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how much does pine shrink in a kiln?

Started by Compensation, February 28, 2013, 10:15:33 PM

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Compensation

This weekend i wanna cut up 3 pine trees into 2x2's (1.5x1.5) to use as framing for my bar walls. The stuff you get at lowes is like 1.5x1.5" right? Well i dont want to plane it down after i pull it out of the kiln. What should i cut them down to on the mill to get close to 1.5x1.5" after any shrinkage?
Thanks!
D4D caterpillar, lt10 Woodmizer, 8x12 solar kiln, enough Stihl's to make my garages smell like their factory :) Ohh and built Ford tough baby!

beenthere

Which pine?

There several tables available on the net, and here is one example.
http://pods.dasnr.okstate.edu/docushare/dsweb/Get/Document-2535/NREM-5009web.pdf

Also
http://www.fs.fed.us/ccrc/topics/urban-forests/docs/physical%20properties%20and%20moisture%20relations%20of%20wood.pdf

Shows the shrinkage for radial and tangential directions.

And WDH has your best bet covered. :)
south central Wisconsin
It may be that my sole purpose in life is simply to serve as a warning to others

WDH

It is going to be hard to get them exact without planing.  Wood shrinks differently depending on the orientation of the growth rings, so each piece may behave just a bit different.  Planing may be your best option.
Woodmizer LT40HDD35, John Deere 2155, Kubota M5-111, Kubota L2501, Nyle L53 Dehumidification Kiln, and a passion for all things with leafs, twigs, and bark.  hamsleyhardwood.com

Compensation

I am not good on my trees yet. One is a blue spruce, one had 5"pine cones, and the other i dont think had cones but it was lighter color and killed my grass like crazy :)

I have a nice craftsman pro planer so if its inevitable then i can but just wanted to avoid it if i could.
D4D caterpillar, lt10 Woodmizer, 8x12 solar kiln, enough Stihl's to make my garages smell like their factory :) Ohh and built Ford tough baby!

Ianab

You want a ""rule of thumb"?

Cut them 1.75"

Then you should have enough left to plane them to the exact size, without spending all day making shavings.

Ian
Weekend warrior, Peterson JP test pilot, Dolmar 7900 and Stihl MS310 saws and  the usual collection of power tools :)

GeneWengert-WoodDoc

Make sure that you saw them so that the annual rings run parallel to two faces and perpendicular to the other two faces.  In other words, avoid having the rings go diagonally, from one corner to the opposite corner.  With diagonal rings, the pieces will become diamond shaped as they dry.

As a rule of thumb, if you dry to 10% MC, most conifers will shrink 5% in one direction (running parallel,to the rings when looking at the end grain) and 2-1/2% in the other.  So, you could technically cut the piece 1.58" x 1.54", with the large dimension running parallel to the rings, which would also be the width of flatsawn lumber.

But wood likes to warp a little bit and your saw will have a little roughness.  Also, the shrinkage values are average values and so we would see half the pieces with a little less and half with more shrinkage.  So, we need to add a JIC (just in case) number...perhaps 0.09" but this is just an estimate.  Plus, a planer does not like to remove under 1/32" or 0.03".  So, add 0.12" to both dimension numbers.  Then add a little more to account for the fact that when you set 1.70" x 1.66" on the mill there will be a little variation from piece to piece and also within an individual piece, so add 0.05".

Bottom line is that Ianab knows what he is talking about!
Gene - Author of articles in Sawmill & Woodlot and books: Drying Hardwood Lumber; VA Tech Solar Kiln; Sawing Edging & Trimming Hardwood Lumber. And more

Compensation

This is why i signed up to FF. I could spend hours online going no where, and you guys give the right answer within a few hours. Amazing! Thanks so much!
D4D caterpillar, lt10 Woodmizer, 8x12 solar kiln, enough Stihl's to make my garages smell like their factory :) Ohh and built Ford tough baby!

