Wood Science 101?

[Don P]

I just looked at the heat loss calcs page on the plans accompanying this house.
The logs are a mix of red and white pine, and I'm sure the numbers must be used conservatively.
For the 1/2 log siding 2" minimum dimension to 5" at the belly of the round they used R=2.66. For the 8" tall full log (the one I showed how to do on your mill) they claimed R=5.32 +0.17 exterior film +.68 interior film for a total R=6.17. Even with that said we have told HVAC guys to calculate as if a R19 wall and have yet to be undersized. DOE has a MEC (model energy code) calculator download on their website that includes log. Haven't been there since I learned how to read source code to see what numbers they use but it seemed to give better results than the raw R values I just quoted. This is and always has been a hot button issue in log circles.
One more thought on hardwoods vs. soft look at the shrinkage values.
Ron, my sister always said she wanted to get a t-shirt for me with the slow children sign on it...so what your saying is the 4 rings per inch pines have more rows of the same diameter cells per ring as compared to the many rings per inch wood?

[Ron Wenrich]

Don

That's the way I read it.  Better growth in the early wood would give it lower density.

I know that slow growing wood is a lot heavier and harder to saw as compared to faster growing wood.  However, slower grown wood is more stable.

[L. Wakefield]

   A quibble- a few messages back in this thread someone stated that the lower the density, the higher the R-value. I accepted that at the time- seemed logical- but I was just re-reading and it seems to me that this would only be true if the wood were analogous to a 'closed cell' material rather than an 'open cell' material (think about foams of these 2 types). If each cell is isolated from the next in terms of being able either to conduct or convect the heat (or cold- think of it either way)- then more air space means more insulation. But if the spaces are NOT isolated from each other, then more space (lower density) just means easier transmission of the heat/cold. I know this is a theoretical quibble, but I'm not sure how closely it applies to wood. The insulation quality might even vary with the orientation of the wood and the type of cut.   lw

[Ron Wenrich]

Let's see if I can't get a better explanation.  Air, is a pretty good insulator.  It doesn't really conduct heat or cold all that well.  If that would be the case, we would burn during the day and freeze at night.  Much like planets that don't have air.

Also, old stone homes were built with an airspace in between the walls.  Actually a house inside a house.  The air was the insulator, since stone conducts heat better than air.

The air spaces in the cells of the lower density wood gives it the better insulating factor.  Much like fiberglass insulation.  It's the air trapped in the fiber that insulates, not the fiberglass.

The heavier density woods have less air, and will transmit the heat/cold at a faster rate.

[Don P]

I've seen sawdust used in those old houses for insulation also. Cordwood builders use typically 2' lengths as they claim heat does move thru end grain more readily. Windows are typically R-2. Kinda like putting on a down coat and not zipping it up.

 Why is the slower grown piece more stable? There are the same number of cells from heart to bark in both pieces. I think the same proportion of early and latewood (both bands are wider) only the alternation rate between bands changes.

Do latewood cells shrink more than earlywood? I am assuming that since there is more cellulose in their cell walls as the chemically bound moisture is removed there is more dimension loss as compared to the empty area that would be in that area of an earlywood cell.

[Ron Wenrich]

Sawdust has plenty of air space.  My house has soft brick as insulation.  Not great, but better than nothing.  It cuts down the wind.

The reason I say slow growing wood is more stable is by looking at old furniture and woodwork.  My attic has 16 inch wide plank flooring.  My house had 12" and wider vertical siding.  All was old growth, and none of it moved or bowed.

How many times have you seen old tables with wide board tops?  How many do you see today?  Reason is stability.  They now cut all lumber into strips and glue them together.  One plant I was through cut from 2" to 4" in widths, and many are cutting smaller.  

Early wood is less dense and the fibers are shorter than in late wood.  Slow growing species have less early wood than fast growing species. So, there is less variation within the tree between the density levels.  

Does this make sense or not?

[Jeff]

"Does this make sense or not?"


Couldn't tell Ron, but is that your new signature??


 :D

[Tom]

Hey Ron,  it makes a lot of sense to me.  One thing that you said about their not using wide boards anymore may be because there aren't too many "wide" trees anymore.

