iDRY Vacuum Kilns

Sponsors:

SYP for posts & 2x, end to end shrink

Started by Sedgehammer, March 16, 2021, 10:05:11 AM

Previous topic - Next topic

0 Members and 1 Guest are viewing this topic.

Sedgehammer

How do. What's a good rule of thumb on SYP end to end shrink on like a 12x 8' post?

What about 2x lumber?

Building a shed with off the mill lumber and just trying to get what I can figures.

Thanks
Necessity is the engine of drive

firefighter ontheside

 They say wood only shrinks about a tenth of a % in length.  An 8' timber would shrink by around 1/10 of an inch.  Now in width it can shrink by around 5/8" per foot.
Woodmizer LT15
Kubota Grand L4200
Stihl 025, MS261 and MS362
2017 F350 Diesel 4WD
Kawasaki Mule 4010
1998 Dodge 3500 Flatbed

Tom King

If looking down the board, the grain looks straight, you don't have to worry about it.

If the grain looks like a dog's hind leg, it will shrink more in length than the best of us can guess.

Trackerbuddy

Try any of the online wood shrinkage calculators. When I punched in your info it didn't calculate length shrinkage.  There wasn't even a box for shrinkage over length.  It might cup, twist, bow and lose 1/2" in width but I think your safe as far as length goes 

Don P

Reaction wood, either juvenile or compression wood is the other thing that will cause lengthwise shrinkage, compression wood is a dull "peanut butter" looking grain from a leaner, juvenile is the first 20 or so years around the pith. The cell wall structure is laid up on a bias so shrinks lengthwise. Not likely going to happen in a timber but can in a stick of dimensional or a board. Generally causes one of the objectionable warps which rejects it. I've had up to 1" lengthwise a time or two.

Layer S2 is the main concern for shrinkage. Think about what happens as those fiber angles lose moisture and move closer together.



 


WDH

A very important key to sawing pine is to understand these relationships, especially the behavior of the juvenile core with the cellulose chain orientation in the cell walls leading to a host of issues like warp, twist, cup, splitting/cracking, and shrinkage.  Sawing a board with juvenile wood on one edge and mature wood on the other is a recipe for crook and warp.  This is one reason that 2x4's in the lumber stores can be such poor quality as the logs are sawn as fast as possible, as much as 10 to 15 logs per minute.  Basically ran through the breakdown machine as fast possible with an attempt at positioning the log the best way.  If the pith is centered in the log, i.e. the log is straight without sweep, you get better lumber.  Sweep, which is common in all logs, makes this more complicated. 

When buying lumber that is mass produced, look at the end grain to see if the board contains the pith or juvenile wood.  If the pith is not centered and the rings balanced, this board may be a poor choice and is likely already displaying one of the common defects.  Boards from the outside of the log will be flatter with less twist and warp and crook.  There may be bow, but that is not as critical in framing and construction as warp, twist, and crook.  So, when sawing a log with the pith that cannot be centered on both ends, if bow is better than crook. saw boards with the horns up or down.  If bow is a critical defect and crook is easier to deal with in the finished product, saw the boards with the horns side to side.

When sawing a log, it is important to know or guess at the end use.  In furniture grade wood, bow is a critical defect while crook and be dealt with better as a crooked edge can be straightened.  A bowed tabletop is a major no-no.  The opposite is true in framing or with joists, rafters, etc. 

A good rule of thumb when sawing any log is to balance the growth rings when looking at the end grain of the piece.  If you draw a vertical imaginary line in the center of the board, the rings on each side should be balanced; if it contains the pith, the pith should be centered.  An offset pith is an indication that the board probably will not dry straight and flat without twist, warp, or crook, especially in pine. 

So, slab the log and remove side boards until you have a square cant that you create with the pith as much in the center of the cant as you can get it.  You will have to look at both ends of the log because the pith may not be centered on both ends, and you have to do the best you can to get the pith centered.  If you take a board off one face, flip flip 180 degrees if you want to take another board on another face.  Now the cant can be turned 90 degrees and you can take a board, then flip 180 degrees to take another.  You have essentially sawed around the cant a full 360 degrees, but in doing so, you have balanced out stress and you have kept the pith centered in all four boards.  Also, you have removed boards from each face from the outside of the tree which will have the best quality, fewest knots, smallest knots, etc. This is called grade sawing as you rotate around the faces to get the best quality boards, but always try to keep the pith centered and the rings balanced as much as possible.

If you are sawing to a specific board size, say 2x6's, create the cants that you will saw the finished pieces from without any juvenile wood in those cants, or if there is juvenile wood in any cant, make sure that the juvenile wood and pith are centered in that cant as much as possible.  So, in a large log where you are cutting rather narrow boards like 2x6's, break that log down into several 6" cants the narrow way, with only one cant containing the juvenile core with the pith centered.

