Thread: Wood Movement

That is way to much information John. The only thing I know about wood movement is it is greater than zero. It works for me.

Originally Posted by Wongo

That is way to much information John. The only thing I know about wood movement is it is greater than zero. It works for me.

I know.

But I did warn you that I was a sick puppy ... full of information that I find interesting but which is often useless.

It gets worse when I am in Saudi ... nothing else to do after hours.

Thanks John for sharing your findings.

With regards to the movement values. Are those values considered fairly consistent regardless of time since the tree was cut down ? Just a suspicion, but with some of those timbers, I betcha, would move differently say 3 years after cut compared to say 30 years down the track even if sitting at 10% or whatever the whole time. Aging may lock up the cells somehow ? or stop the absorption of moisture… ? …….. Its Just that I've noticed with some old timbers, near no movement at all despite the high movement values associated with them. There's probably a scientific name associated with this ( too ed too move anymore syndrome)

Originally Posted by John Samuel

Then Density was correlated with Tangential movement. For most woods density is a reasonable predictor of movement in the wood. This means timbers such as red and white cedar, cheesewood, celery top and black pine, all of which are low density, are low movement timbers. The eucalypts tend to move a lot more, because they are dense.

I think thats a general interesting thing worth remembering (and easy to remember). generally denser -> more movement.

Despite the initial interest, I've always found it hard to use statistics like this. Steam bending complicates things for me as well.
eg. If you steam bend a quarter sawn pieces of timber that has strong medullary rays ( rose she oak, silky oak, river oak, banksia) from my experience you'll have a great chance of popping the rays on the tension side of the bend, so you have to choose flat sawn or rift sawn piece which doesn't look as pretty. (then criticised for apprantley making a poor choice of timber for that part)

Other things that complicate the findings I think, is where abouts in the tree the timbers from. For some species, I've noticed, if its near the heart the density jumps like 3 times. So really can't use a single density value. Riveroaks like that. Maybe have 'heart' river oak, and middle stuff river oak values.

Another factor that changes values to some significance I'd say is the soil quality. Riveroak taken from a hill tends to be harder than the oak near the creek.

Another factor I've noticed is daily massage. Those tree's residing near a place where cows hang out are more flexible, because the cows move the trees in attempting to scratch there arses.

another factor is love. Loved trees bend better.

So the best steam bendable trees I've found are ones that stand alone, near a creek, amongst a herd of cows, that is hugged daily by a hippy free loving farmer (best types). (sorry an attempt at humour)

You take your conversions very seriously, John!

Nothing wrong with delving into the nitty gritty of a subject - getting into the minutiae was everyday stuff for me in my former existence, & gets to be a habit that spills over, even into hobbies, so I can understand where you are going.

However, not sure you can generalise that denser woods move more for a given humidity change, that's a limited sample size you are working with. And in any case, I'm not sure how we can always apply knowledge of potential wood movement it in a practical way. To get the figures you used, they would have given smallish pieces of each species plenty of time to equilibrate at each MC point, to make sure all of the cell walls had absorbed the full amount they are capable of. Thicker bits are going to take far longer to equilibrate evenly. What that means to everyday woodworking is that with denser woods, by the time the inner wood is changing to reflect a change in humidity, the season has turned & things are going the opposite way at the outer surface. Moisture-inhibiting 'barriers' slow down the ingress/egress and may add to stability, but they don't hermetically seal the wood as some seem to believe, so given enough time or sufficient gradients, water still comes & goes as it pleases. Adding all this to the tangential/radial data & trying to figure out all the variables would make my head spin, so in the end, you rely on experience & a bit of guessing.

Some woods of medium density move a lot. I made a table top of Jacaranda, and it shows the greatest amount of movement I've ever come across; at least 15mm from max to min width as the seasons roll round (& it's not all that wide!). I just avoid using such 'lively' woods, whatever their density, in situations where a large amount of seasonal movement might be embarrassing. One thing you can bet your socks on though, is that the denser the wood the more power it develops when it absorbs moisture. You can often get away with less-wise construction techniques with Cedar or soft pine, where you wouldn't if you'd used Ironbark, not only because they develop less power, but because the softer wood compresses &/or is more elastic.

