult wood is formed.  Distance from the top does.

As for extractives in the lumen, isn't that when heartwood forms?  
Never under estimate the power of stupid people in large groups.

Offline swampwhiteoak

  • Senior Member
  • ****
  • Posts: 385
  • Gender: Male
    • Share Post
Re: Wood Science 101?
« Reply #46 on: June 13, 2001, 03:53:48 PM »
Don,

IIRC - "if I recall correctly" - Shorthand for message boards 101

I'm not sure that just because there are wide growth rings that necessarily corresponds to a diagonal S2 angle.  If I'm correct (and I'm working off what I remember in a class I took years ago) S2 fibril angles are correllated with age, genetics, and species.  So if you've got a wide growth ring in juvenile wood it would be more prone to twisting, but if a 80 year old tree had a really good couple of years the S2 angle wouldn't necessarily be more diagonal than normal.  All things equal, though, I'd rather have tighter growth rings.

Purdue University claims their famed "Purdue Walnut" (no.2 I think) doesn't have juvenile wood characteristics or any wood defect problems even though it grows twice as fast as normal walnuts.  So that shows genetics plays a role too.

Of course there's more going on than that, like everyone else has hit one, the orientation of the board when it was sawed, ring density, ect.  It makes me glad I'm a forester and not a wood scientist. ;D

As for a table on fibril angles and such, I'm not sure.  You might try:

The FS northeast research station pubs-
http://www.fs.fed.us/ne/home/publications/scanned/oldonline.html

Or the Southern research station pubs-
http://www.srs.fs.fed.us/pubs/index.jsp

I don't have time to search right now.  Let us know if you find out anything.

Offline Gordon

  • Senior Member
  • ****
  • Posts: 708
  • Age: 57
  • Location: DE
  • Gender: Male
  • smoke free growing trees †raising my 6 kids
    • Share Post
    • JGforestry
Re: Wood Science 101?
« Reply #47 on: June 13, 2001, 04:00:56 PM »
I don't have any value to add to this thread other than keep it going guys. It's great!

I have one question, does it make a difference how the wood is dried reguardless of young or old growth when it comes to twisting?

Thanks
Gordon

Offline swampwhiteoak

  • Senior Member
  • ****
  • Posts: 385
  • Gender: Male
    • Share Post
Re: Wood Science 101?
« Reply #48 on: June 13, 2001, 04:05:50 PM »
Ron, you just posted right in front of me.

My textbook (which I don't have at my disposal) was written in the late 80's and talks about fibrils.  Maybe the term has been revived, or maybe my professor just picked out a bad book.

Quote:
Formation of juvenille wood is associated with the prolonged influence of the apical meristems in the regions of active crown.  As the tree crown moves up, the cambium at a given height becomes less influenced by the elongating crown and adult wood is formed.
- end quote

I always heard it had more to do with age than growth, i.e. two loblolly's the exact same size and height, one 20 years old, one 40 years old, the younger one will have more juvenile wood.  I like your explanation better, though. Your saying grow the tree as quick as possible to help the apical meristem lose its dominance over the trunk.

I guess I'll have to pull my book out to participate further.

Offline swampwhiteoak

  • Senior Member
  • ****
  • Posts: 385
  • Gender: Male
    • Share Post
Re: Wood Science 101?
« Reply #49 on: June 13, 2001, 04:39:32 PM »
Alright, found my book!

According to Forest Products and Wood Science

"Juvenile wood has been defined as secondary xylem produced by cambial regions that are influenced by activity of the apical meristem...as the cambium in a given location continues to cause diameter expansion, it also becomes progressively farther from and therefore less subject to the influence of the apical meristem."
(Tried to quote as little as possible)  This backs Ron up on what he said before.

The large S2 fibril angle causes a high degree of longitudinal shrinkage and a corresponding decrease in transverse shrinkage; along-the-grain shrinkage has been reported to average 3 times that of adult wood. (The 3X quote comes from the text, the table suggests a 7X or greater figure)

In a study of slash pine the value of lumber obtained from a 20-yr old 14.3 in diameter trees was only 66% of the value obtained from 50yr old 15.1 in diameter trees. (Due to less yield b/c of shrinkage and twisting)

There's also a table comparing properties of mature wood and juvenile wood.  S2 fibril angles for conifers were 20 degrees (for mature wood) vs. 55 degrees for juvenile.  10 degrees vs. 28 degrees for hardwoods.

Specific gravity, density, fiber length, cell wall thickness are all much greater for mature wood.  Lumen size and cell diameter are greater for juvenile wood.

So all else equal, you don't want to make anything but pallets or pulp out of juvenile wood.