Sorry about the long dissertation, but Don's illustration made me go crazy for a few minutes.  Many sawyers just saw boards and then there are those that saw boards correctly.
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

Don P


Sedgehammer

Quote from: WDH on March 18, 2021, 08:48:58 AM
A very important key to sawing pine is to understand many sawyers just saw boards and then there are those that saw boards correctly.
Hope you don't mind i changed up your quote a lil'bit........

And thanks for the info @Don P

I won't have a chance to 'choose' the lumber. It wood just 'show up' in my yard and i'd unload it. No recourse.

Green is about $8,500 cheaper. 1,000 miles away. $3,500ish for trucking. Not sure it's worth the issues and that price difference isn't allowing any wastage, as I'm sure there wood be at least 10%.

i did find some old 10x oak posts at $8 a bf in virginia.

And that below scares me........


Huh?  :D


Necessity is the engine of drive

Walnut Beast

Quote from: WDH on March 18, 2021, 08:48:58 AM
A very important key to sawing pine is to understand these relationships, especially the behavior of the juvenile core with the cellulose chain orientation in the cell walls leading to a host of issues like warp, twist, cup, splitting/cracking, and shrinkage.  Sawing a board with juvenile wood on one edge and mature wood on the other is a recipe for crook and warp.  This is one reason that 2x4's in the lumber stores can be such poor quality as the logs are sawn as fast as possible, as much as 10 to 15 logs per minute.  Basically ran through the breakdown machine as fast possible with an attempt at positioning the log the best way.  If the pith is centered in the log, i.e. the log is straight without sweep, you get better lumber.  Sweep, which is common in all logs, makes this more complicated.  

When buying lumber that is mass produced, look at the end grain to see if the board contains the pith or juvenile wood.  If the pith is not centered and the rings balanced, this board may be a poor choice and is likely already displaying one of the common defects.  Boards from the outside of the log will be flatter with less twist and warp and crook.  There may be bow, but that is not as critical in framing and construction as warp, twist, and crook.  So, when sawing a log with the pith that cannot be centered on both ends, if bow is better than crook. saw boards with the horns up or down.  If bow is a critical defect and crook is easier to deal with in the finished product, saw the boards with the horns side to side.

When sawing a log, it is important to know or guess at the end use.  In furniture grade wood, bow is a critical defect while crook and be dealt with better as a crooked edge can be straightened.  A bowed tabletop is a major no-no.  The opposite is true in framing or with joists, rafters, etc.  

A good rule of thumb when sawing any log is to balance the growth rings when looking at the end grain of the piece.  If you draw a vertical imaginary line in the center of the board, the rings on each side should be balanced; if it contains the pith, the pith should be centered.  An offset pith is an indication that the board probably will not dry straight and flat without twist, warp, or crook, especially in pine.  

So, slab the log and remove side boards until you have a square cant that you create with the pith as much in the center of the cant as you can get it.  You will have to look at both ends of the log because the pith may not be centered on both ends, and you have to do the best you can to get the pith centered.  If you take a board off one face, flip flip 180 degrees if you want to take another board on another face.  Now the cant can be turned 90 degrees and you can take a board, then flip 180 degrees to take another.  You have essentially sawed around the cant a full 360 degrees, but in doing so, you have balanced out stress and you have kept the pith centered in all four boards.  Also, you have removed boards from each face from the outside of the tree which will have the best quality, fewest knots, smallest knots, etc. This is called grade sawing as you rotate around the faces to get the best quality boards, but always try to keep the pith centered and the rings balanced as much as possible.

If you are sawing to a specific board size, say 2x6's, create the cants that you will saw the finished pieces from without any juvenile wood in those cants, or if there is juvenile wood in any cant, make sure that the juvenile wood and pith are centered in that cant as much as possible.  So, in a large log where you are cutting rather narrow boards like 2x6's, break that log down into several 6" cants the narrow way, with only one cant containing the juvenile core with the pith centered.

Sorry about the long dissertation, but Don's illustration made me go crazy for a few minutes.  Many sawyers just saw boards and then there are those that saw boards correctly.
Thanks for going crazy 👍. Great information 

scsmith42

Don / Danny:

Great explanations!  I never get tired of learning from y'all.

Scott
Peterson 10" WPF with 65' of track
Smith - Gallagher dedicated slabber
Tom's 3638D Baker band mill
and a mix of log handling heavy equipment.

