I was wondering if there is interest in something like "Wood Science 101". The reason I ask is in my log home business I deal with average people who need a resource of clear,accurate, understandable info on the hows and whys of basic wood science.
Topics that come to mind, How and why does wood shrink, relationships between humidity and size, why and how wood rots...:P?????
Topics like that will scare the living daylights out of them. :D
I hate to direct you to other sites, since this one has all you need, but www.woodweb.com does have a lot of useful information.
EUUUURJ:J:JAAAAAAAAAHHHHHHHHHHHHHHHH!!!!!!!
With that out of my system, Ron is right, they do have a great site. BUT LIMITED, THEY DON'T HAVE..........................................
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I think you under estimate the general public. I am the general public, and that stuff interests me. You do not have to have a college degree to seek and understand applicable information in a subject of interest.
I agree with both points. I'll just send the brave ones.;D
8)My first question has to do with shrinkage. I know that denser species shrink more than woods with a low specific gravity. My next leap of logic is that I assume denser pieces of wood within a species should shrink more than less dense pieces. So, if I am faced with 2 logs one has a zillion growth rings per inch the other has 4 rings per inch, which log is denser? Which will shrink more?
The more growth rings you have, the denser the wood. Shrinkage has to do with cell wall material.
The example I have seen has to do with a comparison of mahogany and sweetgum. Both have the same density, but mahogany shrinks about half of the sweetgum. The factor lies in there being more lignin in the tropical hardwoods than in sweetgum.
Density is not a factor in shrinkage rates. Honeylocust shrinks less than aspen, but is 80% more dense. Catalpa is just a tad more dense than aspen and shrinks much less.
Your piece with a zillion rings will be less apt to warp or twist. Shrink more? I don't know, but I would think it would be about the same.
Jeff:
If you told the average homeowner that his hardwood floor moves, they would be concerned. They would want something more stable, like concrete.:D
Lets not aim for average then, cause the average won't frequent and post on such a fine board.
Wood Technology was never my favorite subject. I left that for the people in the lab.
Thanks for the responses! Yes it does scare the average homeowner to hear that wood moves. I don't feel ignorance is bliss though (although I do have a silly grin often):D
You have dashed a theory that took me nearly a decade to form bouncing around on my own in the dark. I love it, at best I was on track for about 3 more wrong theories.
Every answer asks a new question! Since I can no longer advise people to stick to the lighter weight, low specific gravity woods for shrinkage reasons (that had always been my pet answer) what do I tell them? I will try to recall two recent posts one asked which species is best
White Cedar, Red Cedar, Lodgepole Pine, Cypress, Oak, White Pine and are there regional differences in White Pine that make Pine from one area better than another? The next is conventional wisdom among cordwood builders. They use only softwoods claiming hardwoods shrink and swell (disasterous to cordwood construction) too much, now you've stood that on its head. So my question would be which species within economic reason are the most stable both through the drying process and in service?
As for not caring for wood tech, yes it is tedious. There is alot of garbage being put up out of ignorance. It does not give a feeling of satisfaction to re-invent the wheel. My goal for myself is to have a thorough knowledge down to the molecular level of the medium I work in, kinda scarey (but then dad was a bit nervous when he got home and I had the family car apart)::) Knowing how something works is an accomplishment, knowing why is to have mastered ones craft.:P
When we put up a barn down in WV, we did the upper level walls out of rough cut (probably tulip poplar, but I can't remember..) nailed on vertically, butted tight together. After about 6 months there was at least 1/2" gap between boards. Suddenly I could see where the board and batten building method came from.. LW
The regional differences in white pine that I am aware of is the called red knot and black knot pine. Red knot pine grows in the colder areas, and black knot in the more southern reaches of the range.
Black knot pine seems to retain the bark on the knots as the tree grows around them. When cut into boards, they will fall out when dried and machined.
You also have a difference in western white pine vs eastern white pine. Both probably get sold under the white pine label.
My info on variations within a species is dated (1970). It said there is some variation, but they don't know why. Studies were inconclusive and incomplete, meaning that it was worthless research.
Softwood is a better construction wood for log cabins since it has a higher R factor, which is important for insulating factors. This is due to more air space being in the less dense woods. Besides the logs are easier to handle.
Post and beam construction was done primarily with softwoods due to availability, and ease of making joints. For strength, hardwoods were used for rafters and joists.
Lodgepole pine has a problem with spiral grain. That will cause a log to turn as the moisture levels change. A scary thought in a cabin, even worse in a utility pole. It was know to snap lines when they used cross bars.
As a rule of thumb, softwoods don't have as much volume shrinkage as hardwoods. But, it depends on the hardwood and the softwood. The least shrinkage in softwoods are: redwood, western red cedar, northern white cedar, incense cedar and eastern red cedar. For hardwoods: catalpa, osage orange, black locust, sassafras, and butternut. Interesting to note that catalpa would be #4 in softwoods.
Traditional hardwoods such as oak, beech, and maple will shrink about 50-75% more than hemlock or white pine.
hmm..I never heard of incense cedar- as a favor to resinwoman here, can you tell me genus, species, and distribution of this tree, also if it, as its name suggests, is specially aromatic? I have compared essential oils of domestic and foreign cedars, having cedrus atlantica or cedrus deodara as my current favorite- but always looking for either domestic or naturalized competitiors..LW
Incense cedar: Cupressaceae Libocedrus Decurrens
Grows out west, primarily in Oregon and California. Slow grower.
Want a sample? Think pencil. That's what many pencils are made from.