And Jake, it's quite possible that older wood is different. I've noticed, too, that older wood not only seems to move a little less, it seems to dry & 'settle' quicker if it gets soaked. There could be several reasons for that, such as compression of inner fibres altering the physical structure, or chemical changes in the lignin & other chemicals in the cell walls that alter their hygroscopic properties.

It's interesting, but all too hard for me to figure out. I just make sure there is plenty of elbow-room for panels & try to minimise cross-grain joints....

Cheers,

Yes I think any attempt to treat wood as an homogeneous material is doomed to fail. You can make lots of general statements about it, but every lump is different. Bit like people I suppose.

Wood generally defies any attempt to treat it with the same precision as you might a lump of metal, which is one of the reasons I like working with it. I'm not capable of the type of precision that you see in metal machining, wood is a lot more tolerant and a mm each way is forgiven, because it's pointless trying to get any closer as tomorrow the measurement will be different

If movement is directly related to density it must make lawn bowls a very difficult sport if you're using the old ebony and/or lignum vitae bowls. They'd be kept well sealed I expect.

Of course, the comments made below all have merit.

There is no doubt that very old wood tests differently to newly dried wood. Anyone who has worked on an old Queenslander and broken ten drill bits trying to put in five nails knows that.

Also, wood from different parts of the tree test differently and environmental issues and rate of growth all impact the data. It goes on ...

That is why so much of the data and analysis is interesting but limited in its usefulness, which was clearly stated at the outset. I was just a sick puppy having fun.

Nevertheless, whilst we are dealing with a variable biological product decent studies can guide us without ever being absolute. I think we agree that generally density correlates with movement ... and it does ... according to the CRISO data and to Bootle ... generally. But there are exceptions. That was the whole point of separating the yellow group, and especially the banksias out of the main group of data. They are different. This was a limited data set. There will be other exceptions.

CT pine stands out for being medium density and low movement. Black Bean and Red Banksia have similar density, but twice the tangential movement ... generally. To me, this might be useful if not exact information. I know my father and grandfather considered these things when selecting wood for boats. This understanding leads me to regularly use NG rosewood. It is a pretty, firm, medium density timber with low movement, and it is readily available. This forum is chokka with stories of well-built cabinet and table tops getting "wriggly" from individual boards cupping as the timber moves. My NG rosewood cabinet/table tops have not had that problem ... touch wood.

I am at an analytical conference in Saudi Arabia and this morning delivered a keynote address on analytical error, including sampling as well as test error. What we are discussing here is sampling error. If we take a sample from one side of the tree we might get different results from the other side of the same tree, let alone from the heart or from a different tree of the same species, perhaps grown under different conditions.

One of the tricks to making good use of data is to have a reasonable understanding of not only what information is contained in the data, but also an understanding of what information is NOT in the data. No data are complete ... ever. With wood, we are always generalising, because the data are so variable and the data are not normally distributed. That's fine, so long as we understand the limitations in the data.

I'm still having fun. Hope you are, too.

Cheerio!

John

Not trying to pour cold water on your fun, John, just steadying the ship a bit.

I spent much of my working life collecting data & trying to massage it to prove my prejudices (aka 'research' ). There is a lot that interests me, too, in the way different woods move, and some of the data are definitely useful. For example, a wood that moves roughly equally in tangential & radial planes is going to keep its shape better as the seasons roll round, i.e., less warp, provided the rings are roughly symmetrical in each board.

I found the data on She-oak interesting, too. I wouldn't have expected its tangential movement to be less than radial, quite the opposite, given the way it destroys itself if left in the round for anything more than 2 minutes after felling.
This is a billet of She-oak firewood a few weeks after being cut:she-oak.jpg

I would have assumed from this that tangential shrinkage far exceeded radial.

Not the first time I've been wrong....
Cheers,

She oak is an interesting one. It's the only timber I've ever had a failure due to shrinkage/expansion with. It destroyed a coffee table that I'd sold, even though I thought I'd allowed for plenty of movement.