SwampDonkey

We've (forum) looked at the tables of empirical data a few times to 'estimate' shrinkage and I think we came to the conclusion to leave 1/8" per 2" of material. If your not planing. Add a little more for planing as Ian suggested

For academic purposes, when your using math, I've used figures from 'Textbook of Wood Technology' or the "Wood Handbook", same numbers. 99.99% aren't interested in that, unless out of curiosity.

Anyway, to be practical assume an additional 1/8" for shrinkage per 2" of thickness/width plus another 1/8" for planing and uniformity as suggested.
"No amount of belief makes something a fact." James Randi

1 Thessalonians 5:21

2020 Polaris Ranger 570 to forward firewood, Husqvarna 555 XT Pro, Stihl FS560 clearing saw and continuously thinning my ground, on the side. Grow them trees. (((o)))

GeneWengert-WoodDoc

just remember that the table values are the average, not max or min.  The 1/8" rule is for flatsawn.
Gene - Author of articles in Sawmill & Woodlot and books: Drying Hardwood Lumber; VA Tech Solar Kiln; Sawing Edging & Trimming Hardwood Lumber. And more

Planman1954

Make sure that you weight them down to prevent warpage. They will usually bend when drying!
Norwood Lumbermate 2000 / Solar Dry Kiln /1943 Ford 9n tractor

SwampDonkey

Gene, yes flat sawn. And yes the empirical numbers are based on stats from sampling.  But I think most will carry it forward for quartered to, that way only gotta remember one number. Even though quartered has less shrinkage. Again it's a uniformity factor if we're planing. kinda like splitting hairs. ;D A 1/16" per 2" might get you by on the radial shrinkage. I'd rather stick with the 1/8". The thing is, you can't be certain a piece is quarter all the way down, say for 10', the grain could run out and then look flat saw on the far end. Easier to go with the 1/8" rule.
"No amount of belief makes something a fact." James Randi

1 Thessalonians 5:21

2020 Polaris Ranger 570 to forward firewood, Husqvarna 555 XT Pro, Stihl FS560 clearing saw and continuously thinning my ground, on the side. Grow them trees. (((o)))

GeneWengert-WoodDoc

Maybe I was not clear enough...let me try again.  The table values for U.S. softwoods, tangential direction, run from 6.0 to 7.8% from green to oven dry.  As we usually dry only to 10% MC at the driest, then we would use 2/3 of the table values for green to 0% MC.   Then because a piece of wood is seldom true flatsawn, but has some angle, then the shrinkage will be even less than the table vales.  The table values are for thin pieces of wood (1/16")...Thick pieces shrink less.  However, the table values are averages, so half the pieces will shrink slightly more than the table.  So, with these plusses and minuses, the table value adjusted for MC is a good estimate...at 10% MC, most softwoods will shrink a maximum of 4.0% 5.5%, depending an species.  Now the 1/8" rule for a piece of nominal 2" width (actual when sawing is 1.75") is 7.1% Over size.  So, the 1/8" for every 2" rule for shrinkage alone (and not sawing variation, planer allowance, warp) is quite a bit more than needed for shrinkage only.  But it is not enough for the other variations, so that is why 1/4" thicker was suggested by Ianab and confirmed by the calculations I made.  The point is that shrinkage alone does not give us a good estimate of the green size required
Gene - Author of articles in Sawmill & Woodlot and books: Drying Hardwood Lumber; VA Tech Solar Kiln; Sawing Edging & Trimming Hardwood Lumber. And more

SwampDonkey

Yes, even a 1/8th" per 2" can be a little on the high side depending on how low you go in MC for the the application of the wood.

For instance Loblolly pine

Sp gravity green is 0.47, Vsh%= 12.3% (green to OD), tangential shrinkage is 7.4%, target MC = 10%, want say a 1.5" x 7.5" flat sawn.

Fibre saturation point is 12.3%/0.47 = 26.17%

→10% = 7.4 * (26.17-10)= 4.57%
Tsh        26.17

width = 7.5"
            (1-0.0457)
         = 7.859  not quite 3/8 difference but more than 5/16th for shrinkage allowance.

Really just academic arguments. It doesn't appear to me that the estimate is showing too much waste in thickness allowance for shrinkage.

