You shouldn't need this for most work in UK timber. It's really just for exotics. Bowls are normally turned from halved logs, not as end- grain disks from across the log. So long as you avoid the pith and you dry them slowly, you can avoid cracking - they'll warp instead.
I have most of a chestnut still to turn up, after it was felled a few months ago. I turn the untreated logs green to be thick-walled bowl blanks, coat them in wax emulsion (not PEG) and leave them to dry for a year or two. Then I finish turn them to shape. They'll warp in this time and a few will crack, but the walls were left thick enough that I should still get an unwarped bowl out from inside. It's also easier to store bowl blanks than to store a whole tree.
I had some no good wood to burn once, and it wouldnt stay alight at all. Think it was elder. What worked was to create an outer perimeter of it around the edges of the grate, then build a fire with good wood in the centre. Gradually the elder all got burnt.
Thanks everyone for your replies. I've decided not to try to turn it on a lathe, just cut and polish a slice for use as a clock. To that end I took a cut piece standing on it's end on the wet ground, with another bit sitting flat on top, and cut a thick slice off each end of the bottom piece then sealed the ends with a coat of PVA. Later I'll take a slice from the middle to polish as a clock. Any ideas how long it will take to dry?
I've got some coppiced Ash pieces to take down. There about six inches thick. If I sealed the ends with PVA as soon as they were cut would they dry okay? I'd like to turn them but if I split them they would be pretty thin.
There is also what is definitely a Lime tree that a friend wants me to fell, it's tall, straight and without branches until about half way up. Though this is thicker, a good eighteen inches. If I wanted to prepare it for carving would I still need to quarter it as well as a PVA coat for the ends?
By "slice", I'm guessing you mean a transverse disk. You have pretty much no chance of this drying without splitting (anything over 4" diameter). The reasons are slightly complicated to explain in detail, so if the usual pinheads could please go and read Bruce Hoadley before arguing, we'd all save some time.
You might want to make some backup slices. Then when they've split, you can bandsaw them into radial segments and rejoin them to make a fair approximation of a disk.
A year an inch of radial thickness for long timber. A summer for short stuff.
I use wax emulsion for sealing, but PVA is probably OK. Certainly if that's what you've got handy. Some people use emulsion paint.
Ash logs are going to split at the ends, so you'll lose some length. However ash is so dry straight off the tree that it's fairly easy to dry otherwise and you might keep logs of this size intact. It's so well behaved that it's even one of the few timbers you can turn with the pith intact, just keep it buried in the middle and don't expose it.
Lime is much more stable. I've two foot diameter logs of it in the woodshed that are just rounds (about 10 years old now) and no splitting. Must uses do want to lose the pith though, so halving it is a good move. Make good use of it though, it's too good to waste. If you can't use it, sell it to carvers.
Assuming I don't have Bruce Hoadley to hand, but don't see any reason to argue, is this because the thin stuff isn't strong enough? You say it's complicated in detail, but could you give an idiot's summary? (mostly I can see why it would split, but am vague as to why bigger stuff wouldn't).
The recent gales caused a mature Oak, semi-sound, (around 3'6" trunk) to assume a horizontal position here.
At some time in the next few weeks I will have to make decisions as to its fate. Previously I have engaged a mobile saw mill contractor to convert to 8"x4" and 4"x4" for construction jobs. This time I am considering 8"x1" for floor boarding. Due to the nature of in field milling, cuts of up to 8" horizontal or vertical can be made.
Bearing in mind this is Oak. Is it worth attempting to maximise the production of boards with growth rings at less than 30deg. or not bother? Boards will be stacked for air drying.
You get the best figure from the boards that warp the most.
IF its for inside use, Id simply flat saw the lot, bin the pith, wait till the lot has warped and then plane to board sizes. And hope they don't warp again..
Use the center bits for structure, and the edge bits for show
Sorry, but every time this comes up, the usual idiots start arguing about how they've dried a giant redwood in their shed and it didn't split.
If you don't have Hoadley, buy it, as it's a damn good book. If you don't want to do that, the US Forest Products Handbook is on-line for free (and also available printed and bound for a reasonable price). OTOH, Hoadley is clearer to read.
