I think you’re off by an order of magnitude. With those numbers, a 12” board would expand and contract 1.2”, and an 8’ long board would vary by almost an inch.
Much more reasonable would be 1% across the grain and 0.1% along it. You can confirm this in some of the wood movement calculators found online.
To those learning about wood movement, these ratios are decent but approximate; if you end up caring about these things you’ll want to check the species of the lumber you plan to work with.
They aren't off by that much. You are further off if you assume some standard parameter ranges :)
But in the end, it depends on factors i didn't see listed.
Overall, the percents are usually calculated by swelling coefficient. Swelling coefficient is percent change in radial/tangential for each 1 percent of moisture change. There are well-known sources for these that calculated them in sane ways. The US forest service is one of them, and they publish their methodologies/etc for how they determine them.
See, e.g., https://wfs.swst.org/index.php/wfs/article/download/1004/100...
Take standard flat sawn red oak.
The swelling coefficient is 0.001-0.002 for radial (0.1% per 1%), and 0.004-0.005 for tangential (0.4% per 1%).
So in initial drying, which is usually 30%->15%, it will move 1.5-3% radial and 6-7% tangential.
Without humidity control, houses swing from 30%<->60%. Sometimes per day, sometimes per month, sometimes per season. So even more than initial drying. But because the swing varies, depending on thickness/etc, how much moisture change you get in the wood, and how fast, will vary a lot.
If you assume it causes a 10% change in moisture content over the year, throughout the wood, we get 1-2% radial movement, and 4-5% tangential movement for red oak. But that is both swelling and shrinking, not solely one or the other.
So the GP would be off by a factor of 2 in one, but not off in the other.
It's obviously trickier in practice to calculate the actual rates because the moisture is going to diffuse through the wood at some rate, and as long as the RH is changing faster than the diffusion rate, the wood will not really have a consistent moisture content all the way through. To be accurate, you'd have to slice it into enough pieces to capture the different moisture levels in the wood, apply the coefficients to each slice, and, etc. Worse, because boards are rarely square, and instead often much wider than they are thick (IE 12"x1") , you'd have to slice and calculate it one way to deal with this for radial, and slice and calculate it the other way to deal with tangential.
I'm too lazy to calculate how coarse/fine of a slice you'd need to get within say 5% of the "real" number.
I'm also assuming you are trying to do it by hand, since this is obviously an integral of some sort that you could also just directly solve. I'm sure it's in a paper somewhere.
This is all for bare wood too, with no topcoats. The topcoat would seriously affect absorption rates, etc, even assuming you applied it to all sides.
Nobody does any of this calculation in practice, we just accept large error bars and build floating tables :)
I can't tell where their data comes from, and they don't cite it.
The 10% number was not meant to be real, i just was giving an example :)
Real is much harder.
4% is not a horrible guess from as best i can calculate (but see below because this page has some crazy claims). Studies suggest that wood RH tracks RH pretty closely, slowing down with depth. Transport also appears to depends on temperature, independent of humidity itself. But if you assume it's going to track RH closely and throw out the rest, you can just assume the wood will always fall within the EMC range for the RH range.
You can see that between 30-60% RH, you really don't get more than like a 7% span (i'm eyeballing it) of EMC that the wood could vary around at any temperatures likely to exist in your house.
So 4% is probably not a horrible guess.
However,the site you link to says some very wrong things, interestingly:
"Temperature Has No Significant Effect on Wood MC"
This is 100% wrong, in more ways than one.
First actually even wrong if you ignore humidity entirely, because studies suggest wood moisture transport changes at high/low temperatures, even ignoring humidity. The exact mechanisms are not pinpointed (AFAICT from skimming), but that's what real data says.
Second, the temperature affects the EMC (and relative humidity).
It's very weird for them to go on and on about how humidity affects would but then say temperature doesn't matter at at all.
You can't actually separate these things, and say humidity level matters but temperature doesn't, because they are linked.
If you want real data/simulations to try to figure out more, here's some references - i didn't read all of them, busy morning, but i did at least look at most of them.
Given limited absorption rates, does that mean varnish etc helps keep the internal moisture content more steady over time (and therefore less variation across the wood internally as well)?
I see a couple of sibling comments giving you great tips already. I am still in the painful stage of failing my way to success (though closer to the end than the beginning)
I will suggest a few things. Follow up each of these points with more research if you can.
Spend as little money as possible and prove to yourself you’ll actually like it. Then buy only the good tools you actually need for the project at hand. I have tools I bought that remain unused and I regret spending the money. Its not the tool’s fault but me going in a different direction.
