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Best time to cut Douglas fir

Started by sawbuckacres, December 12, 2009, 05:30:14 PM

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sawbuckacres

Been poking around various threads looking for info on the best time to tip over Douglas fir.  I want to rough mill them next summer into boards and beams for air drying, and am of the understanding that they should be cut during winter months when the sap has dropped into the roots, thereby decreasing drying time.  Not sure if this is a truth or a rural legend.  Is is in fact true that this occurs?

WDH

I believe that it is a rural legend.  The moisture content inside the tree does not vary considerably over the seasons.  It is best to cut the trees just before milling them. 
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

SwampDonkey

You'll also find that interior Doug. Fir does not require all that long to dry. Only 2 lbs/ft3 are liberated from green to 12% MC, compared to western hemlock which loses 10 lbs/ft3. Water is 62.4 lb/ft3 for gauging (@ 40-70 degrees).
"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)))

sawbuckacres

All right then.  I appreciate the insight.  Up to now, I have been milling the logs and letting them air dry for about 6 weeks, which has reduced the moisture to around 16-18%.  Additional time doesn't seem to decrease it much more so maybe I'll just wait till spring to cut the trees, then rough saw them and stack them to dry.

Thank you very much for your help.

golden foot

Sorry,
You might want to keep your snow packs handy. When I am selling Doug Fir house logs I can get more money for them from the best builder around. The deal is the sap wood. When the sap stops running in Jan. that is when you want to cut them if you are doing your own custom stuff like we are. Every little bit helps don't you know.
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stumphugger

The thing to consider about cutting them when the sap is up, will you have other DFs or conifers left standing?  If you hit a leave tree during the sap running time, it'll skin up a lot more. This means scarring of your standing trees and less value in the future for them.  That is what you need to watch out for. 

sawbuckacres

 :-\  Alright, now I'm confused again.  Stump hugger and Golden foot are talking about the "sap running."  I guess I need a primer on conifer physiology.  WDH said that moisture content doesn't change seasonally.  I assume he is referring specifically to water - both intra and intercellular.  When we're talking about "sap," this appears to be a different story.  Sap is apparently moving through the tree at different rates by season, which suggests an optimal time for felling??  Dumb question, but where is the sap going? 

I guess I thought that conifers didn't go through the same level of dormancy as do deciduous trees, but apparently that is not the case.

Another related issue here is that I will be trying to avoid both sap and heart wood when I am cutting beams, as I understand I will experience less movement of the wood as it dries if I do so. 

woodtroll

House logs around here are cut during the winter. Less sap - less dirt sticks to the log. Rural legend? I don't know, the buyer will only buy in the winter.

sawbuckacres

Okay, but what I'm most concerned about is how winter versus summer felling influences the end product.  If I cut and mill the trees in the spring, will I be experiencing different drying, shrinking, or twisting than if I cut them in the winter and mill them later in the year?  Is there a difference in the characteristics of wood that is felled in the winter, than in the summer?

beenthere

Listen to what WDH says. He is right.  8)

south central Wisconsin
It may be that my sole purpose in life is simply to serve as a warning to others

beenthere

Quote from: sawbuckacres on December 15, 2009, 01:39:20 PM
Okay, but what I'm most concerned about is how winter versus summer felling influences the end product.  If I cut and mill the trees in the spring, will I be experiencing different drying, shrinking, or twisting than if I cut them in the winter and mill them later in the year?  Is there a difference in the characteristics of wood that is felled in the winter, than in the summer?
No difference that can be measured.  When the wood dries it will shrink. If the grain is twisted, then the piece of wood will twist when it dries.
There will be a difference from exposure to warmer air in the Spring, so stain from bacteria and fungi growing can be a force to consider.
south central Wisconsin
It may be that my sole purpose in life is simply to serve as a warning to others

sawbuckacres

It will be a lot easier for me to fall trees in the spring/summer than in winter.  Winter access is very poor and snow will be deep. 

Thank you very much for taking the time to help  ;D

SwampDonkey

As WDH and beenthere said, there is little variation in seasonal moisture. Although, we did have a contract stipulation for years with a pulp mill called "seasonal moisture adjustment". It amounted to $3-4 a tonne extra in the winter months. No it wasn't a snow bonus. Although, it amounts to the exact same thing in the end, your pay cheque. :D Just a little something extra the mills do to get wood delivered. ;)
"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)))

sawbuckacres

I guess it would depend on which direction they adjust it.

