quote:
“Hi Bob, Could you possibly create a post explaining why and how tight ring counts
improve lumber qualities? I know that tight ring counts are preferred, but why is it better?â€
My pleasure…it’s really quite simple, looking at a close-up of the growth rings:
In early spring the wood grows quickly with large, thin-walled cells…â€earlywoodâ€â€¦seen as the lighter colored portion of the growth ring. As the season progresses and growth factors such as light, temperature, nutrients and water become more limiting, the cells get smaller, thicker-walled, denser and more resinous…â€latewoodâ€â€¦seem as the darker portion of the growth ring. You can actually see the cells get smaller in the photo as they darken. Smaller, denser cells with more natural resins are stronger…and a higher proportion of them in the wood makes for stronger and more durable timber…significantly stronger and more durable timber.
Even in the tropics there is usually some limiting factor to create latewood…like an annual dry season…and it is the rare tree that doesn’t show some sort of growth ring.
But it also helps to understand something of how the tree grows…many folks think of growth rings in three-dimensional form as cylinders, but they are really cones as shown above. That’s useful to understand when ripping bending stock from wood originally milled from a cant as most sawmills do…there is almost always some grain runout in straight, sawn boards that should be identified before selecting stock for bending. That’s why riven or split boards like the Vikings’ early lapstrake planking are almost always stronger than straight boards, and for most store-bought wood, boards milled from nearer the pith will have less grain runout.
There are some sawmills that can compensate for log taper without making a cant, taking their waste from the pith rather than the slab…the Lucas and Peterson swing-blade mills come immediately to mind. If you can find a local sawyer using one and explain your requirements, you can obtain higher quality bending stock.
Wood is composed of hollow, spindle-shaped cells of cellulose cemented together by lignin and arranged parallel to each other along the trunk of the tree. Trees grow by adding cells in the (again, cone-shaped) cambium layer immediately beneath the bark…the trees’ existing cells do not grow larger. Thus new wood is laid down atop of old and the diameter of the trunk increases…stretching, cracking and sloughing off the bark as the tree grows.
The wood immediately beneath the cambium layer …the sapwood…stores and transports the tree’s water and nutrients. As sapwood contains much water and minimal resins, it is never rot resistant…even in rot resistant species…and is undesirable for use in boats. Generally, the faster the tree species grows, the higher percentage of sapwood…yellow pines from modern plantations take decades to develop heartwood and today’s SYP lumber generally contains no heartwood. Black Locust is an exception…a fast-growing pioneer species that generally only contains a half-inch of sapwood and high rot resistance and strength in its heartwood…hence an excellent boatbuilding timber to propagate.
Heartwood consists of dead, inactive cells that no longer transport or store food and water. The transformation of sapwood to heartwood is accompanied by a general loss of water and a dramatic increase in the “extractive†content…the resins, tannins, gums, oils and minerals that give heartwood its distinctive darker color and in some species resist rot.
Most woods like also have “raysâ€â€¦which are horizontal cells that transport water radially across the grain. In White Oak these cells are larger and more conspicuous, especially in quartersawn wood. “Tyloses†also occur in some hardwoods like W. Oak, ash and hickory. These are ingrowths that clog the sapwood’s pores as it transforms to heartwood and prevent water transmission. This makes White Oak excellent for boats and cooperage, but also prevents the penetration of preservatives in the wood, so there is a trade off. Softwoods transmit water differently than hardwoods…they transmit water from longitudinal cell (tracheid) to longitudinal cell and don’t have pores…. that’s how you tell a “softwood†from a “hardwood†botanically, not from the leaves. The Ginkgo or Maidenhair Tree in your local park is certainly a broad-leafed tree…but it also has tracheids and is really a “softwood†botanically.
As a practical example above, here’s a Doug Fir log in my stack yard recently harvested from a neighbor’s farmstead. The tree above is what we call locally a “mini-old growthâ€. It was a seedling in 1900…well before the area was first selectively logged in 1936…yet it is only 21†in diameter. You can see that as a seedling, it had a tough time competing with its larger forest neighbors, and there are 20 rings to the inch until its larger neighbors were thinned in 1936. Then with more, but not full sun, the tree grew at a rate of 8 rings to the inch…and you can see those rings tighten up some as its neighbors also shot up…until the area was completely cleared for a farmstead in the 1970’s, where it got full sun and grew at an even faster rate of 4 rings to the inch.
In contrast, its close neighbor was also the same size…around 21â€â€¦yet this tree didn’t sprout until the around 1975 when the farmstead was cleared, and has spent its entire life in full sun…3 rings to the inch.
There’s little doubt which log will become boat framing and which log will become studs.