It doesn’t matter what species of wood your first projects use. Prefer wood with straight grain and you should be fine for your first half dozen projects.
Read widely or watch many YouTube videos. There’s a lot of space for ideas, from carving spoons to making stick chairs to making furniture of any style. Note what inspires you but be aware the path to making what you like may take awhile.
First project: make a cutting board (only one piece! Learn how to make it look great and learn a finish) Second project: make a simple box (learn how to make things square, learn some simple joinery)
Safety first! I put this last so it’ll be the first thing you remember. There are so many ways to ruin your health, from breathing sawdust to using toxic finishes. Hand tools are generally better for your lungs than power tools. Soap or wax finishes are healthy and easy to apply. Just about everything else is toxic and you must protect yourself accordingly. Invest in safety glasses, masks and gloves. And a first aid kit.
Woodworking is an extremely rewarding pastime and I hope you get hooked. Best of luck!
He's got a very nice approachable style (almost the Bob Ross of woodworking?) and has some great beginner videos. He also sells a course with plans for gradually increasingly challenging projects. No affiliation, just watched a lot of his videos when I was first getting started with woodworking.
There are also (as you'd expect) thousands of other Youtubers doing woodwork, too. Steve's just a great starting place.
While conventional tools are nice and necessary, having access to a gantry CNC machine for cutting wood is a HUGE thing.
A CNC makes many projects a single step. Anything having to do with cutting plywood to non-rectangular shape or stencils or carving letters or ... yeah, do it on the CNC.
And, even if the project isn't a single step, a CNC can compress a bunch of steps and make the project way easier. And even the canonical "cutting board" may require the CNC for a flattening pass (edge grain through a planer has issues).
Whatever you do, do not get suckered into buying a bunch of machines right at the outset. They're loud, expensive, often dangerous and there's no limit to how many you might need.
Start with small projects and hand tools. People have been building beautiful things with a small variety hand tools for centuries and the lack of noise alone changes the entire experience.
I spent a couple years buying books and watching YT, especially Paul Sellers[0] before building anything at all.
The reality is that fine woodworking is a craft and takes years to master (I certainly have not mastered it), but one can create objects pretty quickly that feel wonderful to hold.
When you do get down to buying machines, a decent track saw can be much more versatile (and space efficient) than a table saw for a first purchase. FWIW, I have both and use the track saw 2-3 times more frequently because it's easier (though much slower) to safely and accurately break down large sheet stock. It's also the only Festool product I own.
I'm going to counter this with a simple "I ain't got time for that". The "that" being hand tools. I did take a course from Roy Underhill and loved the crafty vibe of hand tools, even bought a No. 4 smoothing plane in the shop above the classroom that I use occasionally. My personal preference is to use power tools for the majority of work because hand tools take too long to learn in order to get good output. Given that its a hobby for me, I don't have a lot of time for projects so I want to complete them and not spend all my time just getting better with a hand plane or a chisel. I am impatient.
Another personal anecdote is having a US software engineer salary provides for a tool purchase not being a big deal. There are tons of people that have expensive hobbies like photography, guns, drones, 3D printers, etc. so to me I'd rather buy a $600 planer than have to hand plane boards to make a desktop. I did discover a Milwaukee track saw recently which hands down I should have gotten years ago. So I will agree that should be the first purchase for someone starting... you can likely use that for almost all use beginner use cases that might call for table or miter saws.
Learn to sharpen tools properly. A sharp chisel and plane, and something like a Japanese pull saw to handle the big stuff (with a measure of delicacy due to its flexibility) will get you an impressively long way. But such implements can dull quickly, and there’s nothing more dispiriting (or dangerous) than a dull tool.
See if your local community college offers a class. I know that's not a sexy answer but I think there is something to be said for having access to all the big tools and not filling up your garage with random bits of lumber before you know how serious your interest in woodworking is going to shape up to be.
The old PBS New Yankee Workshop episodes are on YouTube. Norm Abram uses a lot of power and specialty tools especially in the later seasons but in the first season or two his shop and projects are pretty simple.
Apologies for going off subject but I want to ask about that background image on that page.
I remember seeing that art a long time ago and I remember that it was algorithmically generated but I don’t remember anything else. Does anyone have a name or link they can share to the original source?
Any handbook about the strength of materials has a chapter about creep a.k.a. cold flow.
The handbooks from immediately after WW2 already included such a chapter, but I believe that the first studies of this problem must be much older.
When any metallic structure is designed, it must be verified that it will not fail in any of the possible modes, including due to flow over the intended lifetime.
By the approximate rule mentioned there, zinc begins to have non-negligible creep already above minus thirty Celsius degrees, so at normal ambient temperatures you must always compute the creep of zinc for any structural design.