Seriously though, We are getting more and more folks using wide boards around here because we have made a point of challenging woodworkers to use them.  They have been brainwashed by "whomever" into believing that wide boards are not good, southern wood is no good, gum is no good and that only thin boards that have their bark sides alternated and glued together will make a stable panel.  

It amazes me the kinds of head games that get played even with woodworkers.  Granted there are different ways of using wood and some woods may be better for a project than other woods. But, beauty is in the eye of the beholder and justification rather than generalization is the more responsible answer.

When a so-called knowledgable person says that something is no good or won't work he can actually stop a percentage of the population from even trying it.  Eventually they do the same thing to someone else and then "for no reason" a wood is cast aside.

I haven't paid so much attention to slow growth not moving as I have to grain orientation leading to stability. Vertical grain makes a better floor because it wears better (more winter wood rings take the punishment) and because it tends to move towards the bark side of the board.  This means that it's movement is side to side rather than up or down as a flat sawn board would be and can be pulled up to the first board, nailed and held in place by the second board. Once the floor is in place there is no place for the wood to go.

If the floor is flat sawn then it tries to lift up and the only thing holding it down is the nail.  It also exposes a  wide and thin layer of each ring to the wear surface. If the exposed ring happens to be early wood then it will not last as long as the late wood ring. Therefore the floor will wear unevenly.  Rings can lift in flat sawn boards which will cause sharp edges. This isn't good in a floor.

Vertical grain boards used for siding don't hold fasteners as good as flat sawn boards.  In this instance flat sawn can be used very effectivly.

LW you're right about discovering the use of a batten.  I like Board and Batten because 1. it is weather resistant 2. it allows the use of any size board and 3. any size board or boards can be used in it's repair.  When the siding is placed horizontally it must be lapped and all boards in a run must be the same size. It is also very difficult to repair with whatever is handy.

I believe that if I were to build a log home, I would lean toward Balsa and treat it if necessary.  The logs would be easy to handle and the R factor high.
 
That doesn't mean that Balsa would make a better wall than SYP but I think that the important thing is to not say that one is no good.
  

[Ron Wenrich]

Today's building practices do not lend as well to board and batten as in past times.  I'm residing my house, so I have gotten a good view of how they used to build houses.

My house is post and beam.  Not the big posts, as barns were built.  Primarily 4x4s with wind braces on every corner, bottom and top.  4x4s were used only on corners and where windows and doors were fitted.

Some runs would stretch as much as 4' between centers.  Everything was pegged.  The boards would lend to the strength of the building by helping to tie it together.  

Very few nails were used, and they held the boards better than today's nails.  Old nails are brittle and are square and tapered.  

I'm replacing with sawn pine, 10" and wider.  Very similar to the old wood.  Reason for the replacement was that the older wood wouldn't hold paint, and had some deep cracks, and was rotted at a few places, but not badly.   Total useful life of the original siding was 150 years.

Original foundation is loose rock foundation.  As I was hanging the siding, I put a level on the side of the building.  It is still dead on.  My belief is the wind bracing makes all the difference in the world.

As for wide boards, we still get a lot of wide tulip poplar.  There is a market for 12" and wider.  

But, a lot of people are cutting smaller trees that don't give that yield.  There is more juvenille wood, and that moves more than the older growth.  This is one of the reasons for the smaller cuts in paneling.

Another reason is to use lower grade material to make panels.  Cost/sq in of usable wood is much lower in 2 Com than in FAS.

[Tom]

Ron,

I hope you are taking pictures of the inside of your walls and the fact that it is square etc.  I would like to see a picture but even if it weren't posted  it would make a good house scrapbook. Even pictures of the nails are interesting to someone who has never seen a cut nail or square nail.

You are right.  Today's building techniques don't lend themselves to board and batten.  We still have a lot of old timers around here and old time families that believe in it.  Farms still build a lot of board and batten and board on board buildings, barns and houses.

The zoning people and building inspectors have nervous breakdowns everytime they get near one.  I think it is because the spend so much time around these "kit" houses in the subdivisions.

It amazes me when a building inspector wants someone to take a rough cut 2x12 down and replace it with a dressed 2x10 because that was what was on the plans.

A lot of these farmers use drawn plans to get started and then adlib with heavy beams and logs sawed on 3 sides or crooked trees that have been squared as best as they can.  This stuff is usually ornamental but it gives the inspectors fits.