Port Orford(sp?) Cedar? L. are you giving up any extraction secrets?
well, with the name sequence (2 posts back), 'cupressaceae' would be a family designation, and then Libocedrus decurrens would be the genus and species names. The only domestic cedar oil I currently have a sample of is Texas cedarwood (Juniperus mexicana)- which does indeed smell like pencils. I don't use it much in blends because it reminds me of gradeschool. The Himalayan cedarwood sample I have is either Cedrus atlantica or Cedrus deodara- I have yet to get those 2 together for comparison.
At some point when I was doing the search for Populus balsamifera, I came across an extensive discussion of cedars- I think it was a site out in Oregon- that let me know just how popular and exotic this genus is. I suspect the decurrens will turn out to be one of the ones with the sweeping (almost weeping) branches. but that's just a guess.
The eastern division of 'cedars' into red vs white cedar seems to rest on Juniperus as the red, and Arborvitae as the white. I've seen both of those, but Cedrus, and 'Libocedrus'are not something known to me just yet. LW
test
I've got a couple of questions for wood 101.
In building log homes what is the wood of choice?
Is it because it's the best wood for the job or the least expensive.
Even when dried softwood is better than hardwood for a log home. Why because of the R-value?
What if the hardwood was sealed would that help the shrinkage rate versus the humidity level?
Thanks in advance
Gordon
Hmmmmm.....there can be a huge difference in shrinkage even between two trees 100 ft apart, depending on age and health, how much sun they get, etc. I cut mostly white cedar, and some are like cork, some are like hemlock, wet and heavy, but all seem to air-dry well. Gordon, I think that the reason for most log homes being built from softwoods is than they are inherently more rot resistant. I thinks it's the resins in the wood. One certainly wouldn't want to build a log home with white birch!! Oak is relatively rot-resistant for a hardwood, but can you imagine the extra work due to weight?
Rot resistance has little to do with it. Many logs houses in my area are made from white pine, with red pine being second.
It has to do with R value, at least with pine. 6" thick pine wall is an R value of 20. For oak, I believe it would be about 12.
It is all due to density. The lighter the wood, the less dense, the higher the R value due to the air inside the cell walls.
Pine is also easier to mill, lighter to lift, so you can haul more on the trucks to the job. Cant expense between hardwood and softwood is not a great deal at that grade level.
There is a Missouri (I think) company that handles oak log houses. No one uses hemlock or soft hardwoods, that I know of.
While I haven't seen any of these commercially available I do know of a few houses that were built using trembling aspen.
The trick was to keep the bottom course of logs out of contact with the earth and to have the roof overhang the walls by what seems to be 2 feet.
The exterior was treated with some type of stain but to the best of my knowledge the owner hasn't had any problems with it to date.
Bill
Well, donchaknow, my chances to catch up on reading here have been very spotty- computer glitches and then killer busy with planting and growing season- but this is one of the MOST interesting threads I have seen on here. Not at all to diss the others- but the fella who said he liked to get right down to the molecular level in understanding is most definitely a kindred spirit. That's how I learned biology, chemistry, anatomy, physiology, what little I know of physics- etc etc etc. That's science. Being able to conceptualize a zoom lens appreciation of the fabric of whatever-you-are-studying. Admitted that the mechanics of growing, cutting, processing, or using (let's say, uh, wood- for a random example) may be performed without such understanding- predicting the outcomes of certain untried maneuvers is made much safer, and allows increased competence in engineering processes. If you call it engineering with wood. (Why not- it's engineering with steel, and you can make a bridge or a tower out of wood, so knowledge of the material on a molecular level has to be useful.) I loved the part about the R-value and relative density. Surely this would be affected also by percentage of dryness- the drier the better for empty spaces to be 'air' spaces, rather than 'water' spaces (but remember folks, if it gets too dry that nasty old 'dry rot may set in :D :D :D) lw
If its a fungus, it needs water and oxygen to rot. That is why wood that is dried doesn't rot. Dry rot ususally occurs in high humidity areas, such as underneath a floor where there is poor air circulation.
As for oxygen, that is why utility poles and fence posts don't rot below 1' ground level. Also one of the reasons submerged material doesn't rot very fast.
Temperature is another factor contributing to rot.
Gordon, finishes cannot seal out changes in equilibrium moisture content, only slow vapor movement down. The old cabins in my neighborhood are all species. Heavy and rot resistant logs are low.
Ron, I was told average R=1 per inch of thickness for most species. I avoid hardwoods as my technique of lagging has little ability to straighten strong, hard woods.
Next question, Are cells the same size in a high ring count piece of wood as a low ring count piece,ie is the difference the number of cells or the size?...Got pics?
I don't think the R value of 1 per inch is valid and definetly not universal for all woods. I remember the statement that 1 inch of wood insulates as good as 12 inches of brick and 1440 inches of aluminum.
The density has a lot to do with the R value. Lower density means higher R value.
Your last question on ring size. What I've been able to look up suggests that the cell size is all the same. However, there is fewer due to some sort of minimizing effect, ie sunlight, moisture, or nutrients.
Shade loving trees do not have as much ring variation as sun loving trees.
There is a difference in density within the tree ring. There is higher density within the latewood over the earlywood. With better growing conditions, rapid earlywood expansion would make for overall less density.
Thanks for the info on log homes. Never occured to me about the R-value factor. That along with the workability really makes pine the log of choice.
Gordon
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?
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.
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
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.
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.
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?
"Does this make sense or not?"
Couldn't tell Ron, but is that your new signature??
:D
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.
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.
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?
:)
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?
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.
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.
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 ::) ::) ::)
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.
(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
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.
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.
(https://forestryforum.com/images/YaBBImages/userpics/image002.jpg)
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?
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. :)
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?
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?
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.
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
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.
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.
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.
Hey Gordon,
I'm wif ya
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
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?
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.
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?
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
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?
"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?