On the other hand, metals like iron or copper have negligible creep at room temperature, even when pure.
Aluminum and magnesium begin to have non-negligible creep at temperatures only a little above normal ambient temperatures.
Hard alloys can have much lower flowing speeds than the metals included in their composition.
In integrated circuits, the metal connections are affected by electromigration, which is the flowing of the metal due to electrical current instead of mechanical stress.
The electromigration properties and creep properties of a metal are closely related. In the beginning, the ICs used pure aluminum for interconnections, but when their size was reduced, the connections began to fail after a too short lifetime.
The first solution for this problem was the replacement of pure aluminum with harder aluminum alloys, including small quantities of copper and/or silicon.
When the ICs became even smaller, the aluminum alloys had to be replaced with a metal having a higher melting temperature, i.e. copper, which fortunately also has a lower resistivity.
Sometimes it’s worth pausing a moment when seeing a “It’s well known that…” to check the timeline because the construction of Arecibo might well have taken place (or planned) before it was known (let alone well known).
Edit: a bit more searching suggests that this was studied in 1947 (Andrade’s Creep Law and the Flow of Zinc Crystals, by AH Cottrell)
This feels like the facility was in operation for so long, that the people who knew about this potential problem all retired and with them went that knowledge.
Andrade is the namesake of Andrade creep due to his work in the early 1900s, but the existence of creep had been known for a long time by then. I'd imagine smiths have been aware of creep throughout the history of metallurgy.
It's a simplified explanation of the geometric concept of "tiling the plane" where shapes are placed, like flooring tiles, onto a 2D surface, a plane. In this case I think pattern is just the layman's terms being used for simplicity's sake because, when you look at the assembled tiles, it's the same shape repeated (but not the same repeated configuration of several of these shapes, which is what makes this novel).
Some countries (I know Canada is one, Germany, where the artist works, is possibly another) have the concept of moral rights enshrined into law. Boiled down, this means that anyone who wants to use an artist’s work in some context must get permission and/or be prepared to compensate the artist (ianal but I did study copyright law for artists in Canada)
The canonical example Canadians refer to is the Eaton Center adorning Michael Snow’s sculpture Flight Stop with ribbons over Christmas. Snow sued the Eaton Centre for compromising the integrity of his art and won.
If a similar mechanism exists in German law (my quick research suggests it does) then the artist may well have an argument to make about AI comprising the integrity of his work.
CGPT: "Hi, Mr Anchovy, my name is William. Welcome to the career counseling session today. Any time you want to end this session, please type '$exit'. Can you please introduce yourself? Please start by introducing what you are doing and what are any other industries and nature of the job that you are looking for"
Me: "I am a chartered accountant but I want to become a lion tamer!"
CGPT: "That's an interesting career change! Let me help you explore what other industry is suitable for you and what different job positions you can pursue.…"
Looks like even CareerGPT has reservations about going from a CA to a lion tamer.
I see a few people advocating for putting one person on support each sprint, rotating through the team.
This works fine for small teams but for larger (and with large, older codebases), the ramp-up time for being an effective support dev becomes a drag because it can be months between support stints. We don't all have eidetic memories and forget the tricks we use to diagnose production issues.
To counteract that we've recently put a developer on a 6 month rotation, and support them with a rotating backup. This allows the primary support developer to not only stay productive fixing issues but also surface intelligence around the problem areas in our app (ie: what's always needing support) and construct tools to make resolution easier or better yet convert to a self-serve.
I infer from your comment that you're a smaller team so perhaps you won't need to put someone on a long stint, but you might want to consider doing so anyway in order to have a resource pave the proverbial cow-paths and make it easier for the team in the future.
I am very much in favor of putting engineers on customer support/success. I believe it is important to develop empathy and understanding of the user's experience with the product you build. Not only will it help you implement what they need, it will also serve as a way to call BS against product managers who try to get you to build things that look good on their resume (but don't help the customer.
But after reading through the comments from those who are against the idea, I wonder if there might be a productive middle ground - have engineers listen in on (but not participate in) any calls between the customer and the Support/Success team. This doesn't need to be done for a solid week, but perhaps a steady diet of 2 calls per week for a few weeks would help.
I'm sure you could imagine other 'middle-ground' ways to achieve this - but clearly nothing will work until engineers at a minimum buy into the reasons why some direct exposure to customers would be a good idea.
Much more reasonable would be 1% across the grain and 0.1% along it. You can confirm this in some of the wood movement calculators found online.
To those learning about wood movement, these ratios are decent but approximate; if you end up caring about these things you’ll want to check the species of the lumber you plan to work with.