I think we all agree there are other factors at play, whether stated or not. But it's always good to mention them on this topic. :)

"No amount of belief makes something a fact." James Randi

1 Thessalonians 5:21

2020 Polaris Ranger 570 to forward firewood, Husqvarna 555 XT Pro, Stihl FS560 clearing saw and continuously thinning my ground, on the side. Grow them trees. (((o)))

GeneWengert-WoodDoc

The fsp for almost all US woods is 30% MC.  I have never seen dividing the Volumetric shrinkage by SG to get the fsp.  For redwood, it gives a fsp of 18.9%, no. Red oak 21%, so red oak 26%.  These values are all incorrect.  I suggest that you redomyour calculation using 30% MC for fsp.  We sometimes see tropical woods with a fsp depressed to 22 to 25% MC but that is rare.  For reference, see Chapter 3 of the WOOD HANDBOOK, for instance figure 3-6 and associated text.
Gene - Author of articles in Sawmill & Woodlot and books: Drying Hardwood Lumber; VA Tech Solar Kiln; Sawing Edging & Trimming Hardwood Lumber. And more

SwampDonkey

30 % for FSP is used by the Wood Handbook for simplification as a good guideline. This has been discussed on the forum before.

However, 'The Wood Handbook' uses the same formula for shrinkage and the same values that I use. Only difference is I calculate FSP instead of using the 'standardized' 30 %, which in itself is subject to large standard deviations.

The calculation of FSP must be new to you, because it's straight from Dr. Sebastian's "Fundamental Physical Properties of Wood" at the Dept of Forest Resources at UNB. He was the wood science professor for a number of years, now deceased.  The formula is also used by many authors and unless you have an account online to access research and texts Google won't do much good.

If you use the magic 30 % you'll have your 1/8" shrinkage per 2" in fact a little more. So to say the 1/8" per 2" rule is too much, is false.
"No amount of belief makes something a fact." James Randi

1 Thessalonians 5:21

2020 Polaris Ranger 570 to forward firewood, Husqvarna 555 XT Pro, Stihl FS560 clearing saw and continuously thinning my ground, on the side. Grow them trees. (((o)))

GeneWengert-WoodDoc

If you have a page number, that would help. 

It is not mentioned in the WOOD HANDBOOK.  I do not see it in TEXTBOOK OF WOOD TECHNOLOGY.  Although there is indeed some variation in the value of fsp, I cannot believe the values for redwood or red oak that I quoted, 19% and 21%.  I just checked basswood and that has volumetric of 15.8 and the SG is .38, so that gives the fsp of 42%, which I cannot imagine at all.  I would think that if fsp actually varied that much, it would have been mentioned.  I have carved basswood that was stored at 65% RH and it was at 12% MC which is,normal for 30% fsp.

I did do some research on the value of MC for wood stored at 80% (16% EMC) RH for my work at the Univ of Wisc in 1976 and I did not see more than two percent variation maximum for different species.
Gene - Author of articles in Sawmill & Woodlot and books: Drying Hardwood Lumber; VA Tech Solar Kiln; Sawing Edging & Trimming Hardwood Lumber. And more

SwampDonkey

First off, we have to make a distinction here between variation within a tree or species, and that magic number of 30. A tree may vary by 2-3% as you already suggest. But, if you look in the Textbook of Wood Technology', 4 ed, pg 281 a couple examples are given showing this variation, but one species is as low as 27% and another as high as 36%. And also note that FSP is influenced by specific gravity (green) as mentioned in the text. So, now I guess you can except that I just mentioned (with text reference) two species are 9 points apart, one as much as 6 points above the magic 30%. ;D

Consider that most of the sapwood is in the slab pile when sawed. Take the 'heartwood' of the hard pines like red pine and loblolly, the green condition is around 32 MC%. You trying to convince me that green condition of hard pine heartwood equals FSP? That would suggest not a lot of water in cell lumens, in fact just about dried up. In drought times that could cause some unfavorable internal stresses.   And yes bound water loss causes shrinkage, not free water. The example in the document below shows that red pine FSP is below 28%. Basswood has a MC 81% in the heart when green, where as beech has 55% and much denser. When you use the values for beech FSP = 17.2/.56 = 31 %, white oak 15.9/0.59 = 27%

Attached is a PDF with excerpts on FSP from Dr. Sebastian's 'Fundamental Physical Properties of Wood'. How it is derived and an example on the following page. Any page references in the document refer to the 'Textbook of Wood Technology', 4th ed.