Offline Ron Wenrich

  • Forester
  • Administrator
  • *****
  • Posts: 14159
  • Age: 72
  • Location: Jonestown, PA
  • Gender: Male
    • Share Post
Re: Wood Science 101?
« Reply #50 on: June 13, 2001, 07:12:05 PM »
My text is Textbook of Wood Technology by Panshin and DeZeeuw.

I've always noted that you can box your heart, and not have too many problems with the wood.  Where you split the heart, you get into major problems.  This is especially true for cabin logs and bridge timbers. 

Tie buyers will take no exposed pith.  They prefer boxed heart.

I have been able to saw logs by taking the heart out in a pallet board and putting cabin cants on the outside.  Also do this for no heart basswood carving stock.  6x8s for swans.
Never under estimate the power of stupid people in large groups.

Offline Jeff

  • Fearless Leader
  • Administrator
  • *****
  • Posts: 49952
  • Age: 59
  • Location: Harrison MI
  • Gender: Male
  • I know that I do not know.
    • Share Post
    • THEE Forestry Forum
Re: Wood Science 101?
« Reply #51 on: June 13, 2001, 08:02:38 PM »
Hey Gordon,

I'm wif ya
Just call me the midget doctor.
Forestry Forum Founder and Chief Cook and Bottle Washer.

Commercial circle sawmill sawyer in a past life.
Ezekiel 22:30

Offline Tom

  • In Memoriam
  • *
  • Posts: 25838
  • Age: 77
  • Location: Jacksonville, Florida
  • Gender: Male
    • Share Post
    • Toms Saw
Re: Wood Science 101?
« Reply #52 on: June 13, 2001, 08:39:43 PM »
This is great.  I feel like I am back in my old Botany class.  I don't have any of the info you all are talking about so I sure appreciate it.  The description of Juvenile wood is clear as a bell and will help me to describe it to customers one day.

Your right about Juvenile wood only being good for pulp and pallets.  Most of the plantations in the southeast are being cut at 10-15 years, run through a chipnsaw, squared to 4x4,split to (2) 2x4's, stamped with a #2 grade stamp and sold to the Mega lumber store. Both pieces have pith. @#$%^&*(

I always figured it was the ink that made quality lumber.

Of course the carpenters don't like mature SYP.  It takes 5 or 6 whacks to drive a 16 penny. :D
extinct

Offline Tom

  • In Memoriam
  • *
  • Posts: 25838
  • Age: 77
  • Location: Jacksonville, Florida
  • Gender: Male
    • Share Post
    • Toms Saw
Re: Wood Science 101?
« Reply #53 on: June 13, 2001, 09:12:23 PM »
Ron W. because of your post, Jeff, because you sit in a saw booth and anybody else who wishes to offer an opinion: I have a question about cutting timbers.

I Box hearts when I can but cut 6x6 6x8 and 4x12 type stuff for customers who are using them for exposed beams in their homes. They like the heft.  I am cutting these, many times, out of large logs and will box the center cut but create beams from the outside as well.

Tension in a beam cut from the outside will usually cause it to pull to the bark side.  I cut it thick so I can trim it and relieve the stress, hoping that it won't return as it drys.

I try to create all beams flat sawed or boxed for strength.

The other side of the Non-boxed beam logic is that they don't tend to check as badly or as deeply as the boxed beam.

What is your technique and logic?


extinct

Offline Ron Wenrich

  • Forester
  • Administrator
  • *****
  • Posts: 14159
  • Age: 72
  • Location: Jonestown, PA
  • Gender: Male
    • Share Post
Re: Wood Science 101?
« Reply #54 on: June 14, 2001, 03:28:30 PM »
For me, it depends on the final usage.  If you are looking for strength, then boxing the heart is the best.  They won't take any bridge timbers without boxed heart (and their pretty fussy about other defects as well).

Pallet stock, I don't care.  I split a lot of cants, especially since 2 Com has dropped in price.

For cabin logs, I will take a cant off the side if it is a short length.  Long ones are too hard to pull straight.

For smaller beams, I will split logs.  A 4x12 isn't that much different than 2 2x12s.  I will split floor joists, with little difficulty on the construction end.  Most guys around here use 4x8 or a 4x10 for cabin construction.
Never under estimate the power of stupid people in large groups.

