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Author Topic: Wood Science 101?  (Read 13626 times)

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Offline Don P

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Wood Science 101?
« on: February 18, 2001, 01:38:54 PM »
 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?????
A laborer works with his hands
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Offline Ron Wenrich

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Re: Wood Science 101?
« Reply #1 on: February 18, 2001, 03:58:13 PM »
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.  
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Offline Jeff

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Re: Wood Science 101?
« Reply #2 on: February 18, 2001, 04:06:52 PM »
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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.................me
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Offline Jeff

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Re: Wood Science 101?
« Reply #3 on: February 18, 2001, 04:19:30 PM »
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.


Just call me the midget doctor.
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Offline Don P

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Re: Wood Science 101?
« Reply #4 on: February 18, 2001, 06:49:22 PM »
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?
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Offline Ron Wenrich

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Re: Wood Science 101?
« Reply #5 on: February 19, 2001, 03:22:04 PM »
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.

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

Offline Ron Wenrich

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Re: Wood Science 101?
« Reply #6 on: February 19, 2001, 03:24:46 PM »
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

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

Offline Jeff

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Re: Wood Science 101?
« Reply #7 on: February 19, 2001, 04:39:18 PM »
Lets not aim for average then, cause the average won't frequent and post on such a fine board.
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Offline Ron Scott

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Re: Wood Science 101?
« Reply #8 on: February 19, 2001, 05:21:55 PM »
Wood Technology was never my favorite subject. I left that for the people in the lab.
~Ron

Offline Don P

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Re: Wood Science 101?
« Reply #9 on: February 24, 2001, 01:58:03 PM »
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
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Offline L. Wakefield

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Re: Wood Science 101?
« Reply #10 on: February 24, 2001, 03:58:52 PM »
   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
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Offline Ron Wenrich

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Re: Wood Science 101?
« Reply #11 on: February 24, 2001, 04:49:33 PM »
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.

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Offline L. Wakefield

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Re: Wood Science 101?
« Reply #12 on: February 27, 2001, 07:31:40 PM »
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
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Offline Ron Wenrich

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Re: Wood Science 101?
« Reply #13 on: February 28, 2001, 02:39:49 PM »
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.
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Re: Wood Science 101?
« Reply #14 on: February 28, 2001, 05:06:57 PM »
Port Orford(sp?) Cedar? L. are you giving up any extraction secrets?
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Re: Wood Science 101?
« Reply #15 on: February 28, 2001, 05:48:56 PM »
   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
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Offline Gordon

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Re: Wood Science 101?
« Reply #16 on: May 21, 2001, 04:49:04 PM »
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

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Re: Wood Science 101?
« Reply #17 on: May 21, 2001, 05:29:53 PM »
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?
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Offline Ron Wenrich

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Re: Wood Science 101?
« Reply #18 on: May 22, 2001, 03:38:47 PM »
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.
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Offline Bill Johnson

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Re: Wood Science 101?
« Reply #19 on: May 22, 2001, 06:33:12 PM »
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
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