“When we build, let us think that we build forever. Let it not be for present delight nor for present use alone. Let it be such work as our descendants will thank us for; and let us think…that a time is to come when those (heirlooms) will be held sacred because our hands have touched them, and that men will say, as they look upon the labor and wrought substance of them, ‘See! This our father did for us.’ “ –John Ruskin.
Replies
Bob, thanks for the well-written, informative post. I liked the two pictures of the log cross sections and their accompanying histories, thanks.
I'm concerned for your mental health though. Isn't responding to your own questions a bit like talking to yourself and then answering? I haven't been around here much lately, so I'm not familiar with you; I hope you don't mind a little ribbing.
Woody
Never thought of it that way...oh, well, hope the world still has room for some harmless eccentrics today.“When we build, let us think that we build forever. Let it not be for present delight nor for present use alone. Let it be such work as our descendants will thank us for; and let us think...that a time is to come when those (heirlooms) will be held sacred because our hands have touched them, and that men will say, as they look upon the labor and wrought substance of them, ‘See! This our father did for us.’ “ --John Ruskin.
Bob believe it or knot, I understood your whole post!
Good explanation.
Did you have any formal edjycayshun in this stuff?
Or did you learn the hard way.
I got mine at SUNY ESF @ Syracuse , Wood Products Engineering.
then i became a carpenter to learn all the useful stuff!
Love your posts!!
Keep up the good work!Mr T
Happiness is a cold wet nose
Life is is never to busy to stop and pet the Doggies!!
By trade am a Habitat Biologist consulting for loggers and landowners on environmental/wetlands protection and remediation.
By avocation I own a small tree farm, large, portable sawmill and have been a lifetime woodworker and boatbuilder like my Dad and Uncles.
Currently on sabbatical for three years to build that retirement home for Mama from the trees taken from the house site...DF stick frame farmhouse w/ beveled cedar siding, home cut cedar shingles, local Madrone floors and local hard maple and alder trim and cabinets...all site built. Began digging the foundation hole this week, in fact.
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And the view from the kitchen:
View Image“When we build, let us think that we build forever. Let it not be for present delight nor for present use alone. Let it be such work as our descendants will thank us for; and let us think...that a time is to come when those (heirlooms) will be held sacred because our hands have touched them, and that men will say, as they look upon the labor and wrought substance of them, ‘See! This our father did for us.’ “ --John Ruskin.
Bob
As others, enjoy the info tree-mendously.
Man that's some building site!!!
Thanks
Doug
It took almost 20 years of land trading and cajouling and being somewhat of a PITA to acquire that isolated 5-acre pond and surrounding land.“When we build, let us think that we build forever. Let it not be for present delight nor for present use alone. Let it be such work as our descendants will thank us for; and let us think...that a time is to come when those (heirlooms) will be held sacred because our hands have touched them, and that men will say, as they look upon the labor and wrought substance of them, ‘See! This our father did for us.’ “ --John Ruskin.
Appears to be well worth it though!
Doug
Good post. Learned a lot. Thanks.
Don't worry about asking your own questions. Do the same thing in my posts, don't take this to mean your not crazy, because it seems a good way of expressing concepts and avoiding misconceptions.
Bob
Here is a typical rafter from my garage re-roof project. Garage was built in 1924 and this is the first tearoff. Sure wish I could find 2x4 rafters like this for less than $8/bf. I came up with 20+ growth lines/inch before my eyesight failed from counting. I recently replaced the basement steps and will be building furniture from those recovered boards, seen here before and after a pass through the planer. Almost makes me want to swap out the 110 linear feet of 6x10 beams on my front porch with some newly milled wood.
Lovely material.
I've a whole 5-acre beaver pond chock full of it and old-growth WRC...all sunk in the pluff on the bottom. When beavers dam up ponds, the trees die and fall...and last for thousands of years in our cold, clear water.
Problem is, many are 6' in diameter and 120' long...and will be a real challenge to get out once I get around to trying.“When we build, let us think that we build forever. Let it not be for present delight nor for present use alone. Let it be such work as our descendants will thank us for; and let us think...that a time is to come when those (heirlooms) will be held sacred because our hands have touched them, and that men will say, as they look upon the labor and wrought substance of them, ‘See! This our father did for us.’ “ --John Ruskin.
Ya but won't you feel giddy when you succeed!
Man I hate it when I'm just tryin to cruse thru here and I run across one of your replys.
Ther goes another hour lookin and thinkin,
Good Stuff.