There are a number of formula's in the 'Wood Handbook' and 'Textbook of Technology' However, there are a few more you will not find there.

Believe me I don't dream this stuff up. ;D
"No amount of belief makes something a fact." James Randi

1 Thessalonians 5:21

2020 Polaris Ranger 570 to forward firewood, Husqvarna 555 XT Pro, Stihl FS560 clearing saw and continuously thinning my ground, on the side. Grow them trees. (((o)))

GeneWengert-WoodDoc

Thanks for posting.  I do believe that the error that Dr. Sebastian makes is when he replaces V (bound water) with Vg - Vo.  That is, the shrinkage of wood when going from green to oven dry does not represent the volume of water lost.  This is an incorrect assumption.  On a molecular level, when a water molecule leaves the wood, the wood does not close up the gap or void left.  The reason is due to the crystallinity of the cellulose.  Dr. Chris Skaar discusses this in his book WATER IN WOOD.

As another example, consider Brazilian rosewood with a volumetric shrinkage of 8.5 and SG of 0.8 which gives a fsp of 11% MC, which is not even close.

Or consider balsa wood with volumetric shrinkage of 10.8 and SG of 0.16, giving a fsp of over 60% MC.

If indeed the fsp varied that much, I cannot image why the Wood Handbook would not even mention it.  Likewise, the Textbook of Wood Technology.
Gene - Author of articles in Sawmill & Woodlot and books: Drying Hardwood Lumber; VA Tech Solar Kiln; Sawing Edging & Trimming Hardwood Lumber. And more

GeneWengert-WoodDoc

Regarding the amount of liquid water in species that have a green MC close to 30% MC, we find that in those species we do not have to dry the heartwood in order to treat the wood with preservatives.  There is indeed very little water present.  Because the heartwood does not participate in movement of water within the tree, the lack of water in the heartwood is not a issue in times of drought.
Gene - Author of articles in Sawmill & Woodlot and books: Drying Hardwood Lumber; VA Tech Solar Kiln; Sawing Edging & Trimming Hardwood Lumber. And more

SwampDonkey

Not as far as moving water up the stem, but drying stress dropping below FSP.

If volumetric shrinkage isn't caused by water lost (water has volume) than you have me baffled. ;D Cell lumens is another matter, that is free water in there. No shrinkage, it's in the cells walls from loss of bound water that shrinkage occurs. No two atoms or molecules can occupy the same space at once.

You misinterpret the formula, he is talking volume of bound water.
"No amount of belief makes something a fact." James Randi

1 Thessalonians 5:21

2020 Polaris Ranger 570 to forward firewood, Husqvarna 555 XT Pro, Stihl FS560 clearing saw and continuously thinning my ground, on the side. Grow them trees. (((o)))

SwampDonkey

And heartwood has a dead zone and a live zone. The live zone functions the same as the sapwood but in some trees it has color changes from extractives, both are xylem and conducting tissue. The sapwood is just newer xylem. If you have ever harvested trees, you will notice water comes up not only in the outter portion of the stump, but also toward the pith until in the dead zone. With some species water will flow in reverse when severed from the stump. A number of forum members will bear witness to this. Misinterpreting this can lead one to believe there might be confusion over xylem and phloem tissue. Phloem is what brings stuff down from the food factory dissolved in water to feed the tree and rays deliver it and oxygen radially to live cells to both store food and live off it. Pores are also involved. Rays extend from the bark of the tree inward.