I found your analysis interesting, and I'm sure it will be useful when I've thought more about it.

Originally Posted by IanW

Not trying to pour cold water on your fun, John, just steadying the ship a bit.

I found the data on She-oak interesting, too. I wouldn't have expected its tangential movement to be less than radial, quite the opposite, given the way it destroys itself if left in the round for anything more than 2 minutes after felling.

I would have assumed from this that tangential shrinkage far exceeded radial.

Not the first time I've been wrong....
Cheers,

Ian,

It never occurred to me that you were pouring cold water. My experiences corresponding with you have all been positive, and I am grateful for all of your advice and guidance.

You are correct. The Beach She Oak has wicked tangential movement. From what I can see, your experience confirms this. At 5.6 it is the highest in the CSIRO data set. What made it stand out for me was the relationship between tangential and radial. It's radial movement is only 1.8, putting it in the middle of the data set. The yellow group in the first post stood out because the radial movement was low when compared with the tangential movement. One sort I did was to create a Tangential/Radial ratio. The biggest ratios or deltas were the Banksias and the She Oaks, as well as black bean and the silky oaks. The Banksias and the Beach She Oak were in a class of their own in this respect, with more than three times as much tangential movement as radial. That's a bunch. However, if they were quarter cut boards they should prove to be reasonably stable in service. Tangentially cut, they are likely to be a disaster.

As a layman, the yellow group caused me to wonder if there were any good biological reasons for the yellow group to behave differently to the red group. Is there a biological link between the Banksias, the she-oaks and the silky oaks?

Cheerio!

John

Originally Posted by AlexS

She oak is an interesting one. It's the only timber I've ever had a failure due to shrinkage/expansion with. It destroyed a coffee table that I'd sold, even though I thought I'd allowed for plenty of movement.

I found your analysis interesting, and I'm sure it will be useful when I've thought more about it.

Alex,

According to the CSIRO data, Beach She Oak has wickedly high tangential movement, and the ratio between the tangential and radial movement is horrible, trumped only by Red Banksia. Rose She Oak is also at the wicked end of the scale for this data set. So, if your timber was cut tangentially, that might explain your failure. The stuff moves a lot tangentially, but has medium to low radial movement. So, it is easy to imagine what looks like a pretty board with swirling grain trying to turn itself into a propeller.

Years ago (before I got into woodworking) I was given a couple of old she-oak logs. I cut them up and used them as firewood; and they make great firewood. But they were a beautiful salmon pink colour, and I would dearly love to have them in my shed now.

Cheerio!

John

Originally Posted by apricotripper

I think thats a general interesting thing worth remembering (and easy to remember). generally denser -> more movement.

Bootle gives this general relationship between density and movement, and the CSIRO data matches up pretty well. Also Bootle says that generally (not always) whilst low density timbers move LESS they move FASTER. That is they respond faster to changes in humidity. This in turn marries up well with IanW's comment, "What that means to everyday woodworking is that with denser woods, by the time the inner wood is changing to reflect a change in humidity, the season has turned & things are going the opposite way at the outer surface", which sounds on the money to me.

Before the two Ians, Wongo et al alerted me to my sins I was doing some pretty naughty things ... failing to allow for movement. I have now seen the light and have corrected my wicked ways. Initially I was surprised that I had experienced so little trouble with my work ... so far. It now seems I just got lucky. Most of my cabinets were in timbers such as cedar and NG rosewood, which are at the low movement end of the scale. The only piece that gave me any grief was a cabinet made from Vic Ash. One of the (improperly constructed) doors refused to stop moving and generally misbehaving. Now I know why. Vic Ash is a high density eucalypt, and it has relatively high movement.

Have fun!

John

Originally Posted by John Samuel

, "What that means to everyday woodworking is that with denser woods, by the time the inner wood is changing to reflect a change in humidity, the season has turned & things are going the opposite way at the outer surface", which sounds on the money to me.