Timber drying highlights how much some species differ in some aspects, but also (surprisingly, to me anyway) how much other aspects are consistent between species. Moisture content (EMC) has a consistent relationship with air humidity (RH). Moisture content of a felled log varies a lot (why felled ash will burn, but others needs to be dried). Shrinkage with MC varies across species, but total shrinkage from "felled log" to "dry board" ends up consistent again. The breaking point of timber varies a lot measured as a stress (i.e. force) but is consistent as a strain (i.e. dimensional change). The ratio between tangential, radial and longitudinal shrinkage is consistent, even though the absolute values vary.
Tangential, or hoop, shrinkage is twice the radial shrinkage (and lengthways is near zero). If they were the same, then wood would shrink isotropically, by the same in every direction. The total shrinkage is about 10% tangentially and 5% radially, for a wet log to a dry board, for any species. Considering the log as a set of "onion rings", you should realise that it's now increasingly difficult for the outer rings to stretch all the way to reach round the inner layers
- and so they crack radially, from excess tension.
Why does it crack? Well the shrinkage will hit 10%, which will generate some unknown tension in the rings. The tensile force is enough to break the timber. Now I know neither the force generated, nor the tensile strength (in force units) of the timber, but I do not that the maximum strain (as a dimension change ratio) for all timber is about 8% (AFAIR, can't remember the precise figure). So _whatever_ the species, wet to dry is enough to break a constrained piece of it.
We can avoid this in a few ways.One is a radial cut, or halving the board. Note also that a log that develops a split early just develops the one major split. That split relieves much of the tension. Another way is to take the centre out of the log and to allow it to collapse as rings.
Another way is to crush the central core of the log (by an imperceptible amount). If the central core is simply small, then it's crushed by the larger outer ring. The square law for cross-section area is such a small core surrounded by a ring an extra inch thick is far less cross-section than the ring, but for larger cores that extra inch of ring becomes a progressively smaller cross-section compared to the core. Small cores get crushed, large cores burst the ring. This varies by species, as it depends on the species-varying ratio of tensile strength vs. crush strength. When a species, like lime, is easy to dry without cracking, it's usually down to this ability to crush the core slightly.
Elm, noted for its interlocking grain, has a much stronger tensile strength in a large piece than a small piece, so drying elm will tend to generate many microcracks, rather than a single big crack.
I'd halve it, maybe quarter it as it's a decent size, and then decide on the basis of how good the figure looked. I might even hand-plane a piece of a quartered log before deciding, just to see it better.
If the figure is good (some of which depends on why it's down), then I'd quarter-saw it and hope to make furniture-grade boards from it. As I'd be doing this on a Wood-mizer or similar (a portable railway line in the woodland, with a horizontal bandsaw on a carriage), I'd do this by rolling the quartered logs from face to face, not by sawing at 45=B0.
If the figure was poor, or the trunk was too small to produce useful width otherwise, I might saw it as through-and-through.
You can sell good quartersawn oak and buy as much flatsawn flooring as you could want.
Grain in oak always looks crap, which is why most finishes for it will try to fill and hide it as much as possible.
Figure in flat-sawn oak (i.e. ring figure, the stuff that's usually most noticeable in most non-tropicals) is near indistinguishable from stained ash, which is why my oak-panelled dining room is getting ash skirting boards (cheaper than oak, and indistinguishable down there).
In quarter sawn oak, you will also see the rather less common medullary ray figure, aka "ray fleck" or "tiger stripe". This is caused by slicing the radial rays at a shallow angle, not something that shows up in many timbers apart from oak. It's a valuable figure, as you have to have good timber to show it (American oak is better than English oak) and you also have to quarter-saw to show it at its best.
You might not like this personally (I do, although some US use of it as tiger stripe is a bit much), but it's certainly a premium cut, and priced accordingly.
Quite. However the initial choice which I had not mentioned is to sell it in the bark to my sheep grazier who has an employee doing a *grand designs* barn:-) They have one of the travelling chain saw mills.
The tree has some deadwood/rot on the sheltered side: roots and branches. I should know more when I have removed the branches. Not soon because the ground is soft and it is lying down a steep slope.
I know the Wood Mizer. Lot less waste with the band saw. How would you initially quarter such a large log?
I have access to a Lucas Mill. I'm no hand at Ascii art but if you can imagine the log end on divided into 9 portions by two sets of parallel lines at 90deg. The right hand ninth would cut horizontally, the middle vertically and the LH horizontal again. 4/9ths should thus give good boards.
I think the first move after removing the branches must be to find someone with a long enough chain saw bar to knock off the roots and expose the butt. If there is serious rotting I'll let the *grand designs* barn man have it. Otherwise try to maximise the amount of quarter sawn planks.
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