Well here's another one...some pretty good comments from other forums:
Written in the context of boatbuilding softwoods…your comments are excellent…I probably shoulda left more-complicated hardwoods out entirely. I agree with you, and have certainly read that before...but not having much oak out here to play with, I wonder what the strength differences really are?I doubt shipwrights (and ships) of the 16th and 17th Centuries when those original virgin oak forests were used thought it to be much of a disadvantage…after all, those uneven-age forests had younger, sun-grown trees to select from, too.Doug Fir has been downgraded in strength a couple times since the 1930's as an engineering material...minor downgrades...the last downgrade quite recent. My lumber grader the other day thought the reason for the downgrade was because,"…it wasn't as strong as we thought it was." My answer was yes, but there's little doubt in my mind as to why when you look at the two example logs from my stacks.Perhaps the difference between new and old oak is akin to the DF dynamic only in reverse?“When we build, let us think that we build forever. Let it not be for present delight nor for present use alone. Let it be such work as our descendants will thank us for; and let us think...that a time is to come when those (heirlooms) will be held sacred because our hands have touched them, and that men will say, as they look upon the labor and wrought substance of them, ‘See! This our father did for us.’ “ --John Ruskin.
Roy Underhill goes into that detail in one of his books albeit short. Basically slow grown Oak and Ash tend to be "Brash" a term used mainly by chair bodgers , with brash relating to the slow grown being less flexible for green bending as opposed to faster grown stock.
It has been in my experiances that slow growth oak is too brittle for some applications, where a more even grained oak has more resiliancy. And moisture content plays a big part of it, with slow growth tending to behave "drier" maybe due to less earlywood in general..and less porosity.
FWIW
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Spheramid Enterprises Architectural Woodworks
Repairs, Remodeling, Restorations.
Speaking of logs in the lake. Here is a picture of the "new" spirit lake following the eruption of Mt St Helens. What appears from the distance to be a sandy beach is actually hundreds of thousands of fully grown trees which were knocked down on the surrounding hillsides by the eruption-induced tidal wave. They then were carried back into the lake as the wave receded. The same environmentalists who don't want any of the forests harvested are the same idiots who also don't want these logs harvested, lest it set a precedent that fire and volcano damaged areas be harvested for the timber. They believe companies will set fire to old growth forests in order to harvest the wood after the disaster. I've heard estimates of hundreds of millions of board ft of wood, much of it old growth doug fir, is now rotting in the lake because some environmental scientists want to see how volcano ravaged areas recover. Talk about useless and ultimately wasteful science. I wonder if these same idjits lived in NYC that they'd want the rubble of the world trade center to saty where it was so they could study how people in the city dealt with the mess.
More from a sawyer in Australia:
"Bob I have never heard of fast grown wood being stronger before. Is this only for Oak, Ash & Hickory or for all hardwoods? I can grade wood here (Australia) Pine can fail visual grading if any of the growth rings in the inside 100mm diameter are over 13mm whereas ring width does not get a mention in hardwood grading.
I read somewhere that the sap wood in hickory is the best part and that the heartwood was not as strong do you know anything about this?"
That's what the discussion above is about. The argument is that in "ring-porous" like oak, ash and hickory as opposed to "diffuse-porous" woods like cherry and maple...woods that have pronounced, open pores in rings....that those ring-porous woods are stronger with fewer rings per inch.
The logic is there, well enough...the question is, how much stronger or weaker and is it significant?
We don't have many of these woods out west in any quantity and I don't mill them much....no oak expert here, by a long shot...but the family milled oak when I was a kid back east and having used a bit of it...including 200+ year-old W. Oak...I suspect the issue is overstated:
1) What you lose in more pores you gain in a higher proportion of smaller, latewood cells just like in softwoods.
2) The gains in terms of durability from higher extractive content in the latewood are well worth any minor strength issues.
3) I haven't seen any results of lab testing on this to determine any differences on strength and would want to before drawing firm conclusions. Doug Fir, in contrast, is tested frequently because it's our Number One structural wood over here.
I just ordered am 8-dollar copy of Hoadley's out-of-print book, "Understanding Wood", because that's where I've been told the issue is raised....I'll let you know...."Because I said it is" or modern lore passed down through magazine writers doesn't cut it - I want to see the numbers.
Wood for bending is a different issue and wood from young second-growth trees is preferred because of pliability. Faster growth and correspondingly larger cells are desirable here.
“When we build, let us think that we build forever. Let it not be for present delight nor for present use alone. Let it be such work as our descendants will thank us for; and let us think...that a time is to come when those (heirlooms) will be held sacred because our hands have touched them, and that men will say, as they look upon the labor and wrought substance of them, ‘See! This our father did for us.’ “ --John Ruskin.
Hoadley's "Understanding Wood" was "completely revised and updated" in 2000. Published by Tauton. Available on Amazon, no problem.