Heartwood classification is presented on pages 24-25 in "Text of Wood Technology", 4th ed.
"No amount of belief makes something a fact." James Randi

1 Thessalonians 5:21

2020 Polaris Ranger 570 to forward firewood, Husqvarna 555 XT Pro, Stihl FS560 clearing saw and continuously thinning my ground, on the side. Grow them trees. (((o)))

GeneWengert-WoodDoc

I am indeed talking about bound water and its relationship to shrinkage...that is, shrinkage is indeed caused by bound water loss.  The amount of bound water  volume loss is, however, not equal to the shrinkage volume.  The fsp calculations I gave show that is not true....fsp is not 60% MC.  The reason is that when a water molecule leaves the wood, the void created is not closed completely by the movement of the wood molecules.  One effect, if it were true, is that the curve of shrinkage versus MC would be a perfectly straight line, but all the data shows that is not true.  One reason for the shape of the curve at high MCs is that the water molecules at high MC are not held by the wood molecules directly but are in several layers and are bound to each other via hydrogen bonds rather than to cellulose OH bonds.  So, when high MC bound water leaves, the water molecules move to satisfy the bond and not necessarily the wood.  Siau wrote a good explanation in his book, as well as Skaar's book.

Regarding dead or alive, you are stating that chapter 3 page 3 of the WOOD HANDBOOK (FPL 190, 2010 version) is incorrect?  Here is the definition in the glossary.  "Heartwood. The wood extending from the pith to the sapwood, the cells of which no longer participate in the life processes of the tree. Heartwood may contain phenolic compounds, gums, resins, and other materials that usually make it darker and more decay resistant than sapwood"

In the TEXTBOOK OF WT, the definition of heartwood is the loss on the nuclei from the cell, which means it is dead.  P.56.  I do not debate that sapwood in transition to heartwood may still be active. 

Another quote from the Wood Handbook is  "The fiber saturation point of wood averages about 30% moisture content, but in individual species and individual pieces of wood it can vary by several percentage points from that value."  Note that they say several points.
Gene - Author of articles in Sawmill & Woodlot and books: Drying Hardwood Lumber; VA Tech Solar Kiln; Sawing Edging & Trimming Hardwood Lumber. And more

Den Socling


drobertson

Lots of numbers for someone who want to build a bar ;D  I think I would have to drop back 15 and punt :D  or, just cut the stock 2x2, kiln it , rip the extra off with the table saw then plane to size, if I wanted to use what I sawed.  Or buy the finish stock and simply build the bar and enjoy 8)  For me building a project, all the facets of it, is what it is all about.  david
only have a few chain saws I'm not suppose to use, but will at times, one dog Dolly, pretty good dog, just not sure what for yet,  working on getting the gardening back in order, and kinda thinking on maybe a small bbq bizz,  thinking about it,

jimF

There seems to be a confusion of terms being used and assumptions in the derivation of the discussed equation.  We have oven-dry( or 0%MC),  FSP ( as stated in both the discussed article and Wood Handbook being ~30%), green moisture content ( which as stated can vary in and between trees) and maximum moisture content.   The assumption that the water has a constant density, no matter which state it is in as it occupies various positions within the wood material comes into play.  The water is in different states within the wood: 1) free which can be assumed to have the density of water as in a drinking glass, 2)vapor similar to vapor in the atmosphere and 3) bound which has a range of density depending on the MC, from 0 to 30% MC( Gene hinted to).  Consider water in a solid state, ice, which actually has many different densities.  There are many different states in which ice can be and still be a solid crystal.  In a similar way bound water can be in a different density depending on the MC because the bond energy is dependent on the the number of water molecules that are between the molecular we are considering and the cellulosic polymere.  Actually, there a a few different theories that have been presented to explain the precise arrangement the water molecules are in but all agree the bond length is shortest at say .01%MC as compared to 25%.

Another assumption in the discussed equation is that the cellulosic polymere do not stay spread apart as the water is lost.  When the water is lost, some voids between the cellulosic polymeres do develop. Both of these facts alter the end result of using the discussed equation.  Also, if there is confusion in the terms for the level of moisture content the equation can be used incorrectly.  Bill Simpson produced a booklet on this subject with extensive tables that is helpful.

To keep this explanation short it was confined to cellulose but to be accurate water does bond with the other constituents of wood.

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