Offline Don P

  • Senior Member x2
  • *****
  • Posts: 7243
  • Location: Southwestern VA
  • Gender: Male
    • Share Post
    • Calculator Index
Re: Wood Science 101?
« Reply #55 on: June 15, 2001, 06:41:59 PM »
This is where I've been this evening so far trying to find a clear description of what leads up to the cell structure posts.

http://www.psrc.usm.edu/macrog/cell.htm
http://www.psrc.usm.edu/macrog/fiber.htm
http://www.psrc.usm.edu/macrog/crystal.htm

Can one of you guys explain apical meristem?
A laborer works with his hands
A craftsman uses his brain and his hands
An artist uses his brain, his hands, and his heart

Offline L. Wakefield

  • Senior Member x2
  • *****
  • Posts: 1278
  • Age: 69
  • Location: Hollis Maine
  • Gender: Female
    • Share Post
Re: Wood Science 101?
« Reply #56 on: June 18, 2001, 10:19:11 AM »
    As best I can wing this one from years ago- the apical meristem is portion of the growing shoot or branch (or root!) that has the most rapidly dividing cells. Apex means the top, the tip, or the point. Meristem is not the outer dead cells but rather a very actively dividing tissue. If you want to do 'tissue culture' to propogate your plants, meristem is what you use (It's sometimes called 'meristemming'- they do it with orchids, but I think the same holds true for trees as well as herbacious plants).

This tissue suppresses growth below ip (can't remember the name for this inhibition)- and if you want to have sprouting shoots below the growing tip, you lop off the tip. (Just what you DON'T want to do to timber if you want a single straight trunk for lumber).
 
  This explanation has 2 weaknesses. I can't remember what actual layer of the growing tip copmprises meristem; and I can't remember how far down the tip it extends.
  The botany text I just consulted isn't much help- it shows the cells, but doesn't describe their limits, and it shows very young shoots. It does state that 'any living parenchymatous cell is potentially able to develop into a secondary meristem'- responding to injury- or to removal of the suppression from previously active meristem above, I guess.  :o :o :olw
L. Wakefield, owner and operator of the beastly truck Heretik, that refuses to stay between the lines when parking

Offline Don P

  • Senior Member x2
  • *****
  • Posts: 7243
  • Location: Southwestern VA
  • Gender: Male
    • Share Post
    • Calculator Index
Re: Wood Science 101?
« Reply #57 on: June 24, 2001, 06:59:22 PM »
This link has the best description I've found of the microfibril angle and shows x-rays they took of them showing how they determined their angles.
http://www.esrf.fr/info/science/highlights/1999/materials/wood.html#anchor91

Try this weeks theory on and see if it will fly.

Within a single species the number of cells between heart and bark remains constant.
Density does not.
So what varies is the thickness of the cell walls,the number of fibrils making up the wall.

I've realized another criteria of stability for me is a timber that dries with as little checking as possible.One thing that causes checking and drying stresses is a high moisture gradient(wet and swollen at the core and a dry shrinking shell)

Thinner cell walls means less bound water within the timber so the gradient should equalize throughout the timber more readily.As a side benefit the thin wall means more lumen so a slightly higher r value.

As I've been cutting this week this has held up(I think).What I've been noticing is low density wide ring spacing having the fewest surface checks.
Does this make any sense?
A laborer works with his hands
A craftsman uses his brain and his hands
An artist uses his brain, his hands, and his heart

Offline Ron Wenrich

  • Forester
  • Administrator
  • *****
  • Posts: 14159
  • Age: 72
  • Location: Jonestown, PA
  • Gender: Male
    • Share Post
Re: Wood Science 101?
« Reply #58 on: June 25, 2001, 05:41:25 PM »
"Within a single species the number of cells between heart and bark remains constant."

I'm not sure what you mean here.  Are you saying the sapwood contains a constant amount of cells?  

From pith to bark would vary according to age and growing conditions.

"Does this make any sense?
Density does not.
So what varies is the thickness of the cell walls,the number of fibrils making up the wall."

My only question here is does a higher number of fibrils make wood denser?

A couple of questions come to mind about checking.  Do longer logs check more than shorter ones?  Do butt logs check less than 2nd and 3rd cuts?  Does tree size make any difference?



Never under estimate the power of stupid people in large groups.


Share via delicious Share via digg Share via facebook Share via linkedin Share via pinterest Share via reddit Share via stumble Share via tumblr Share via twitter

lamp
Wood Science 202

Started by Don P on General Board

3 Replies
1129 Views
Last post April 03, 2002, 07:30:52 PM
by Gordon
xx
Wood Science

Started by Forester Frank on General Board

5 Replies
3458 Views
Last post February 05, 2001, 02:05:13 PM
by Forester Frank
xx
Wood science question - hysteresis

Started by Dan_Shade on Drying and Processing

5 Replies
840 Views
Last post February 29, 2016, 07:22:22 AM
by GeneWengert-WoodDoc
xx
The art and science of stringing a bed

Started by Kevin on Sawmills and Milling

4 Replies
1445 Views
Last post May 10, 2003, 11:12:44 PM
by WoodChucker
 


Powered by EzPortal