Don P

I started a post this morning but then got the notion to head down to Denton to look at bobcats... they sure looked better in the ad  :D

More stuff on shrinkage.
Take a look at the sketch above again, the top right section cut. Radial grain is the right side, notice the ray and the ends of 2 more showing on the left, tangential, face.

Wood shrinks in the radial, quartersawn, direction about half as much as it does in the tangential direction. Those rays are straps that lock up the cell shrinkage in the radial plane. The sketches of the cells are very simplified. Look at the sketch of the ray again and notice the little donuts sketched in along its length. Those are pits, valves, that connect to pits in the vertical tracheid cell walls. At the high powered microscope level, in the microfibrils that form the cell walls, the pit pairs look much like the grain surrounding a knot. The "grain" of the cell wall swirls around and thickens at each pit, again reducing shrinkage on the radial faces of each cell. The hollow tracheids are vertical transport, the rays are horizontal transport for the fluids and nutrients, and waste, in the tree. Each pit pair contains a valve that can be opened or closed to direct flow.

Pit (botany) - Wikipedia

WDH

The water conducting cells in softwoods, tracheids, are closed on the ends.  Water moves between the tracheids through the bordered pits that contain the little valves.  So, the small individual cell tubes that the water flows in are sealed but for the valves.  

The water conducting cells in hardwoods, vessel elements, are not closed on the ends of the individual cells.  They are open and stack one on top of the other to form continuous open pipes from the roots to the shoots.  They also contain the pit valves in the cell walls. 

This is a very important difference.  As you go North where the glaciers reside, which is anywhere North of the Mason Dixon line, and as you even go to the Most extreme North into "Eh" country, hardwood diversity begins to wane and softwoods are more prevalent.  There is a reason for this.  Think about the Rocky Mountains.  As you gain elevation, hardwood species Peter out and there are more softwoods.  As you near the "tree line", there are only softwoods.  The reason is temperature.  

When it gets colder as you go North or as you gain elevation as in going up Mt. Denali, the water in trees freeze.  When water freezes, it expands. As it thaws, there is contraction, and in the individual cell, this cycle can create an embolism or air pocket.  In the case of softwoods with the water conducting cells closed on the ends, an embolism is isolated in the individual cell where it occurs because the pit valves close.  This way, the water column is not broken, but re-routed around the cell with the embolism.  

In hardwood with the continuous pipes, an embolism breaks the water column and the pipe loses its "prime", essentially rendering this particular pipe chain of vessel element cells useless.  The pit valves in the surrounding "pipes" close to isolate this pipe, but that whole pipe from the root to the shoot is no longer able to function now and in the future.  The significance of this is that the water conducting cell structure in softwoods is much better adapted for cold temperatures as you go North and as you gain elevation in high mountain chains.  At the tree line or timber line, there are only softwoods.  

If Don would quit posting these diagrams, I would not go crazy as much  :D.
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

DonW

Maybe obvious but this explanation describes why hardwoods are porous - ring, semi-diffuse, diffuse - and softwoods are pore less and does away with the confusing distinction hardwood/softwood since some softwoods -yew for example - are hard but have no pours and some hardwoods - willow - are soft but are porous (diffuse). 
Hjartum yxa, nothing less than breitbeil/bandhacke combo.

Don P

Quote from: WDH on March 20, 2021, 10:04:27 AMIf Don would quit posting these diagrams, I would not go crazy as much  .


I'm delighted and intend to drive you crazy whenever possible :D its very educational, Thanks Danny

WDH

When we need to identify sawn wood, not trees with leaves and bark, the pore structure and the pore arrangement are what we need to see.  By pore, I mean a wood cells.  When someone needs help identifying what wood they have, the most important feature to provide is a close up pic of the end grain.  As close up as possible.  
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

Sedgehammer

Thanks guys for the inputs. With all of those variables I have some questions if you wood please.

1. If building a shed with 18' tall walls, some a single story and other a 2 story (9' & 8'), what length wood you cut the studs to allow for shrink in length?

2. On said shed, the 2nd story has a center beam (4 ply 2x12s I'm thinking kiln dried) 24' long (20' under 2nd story and 4' under a balcony) that requires I'm thinking 2 support posts (1 at 12' and the other one at the 20' mark, so a 4' over hang). What length wood you cut these posts? Perfect fit wood be around 8' since the ceiling is 9' and the beam is actual rough cut 2x12s. Or does one buy an old reclaimed 10x10 post?

3. How much wastage can one expect when buying sight unseen and you take what they cut?

4. Buying green saves us about $8,600. Have to truck it, so that's $3,500ish if one load. So about a 5k savings overall. Is that enough to use green? 
Necessity is the engine of drive

Thank You Sponsors!