Thanks for you help  ;D

stumphugger

Conifers  do go dormant during the winter.  They break bud in the Spring and that is when the sap starts running, or growth starts.   It varies but in the elevations I work in, it runs anywhere from May through August.  Then the tree hardens up.  You can get away with rubbing a turn against a leave tree in December, but not in June.  The bark sloughs off easily during sap time.  That's what we call it...sap season.  Which might just be only a local term, but that's what we call it.  

If you are clearcutting, it makes no difference.  In partial cuts, the logging crews have to be much more careful during that time.  
Loggers have claimed that there is a weight difference, I don't know for sure.  The mills don't care what season the trees are cut in.
But the landowner might.  


WDH

In most cases, when the "sap is running" or the "sap is up", that means that the tree has broken dormancy and water is being pulled from the soil by the roots as a result of transpiration/evaporation of water in the crown.  This does not change the inherent moisture content in the wood, it just means that the tree is actively moving water from the roots to the leaves/needles/crown and sugars from the crown through the inner bark to feed the roots.

As the tree begins the new growth, the cambuim turns on and starts laying down new wood.  This early activity of the cambium as it is actively dividing causes the inner bark at the cambuim and wood interface to adhere less tightly since the cambium is dividing, putting new inner bark on the outside and new wood on the inside.  This makes it easy for the bark to "slip" and be easy to remove or damage from any kind of mechanical contact.  This is the best time to "peel" wood to remove the bark, and it is the best time to damage a tree from contact with the bark. 

In the conifers, the tree produces resin to protect itself from insects and other physical damage.  This resin is produced in the wood thru specialized cells that are associated with the rays.  Pines, for one, have well developed resin canals that form radially in the wood like rays that conduct the resin to the outer layers of the tree to gum up the works if there is an insect invasion or a wound.  This is also called "sap".  In hardwoods, like the maple family, sugars transported in the inner bark are recovered by tapping the tree to let the "sap" ooze out for our use in making syrup. 

So, there are several things that are called "sap".   
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

sawbuckacres

This is all really interesting, and helpful.  Thank you all.  Here's my take-home thus far.

1.  As I will be select cutting, I need to be careful about when and how I cut to avoid damaging neighboring trees.

2.  Moisture, at least relative to water content, is not a seasonal issue as the moisture content doesn't really vary throughout the year.  "Water movement" is simply more active during the spring growth period.

3.  Then there is the "true sap," aka resin, that is moving radially.  WDH, you didn't say so specifically, but I assume from your comments that this radial movement is most active during summer when insect (or maybe bird) attacks are most likely.  Am I correct in also assuming that this resin is always present throughout the wood, which, as with water moisture, doesn't really affect the milling or drying character of the wood, regardless of when it is harvested.

Just as a side note, I had a large (~30" dbh) engelmann spruce blow over early last summer.  I thought it might make some nice cabinet lumber so I bucked it into 8' sections for the mill.  I was amazed at the quantity of resin that accumulated on my saw. Nothing like I've ever seen  :o with any other conifers.


SwampDonkey

Quote from: sawbuckacres on December 16, 2009, 12:14:30 AM
Then there is the "true sap," aka resin, that is moving radially.  WDH, you didn't say so specifically, but I assume from your comments that this radial movement is most active during summer when insect (or maybe bird) attacks are most likely.  Am I correct in also assuming that this resin is always present throughout the wood, which, as with water moisture, doesn't really affect the milling or drying character of the wood, regardless of when it is harvested.

If the resin isn't "set", by drying at a temperature at least as warm as where it will be used in service, then you can get bleeding of resin like any conifer with resin canals.

Resin canals are much like cells in rays (specialized parenchyma cells called epithelial which are excreting cells) and can be seen by hand lens on the surface of flat sawn lumber, not as distinct as white pine which can be seen unmagnified. They remain functional only in the living part of the sapwood. That is why you see a ring of pitch oozed in the sapwood of a log, a response to injury. Resin is not sap, it's manufactured and secreted by the epithelial cells making up the resin canals in the sapwood. Sap is transported down the inner bark of a tree, consisting of water carrying products made during photosynthesis like sucrose to feed the live cells. Water is the means to transport it. Resin is not very soluble in water, try washing it off. :D Amber of course, is fossilized resin.