I agree. But how do you apply it ? Because this difference maybe dependent on thicknesses as well. ruff example. a thin dense wood will move as quickly as a thick less dense wood.

My works different , but I think most concerns are consumed simply by frame and panel joinery. Putting as much quarter sawn timber as possible into the widest sections which want to move the most (panels) and making sure the panels are free enough in the frames (else the panels won't want to move and split anyway). And creep up on final dimensions with big rest periods in between (even though this is probably not practical for most. ) So KD it, so its not wood anymore. If your in winter and springs starting to creep in, maybe make your joinery a fraction tighter than usual, to anticipate that first sudden hot day messes with everything. And if your in a hot dry summer make your joinery a little looser than usual ( the rain messes with everything) . My thoughts anyway in a nutshell.

I still think love could be graphed. Or music.

say a comparison. Get some big concert speakers and set them up in front of a plantation. Blast the trees with beethoven for 10 years. And do the same to another plantation out of earshot, but this time using Duf music. Then graph that with density/movement. ??

Originally Posted by John Samuel

......As a layman, the yellow group caused me to wonder if there were any good biological reasons for the yellow group to behave differently to the red group. Is there a biological link between the Banksias, the she-oaks and the silky oaks?

John, Banksias and Silky oaks are indeed cousins, in the family proteacea, but she-oaks are not at all close rellies. They belong in a different group which is pretty much endemic to Australia, with some interesting adaptive features like their "leaves" being branchlets, and nothing at all like pine needles, with which they are often compared ("she-pines" is another common-name for theem in some parts of the country).

What they all have are large medullary rays, or cells that carry fluids radially. All hardwoods have them, but in some species they are harder to see with the naked eye (& some so tiny you need a magnifying glass). Given our predilection for lumping things on the basis of superficial similarity, and the fact that the early settlers only had experience of a much narrower range of species back in Europe/Britain, every tree they came across with prominent medullary rays got a common-name that ends in 'oak'. There are dozens of them, and they come from quite a range of species & families.

I wonder if your boards were River oak (Allocasauraina cunninghamiana) or Forest she-oak (A. torulosa)? They are the two she-oaks around our neck of the woods that make trees you might get something described as a 'board' from. Both species can produce salmon-coloured wood, but both are quite variable, too, depending on age & soil type, particularly River oak, which can range from very pale brown to reddish-browns to black. The black is caused by a fungus, I think. Forest oak is a bit less variable in my experience and often a very pleasing (to me) slightly reddish mid-brown. They both make excellent firewood - that's actually a bit of young Forest she-oak in the pic above, taken on my parents' wood-heap. It has kept the stove burning on the old place since we arrived in 1948, & my mum (in her 90s & still living in the old original house) insists her two nearby sons keep her supplied so she can run her beloved stove! When I were a lad, my dad had a contract to cut firewood for the local butter factory, and we cut truckloads of the stuff. I reckon there would have been many cubic metres of fabulous stuff that went up in smoke. I try not to think about it....

In his declining years, he discovered what a great wood it was for other purposes besides fuel, and regretted he hadn't husbanded the better trees. I made a set of marking gauges from the last bits he gave me a couple of years before he passed on. It's very suited to such applications because of the stability you noted previously (once dry!) as well as its density and ability to take a beautiful tactile finish: All new.jpg


Jake, I agree with what you said, I think many of us operate similarly. There ends up being a lot of just plain intuition & experience & trial & error (plenty of errors in my case!) in how/what wood you use. I don't disregard the science at all, it is all relevant, and helps in many ways, but it's often more in a general way, i.e. pointing at trends. It helps us decide what is likely to be good for what, or tells us why a given species is better at taking bends than another, & so on. But as John will fully appreciate, statistics are of limited use when you have a sample size of one, i.e., that lump of wood in your hand that you are trying to decide whether it will make a good chair leg or not. Given all of the factors we have to consider, such as variation within a species, grain direction, likelihood of any defects, etc., you have to fall back on your own knowledge & experience to figure out if it's likely to make a very good turned leg or a disastrous failure.....

Cheers,