I don't know how you were lucky enough for your 4x4 corners to last 150 years without a grade stamp......Did they have a grade stamp?
 

[Don P]

Tom, don't get me started on my fiend oops I mean friend the inspector. I was trying to use my "homemade" poplar framing at home...not without a stamp or certificate, closest stress grader is 200 miles away and the old building was made of sawmill! After today balsa is sounding pretty good.

Ron, I'm still unconvinced...not that I don't agree with you ,I don't agree with your reasons and don't know enough to offer better ones. Cell length shouldn't matter to stability if we are talking check,cup, twist...maybe bow.Modulus of elasticity or fiber stress in bending, yes, stability ,no. Proportion of latewood higher in slow growth, well I've been staring at the pile for hours. The transition zone between early and late is quite wide in the fast grown trees so earlywood or late is kind of a judgement call where in slow grown it seems to be abrupt. I think the proportion is about the same. One big diff is the amount of heartwood. Dunno gotta cypher on it awhile yet.

Signed,
make any sense to you?

[Tom]

Don and Ron, at the risk of being over my head in this conversation ....

Doesn't stability have to do with the relative release of moisture between one cell and the other?

If the cells on the surface release more water than the cells beneath them then you have checking.

If the cells on one side of a piece of wood dry faster than the cells on the other side you get warp.

If early wood releases it's water faster than late wood then wouldn't the relative differences from interior to exterior or top to bottom tend to be greater than the denser late wood which would seem to me  to stay more in an equilibrium as it dried?

Everything I have been able to read in the past couple of days has related stability more toward grain orientation and growth stresses. ie) reaction wood or juvenile wood.  

This site/book has provided me most of my current info.http://www.fpl.fs.fed.us/documnts/FPLGTR/fplgtr113/fplgtr113.htm

The Encyclopedia of Wood has provided me more but mirror images the above book.

I may not be able to join in very intelligently but I am interested and want you to know I am listening.

[Don P]

Tom, I'm in way over my head but that was why I started this thread, Thanks for chipping in. I've woken up in the FPL handbook more times than I can count. It and everything else I've been able to read seems to stop with the same observations we've been making. I want to know specifically the whys. My reason in this particular instance is that in my log homes using a log that takes 35 years to grow and turning it into a structure that should last a century is a good thing. I'm constantly bombarded by the crowd that wants to use old growth in this application and although this stuff is fun to use I don't feel right counting a couple of hundred rings in the end of a log. Call me a bunny buddy but it just doesn't add up.

Stability in my application would be the ability to stay where I put the log assuming proper drying practices were used in manufacture.

Ron, your comment about wind bracing is accurate.  A triangle can't be distorted. In the Kyoto earthquake japanese traditional houses sustained so much damage because their traditional timber frames don't have knee bracing,the strength is all in the joinery. The triangle within the joint is small compared to the lever length of the beam.

[L. Wakefield]

   All I can say after those last few posts is 'hmmmmm...' (indicates that the eyes are crossed, the generator is humming, but the lightbulb is NOT on). As they say- 'you- ARE- the weakest link!' (I refer, of course, to myself in this case..)           LW : : :

[Tom]

Me too LW..HMMMMMMMMMMM

Don, I think "old growth" is just a popular term today and some people use it for emphasis without giving a lot of thought as to what it is.

Fast growing trees produce an abundance of summer(early) wood and I've found that to be the first meal an insect will go for.  Do you suppose that may be one reason people want "old Growth", because it grew slower there is less soft stuff in it.

Ron I have some acquaintances with your caliber of education and I am going to ask them this question the next time I see them.  The question being the Post of 6/5 at 22:51.

I guess I lose the picture when talking about stability in logs.  A sawyer releases all kinds of stresses in a log when he cuts the board and the board reflects this.  When a board has the stresses equalized by the heart being centered then the movement is less.  I've got to "go to school" on an intact log.

[L. Wakefield]

   (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

[Ron Wenrich]

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.

[Don P]

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?

[swampwhiteoak]

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.

[Don P]

 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?

[Ron Wenrich]

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?  

[swampwhiteoak]

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.

[Gordon]

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

[swampwhiteoak]

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.

[swampwhiteoak]

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.