Become a tree licker :D , and lick a fresh scraped tree where the bark was scraped off in the active growing season. It tastes sugary. ;)
"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)))

Rocky_Ranger

Tree Licker?  I've been called many things in my life but never a "tree licker" - cool thought though, I've licked many a xs pieces of cut wood for wood tech identification.  I always considered them Georgia boys tree lickers anyway  :D.   Funny how as Doug fir ages the resin canals fade into the older bark, can still be found in the thin bark up on the limbs and upper reaches of the tree.
RETIRED!

SwampDonkey

Quote from: Rocky_Ranger on December 16, 2009, 08:57:37 AM
I always considered them Georgia boys tree lickers anyway  :D.   

I know there is at least one in Alabama, self professed to. :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)))

sawbuckacres

I am a wildlife biologist by trade.  Spent most of my career smelling wolverine's butts  :-X- might as well go out a tree licker.

I mentioned earlier that I have read that one should try to avoid sapwood and heartwood in the milling - if one has the luxury to be so selective - as beams and boards that contain neither are subject to less twisting.  The literature seemed to suggest this was due to the resin itself, but after reading all your posts, I'm not sure if that's the case.  May be just a function of grain and tension variation throughout the log.  My stand of Doug fir is about 110 years old.  The sapwood generally extends about 2" into a 20" log.

beenthere

QuoteI have read that one should try to avoid sapwood and heartwood in the milling

The log is sapwood surrounding the heartwood. All the wood in the log is either sapwood or heartwood.
Don't think you can avoid them both.

(and I'm not gonna ask about the wolverine butts... ::) ::) ::)  )
south central Wisconsin
It may be that my sole purpose in life is simply to serve as a warning to others

sawbuckacres

Man!  You guys are debunking everything I thought I ever knew about trees.  :-\ I guess that's why I'm on here.

Some of the timberframeing folks suggest that the ideal wood, relative to strength, lack of warping, and lack of rotting, occurs in that portion of the tree, away from the core and away from the sapwood.  They suggest that if you cut a tree and watch the cut for a few days, you will notice a "ring" of exterior wood from which the sap will extrude.  In old growth, this ring may be only a few centimeters thick, while in second or third generation, it may constitude as much as half or more of the wood.  They contend that it is this sapwood that tends to decompose rapidly and suggest that a post cut from a typical pine, or Doug fir, that contains none of this sapwood will be very rot resistant - one could plant such a Doug fir post and expect it to persist for 50 years, simply by avoiding this sapwood. 

I have watched the end cuts of my logs and have noticed this - that there is a ring of about 2 inches that exudes a fairly high degree of resin, while the remaining 8 or 10 inches exudes none.

And as far as the wolverine butts thing, I've been doing chemical analysis on wolverine anal musk in an attempt to develop a lure for noninvasive sampling of wolverine populations.  Somebody's got to do it.

Ianab

You are correct about sapwood being less durable. It's the 'living' part of the tree where water and nutrients are transported around. After a few years it gets changed to heartwood and the tree lays down chemical extractives in the structure. These make it less desirable for bugs to eat, and more resistant to rot and fungus. I dont know about Doug Fir lasting 50 years in the ground, but the heart wood will last MUCH longer than sapwood.

The stability of the wood around the pith is also an issue. The wood there is juvenile wood, laid down when the tree was just a sapling, and the small growth rings are unstable as it dries. It's almost certain to star check around the pith and generally mis-behave.

So yes your best boards and beams will be the ones that are cut 'Free Of Heart', and without sapwood will be more durable. The other option is "Heart Centered" when the pith is kept in the middle of the beam. That way the wood on each side is balanced and hopefully keeps things straight. Thats the best option if the logs are smaller compared to the beam size.

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

SwampDonkey

Sapwood is xylem, the conducting tissues, this conducting tissue includes heartwood. But, heartwood becomes less efficient toward the pith of the tree as tracheads, pores and such get clogged with extractives and other deposits. Now the inner bark is phloem tissue, bringing food down the tree. How does food get into the live sapwood you say? Wood rays and other parachyma cells do this. They have to be living cells, they also store excess carbohydrates until needed. Tree species more efficient in utilizing carbohydrates have a wider sapwood and those trees more dominant in the canopy have a wider sapwood as well.
"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)))

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